Obradović, Maja

Link to this page

Authority KeyName Variants
orcid::0000-0003-2839-6548
  • Obradović, Maja (25)
Projects

Author's Bibliography

CO tolerant Pt/Ru0.7Ti0.3O2 nanocatalyst for hydrogen oxidation reaction

Obradović, Maja; Gojković, Snežana Lj.

(Engineering Society for Corrosion, Belgrade, Serbia, 2018)

TY  - JOUR
AU  - Obradović, Maja
AU  - Gojković, Snežana Lj.
PY  - 2018
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/3827
AB  - The oxidation of pure H2 and H2/CO mixture (100 ppm CO) was investigated on Pt nanocatalyst supported on Ru0.7Ti0.3O2 (Pt /Ru0.7Ti0.3O2) by linear sweep voltammetry at a rotating disc electrode in 0.1 M HClO4. The results were compared with those on the commercial Pt/C catalyst. It was demonstrated that Pt/Ru0.7Ti0.3O2 electrode possesses good conductivity and stability of the supports in the electrochemical experiments. The onset potential of COads oxidation on Pt/Ru0.7Ti0.3O2 is lower than Pt/C indicating that the Pt nanoparticles are in close contact with Ru atoms from support, which enable bifunctional mechanism and electronic effects to be operable. The influence of the poisoning of Pt/Ru0.7Ti0.3O2 and Pt/C catalyst by COads on the HOR was examined at several surface coverages ranging from 0 to 0.6. The decrease in HOR current on COads poisoned surface in low over-potential region of 0.05-0.50 V is less pronounced on Pt/Ru0.7Ti0.3O2 than on Pt/C. This is ascribed to a weakening of the Pt-CO interaction and consequently higher mobility of COads on Pt particles contacting Ru from the Ru0.7Ti0.3O2 support.
AB  - Oksidacija čistog H2 i smeše H2/CO (100 ppm CO) je ispitivana na nanokatalizatoru koji se sastojao od čestica Pt na nosaču Ru0,7Ti0,3O2 (Pt/Ru0,7Ti0,3O2). Korišćene su metoda linearne voltametrije u rastvoru 0,1 M HClO4 i rotirajuća disk elektroda. Rezultati su upoređeni sa komercijalnim katalizatorom Pt/C. Za katalizator Pt/Ru0,7Ti0,3O2 je utvrđena dobra provodnost i stabilnost nosača u elektrohemijskim eksperimentima. Pokazano je da oksidacija adorbovanog CO na Pt/Ru0,7Ti0,3O2 počinje na negativnijim potencijalima nego na Pt/C. To ukazuje da su nanočestice Pt u bliskom kontaktu sa atomima Ru iz nosača, što omogućuje odigravanje bifunkcionalnog mehanizma i ispoljavanje elektronskog efekta. Uticaj trovanja katalizatora Pt/Ru0,7Ti0,3O2 i Pt/C adsorbovanim CO na oksidaciju H2 je ispitivan na nekoliko stepena pokrivenosti u opsegu od 0 do 0,6. Smanjenje struje oksidacije vodonika na površini delimično pokrivenoj adsorbovanim CO u oblasti malih prenapetosti 0,05-0,50 V je manje izraženo na Pt/Ru0,7Ti0,3O2 u odnosu na Pt/C. Ovo se pripisuje slabljenju interakcija Pt-CO što dovodi do povećane pokretljivosti CO na česticama Pt koje su u kontaktu sa Ru iz nosača Ru0,7Ti0,3O2.
PB  - Engineering Society for Corrosion, Belgrade, Serbia
T2  - Zaštita materijala
T1  - CO tolerant Pt/Ru0.7Ti0.3O2 nanocatalyst for hydrogen oxidation reaction
T1  - Pt/Ru0,7Ti0,3O2 kao nanokatalizator za oksidaciju vodonika i njegova tolerancija na CO
EP  - 272
IS  - 2
SP  - 265
VL  - 59
DO  - 10.5937/ZasMat1802265O
ER  - 
@article{
author = "Obradović, Maja and Gojković, Snežana Lj.",
year = "2018",
abstract = "The oxidation of pure H2 and H2/CO mixture (100 ppm CO) was investigated on Pt nanocatalyst supported on Ru0.7Ti0.3O2 (Pt /Ru0.7Ti0.3O2) by linear sweep voltammetry at a rotating disc electrode in 0.1 M HClO4. The results were compared with those on the commercial Pt/C catalyst. It was demonstrated that Pt/Ru0.7Ti0.3O2 electrode possesses good conductivity and stability of the supports in the electrochemical experiments. The onset potential of COads oxidation on Pt/Ru0.7Ti0.3O2 is lower than Pt/C indicating that the Pt nanoparticles are in close contact with Ru atoms from support, which enable bifunctional mechanism and electronic effects to be operable. The influence of the poisoning of Pt/Ru0.7Ti0.3O2 and Pt/C catalyst by COads on the HOR was examined at several surface coverages ranging from 0 to 0.6. The decrease in HOR current on COads poisoned surface in low over-potential region of 0.05-0.50 V is less pronounced on Pt/Ru0.7Ti0.3O2 than on Pt/C. This is ascribed to a weakening of the Pt-CO interaction and consequently higher mobility of COads on Pt particles contacting Ru from the Ru0.7Ti0.3O2 support., Oksidacija čistog H2 i smeše H2/CO (100 ppm CO) je ispitivana na nanokatalizatoru koji se sastojao od čestica Pt na nosaču Ru0,7Ti0,3O2 (Pt/Ru0,7Ti0,3O2). Korišćene su metoda linearne voltametrije u rastvoru 0,1 M HClO4 i rotirajuća disk elektroda. Rezultati su upoređeni sa komercijalnim katalizatorom Pt/C. Za katalizator Pt/Ru0,7Ti0,3O2 je utvrđena dobra provodnost i stabilnost nosača u elektrohemijskim eksperimentima. Pokazano je da oksidacija adorbovanog CO na Pt/Ru0,7Ti0,3O2 počinje na negativnijim potencijalima nego na Pt/C. To ukazuje da su nanočestice Pt u bliskom kontaktu sa atomima Ru iz nosača, što omogućuje odigravanje bifunkcionalnog mehanizma i ispoljavanje elektronskog efekta. Uticaj trovanja katalizatora Pt/Ru0,7Ti0,3O2 i Pt/C adsorbovanim CO na oksidaciju H2 je ispitivan na nekoliko stepena pokrivenosti u opsegu od 0 do 0,6. Smanjenje struje oksidacije vodonika na površini delimično pokrivenoj adsorbovanim CO u oblasti malih prenapetosti 0,05-0,50 V je manje izraženo na Pt/Ru0,7Ti0,3O2 u odnosu na Pt/C. Ovo se pripisuje slabljenju interakcija Pt-CO što dovodi do povećane pokretljivosti CO na česticama Pt koje su u kontaktu sa Ru iz nosača Ru0,7Ti0,3O2.",
publisher = "Engineering Society for Corrosion, Belgrade, Serbia",
journal = "Zaštita materijala",
title = "CO tolerant Pt/Ru0.7Ti0.3O2 nanocatalyst for hydrogen oxidation reaction, Pt/Ru0,7Ti0,3O2 kao nanokatalizator za oksidaciju vodonika i njegova tolerancija na CO",
pages = "272-265",
number = "2",
volume = "59",
doi = "10.5937/ZasMat1802265O"
}
Obradović, M.,& Gojković, S. Lj.. (2018). CO tolerant Pt/Ru0.7Ti0.3O2 nanocatalyst for hydrogen oxidation reaction. in Zaštita materijala
Engineering Society for Corrosion, Belgrade, Serbia., 59(2), 265-272.
https://doi.org/10.5937/ZasMat1802265O
Obradović M, Gojković SL. CO tolerant Pt/Ru0.7Ti0.3O2 nanocatalyst for hydrogen oxidation reaction. in Zaštita materijala. 2018;59(2):265-272.
doi:10.5937/ZasMat1802265O .
Obradović, Maja, Gojković, Snežana Lj., "CO tolerant Pt/Ru0.7Ti0.3O2 nanocatalyst for hydrogen oxidation reaction" in Zaštita materijala, 59, no. 2 (2018):265-272,
https://doi.org/10.5937/ZasMat1802265O . .
2

Electrochemical oxidation of ethanol on palladium-nickel nanocatalyst in alkaline media

Obradović, Maja; Stancić, Z M; Lačnjevac, Uroš; Radmilović, Vuk; Gavrilović-Wohlmuther, Aleksandra; Radmilović, Velimir R.; Gojković, Snežana Lj.

(Elsevier, Amsterdam, 2016)

TY  - JOUR
AU  - Obradović, Maja
AU  - Stancić, Z M
AU  - Lačnjevac, Uroš
AU  - Radmilović, Vuk
AU  - Gavrilović-Wohlmuther, Aleksandra
AU  - Radmilović, Velimir R.
AU  - Gojković, Snežana Lj.
PY  - 2016
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/3437
AB  - Pd-Ni/C catalyst was synthesized employing a borohydride reduction method. The high area Ni was first dispersed on the carbon support and then modified by Pd nanoparticles. Transmission electron microscopy confirmed relatively even distribution of Ni across the carbon support with discrete palladium particles of about 3.3 nm mean diameter on it. Cyclic voltammetry confirmed the presence of Ni on the catalyst surface. The activity of the Pd-Ni/C catalysts for ethanol oxidation reaction (EOR) in alkaline solution was tested under the potentiodynamic and potentiostatic conditions and the results were compared to those obtained on the Pd/C catalyst. It was found that Pd-Ni/C is more active for the EOR compared to Pd/C by a factor up to 3, depending on the type of experiments and whether specific activity or mass activity are considered. During the potentiodynamic stability test an interesting phenomenon of activation of Pd-Ni/C catalyst was observed. It was found that maximum activity is attained after fifty cycles with the positive potential limit of 1.2 V, regardless of whether they were performed in the electrolyte with or without ethanol. It was postulated that potential cycling of the Pd-Ni surface causes reorganization of the catalyst surface bringing Pd and Ni sites to a more suitable arrangement for the efficient ethanol oxidation.
PB  - Elsevier, Amsterdam
T2  - Applied Catalysis B-Environmental
T1  - Electrochemical oxidation of ethanol on palladium-nickel nanocatalyst in alkaline media
EP  - 118
SP  - 110
VL  - 189
DO  - 10.1016/j.apcatb.2016.02.039
ER  - 
@article{
author = "Obradović, Maja and Stancić, Z M and Lačnjevac, Uroš and Radmilović, Vuk and Gavrilović-Wohlmuther, Aleksandra and Radmilović, Velimir R. and Gojković, Snežana Lj.",
year = "2016",
abstract = "Pd-Ni/C catalyst was synthesized employing a borohydride reduction method. The high area Ni was first dispersed on the carbon support and then modified by Pd nanoparticles. Transmission electron microscopy confirmed relatively even distribution of Ni across the carbon support with discrete palladium particles of about 3.3 nm mean diameter on it. Cyclic voltammetry confirmed the presence of Ni on the catalyst surface. The activity of the Pd-Ni/C catalysts for ethanol oxidation reaction (EOR) in alkaline solution was tested under the potentiodynamic and potentiostatic conditions and the results were compared to those obtained on the Pd/C catalyst. It was found that Pd-Ni/C is more active for the EOR compared to Pd/C by a factor up to 3, depending on the type of experiments and whether specific activity or mass activity are considered. During the potentiodynamic stability test an interesting phenomenon of activation of Pd-Ni/C catalyst was observed. It was found that maximum activity is attained after fifty cycles with the positive potential limit of 1.2 V, regardless of whether they were performed in the electrolyte with or without ethanol. It was postulated that potential cycling of the Pd-Ni surface causes reorganization of the catalyst surface bringing Pd and Ni sites to a more suitable arrangement for the efficient ethanol oxidation.",
publisher = "Elsevier, Amsterdam",
journal = "Applied Catalysis B-Environmental",
title = "Electrochemical oxidation of ethanol on palladium-nickel nanocatalyst in alkaline media",
pages = "118-110",
volume = "189",
doi = "10.1016/j.apcatb.2016.02.039"
}
Obradović, M., Stancić, Z. M., Lačnjevac, U., Radmilović, V., Gavrilović-Wohlmuther, A., Radmilović, V. R.,& Gojković, S. Lj.. (2016). Electrochemical oxidation of ethanol on palladium-nickel nanocatalyst in alkaline media. in Applied Catalysis B-Environmental
Elsevier, Amsterdam., 189, 110-118.
https://doi.org/10.1016/j.apcatb.2016.02.039
Obradović M, Stancić ZM, Lačnjevac U, Radmilović V, Gavrilović-Wohlmuther A, Radmilović VR, Gojković SL. Electrochemical oxidation of ethanol on palladium-nickel nanocatalyst in alkaline media. in Applied Catalysis B-Environmental. 2016;189:110-118.
doi:10.1016/j.apcatb.2016.02.039 .
Obradović, Maja, Stancić, Z M, Lačnjevac, Uroš, Radmilović, Vuk, Gavrilović-Wohlmuther, Aleksandra, Radmilović, Velimir R., Gojković, Snežana Lj., "Electrochemical oxidation of ethanol on palladium-nickel nanocatalyst in alkaline media" in Applied Catalysis B-Environmental, 189 (2016):110-118,
https://doi.org/10.1016/j.apcatb.2016.02.039 . .
1
100
71
93

RuxTi1-xO2 as the support for Pt nanoparticles: Electrocatalysis of methanol oxidation

Obradović, Maja; Lačnjevac, Uroš; Babić, Biljana M.; Ercius, P.; Radmilović, Velimir R.; Krstajić, Nedeljko V.; Gojković, Snežana Lj.

(Elsevier, Amsterdam, 2015)

TY  - JOUR
AU  - Obradović, Maja
AU  - Lačnjevac, Uroš
AU  - Babić, Biljana M.
AU  - Ercius, P.
AU  - Radmilović, Velimir R.
AU  - Krstajić, Nedeljko V.
AU  - Gojković, Snežana Lj.
PY  - 2015
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/2978
AB  - Two binary Ru-Ti oxides, Rum Ti0.9O2 and Ru0.7Ti0.3O2, were synthesized by the sol-gel method and used as an electrocatalyst support. The system was characterized by XRD, EDS, TEM and cyclic voltammetry. The Rum Ti0.9O2 and Ru0.7Ti0.3O2 consist of two phases of anatase and rutile structure. An average size of the Pt nanoparticles supported on them is similar to 3.5 nm and they are deposited on both Ru and Ti-rich domains. The supports exhibited good conductivity and electrochemical stability. The onset potentials of COads oxidation on the synthesized catalysts and on commercial PtRu/C are similar to each other and lower than that on Pt/C. This suggests that in Pt/Rum Ti0.9O2 and Pt/Ru0(.7)Ti(0.3)O(2) the Pt nanoparticles are in close contact with Ru atoms from the support, which enables the bifunctional mechanism. The activity and stability of the catalysts for methanol oxidation were examined under potentiodynamic and potentiostatic conditions. While the activity of Pt/Rum Ti0.9O2 is unsatisfactory, the performance of Pt/Ru0.7Ti0.3O2 is comparable to PtRu/C. For example, in the potentiostatic test at 0.5 V the activities after 25 min are 0.035 mA cm(-2) and 0.022 mA cm(-2) for Pt/Ru0.7Ti0.3O2 and PtRu/C, respectively. In potentiodynamic test the activities at 0.5V after 250 cycles are around 0.02 mA cm(-2) for both catalysts.
PB  - Elsevier, Amsterdam
T2  - Applied Catalysis B-Environmental
T1  - RuxTi1-xO2 as the support for Pt nanoparticles: Electrocatalysis of methanol oxidation
EP  - 152
SP  - 144
VL  - 170
DO  - 10.1016/j.apcatb.2015.01.038
ER  - 
@article{
author = "Obradović, Maja and Lačnjevac, Uroš and Babić, Biljana M. and Ercius, P. and Radmilović, Velimir R. and Krstajić, Nedeljko V. and Gojković, Snežana Lj.",
year = "2015",
abstract = "Two binary Ru-Ti oxides, Rum Ti0.9O2 and Ru0.7Ti0.3O2, were synthesized by the sol-gel method and used as an electrocatalyst support. The system was characterized by XRD, EDS, TEM and cyclic voltammetry. The Rum Ti0.9O2 and Ru0.7Ti0.3O2 consist of two phases of anatase and rutile structure. An average size of the Pt nanoparticles supported on them is similar to 3.5 nm and they are deposited on both Ru and Ti-rich domains. The supports exhibited good conductivity and electrochemical stability. The onset potentials of COads oxidation on the synthesized catalysts and on commercial PtRu/C are similar to each other and lower than that on Pt/C. This suggests that in Pt/Rum Ti0.9O2 and Pt/Ru0(.7)Ti(0.3)O(2) the Pt nanoparticles are in close contact with Ru atoms from the support, which enables the bifunctional mechanism. The activity and stability of the catalysts for methanol oxidation were examined under potentiodynamic and potentiostatic conditions. While the activity of Pt/Rum Ti0.9O2 is unsatisfactory, the performance of Pt/Ru0.7Ti0.3O2 is comparable to PtRu/C. For example, in the potentiostatic test at 0.5 V the activities after 25 min are 0.035 mA cm(-2) and 0.022 mA cm(-2) for Pt/Ru0.7Ti0.3O2 and PtRu/C, respectively. In potentiodynamic test the activities at 0.5V after 250 cycles are around 0.02 mA cm(-2) for both catalysts.",
publisher = "Elsevier, Amsterdam",
journal = "Applied Catalysis B-Environmental",
title = "RuxTi1-xO2 as the support for Pt nanoparticles: Electrocatalysis of methanol oxidation",
pages = "152-144",
volume = "170",
doi = "10.1016/j.apcatb.2015.01.038"
}
Obradović, M., Lačnjevac, U., Babić, B. M., Ercius, P., Radmilović, V. R., Krstajić, N. V.,& Gojković, S. Lj.. (2015). RuxTi1-xO2 as the support for Pt nanoparticles: Electrocatalysis of methanol oxidation. in Applied Catalysis B-Environmental
Elsevier, Amsterdam., 170, 144-152.
https://doi.org/10.1016/j.apcatb.2015.01.038
Obradović M, Lačnjevac U, Babić BM, Ercius P, Radmilović VR, Krstajić NV, Gojković SL. RuxTi1-xO2 as the support for Pt nanoparticles: Electrocatalysis of methanol oxidation. in Applied Catalysis B-Environmental. 2015;170:144-152.
doi:10.1016/j.apcatb.2015.01.038 .
Obradović, Maja, Lačnjevac, Uroš, Babić, Biljana M., Ercius, P., Radmilović, Velimir R., Krstajić, Nedeljko V., Gojković, Snežana Lj., "RuxTi1-xO2 as the support for Pt nanoparticles: Electrocatalysis of methanol oxidation" in Applied Catalysis B-Environmental, 170 (2015):144-152,
https://doi.org/10.1016/j.apcatb.2015.01.038 . .
25
20
23

Pd black decorated by Pt sub-monolayers as an electrocatalyst for the HCOOH oxidation

Obradović, Maja; Gojković, Snežana Lj.

(Springer, New York, 2014)

TY  - JOUR
AU  - Obradović, Maja
AU  - Gojković, Snežana Lj.
PY  - 2014
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/2648
AB  - Pd black was modified by a very low amount of Pt corresponding to a sub-monolayer (ML). Spontaneous displacement method was employed. The catalysts with 0.02-0.12 ML were characterized by cyclic voltammetry and COads stripping and were tested for HCOOH oxidation under the potentiodynamic and potentiostatic conditions. All the Pt"Pd catalysts were more active for HCOOH oxidation than Pd black. The Pt"Pd with 0.08 ML of Pt exhibited the highest activity with the maximum current density under the potentiodynamic conditions of 8 mA cm(-2) (vs. 2.7 mA cm(-2) on Pd black). Contrasting HCOOH oxidation kinetics on Pt"Pd and Pt"Au catalysts revealed that the current densities are higher, and the poisoning rate is lower on Pt"Pd catalyst. This was ascribed to an optimal strength of the Pt-adsorbate bond when Pt is supported on Pd and to a possible influence of the Pt atoms on the Pd substrate.
PB  - Springer, New York
T2  - Journal of Solid State Electrochemistry
T1  - Pd black decorated by Pt sub-monolayers as an electrocatalyst for the HCOOH oxidation
EP  - 2607
IS  - 9
SP  - 2599
VL  - 18
DO  - 10.1007/s10008-014-2509-9
ER  - 
@article{
author = "Obradović, Maja and Gojković, Snežana Lj.",
year = "2014",
abstract = "Pd black was modified by a very low amount of Pt corresponding to a sub-monolayer (ML). Spontaneous displacement method was employed. The catalysts with 0.02-0.12 ML were characterized by cyclic voltammetry and COads stripping and were tested for HCOOH oxidation under the potentiodynamic and potentiostatic conditions. All the Pt"Pd catalysts were more active for HCOOH oxidation than Pd black. The Pt"Pd with 0.08 ML of Pt exhibited the highest activity with the maximum current density under the potentiodynamic conditions of 8 mA cm(-2) (vs. 2.7 mA cm(-2) on Pd black). Contrasting HCOOH oxidation kinetics on Pt"Pd and Pt"Au catalysts revealed that the current densities are higher, and the poisoning rate is lower on Pt"Pd catalyst. This was ascribed to an optimal strength of the Pt-adsorbate bond when Pt is supported on Pd and to a possible influence of the Pt atoms on the Pd substrate.",
publisher = "Springer, New York",
journal = "Journal of Solid State Electrochemistry",
title = "Pd black decorated by Pt sub-monolayers as an electrocatalyst for the HCOOH oxidation",
pages = "2607-2599",
number = "9",
volume = "18",
doi = "10.1007/s10008-014-2509-9"
}
Obradović, M.,& Gojković, S. Lj.. (2014). Pd black decorated by Pt sub-monolayers as an electrocatalyst for the HCOOH oxidation. in Journal of Solid State Electrochemistry
Springer, New York., 18(9), 2599-2607.
https://doi.org/10.1007/s10008-014-2509-9
Obradović M, Gojković SL. Pd black decorated by Pt sub-monolayers as an electrocatalyst for the HCOOH oxidation. in Journal of Solid State Electrochemistry. 2014;18(9):2599-2607.
doi:10.1007/s10008-014-2509-9 .
Obradović, Maja, Gojković, Snežana Lj., "Pd black decorated by Pt sub-monolayers as an electrocatalyst for the HCOOH oxidation" in Journal of Solid State Electrochemistry, 18, no. 9 (2014):2599-2607,
https://doi.org/10.1007/s10008-014-2509-9 . .
13
13
14

Electrochemical oxidation of methanol on Pt/(RuxSn1-x)O2 nanocatalyst

Krstajić, Mila; Obradović, Maja; Babić, Biljana M.; Radmilović, Velimir R.; Lačnjevac, Uroš; Krstajić, Nedeljko V.; Gojković, Snežana Lj.

(Serbian Chemical Society, Belgrade, 2013)

TY  - JOUR
AU  - Krstajić, Mila
AU  - Obradović, Maja
AU  - Babić, Biljana M.
AU  - Radmilović, Velimir R.
AU  - Lačnjevac, Uroš
AU  - Krstajić, Nedeljko V.
AU  - Gojković, Snežana Lj.
PY  - 2013
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/2353
AB  - Ru-doped SnO2 powder, (RuxSn1-x)O2, with a Sn:Ru atomic ratio of 9:1 was synthesized and used as a support for Pt nanoparticles (30 mass % loading). The (RuxSn1-x)O2 support and the Pt/(RuxSn1-x)O2 catalyst were characterized by X-ray diffraction measurements, energy dispersive X-ray spectroscopy and transmission electron microscopy (TEM). The (RuxSn1-x)O2 was found to be a two-phase material consisting of probably a solid solution of RuO2 in SnO2 and pure RuO2. The average Pt particle size determined by TEM was 5.3 nm. Cyclic voltammetry of Pt/(RuxSn1-x)O2 indicated good conductivity of the support and displayed the usual features of Pt. The results of the electrochemical oxidation of COads and methanol on Pt/(RuxSn1-x)O2 were compared with those on commercial Pt/C and PtRu/C catalysts. Oxidation of COads on Pt/(RuxSn1-x)O2 starts at lower positive potentials than on PtRu/C and Pt/C. Potentiodynamic polarization curves and chronoamperometric curves of methanol oxidation indicated higher initial activity of the Pt/(RuxSn1-x)O2 catalyst compared to PtRu/C, but also a greater loss in current density over time. A potentiodynamic stability test of the catalysts revealed that deactivation of Pt/(RuxSn1-x)O2 and Pt/C was primarily caused by poisoning of the Pt surface by residues of methanol oxidation, which mostly occurred during the first potential cycle. In the case of PtRu/C, the poisoning of the surface was minor and deactivation was caused by surface area loss of the PtRu.
AB  - Sintetizovan je prah SnO2 dopovan rutenijumom, (RuxSn1-x)O2, sa atomskim odnosom Sn:Ru od 9:1, i korišćen kao nosač nanočestica platine. Udeo Pt u dobijenom katalizatoru, Pt/(RuxSn1-x)O2, bio je 30 mas. %. Nosač i katalizator su karakterisani difrakcijom X-zraka, energetski disperzivnom spektroskopijom X-zraka i transmisionom elektronskom mikroskopijom (TEM). Pokazano je da je (RuxSn1-x)O2 dvofazni materijal koji verovatno sadrži čvrst rastvor RuO2 u SnO2 i čist RuO2. Prosečna veličina zrna Pt, određena TEM analizom, iznosi 5,3 nm. Ciklična voltametrija Pt/(RuxSn1-x)O2 ukazala je na dobru provodnost nosača katalizatora i na uobičajene karakteristike Pt. Upoređeni su rezultati elektrohemijske oksidacije COads na Pt/(RuxSn1-x)O2, Pt/C i PtRu/C. Oksidacija COads na Pt/(RuxSn1-x)O2 počinje na negativnijim potencijalima u odnosu na PtRu/C i Pt/C. Potenciodinamičke polarizacione krive i hronoamperometrijske krive za oksidaciju metanola ukazuju na veću početnu aktivnost katalizatora Pt/(RuxSn1-x)O2 u odnosu na PtRu/C, ali i na veće smanjenje gustine struje tokom vremena. Test potenciodinamičke stabilnosti katalizatora je ukazao da je smanjenje aktivnosti Pt/(RuxSn1-x)O2 i Pt/C prvenstveno prouzrokovano trovanjem površine Pt proizvodima nepotpune oksidacije metanola, koje se uglavnom odigrava tokom prvog ciklusa. Kod PtRu/C trovanje površine je minimalno, a smanjenje aktivnosti je prouzrokovano smanjenjem elektrohemijski aktivne površine PtRu.
PB  - Serbian Chemical Society, Belgrade
T2  - Journal of the Serbian Chemical Society
T1  - Electrochemical oxidation of methanol on Pt/(RuxSn1-x)O2 nanocatalyst
T1  - Elektrohemijska oksidacija metanola na katalizatoru Pt/(RuxSn1-x)O2
EP  - 1716
IS  - 11
SP  - 1703
VL  - 78
UR  - https://hdl.handle.net/21.15107/rcub_technorep_2353
ER  - 
@article{
author = "Krstajić, Mila and Obradović, Maja and Babić, Biljana M. and Radmilović, Velimir R. and Lačnjevac, Uroš and Krstajić, Nedeljko V. and Gojković, Snežana Lj.",
year = "2013",
abstract = "Ru-doped SnO2 powder, (RuxSn1-x)O2, with a Sn:Ru atomic ratio of 9:1 was synthesized and used as a support for Pt nanoparticles (30 mass % loading). The (RuxSn1-x)O2 support and the Pt/(RuxSn1-x)O2 catalyst were characterized by X-ray diffraction measurements, energy dispersive X-ray spectroscopy and transmission electron microscopy (TEM). The (RuxSn1-x)O2 was found to be a two-phase material consisting of probably a solid solution of RuO2 in SnO2 and pure RuO2. The average Pt particle size determined by TEM was 5.3 nm. Cyclic voltammetry of Pt/(RuxSn1-x)O2 indicated good conductivity of the support and displayed the usual features of Pt. The results of the electrochemical oxidation of COads and methanol on Pt/(RuxSn1-x)O2 were compared with those on commercial Pt/C and PtRu/C catalysts. Oxidation of COads on Pt/(RuxSn1-x)O2 starts at lower positive potentials than on PtRu/C and Pt/C. Potentiodynamic polarization curves and chronoamperometric curves of methanol oxidation indicated higher initial activity of the Pt/(RuxSn1-x)O2 catalyst compared to PtRu/C, but also a greater loss in current density over time. A potentiodynamic stability test of the catalysts revealed that deactivation of Pt/(RuxSn1-x)O2 and Pt/C was primarily caused by poisoning of the Pt surface by residues of methanol oxidation, which mostly occurred during the first potential cycle. In the case of PtRu/C, the poisoning of the surface was minor and deactivation was caused by surface area loss of the PtRu., Sintetizovan je prah SnO2 dopovan rutenijumom, (RuxSn1-x)O2, sa atomskim odnosom Sn:Ru od 9:1, i korišćen kao nosač nanočestica platine. Udeo Pt u dobijenom katalizatoru, Pt/(RuxSn1-x)O2, bio je 30 mas. %. Nosač i katalizator su karakterisani difrakcijom X-zraka, energetski disperzivnom spektroskopijom X-zraka i transmisionom elektronskom mikroskopijom (TEM). Pokazano je da je (RuxSn1-x)O2 dvofazni materijal koji verovatno sadrži čvrst rastvor RuO2 u SnO2 i čist RuO2. Prosečna veličina zrna Pt, određena TEM analizom, iznosi 5,3 nm. Ciklična voltametrija Pt/(RuxSn1-x)O2 ukazala je na dobru provodnost nosača katalizatora i na uobičajene karakteristike Pt. Upoređeni su rezultati elektrohemijske oksidacije COads na Pt/(RuxSn1-x)O2, Pt/C i PtRu/C. Oksidacija COads na Pt/(RuxSn1-x)O2 počinje na negativnijim potencijalima u odnosu na PtRu/C i Pt/C. Potenciodinamičke polarizacione krive i hronoamperometrijske krive za oksidaciju metanola ukazuju na veću početnu aktivnost katalizatora Pt/(RuxSn1-x)O2 u odnosu na PtRu/C, ali i na veće smanjenje gustine struje tokom vremena. Test potenciodinamičke stabilnosti katalizatora je ukazao da je smanjenje aktivnosti Pt/(RuxSn1-x)O2 i Pt/C prvenstveno prouzrokovano trovanjem površine Pt proizvodima nepotpune oksidacije metanola, koje se uglavnom odigrava tokom prvog ciklusa. Kod PtRu/C trovanje površine je minimalno, a smanjenje aktivnosti je prouzrokovano smanjenjem elektrohemijski aktivne površine PtRu.",
publisher = "Serbian Chemical Society, Belgrade",
journal = "Journal of the Serbian Chemical Society",
title = "Electrochemical oxidation of methanol on Pt/(RuxSn1-x)O2 nanocatalyst, Elektrohemijska oksidacija metanola na katalizatoru Pt/(RuxSn1-x)O2",
pages = "1716-1703",
number = "11",
volume = "78",
url = "https://hdl.handle.net/21.15107/rcub_technorep_2353"
}
Krstajić, M., Obradović, M., Babić, B. M., Radmilović, V. R., Lačnjevac, U., Krstajić, N. V.,& Gojković, S. Lj.. (2013). Electrochemical oxidation of methanol on Pt/(RuxSn1-x)O2 nanocatalyst. in Journal of the Serbian Chemical Society
Serbian Chemical Society, Belgrade., 78(11), 1703-1716.
https://hdl.handle.net/21.15107/rcub_technorep_2353
Krstajić M, Obradović M, Babić BM, Radmilović VR, Lačnjevac U, Krstajić NV, Gojković SL. Electrochemical oxidation of methanol on Pt/(RuxSn1-x)O2 nanocatalyst. in Journal of the Serbian Chemical Society. 2013;78(11):1703-1716.
https://hdl.handle.net/21.15107/rcub_technorep_2353 .
Krstajić, Mila, Obradović, Maja, Babić, Biljana M., Radmilović, Velimir R., Lačnjevac, Uroš, Krstajić, Nedeljko V., Gojković, Snežana Lj., "Electrochemical oxidation of methanol on Pt/(RuxSn1-x)O2 nanocatalyst" in Journal of the Serbian Chemical Society, 78, no. 11 (2013):1703-1716,
https://hdl.handle.net/21.15107/rcub_technorep_2353 .
1
2

Effect of tungsten carbide in carbon Pt catalyst support on electrochemical oxygen reduction in acid solution

Obradović, Maja; Babić, Biljana M.; Krstajić, Nedeljko V.; Gojković, Snežana Lj.

(Association of Chemical Engineers of Serbia, 2013)

TY  - JOUR
AU  - Obradović, Maja
AU  - Babić, Biljana M.
AU  - Krstajić, Nedeljko V.
AU  - Gojković, Snežana Lj.
PY  - 2013
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/2369
AB  - Tungsten carbide was synthesized by calcination of carbon cryogel with embedded tungsten in a form of metatungstate. This material was used as a support for Pt nanoparticles. XRD pattern of W-C support indicated the presence of WC, W2C, and unreacted W, as well as graphitized carbon. According to previous TEM analysis of W-C support, it contains particles with core-shell structure, where the W particle was covered with the shell of a mixture of WC and W2C. The average Pt grain size calculated from XRD pattern was about 6 nm. A cyclic voltammogram of W-C support was recorded within the potential range relevant for its application as a catalyst support in fuel cells. The pair of anodic/cathodic peaks close to the negative potential limit could be ascribed to the intercalation of hydrogen within hydrous tungsten oxide, which is always present on the surface of WC in aqueous solutions. The cyclic voltammogram of Pt/W-C indicated that tungsten oxide species are present on tungsten carbide shell as well as on the surface of Pt nanoparticles. The Pt surface is only partially covered by hydrous tungsten oxide. Hydrogen intercalation in hydrous tungsten oxide is enhanced in the presence of Pt nanoparticles. Also, the presence of hydrated tungsten oxide leads to the decrease of OH chemisorbed on Pt surface. Stripping of underpotentially deposited copper was used for the assessment of Pt surface area and the specific surface area of Pt was estimated to be 41 m2 g-1. The electrochemical oxygen reduction reaction was examined on the synthesized Pt/W-C catalyst and compared with the results on the commercial Pt/C catalyst. It was found that the current densities at Pt/W-C were almost twice as high as those on Pt/C. The Tafel plots for both catalysts are characterized with two Tafel slopes: -0.060 V dec-1 at low current densities, and -0.120 V dec-1 at high current densities. From the rotational dependence of the reaction rate, it was found that oxygen reduction on both Pt/W-C and Pt/C follows the first order kinetics with respect to O2 and that four electrons are transferred per O2 molecule. The results show that the presence of tungsten carbide in support material, i.e. hydrous tungsten oxide on Pt surface, leads to promotion of oxygen reduction on the Pt/W-C catalyst. It was assumed that oxophilic hydrated tungsten oxide hinders OH adsorption on Pt surface, thus increasing Pt surface area available for O2 adsorption and its electrochemical reduction.
AB  - Sintetizovan je nosač katalizatora u kojem se na ugljeničnoj osnovi nalaze nanočestice metalnog volframa obavijene volfram-karbidom i na njega su nanete nanočestice Pt. Karakterizacija sintetizovanog uzorka cikličnom voltametrijom u kiseloj sredini ukazala je na oksidaciju volframovih vrsta iz nosača i formiranje hidratisanih oksidnih vrsta volframa na površini Pt. Elektrohemijska redukcija O2 u kiseloj sredini je ispitivana na sintetizovanom uzorku i rezultati su upoređeni sa komercijalnim katalizatorom u kojem su nanočestice Pt na nosaču od ugljenika razvijene površine. Pokazano je da redukcija O2, bez obzira na nosač katalizatora, sledi kinetiku prvog reda po O2 uz razmenu četiri elektrona, ali da su gustine struje veće u slučaju nosača sa volfram-karbidom. Povećana aktivnost sintetizovanog katalizatora je posledica prisustva oksofiličnih hidratisanih oksida volframa koji sprečavaju adsorpciju hidratisanog oksida na površini Pt i tako povećavaju površinu Pt dostupnu za adsorpciju i redukciju molekula kiseonika.
PB  - Association of Chemical Engineers of Serbia
T2  - Hemijska industrija
T1  - Effect of tungsten carbide in carbon Pt catalyst support on electrochemical oxygen reduction in acid solution
T1  - Uticaj prisustva volfram-karbida u ugljeničnom nosaču Pt nanočestica na elektrohemijsku redukciju kiseonika u kiselom rastvoru
EP  - 311
IS  - 2
SP  - 303
VL  - 67
DO  - 10.2298/HEMIND120307063O
ER  - 
@article{
author = "Obradović, Maja and Babić, Biljana M. and Krstajić, Nedeljko V. and Gojković, Snežana Lj.",
year = "2013",
abstract = "Tungsten carbide was synthesized by calcination of carbon cryogel with embedded tungsten in a form of metatungstate. This material was used as a support for Pt nanoparticles. XRD pattern of W-C support indicated the presence of WC, W2C, and unreacted W, as well as graphitized carbon. According to previous TEM analysis of W-C support, it contains particles with core-shell structure, where the W particle was covered with the shell of a mixture of WC and W2C. The average Pt grain size calculated from XRD pattern was about 6 nm. A cyclic voltammogram of W-C support was recorded within the potential range relevant for its application as a catalyst support in fuel cells. The pair of anodic/cathodic peaks close to the negative potential limit could be ascribed to the intercalation of hydrogen within hydrous tungsten oxide, which is always present on the surface of WC in aqueous solutions. The cyclic voltammogram of Pt/W-C indicated that tungsten oxide species are present on tungsten carbide shell as well as on the surface of Pt nanoparticles. The Pt surface is only partially covered by hydrous tungsten oxide. Hydrogen intercalation in hydrous tungsten oxide is enhanced in the presence of Pt nanoparticles. Also, the presence of hydrated tungsten oxide leads to the decrease of OH chemisorbed on Pt surface. Stripping of underpotentially deposited copper was used for the assessment of Pt surface area and the specific surface area of Pt was estimated to be 41 m2 g-1. The electrochemical oxygen reduction reaction was examined on the synthesized Pt/W-C catalyst and compared with the results on the commercial Pt/C catalyst. It was found that the current densities at Pt/W-C were almost twice as high as those on Pt/C. The Tafel plots for both catalysts are characterized with two Tafel slopes: -0.060 V dec-1 at low current densities, and -0.120 V dec-1 at high current densities. From the rotational dependence of the reaction rate, it was found that oxygen reduction on both Pt/W-C and Pt/C follows the first order kinetics with respect to O2 and that four electrons are transferred per O2 molecule. The results show that the presence of tungsten carbide in support material, i.e. hydrous tungsten oxide on Pt surface, leads to promotion of oxygen reduction on the Pt/W-C catalyst. It was assumed that oxophilic hydrated tungsten oxide hinders OH adsorption on Pt surface, thus increasing Pt surface area available for O2 adsorption and its electrochemical reduction., Sintetizovan je nosač katalizatora u kojem se na ugljeničnoj osnovi nalaze nanočestice metalnog volframa obavijene volfram-karbidom i na njega su nanete nanočestice Pt. Karakterizacija sintetizovanog uzorka cikličnom voltametrijom u kiseloj sredini ukazala je na oksidaciju volframovih vrsta iz nosača i formiranje hidratisanih oksidnih vrsta volframa na površini Pt. Elektrohemijska redukcija O2 u kiseloj sredini je ispitivana na sintetizovanom uzorku i rezultati su upoređeni sa komercijalnim katalizatorom u kojem su nanočestice Pt na nosaču od ugljenika razvijene površine. Pokazano je da redukcija O2, bez obzira na nosač katalizatora, sledi kinetiku prvog reda po O2 uz razmenu četiri elektrona, ali da su gustine struje veće u slučaju nosača sa volfram-karbidom. Povećana aktivnost sintetizovanog katalizatora je posledica prisustva oksofiličnih hidratisanih oksida volframa koji sprečavaju adsorpciju hidratisanog oksida na površini Pt i tako povećavaju površinu Pt dostupnu za adsorpciju i redukciju molekula kiseonika.",
publisher = "Association of Chemical Engineers of Serbia",
journal = "Hemijska industrija",
title = "Effect of tungsten carbide in carbon Pt catalyst support on electrochemical oxygen reduction in acid solution, Uticaj prisustva volfram-karbida u ugljeničnom nosaču Pt nanočestica na elektrohemijsku redukciju kiseonika u kiselom rastvoru",
pages = "311-303",
number = "2",
volume = "67",
doi = "10.2298/HEMIND120307063O"
}
Obradović, M., Babić, B. M., Krstajić, N. V.,& Gojković, S. Lj.. (2013). Effect of tungsten carbide in carbon Pt catalyst support on electrochemical oxygen reduction in acid solution. in Hemijska industrija
Association of Chemical Engineers of Serbia., 67(2), 303-311.
https://doi.org/10.2298/HEMIND120307063O
Obradović M, Babić BM, Krstajić NV, Gojković SL. Effect of tungsten carbide in carbon Pt catalyst support on electrochemical oxygen reduction in acid solution. in Hemijska industrija. 2013;67(2):303-311.
doi:10.2298/HEMIND120307063O .
Obradović, Maja, Babić, Biljana M., Krstajić, Nedeljko V., Gojković, Snežana Lj., "Effect of tungsten carbide in carbon Pt catalyst support on electrochemical oxygen reduction in acid solution" in Hemijska industrija, 67, no. 2 (2013):303-311,
https://doi.org/10.2298/HEMIND120307063O . .
2

HCOOH oxidation on thin Pd layers on Au: Self-poisoning by the subsequent reaction of the reaction product

Obradović, Maja; Gojković, Snežana Lj.

(Pergamon-Elsevier Science Ltd, Oxford, 2013)

TY  - JOUR
AU  - Obradović, Maja
AU  - Gojković, Snežana Lj.
PY  - 2013
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/2545
AB  - The oxidation of HCOOH has been investigated on thin Pd layers ranging from 1 to 17 ML equivalents electrodeposited on polycrystalline Au substrate (Pd"Au). The results are compared to those on Pd black. Potentiodynamic polarization curves suggest that on both types of catalyst HCOOH oxidizes through dehydrogenation path. The high current densities achieved on 4-17 ML Pd"Au surpass more than three times the activity of Pd black. Chronoamperometric test reveals that the Pd"Au electrodes lose their activity faster than Pd black. In the stripping experiment performed after the chronoamperometry COads is detected on all the surfaces. On the 4 ML Pd"Au, which exhibits the highest deactivation rate, the COads coverage is the largest. After the chronoamperometric test repeated in the CO2 saturated supporting electrolyte, the anodic stripping shows that COads is present on all the electrodes, again with the highest coverage on 4 ML Pd"Au. It is concluded that deactivation of Pd surfaces is caused by the COads formed in the electrochemical reduction of CO2, which is the product of HCOOH oxidation. Electronic modification of Pd by Au substrate causes stronger interactions of Pd with HCOOH and CO, which increases HCOOH oxidation rate, but also accelerates the poisoning by COads.
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - Electrochimica Acta
T1  - HCOOH oxidation on thin Pd layers on Au: Self-poisoning by the subsequent reaction of the reaction product
EP  - 389
SP  - 384
VL  - 88
DO  - 10.1016/j.electacta.2012.10.033
ER  - 
@article{
author = "Obradović, Maja and Gojković, Snežana Lj.",
year = "2013",
abstract = "The oxidation of HCOOH has been investigated on thin Pd layers ranging from 1 to 17 ML equivalents electrodeposited on polycrystalline Au substrate (Pd"Au). The results are compared to those on Pd black. Potentiodynamic polarization curves suggest that on both types of catalyst HCOOH oxidizes through dehydrogenation path. The high current densities achieved on 4-17 ML Pd"Au surpass more than three times the activity of Pd black. Chronoamperometric test reveals that the Pd"Au electrodes lose their activity faster than Pd black. In the stripping experiment performed after the chronoamperometry COads is detected on all the surfaces. On the 4 ML Pd"Au, which exhibits the highest deactivation rate, the COads coverage is the largest. After the chronoamperometric test repeated in the CO2 saturated supporting electrolyte, the anodic stripping shows that COads is present on all the electrodes, again with the highest coverage on 4 ML Pd"Au. It is concluded that deactivation of Pd surfaces is caused by the COads formed in the electrochemical reduction of CO2, which is the product of HCOOH oxidation. Electronic modification of Pd by Au substrate causes stronger interactions of Pd with HCOOH and CO, which increases HCOOH oxidation rate, but also accelerates the poisoning by COads.",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "Electrochimica Acta",
title = "HCOOH oxidation on thin Pd layers on Au: Self-poisoning by the subsequent reaction of the reaction product",
pages = "389-384",
volume = "88",
doi = "10.1016/j.electacta.2012.10.033"
}
Obradović, M.,& Gojković, S. Lj.. (2013). HCOOH oxidation on thin Pd layers on Au: Self-poisoning by the subsequent reaction of the reaction product. in Electrochimica Acta
Pergamon-Elsevier Science Ltd, Oxford., 88, 384-389.
https://doi.org/10.1016/j.electacta.2012.10.033
Obradović M, Gojković SL. HCOOH oxidation on thin Pd layers on Au: Self-poisoning by the subsequent reaction of the reaction product. in Electrochimica Acta. 2013;88:384-389.
doi:10.1016/j.electacta.2012.10.033 .
Obradović, Maja, Gojković, Snežana Lj., "HCOOH oxidation on thin Pd layers on Au: Self-poisoning by the subsequent reaction of the reaction product" in Electrochimica Acta, 88 (2013):384-389,
https://doi.org/10.1016/j.electacta.2012.10.033 . .
36
30
35

The kinetics of the hydrogen oxidation reaction on WC/Pt catalyst with low content of Pt nano-particles

Obradović, Maja; Gojković, Snežana Lj.; Elezović, Nevenka R.; Ercius, P.; Radmilović, Velimir R.; Vračar, Ljiljana M.; Krstajić, Nedeljko V.

(Elsevier Science Sa, Lausanne, 2012)

TY  - JOUR
AU  - Obradović, Maja
AU  - Gojković, Snežana Lj.
AU  - Elezović, Nevenka R.
AU  - Ercius, P.
AU  - Radmilović, Velimir R.
AU  - Vračar, Ljiljana M.
AU  - Krstajić, Nedeljko V.
PY  - 2012
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/2127
AB  - The catalytic activity of WC/Pt electrocatalysts towards hydrogen oxidation reaction (HOR) in acid solution was studied. Tungsten carbide (WC) prepared by polycondensation of resorcinol and formaldehyde in the presence of ammonium metatungstate salt and CTABr surfactant was used as the support of a Pt electrocatalyst (WC/Pt). The obtained WC/Pt electrodes were characterized by XRD, HRTEM, EDS, EELS and electrochemical measurements. HRTEM analysis showed that the WC particles possess a core-shell structure with a metallic tungsten core and a shell composed of a mixture of tungsten carbides shell (WC and W2C). The WC/Pt catalyst is composed of well-dispersed sub-nanometer Pt clusters which consist of a few to several tens of Pt atoms. EELS measurements indicate that the WC particles function as nucleation sites for Pt nanoparticles. Based on the Tafel-Heyrovsky-Volmer mechanism the corresponding kinetic equations were derived to describe the HOR current-potential behavior over the entire potential region on RDE. The fitting showed that in the lower potential region HOR on Pt proceeds most likely via the Tafel-Volmer (TV) pathway. The kinetic results also showed that the WC/Pt(1%) when compared to the standard C/Pt(1%) electrode led to a remarkable enhancement of the hydrogen oxidation in an acidic medium, which was explained by H-spill-over between platinum and tungsten carbide.
PB  - Elsevier Science Sa, Lausanne
T2  - Journal of Electroanalytical Chemistry
T1  - The kinetics of the hydrogen oxidation reaction on WC/Pt catalyst with low content of Pt nano-particles
EP  - 32
SP  - 24
VL  - 671
DO  - 10.1016/j.jelechem.2012.01.026
ER  - 
@article{
author = "Obradović, Maja and Gojković, Snežana Lj. and Elezović, Nevenka R. and Ercius, P. and Radmilović, Velimir R. and Vračar, Ljiljana M. and Krstajić, Nedeljko V.",
year = "2012",
abstract = "The catalytic activity of WC/Pt electrocatalysts towards hydrogen oxidation reaction (HOR) in acid solution was studied. Tungsten carbide (WC) prepared by polycondensation of resorcinol and formaldehyde in the presence of ammonium metatungstate salt and CTABr surfactant was used as the support of a Pt electrocatalyst (WC/Pt). The obtained WC/Pt electrodes were characterized by XRD, HRTEM, EDS, EELS and electrochemical measurements. HRTEM analysis showed that the WC particles possess a core-shell structure with a metallic tungsten core and a shell composed of a mixture of tungsten carbides shell (WC and W2C). The WC/Pt catalyst is composed of well-dispersed sub-nanometer Pt clusters which consist of a few to several tens of Pt atoms. EELS measurements indicate that the WC particles function as nucleation sites for Pt nanoparticles. Based on the Tafel-Heyrovsky-Volmer mechanism the corresponding kinetic equations were derived to describe the HOR current-potential behavior over the entire potential region on RDE. The fitting showed that in the lower potential region HOR on Pt proceeds most likely via the Tafel-Volmer (TV) pathway. The kinetic results also showed that the WC/Pt(1%) when compared to the standard C/Pt(1%) electrode led to a remarkable enhancement of the hydrogen oxidation in an acidic medium, which was explained by H-spill-over between platinum and tungsten carbide.",
publisher = "Elsevier Science Sa, Lausanne",
journal = "Journal of Electroanalytical Chemistry",
title = "The kinetics of the hydrogen oxidation reaction on WC/Pt catalyst with low content of Pt nano-particles",
pages = "32-24",
volume = "671",
doi = "10.1016/j.jelechem.2012.01.026"
}
Obradović, M., Gojković, S. Lj., Elezović, N. R., Ercius, P., Radmilović, V. R., Vračar, L. M.,& Krstajić, N. V.. (2012). The kinetics of the hydrogen oxidation reaction on WC/Pt catalyst with low content of Pt nano-particles. in Journal of Electroanalytical Chemistry
Elsevier Science Sa, Lausanne., 671, 24-32.
https://doi.org/10.1016/j.jelechem.2012.01.026
Obradović M, Gojković SL, Elezović NR, Ercius P, Radmilović VR, Vračar LM, Krstajić NV. The kinetics of the hydrogen oxidation reaction on WC/Pt catalyst with low content of Pt nano-particles. in Journal of Electroanalytical Chemistry. 2012;671:24-32.
doi:10.1016/j.jelechem.2012.01.026 .
Obradović, Maja, Gojković, Snežana Lj., Elezović, Nevenka R., Ercius, P., Radmilović, Velimir R., Vračar, Ljiljana M., Krstajić, Nedeljko V., "The kinetics of the hydrogen oxidation reaction on WC/Pt catalyst with low content of Pt nano-particles" in Journal of Electroanalytical Chemistry, 671 (2012):24-32,
https://doi.org/10.1016/j.jelechem.2012.01.026 . .
16
12
15

Core-shell structured tungsten-tungsten carbide as a Pt catalyst support and its activity for methanol electrooxidation

Obradović, Maja; Babić, Biljana M.; Radmilović, Velimir R.; Krstajić, Nedeljko V.; Gojković, Snežana Lj.

(Pergamon-Elsevier Science Ltd, Oxford, 2012)

TY  - JOUR
AU  - Obradović, Maja
AU  - Babić, Biljana M.
AU  - Radmilović, Velimir R.
AU  - Krstajić, Nedeljko V.
AU  - Gojković, Snežana Lj.
PY  - 2012
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/2142
AB  - Tungsten carbide was synthesized by calcination of carbon cryogel containing tungsten in a form of metatungstate. Characterization by X-ray diffraction and transmission electron microscopy indicated core-shell structure of the particles with tungsten core and tungsten carbide shell, attached to graphitized carbon. Pt nanoparticles were deposited on this material and most of them were nucleated on tungsten carbide. Cyclic voltammetry of W-C support and Pt/W-C catalyst indicated hydrogen intercalation in surface hydrous tungsten oxide. Oxidation of COads on Pt/W-C commences earlier than on Pt/C for about 100 mV. The onset potentials of MOR on Pt/W-C and Pt/C are the same, but at more positive potentials Pt/W-C catalyst is more active. It was proposed that promotion of MOR is based on bifunctional mechanism that facilitates COads removal. Stability test was performed by potential cycling of Pt/W-C and Pt/C in the supporting electrolyte and in the presence of methanol. Pt surface area loss observed in the supporting electrolyte of both catalysts after 250 cycles was about 20%. Decrease in the activity for methanol oxidation was 30% for Pt/W-C, but even 48% for Pt/C. The difference was explained by the presence of hydrous tungsten oxide on Pt in Pt/W-C catalyst, which reduces accumulation of poisoning COads.
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - International Journal of Hydrogen Energy
T1  - Core-shell structured tungsten-tungsten carbide as a Pt catalyst support and its activity for methanol electrooxidation
EP  - 10679
IS  - 14
SP  - 10671
VL  - 37
DO  - 10.1016/j.ijhydene.2012.04.114
ER  - 
@article{
author = "Obradović, Maja and Babić, Biljana M. and Radmilović, Velimir R. and Krstajić, Nedeljko V. and Gojković, Snežana Lj.",
year = "2012",
abstract = "Tungsten carbide was synthesized by calcination of carbon cryogel containing tungsten in a form of metatungstate. Characterization by X-ray diffraction and transmission electron microscopy indicated core-shell structure of the particles with tungsten core and tungsten carbide shell, attached to graphitized carbon. Pt nanoparticles were deposited on this material and most of them were nucleated on tungsten carbide. Cyclic voltammetry of W-C support and Pt/W-C catalyst indicated hydrogen intercalation in surface hydrous tungsten oxide. Oxidation of COads on Pt/W-C commences earlier than on Pt/C for about 100 mV. The onset potentials of MOR on Pt/W-C and Pt/C are the same, but at more positive potentials Pt/W-C catalyst is more active. It was proposed that promotion of MOR is based on bifunctional mechanism that facilitates COads removal. Stability test was performed by potential cycling of Pt/W-C and Pt/C in the supporting electrolyte and in the presence of methanol. Pt surface area loss observed in the supporting electrolyte of both catalysts after 250 cycles was about 20%. Decrease in the activity for methanol oxidation was 30% for Pt/W-C, but even 48% for Pt/C. The difference was explained by the presence of hydrous tungsten oxide on Pt in Pt/W-C catalyst, which reduces accumulation of poisoning COads.",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "International Journal of Hydrogen Energy",
title = "Core-shell structured tungsten-tungsten carbide as a Pt catalyst support and its activity for methanol electrooxidation",
pages = "10679-10671",
number = "14",
volume = "37",
doi = "10.1016/j.ijhydene.2012.04.114"
}
Obradović, M., Babić, B. M., Radmilović, V. R., Krstajić, N. V.,& Gojković, S. Lj.. (2012). Core-shell structured tungsten-tungsten carbide as a Pt catalyst support and its activity for methanol electrooxidation. in International Journal of Hydrogen Energy
Pergamon-Elsevier Science Ltd, Oxford., 37(14), 10671-10679.
https://doi.org/10.1016/j.ijhydene.2012.04.114
Obradović M, Babić BM, Radmilović VR, Krstajić NV, Gojković SL. Core-shell structured tungsten-tungsten carbide as a Pt catalyst support and its activity for methanol electrooxidation. in International Journal of Hydrogen Energy. 2012;37(14):10671-10679.
doi:10.1016/j.ijhydene.2012.04.114 .
Obradović, Maja, Babić, Biljana M., Radmilović, Velimir R., Krstajić, Nedeljko V., Gojković, Snežana Lj., "Core-shell structured tungsten-tungsten carbide as a Pt catalyst support and its activity for methanol electrooxidation" in International Journal of Hydrogen Energy, 37, no. 14 (2012):10671-10679,
https://doi.org/10.1016/j.ijhydene.2012.04.114 . .
20
21
23

High Activity and Stability of Pt2Bi Catalyst in Formic Acid Oxidation

Lović, Jelena; Obradović, Maja; Tripković, Dušan; Popović, Ksenija; Jovanović, Vladislava M.; Gojković, Snežana Lj.; Tripković, Amalija

(Springer, New York, 2012)

TY  - JOUR
AU  - Lović, Jelena
AU  - Obradović, Maja
AU  - Tripković, Dušan
AU  - Popović, Ksenija
AU  - Jovanović, Vladislava M.
AU  - Gojković, Snežana Lj.
AU  - Tripković, Amalija
PY  - 2012
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/2148
AB  - Formic acid oxidation was studied on a new prepared Pt2Bi characterized by X-ray diffraction spectroscopy (phase composition), scanning tunneling microscopy (STM) (surface morphology), and COads stripping voltammetry (surface composition). Bulk composition of Pt2Bi revealed two phases-55% PtBi alloy and 45% Pt. Estimated contribution of pure Pt on the Pt2Bi surface (43.5%) determined by COads stripping voltammetry corresponds closely to bulk composition. Pt2Bi reveals high activity and stability in formic acid oxidation. High activity originates from the fact that formic acid oxidation proceeds completely through dehydrogenation path based on an ensemble effect. The high stability of Pt2Bi surface is induced by the suppression of Bi leaching as it was evidenced by insignificant changes of surface morphology and surface roughness shown by STM images before and after electrochemical treatment in formic acid containing solution. Pt2Bi is found to be powerful catalyst exhibiting up to two orders of magnitude larger current densities at 0.0 V and onset potential shifted for similar to 0.2 V to more negative value relative to Pt under steady-state condition.
PB  - Springer, New York
T2  - Electrocatalysis
T1  - High Activity and Stability of Pt2Bi Catalyst in Formic Acid Oxidation
EP  - 352
IS  - 3-4
SP  - 346
VL  - 3
DO  - 10.1007/s12678-012-0099-9
ER  - 
@article{
author = "Lović, Jelena and Obradović, Maja and Tripković, Dušan and Popović, Ksenija and Jovanović, Vladislava M. and Gojković, Snežana Lj. and Tripković, Amalija",
year = "2012",
abstract = "Formic acid oxidation was studied on a new prepared Pt2Bi characterized by X-ray diffraction spectroscopy (phase composition), scanning tunneling microscopy (STM) (surface morphology), and COads stripping voltammetry (surface composition). Bulk composition of Pt2Bi revealed two phases-55% PtBi alloy and 45% Pt. Estimated contribution of pure Pt on the Pt2Bi surface (43.5%) determined by COads stripping voltammetry corresponds closely to bulk composition. Pt2Bi reveals high activity and stability in formic acid oxidation. High activity originates from the fact that formic acid oxidation proceeds completely through dehydrogenation path based on an ensemble effect. The high stability of Pt2Bi surface is induced by the suppression of Bi leaching as it was evidenced by insignificant changes of surface morphology and surface roughness shown by STM images before and after electrochemical treatment in formic acid containing solution. Pt2Bi is found to be powerful catalyst exhibiting up to two orders of magnitude larger current densities at 0.0 V and onset potential shifted for similar to 0.2 V to more negative value relative to Pt under steady-state condition.",
publisher = "Springer, New York",
journal = "Electrocatalysis",
title = "High Activity and Stability of Pt2Bi Catalyst in Formic Acid Oxidation",
pages = "352-346",
number = "3-4",
volume = "3",
doi = "10.1007/s12678-012-0099-9"
}
Lović, J., Obradović, M., Tripković, D., Popović, K., Jovanović, V. M., Gojković, S. Lj.,& Tripković, A.. (2012). High Activity and Stability of Pt2Bi Catalyst in Formic Acid Oxidation. in Electrocatalysis
Springer, New York., 3(3-4), 346-352.
https://doi.org/10.1007/s12678-012-0099-9
Lović J, Obradović M, Tripković D, Popović K, Jovanović VM, Gojković SL, Tripković A. High Activity and Stability of Pt2Bi Catalyst in Formic Acid Oxidation. in Electrocatalysis. 2012;3(3-4):346-352.
doi:10.1007/s12678-012-0099-9 .
Lović, Jelena, Obradović, Maja, Tripković, Dušan, Popović, Ksenija, Jovanović, Vladislava M., Gojković, Snežana Lj., Tripković, Amalija, "High Activity and Stability of Pt2Bi Catalyst in Formic Acid Oxidation" in Electrocatalysis, 3, no. 3-4 (2012):346-352,
https://doi.org/10.1007/s12678-012-0099-9 . .
12
14
15

Electrochemical instability of Pt nanoparticles probed by formic acid oxidation

Obradović, Maja; Gojković, Snežana Lj.

(Elsevier Science Sa, Lausanne, 2012)

TY  - JOUR
AU  - Obradović, Maja
AU  - Gojković, Snežana Lj.
PY  - 2012
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/2232
AB  - A detrimental effect of CO on the stability of Pt nanoparticles, which is important for fuel cells technology, is demonstrated by the change in HCOOH kinetics on Pt nanoparticles caused by the presence of CO in the electrolyte. Pt nanoparticles supported on high area carbon (Pt/C) were applied on gold and glassy carbon substrates (Pt/C"Au and Pt/C"GC) and three different kinds of Pt surface were prepared by potential cycling in the various potential limits in N-2 and CO saturated electrolyte: untreated, OH-annealed and CO-annealed. On untreated Pt/C"Au catalyst HCOOH is oxidized predominantly through indirect mechanism, after OH-annealing direct path is slightly accelerated, but on CO-annealed catalyst the direct path in HCOOH oxidation is predominant. Based on the fact that more contiguous Pt sites are necessary for indirect than for direct path, it was concluded that OH- and especially CO-annealing of Pt/C produces small Pt domains. Since the same pretreatment did not show any effect on HCOOH oxidation on Pt/C"GC electrode, it was postulated that Pt nanoparticles dissolve in the presence of CO on the surface and in the electrolyte, and successively deposit on Au substrate. The results points out pronounced instability of Pt nanoparticles in the presence of CO.
PB  - Elsevier Science Sa, Lausanne
T2  - Journal of Electroanalytical Chemistry
T1  - Electrochemical instability of Pt nanoparticles probed by formic acid oxidation
EP  - 155
SP  - 152
VL  - 664
DO  - 10.1016/j.jelechem.2011.10.016
ER  - 
@article{
author = "Obradović, Maja and Gojković, Snežana Lj.",
year = "2012",
abstract = "A detrimental effect of CO on the stability of Pt nanoparticles, which is important for fuel cells technology, is demonstrated by the change in HCOOH kinetics on Pt nanoparticles caused by the presence of CO in the electrolyte. Pt nanoparticles supported on high area carbon (Pt/C) were applied on gold and glassy carbon substrates (Pt/C"Au and Pt/C"GC) and three different kinds of Pt surface were prepared by potential cycling in the various potential limits in N-2 and CO saturated electrolyte: untreated, OH-annealed and CO-annealed. On untreated Pt/C"Au catalyst HCOOH is oxidized predominantly through indirect mechanism, after OH-annealing direct path is slightly accelerated, but on CO-annealed catalyst the direct path in HCOOH oxidation is predominant. Based on the fact that more contiguous Pt sites are necessary for indirect than for direct path, it was concluded that OH- and especially CO-annealing of Pt/C produces small Pt domains. Since the same pretreatment did not show any effect on HCOOH oxidation on Pt/C"GC electrode, it was postulated that Pt nanoparticles dissolve in the presence of CO on the surface and in the electrolyte, and successively deposit on Au substrate. The results points out pronounced instability of Pt nanoparticles in the presence of CO.",
publisher = "Elsevier Science Sa, Lausanne",
journal = "Journal of Electroanalytical Chemistry",
title = "Electrochemical instability of Pt nanoparticles probed by formic acid oxidation",
pages = "155-152",
volume = "664",
doi = "10.1016/j.jelechem.2011.10.016"
}
Obradović, M.,& Gojković, S. Lj.. (2012). Electrochemical instability of Pt nanoparticles probed by formic acid oxidation. in Journal of Electroanalytical Chemistry
Elsevier Science Sa, Lausanne., 664, 152-155.
https://doi.org/10.1016/j.jelechem.2011.10.016
Obradović M, Gojković SL. Electrochemical instability of Pt nanoparticles probed by formic acid oxidation. in Journal of Electroanalytical Chemistry. 2012;664:152-155.
doi:10.1016/j.jelechem.2011.10.016 .
Obradović, Maja, Gojković, Snežana Lj., "Electrochemical instability of Pt nanoparticles probed by formic acid oxidation" in Journal of Electroanalytical Chemistry, 664 (2012):152-155,
https://doi.org/10.1016/j.jelechem.2011.10.016 . .
8
7
7

Oxidation of carbon monoxide and formic acid on bulk and nanosized Pt-Co alloys

Obradović, Maja; Tripković, Amalija; Gojković, Snežana Lj.

(Springer, New York, 2012)

TY  - JOUR
AU  - Obradović, Maja
AU  - Tripković, Amalija
AU  - Gojković, Snežana Lj.
PY  - 2012
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/2234
AB  - Bulk Pt3Co and nanosized Pt3Co and PtCo alloys supported on high area carbon were investigated as the electrocatalysts for the COads and HCOOH oxidation. Pt3Co alloy with Co electrochemically leached from the surface (Pt skeleton) was employed to separate electronic from ensemble and bifunctional effects of Co. Cyclic voltammetry in 0.1 M HClO4 showed reduced amount of adsorbed hydrogen on Pt sites on Pt3Co alloy compared to pure Pt. However, no significant difference in hydrogen adsorption/desorption and Pt-oxide reduction features between Pt3Co with Pt skeleton structure and bulk Pt was observed. The oxidation of COads on Pt3Co alloy commenced earlier than on Pt, but this effect on Pt3Co with Pt skeleton structure was minor indicating that bifunctional mechanism is stronger than the electronic modification of Pt by Co. The HCOOH oxidation rate on Pt3Co alloy was about seven times higher than on bulk Pt when the reaction rates were compared at 0.4 V, i.e., in the middle of the potential range for the HCOOH oxidation. Like in the case of COads oxidation, Pt skeleton showed similar activity as bulk Pt indicating that the ensemble effect is responsible for the enhanced activity of Pt3Co alloy toward HCOOH oxidation. The comparison of COads and HCOOH oxidation on Pt3Co/C and PtCo/C with the same reaction on Pt/C were qualitatively the same as on bulk materials.
PB  - Springer, New York
T2  - Journal of Solid State Electrochemistry
T1  - Oxidation of carbon monoxide and formic acid on bulk and nanosized Pt-Co alloys
EP  - 595
IS  - 2
SP  - 587
VL  - 16
DO  - 10.1007/s10008-011-1389-5
ER  - 
@article{
author = "Obradović, Maja and Tripković, Amalija and Gojković, Snežana Lj.",
year = "2012",
abstract = "Bulk Pt3Co and nanosized Pt3Co and PtCo alloys supported on high area carbon were investigated as the electrocatalysts for the COads and HCOOH oxidation. Pt3Co alloy with Co electrochemically leached from the surface (Pt skeleton) was employed to separate electronic from ensemble and bifunctional effects of Co. Cyclic voltammetry in 0.1 M HClO4 showed reduced amount of adsorbed hydrogen on Pt sites on Pt3Co alloy compared to pure Pt. However, no significant difference in hydrogen adsorption/desorption and Pt-oxide reduction features between Pt3Co with Pt skeleton structure and bulk Pt was observed. The oxidation of COads on Pt3Co alloy commenced earlier than on Pt, but this effect on Pt3Co with Pt skeleton structure was minor indicating that bifunctional mechanism is stronger than the electronic modification of Pt by Co. The HCOOH oxidation rate on Pt3Co alloy was about seven times higher than on bulk Pt when the reaction rates were compared at 0.4 V, i.e., in the middle of the potential range for the HCOOH oxidation. Like in the case of COads oxidation, Pt skeleton showed similar activity as bulk Pt indicating that the ensemble effect is responsible for the enhanced activity of Pt3Co alloy toward HCOOH oxidation. The comparison of COads and HCOOH oxidation on Pt3Co/C and PtCo/C with the same reaction on Pt/C were qualitatively the same as on bulk materials.",
publisher = "Springer, New York",
journal = "Journal of Solid State Electrochemistry",
title = "Oxidation of carbon monoxide and formic acid on bulk and nanosized Pt-Co alloys",
pages = "595-587",
number = "2",
volume = "16",
doi = "10.1007/s10008-011-1389-5"
}
Obradović, M., Tripković, A.,& Gojković, S. Lj.. (2012). Oxidation of carbon monoxide and formic acid on bulk and nanosized Pt-Co alloys. in Journal of Solid State Electrochemistry
Springer, New York., 16(2), 587-595.
https://doi.org/10.1007/s10008-011-1389-5
Obradović M, Tripković A, Gojković SL. Oxidation of carbon monoxide and formic acid on bulk and nanosized Pt-Co alloys. in Journal of Solid State Electrochemistry. 2012;16(2):587-595.
doi:10.1007/s10008-011-1389-5 .
Obradović, Maja, Tripković, Amalija, Gojković, Snežana Lj., "Oxidation of carbon monoxide and formic acid on bulk and nanosized Pt-Co alloys" in Journal of Solid State Electrochemistry, 16, no. 2 (2012):587-595,
https://doi.org/10.1007/s10008-011-1389-5 . .
15
13
15

Formic acid oxidation on Pt-Au nanoparticles: Relation between the catalyst activity and the poisoning rate

Obradović, Maja; Rogan, Jelena; Babić, Biljana M.; Tripković, Amalija; Gautam, A. R. S.; Radmilović, Velimir R.; Gojković, Snežana Lj.

(Elsevier Science Bv, Amsterdam, 2012)

TY  - JOUR
AU  - Obradović, Maja
AU  - Rogan, Jelena
AU  - Babić, Biljana M.
AU  - Tripković, Amalija
AU  - Gautam, A. R. S.
AU  - Radmilović, Velimir R.
AU  - Gojković, Snežana Lj.
PY  - 2012
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/2242
AB  - Pt-Au nanoparticles supported on high area carbon were prepared by simultaneous reduction of Au and Pt precursors and by reduction of Pt precursor on already prepared Au nanoparticles. The first method produced a solid solution of Pt in Au containing similar to 5% Pt with the remaining Pt on the nanoparticles' surface. For the Pt:Au precursor ratio of 1:4 and 1:9, the surface ratio was found to be 0.70:0.30 and 0.55:0.45, respectively. By the second method with the Pt:Au precursors ratio of 1:12, the surface ratio was 0.30:0.70. The voltammetric peaks of Pt-oxide reduction and CO(ads) oxidation demonstrated electronic modification of Pt by Au in all catalysts. With decreasing Pt:Au surface ratio the activity for HCOOH oxidation increases and surface coverage by CO(ads) decreases. The highest activity under potentiodynamic and quasi steady-state conditions without poisoning by CO(ads) was observed for the catalyst with the lowest Pt:Au surface ratio. Chronoamperometic test showed that its high catalytic activity is associated with a high deactivation rate. It was postulated that too strong adsorption of a reactive or non-reactive intermediate caused by electron modification of Pt by underlying Au, is responsible for the deactivation. This result stresses that high Pt dispersion, necessary for promotion of the dehydrogenation path in HCOOH oxidation, can produce too strong adsorption of intermediates causing deactivation of the catalyst.
PB  - Elsevier Science Bv, Amsterdam
T2  - Journal of Power Sources
T1  - Formic acid oxidation on Pt-Au nanoparticles: Relation between the catalyst activity and the poisoning rate
EP  - 79
SP  - 72
VL  - 197
DO  - 10.1016/j.jpowsour.2011.09.043
ER  - 
@article{
author = "Obradović, Maja and Rogan, Jelena and Babić, Biljana M. and Tripković, Amalija and Gautam, A. R. S. and Radmilović, Velimir R. and Gojković, Snežana Lj.",
year = "2012",
abstract = "Pt-Au nanoparticles supported on high area carbon were prepared by simultaneous reduction of Au and Pt precursors and by reduction of Pt precursor on already prepared Au nanoparticles. The first method produced a solid solution of Pt in Au containing similar to 5% Pt with the remaining Pt on the nanoparticles' surface. For the Pt:Au precursor ratio of 1:4 and 1:9, the surface ratio was found to be 0.70:0.30 and 0.55:0.45, respectively. By the second method with the Pt:Au precursors ratio of 1:12, the surface ratio was 0.30:0.70. The voltammetric peaks of Pt-oxide reduction and CO(ads) oxidation demonstrated electronic modification of Pt by Au in all catalysts. With decreasing Pt:Au surface ratio the activity for HCOOH oxidation increases and surface coverage by CO(ads) decreases. The highest activity under potentiodynamic and quasi steady-state conditions without poisoning by CO(ads) was observed for the catalyst with the lowest Pt:Au surface ratio. Chronoamperometic test showed that its high catalytic activity is associated with a high deactivation rate. It was postulated that too strong adsorption of a reactive or non-reactive intermediate caused by electron modification of Pt by underlying Au, is responsible for the deactivation. This result stresses that high Pt dispersion, necessary for promotion of the dehydrogenation path in HCOOH oxidation, can produce too strong adsorption of intermediates causing deactivation of the catalyst.",
publisher = "Elsevier Science Bv, Amsterdam",
journal = "Journal of Power Sources",
title = "Formic acid oxidation on Pt-Au nanoparticles: Relation between the catalyst activity and the poisoning rate",
pages = "79-72",
volume = "197",
doi = "10.1016/j.jpowsour.2011.09.043"
}
Obradović, M., Rogan, J., Babić, B. M., Tripković, A., Gautam, A. R. S., Radmilović, V. R.,& Gojković, S. Lj.. (2012). Formic acid oxidation on Pt-Au nanoparticles: Relation between the catalyst activity and the poisoning rate. in Journal of Power Sources
Elsevier Science Bv, Amsterdam., 197, 72-79.
https://doi.org/10.1016/j.jpowsour.2011.09.043
Obradović M, Rogan J, Babić BM, Tripković A, Gautam ARS, Radmilović VR, Gojković SL. Formic acid oxidation on Pt-Au nanoparticles: Relation between the catalyst activity and the poisoning rate. in Journal of Power Sources. 2012;197:72-79.
doi:10.1016/j.jpowsour.2011.09.043 .
Obradović, Maja, Rogan, Jelena, Babić, Biljana M., Tripković, Amalija, Gautam, A. R. S., Radmilović, Velimir R., Gojković, Snežana Lj., "Formic acid oxidation on Pt-Au nanoparticles: Relation between the catalyst activity and the poisoning rate" in Journal of Power Sources, 197 (2012):72-79,
https://doi.org/10.1016/j.jpowsour.2011.09.043 . .
44
39
48

Ethylenediamine-modified multiwall carbon nanotubes as a Pt catalyst support

Vuković, Goran D.; Obradović, Maja; Marinković, Aleksandar; Rogan, Jelena; Uskoković, Petar; Radmilović, Velimir R.; Gojković, Snežana Lj.

(Elsevier Science Sa, Lausanne, 2011)

TY  - JOUR
AU  - Vuković, Goran D.
AU  - Obradović, Maja
AU  - Marinković, Aleksandar
AU  - Rogan, Jelena
AU  - Uskoković, Petar
AU  - Radmilović, Velimir R.
AU  - Gojković, Snežana Lj.
PY  - 2011
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/1868
AB  - Multi-walled carbon nanotubes (MWCNTs) were used as a support for Pt nanoparticles prepared by the microwave-assisted polyol method. The MWCNTs were pretreated by chemical oxidation (o-MWCNTs) followed by modification by ethylenediamine (eda-MWCNTs). Characterization of both oxidized and eda-modified materials by UV-spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy revealed that the modification by eda leads to (i) agglomeration of the MWCNTs, (ii) a decrease in the capacitance of the material and (iii) reduced rate of electron transfer between the MWCNTs and solution species. However, the Pt loading of Pt/o-MWCNTs was only 2 mass% while the loading of Pt/eda-MWCNTs was 20 mass%. Much higher efficiency of Pt deposition on eda-MWCNTs than on o-MWCNTs was ascribed to the shift in pH(pzc) value of the MWCNT surface from 2.43 to 5.91 upon modification by eda. Transmission electron microscopy revealed that the mean diameter of the Pt particles in Pt/eda-MWCNTs is 2.5 +/- 0.5 nm and that their distribution on the support is homogenous with no evidence of pronounced particle agglomeration. Cyclic voltammetry of a Pt/eda-MWCNT thin film indicated a clean Pt surface with well-resolved peaks characteristic of polycrystalline Pt. Its electrocatalytic activity for oxygen reduction was examined and the results corresponded to the commercial Pt nanocatalyst. This study shows that modification of o-MWCNTs by eda helps to achieve homogenous distribution of small Pt nanoparticles and does not impede its electrocatalytic activity.
PB  - Elsevier Science Sa, Lausanne
T2  - Materials Chemistry and Physics
T1  - Ethylenediamine-modified multiwall carbon nanotubes as a Pt catalyst support
EP  - 664
IS  - 1-2
SP  - 657
VL  - 130
DO  - 10.1016/j.matchemphys.2011.07.046
ER  - 
@article{
author = "Vuković, Goran D. and Obradović, Maja and Marinković, Aleksandar and Rogan, Jelena and Uskoković, Petar and Radmilović, Velimir R. and Gojković, Snežana Lj.",
year = "2011",
abstract = "Multi-walled carbon nanotubes (MWCNTs) were used as a support for Pt nanoparticles prepared by the microwave-assisted polyol method. The MWCNTs were pretreated by chemical oxidation (o-MWCNTs) followed by modification by ethylenediamine (eda-MWCNTs). Characterization of both oxidized and eda-modified materials by UV-spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy revealed that the modification by eda leads to (i) agglomeration of the MWCNTs, (ii) a decrease in the capacitance of the material and (iii) reduced rate of electron transfer between the MWCNTs and solution species. However, the Pt loading of Pt/o-MWCNTs was only 2 mass% while the loading of Pt/eda-MWCNTs was 20 mass%. Much higher efficiency of Pt deposition on eda-MWCNTs than on o-MWCNTs was ascribed to the shift in pH(pzc) value of the MWCNT surface from 2.43 to 5.91 upon modification by eda. Transmission electron microscopy revealed that the mean diameter of the Pt particles in Pt/eda-MWCNTs is 2.5 +/- 0.5 nm and that their distribution on the support is homogenous with no evidence of pronounced particle agglomeration. Cyclic voltammetry of a Pt/eda-MWCNT thin film indicated a clean Pt surface with well-resolved peaks characteristic of polycrystalline Pt. Its electrocatalytic activity for oxygen reduction was examined and the results corresponded to the commercial Pt nanocatalyst. This study shows that modification of o-MWCNTs by eda helps to achieve homogenous distribution of small Pt nanoparticles and does not impede its electrocatalytic activity.",
publisher = "Elsevier Science Sa, Lausanne",
journal = "Materials Chemistry and Physics",
title = "Ethylenediamine-modified multiwall carbon nanotubes as a Pt catalyst support",
pages = "664-657",
number = "1-2",
volume = "130",
doi = "10.1016/j.matchemphys.2011.07.046"
}
Vuković, G. D., Obradović, M., Marinković, A., Rogan, J., Uskoković, P., Radmilović, V. R.,& Gojković, S. Lj.. (2011). Ethylenediamine-modified multiwall carbon nanotubes as a Pt catalyst support. in Materials Chemistry and Physics
Elsevier Science Sa, Lausanne., 130(1-2), 657-664.
https://doi.org/10.1016/j.matchemphys.2011.07.046
Vuković GD, Obradović M, Marinković A, Rogan J, Uskoković P, Radmilović VR, Gojković SL. Ethylenediamine-modified multiwall carbon nanotubes as a Pt catalyst support. in Materials Chemistry and Physics. 2011;130(1-2):657-664.
doi:10.1016/j.matchemphys.2011.07.046 .
Vuković, Goran D., Obradović, Maja, Marinković, Aleksandar, Rogan, Jelena, Uskoković, Petar, Radmilović, Velimir R., Gojković, Snežana Lj., "Ethylenediamine-modified multiwall carbon nanotubes as a Pt catalyst support" in Materials Chemistry and Physics, 130, no. 1-2 (2011):657-664,
https://doi.org/10.1016/j.matchemphys.2011.07.046 . .
2
3
3

The origin of high activity of Pt-Au surfaces in the formic acid oxidation

Obradović, Maja; Tripković, Amalija; Gojković, Snežana Lj.

(Pergamon-Elsevier Science Ltd, Oxford, 2009)

TY  - JOUR
AU  - Obradović, Maja
AU  - Tripković, Amalija
AU  - Gojković, Snežana Lj.
PY  - 2009
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/1417
AB  - We have investigated the oxidation of HCOOH on Au-modified Pt (Au"Pt) and Pt-modified Au (Pt")/Au) electrodes to establish the role of the ensemble and the electronic effect in the catalysis of this reaction. The surfaces were modified by the electrodeposition of sub-monolayers. Cyclic voltammetry in the supporting electrolyte and COads stripping have shown that the electronic Pt-Au interactions are insignificant on Au"Pt. but considerable on Pt"Au. oxidation of COads on Au"Pt commenced at the same potentials as on bare Pt, whereas on Pt"Au the oxidation was delayed for similar to 0.2 V. Both types of Pt-Au surfaces were found to be more active toward the oxidation of HCOOH compared to bare Pt, exhibiting the maximum activity at Pt fraction between 0.15 and 0.25 with the enhancement factor of more than two orders of magnitude. On bimetallic surfaces the amount of COads formed by HCOOH dehydration was low and decreased with decreasing Pt fraction. it was concluded that the high activity of Pt-Au surfaces is caused by the increased selectivity toward the HCOOH dehydrogenation. Similar behavior of Pt-Au surfaces in the HCOOH oxidation, regardless on the Pt-Au electronic interactions, leads to the conclusion that the ensemble effect plays dominant role in the catalysis of HCOOH oxidation.
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - Electrochimica Acta
T1  - The origin of high activity of Pt-Au surfaces in the formic acid oxidation
EP  - 209
IS  - 1
SP  - 204
VL  - 55
DO  - 10.1016/j.electacta.2009.08.038
ER  - 
@article{
author = "Obradović, Maja and Tripković, Amalija and Gojković, Snežana Lj.",
year = "2009",
abstract = "We have investigated the oxidation of HCOOH on Au-modified Pt (Au"Pt) and Pt-modified Au (Pt")/Au) electrodes to establish the role of the ensemble and the electronic effect in the catalysis of this reaction. The surfaces were modified by the electrodeposition of sub-monolayers. Cyclic voltammetry in the supporting electrolyte and COads stripping have shown that the electronic Pt-Au interactions are insignificant on Au"Pt. but considerable on Pt"Au. oxidation of COads on Au"Pt commenced at the same potentials as on bare Pt, whereas on Pt"Au the oxidation was delayed for similar to 0.2 V. Both types of Pt-Au surfaces were found to be more active toward the oxidation of HCOOH compared to bare Pt, exhibiting the maximum activity at Pt fraction between 0.15 and 0.25 with the enhancement factor of more than two orders of magnitude. On bimetallic surfaces the amount of COads formed by HCOOH dehydration was low and decreased with decreasing Pt fraction. it was concluded that the high activity of Pt-Au surfaces is caused by the increased selectivity toward the HCOOH dehydrogenation. Similar behavior of Pt-Au surfaces in the HCOOH oxidation, regardless on the Pt-Au electronic interactions, leads to the conclusion that the ensemble effect plays dominant role in the catalysis of HCOOH oxidation.",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "Electrochimica Acta",
title = "The origin of high activity of Pt-Au surfaces in the formic acid oxidation",
pages = "209-204",
number = "1",
volume = "55",
doi = "10.1016/j.electacta.2009.08.038"
}
Obradović, M., Tripković, A.,& Gojković, S. Lj.. (2009). The origin of high activity of Pt-Au surfaces in the formic acid oxidation. in Electrochimica Acta
Pergamon-Elsevier Science Ltd, Oxford., 55(1), 204-209.
https://doi.org/10.1016/j.electacta.2009.08.038
Obradović M, Tripković A, Gojković SL. The origin of high activity of Pt-Au surfaces in the formic acid oxidation. in Electrochimica Acta. 2009;55(1):204-209.
doi:10.1016/j.electacta.2009.08.038 .
Obradović, Maja, Tripković, Amalija, Gojković, Snežana Lj., "The origin of high activity of Pt-Au surfaces in the formic acid oxidation" in Electrochimica Acta, 55, no. 1 (2009):204-209,
https://doi.org/10.1016/j.electacta.2009.08.038 . .
105
89
104

A comparative study of the electrochemical properties of carbon nanotubes and carbon black

Obradović, Maja; Vuković, Goran D.; Stevanović, Sanja; Panić, Vladimir; Uskoković, Petar; Kowal, Andrzej; Gojković, Snežana Lj.

(Elsevier Science Sa, Lausanne, 2009)

TY  - JOUR
AU  - Obradović, Maja
AU  - Vuković, Goran D.
AU  - Stevanović, Sanja
AU  - Panić, Vladimir
AU  - Uskoković, Petar
AU  - Kowal, Andrzej
AU  - Gojković, Snežana Lj.
PY  - 2009
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/1420
AB  - Two samples of commercial multi-walled carbon nanotubes (Sigma-Aldrich and Sun Nanotech) and a sample of carbon black (Vulcan XC-72R) were investigated in raw state and after the activation in nitric and sulfuric acid by ultrasound agitation. Atomic force microscopy revealed that activated Sigma-Aldrich nanotubes are straight with corrugated walls (bamboo-like structure), while Sun Nanotech nanotubes are tortuous with smooth walls. Fourier transform infrared spectroscopy showed that abundance of oxygen-containing functional groups was formed on both Sigma-Aldrich and Sun Nanotech carbon nanotubes, as well as on carbon black surfaces. Electrochemical properties were studied by cyclic voltammetry and electrochemical impedance spectroscopy. It was found that the electrochemically active surface area of all carbon samples is expanded, charge storage ability is enhanced and the electron-transfer kinetics, probed by Fe(CN)(6)(3-)/Fe(CN)(6)(4-) redox couple, is promoted upon activation. The characteristics of carbon nanotubes were superior to Carbon black. Morphology of the carbon nanotubes was found to be important; nanotubes with corrugated walls showed faster electron-transfer and pseudocapacitive redox kinetics than nanotubes with smooth walls. This was explained by the higher proportion of edge and defect sites, which are known as more electrochemically active than the walls of uniform graphene structure.
PB  - Elsevier Science Sa, Lausanne
T2  - Journal of Electroanalytical Chemistry
T1  - A comparative study of the electrochemical properties of carbon nanotubes and carbon black
EP  - 30
IS  - 1
SP  - 22
VL  - 634
DO  - 10.1016/j.jelechem.2009.07.001
ER  - 
@article{
author = "Obradović, Maja and Vuković, Goran D. and Stevanović, Sanja and Panić, Vladimir and Uskoković, Petar and Kowal, Andrzej and Gojković, Snežana Lj.",
year = "2009",
abstract = "Two samples of commercial multi-walled carbon nanotubes (Sigma-Aldrich and Sun Nanotech) and a sample of carbon black (Vulcan XC-72R) were investigated in raw state and after the activation in nitric and sulfuric acid by ultrasound agitation. Atomic force microscopy revealed that activated Sigma-Aldrich nanotubes are straight with corrugated walls (bamboo-like structure), while Sun Nanotech nanotubes are tortuous with smooth walls. Fourier transform infrared spectroscopy showed that abundance of oxygen-containing functional groups was formed on both Sigma-Aldrich and Sun Nanotech carbon nanotubes, as well as on carbon black surfaces. Electrochemical properties were studied by cyclic voltammetry and electrochemical impedance spectroscopy. It was found that the electrochemically active surface area of all carbon samples is expanded, charge storage ability is enhanced and the electron-transfer kinetics, probed by Fe(CN)(6)(3-)/Fe(CN)(6)(4-) redox couple, is promoted upon activation. The characteristics of carbon nanotubes were superior to Carbon black. Morphology of the carbon nanotubes was found to be important; nanotubes with corrugated walls showed faster electron-transfer and pseudocapacitive redox kinetics than nanotubes with smooth walls. This was explained by the higher proportion of edge and defect sites, which are known as more electrochemically active than the walls of uniform graphene structure.",
publisher = "Elsevier Science Sa, Lausanne",
journal = "Journal of Electroanalytical Chemistry",
title = "A comparative study of the electrochemical properties of carbon nanotubes and carbon black",
pages = "30-22",
number = "1",
volume = "634",
doi = "10.1016/j.jelechem.2009.07.001"
}
Obradović, M., Vuković, G. D., Stevanović, S., Panić, V., Uskoković, P., Kowal, A.,& Gojković, S. Lj.. (2009). A comparative study of the electrochemical properties of carbon nanotubes and carbon black. in Journal of Electroanalytical Chemistry
Elsevier Science Sa, Lausanne., 634(1), 22-30.
https://doi.org/10.1016/j.jelechem.2009.07.001
Obradović M, Vuković GD, Stevanović S, Panić V, Uskoković P, Kowal A, Gojković SL. A comparative study of the electrochemical properties of carbon nanotubes and carbon black. in Journal of Electroanalytical Chemistry. 2009;634(1):22-30.
doi:10.1016/j.jelechem.2009.07.001 .
Obradović, Maja, Vuković, Goran D., Stevanović, Sanja, Panić, Vladimir, Uskoković, Petar, Kowal, Andrzej, Gojković, Snežana Lj., "A comparative study of the electrochemical properties of carbon nanotubes and carbon black" in Journal of Electroanalytical Chemistry, 634, no. 1 (2009):22-30,
https://doi.org/10.1016/j.jelechem.2009.07.001 . .
46
41
48

Synthesis, characterization and cytotoxicity of surface amino-functionalized water-dispersible multi-walled carbon nanotubes

Vuković, Goran D.; Marinković, Aleksandar; Obradović, Maja; Radmilović, V.; Čolić, Miodrag; Aleksić, Radoslav; Uskoković, Petar

(Elsevier Science Bv, Amsterdam, 2009)

TY  - JOUR
AU  - Vuković, Goran D.
AU  - Marinković, Aleksandar
AU  - Obradović, Maja
AU  - Radmilović, V.
AU  - Čolić, Miodrag
AU  - Aleksić, Radoslav
AU  - Uskoković, Petar
PY  - 2009
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/1512
AB  - Surface functionalization of multi-walled carbon nanotubes (MWCNTs), with amino groups via chemical modification of carboxyl groups introduced on the nanotube surface, using O-(7-azabenzotriazol-1-yl)-N, N,N',N'-tetramethyluronium hexafluorophosphate (N-HATU) and N,N-diisopropylethylamine (DIEA) is reported. The N-HATU coupling agent provides faster reaction rate and the reaction occurs at lower temperature compared to amidation and acylation-amidation chemistry. The amines, 1,6-hexanediamine (HDA), diethylenetriamine (DETA), triethylenetetramine (TETA) and 1,4-phenylenediamine (PDA) were used. The resulting materials were characterized with different techniques such as FTIR, XRD, elemental analysis, TGA, TEM, UV-vis spectroscopy and cyclic voltammetry. MWCNTs functionalized with PDA posses the best dispersibility and electron transfer properties in comparison to the others amines. Functionalized MWCNTs, at the concentrations between 1 and 50 mu g ml(-1), were not cytotoxic for the fibroblast L929 cell line. However, the concentrations of MWCNTs higher of 10 mu g ml(-1) reduced cell growth and this effect correlated positively with the degree of their uptake by L929 cells.
PB  - Elsevier Science Bv, Amsterdam
T2  - Applied Surface Science
T1  - Synthesis, characterization and cytotoxicity of surface amino-functionalized water-dispersible multi-walled carbon nanotubes
EP  - 8075
IS  - 18
SP  - 8067
VL  - 255
DO  - 10.1016/j.apsusc.2009.05.016
ER  - 
@article{
author = "Vuković, Goran D. and Marinković, Aleksandar and Obradović, Maja and Radmilović, V. and Čolić, Miodrag and Aleksić, Radoslav and Uskoković, Petar",
year = "2009",
abstract = "Surface functionalization of multi-walled carbon nanotubes (MWCNTs), with amino groups via chemical modification of carboxyl groups introduced on the nanotube surface, using O-(7-azabenzotriazol-1-yl)-N, N,N',N'-tetramethyluronium hexafluorophosphate (N-HATU) and N,N-diisopropylethylamine (DIEA) is reported. The N-HATU coupling agent provides faster reaction rate and the reaction occurs at lower temperature compared to amidation and acylation-amidation chemistry. The amines, 1,6-hexanediamine (HDA), diethylenetriamine (DETA), triethylenetetramine (TETA) and 1,4-phenylenediamine (PDA) were used. The resulting materials were characterized with different techniques such as FTIR, XRD, elemental analysis, TGA, TEM, UV-vis spectroscopy and cyclic voltammetry. MWCNTs functionalized with PDA posses the best dispersibility and electron transfer properties in comparison to the others amines. Functionalized MWCNTs, at the concentrations between 1 and 50 mu g ml(-1), were not cytotoxic for the fibroblast L929 cell line. However, the concentrations of MWCNTs higher of 10 mu g ml(-1) reduced cell growth and this effect correlated positively with the degree of their uptake by L929 cells.",
publisher = "Elsevier Science Bv, Amsterdam",
journal = "Applied Surface Science",
title = "Synthesis, characterization and cytotoxicity of surface amino-functionalized water-dispersible multi-walled carbon nanotubes",
pages = "8075-8067",
number = "18",
volume = "255",
doi = "10.1016/j.apsusc.2009.05.016"
}
Vuković, G. D., Marinković, A., Obradović, M., Radmilović, V., Čolić, M., Aleksić, R.,& Uskoković, P.. (2009). Synthesis, characterization and cytotoxicity of surface amino-functionalized water-dispersible multi-walled carbon nanotubes. in Applied Surface Science
Elsevier Science Bv, Amsterdam., 255(18), 8067-8075.
https://doi.org/10.1016/j.apsusc.2009.05.016
Vuković GD, Marinković A, Obradović M, Radmilović V, Čolić M, Aleksić R, Uskoković P. Synthesis, characterization and cytotoxicity of surface amino-functionalized water-dispersible multi-walled carbon nanotubes. in Applied Surface Science. 2009;255(18):8067-8075.
doi:10.1016/j.apsusc.2009.05.016 .
Vuković, Goran D., Marinković, Aleksandar, Obradović, Maja, Radmilović, V., Čolić, Miodrag, Aleksić, Radoslav, Uskoković, Petar, "Synthesis, characterization and cytotoxicity of surface amino-functionalized water-dispersible multi-walled carbon nanotubes" in Applied Surface Science, 255, no. 18 (2009):8067-8075,
https://doi.org/10.1016/j.apsusc.2009.05.016 . .
151
137
164

Electrochemical properties of mixed WC and Pt-black powders

Obradović, Maja; Babić, Biljana M.; Kowal, Andrzej; Panić, Vladimir; Gojković, Snežana Lj.

(Serbian Chemical Society, Belgrade, 2008)

TY  - JOUR
AU  - Obradović, Maja
AU  - Babić, Biljana M.
AU  - Kowal, Andrzej
AU  - Panić, Vladimir
AU  - Gojković, Snežana Lj.
PY  - 2008
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/1305
AB  - The electrochemical characteristics of a mixture of Pt-black and WC powders and its catalytic activity for methanol and formic acid oxidation were investigated in acid solution. XRD and AFM measurements revealed that the WC powder employed for the investigation was a single-phase material consisting of crystallites/spherical particles of average size of about 50 nm, which were agglomerated into much larger particles. Cyclic voltammetry showed that the WC underwent electrochemical oxidation, producing tungstate species. In the case of the mixed Pt + WC powders, the tungstate species were deposited on the Pt as a thin film of hydrous tungsten oxide. Enhanced hydrogen intercalation in the hydrous tungsten oxide was observed and it was proposed to be promoted in mixed powders by the presence of hydrogen adatoms on bare Pt sites. The determination of Pt surface area in the Pt + WC layer by stripping of underpotentially deposited Cu revealed that the entire Pt surface was accessible for underpotential deposition of Cu. Investigation of the electrochemical oxidation of methanol and formic acid on Pt + WC and pure Pt layers did not indicate electrocatalytic promotion due to the presence of WC.
AB  - U radu su ispitivane elektrohemijske karakteristike smeše prahova Pt i WC i njena katalitička aktivnost za reakcije oksidacije metanola i mravlje kiseline u kiselom rastvoru. Analiza rezultata difrakcije X-zraka (XRD) i mikroskopije atomskih sila (AFM) pokazuju da je prah WC jednofazni materijal sa prosečnom veličinom kristalita od oko 50 nm, koji su aglomerisani u mnogo veće čestice. Ciklična voltametrija ukazuje na to da WC podleže oksidaciji kojom nastaju volframatne vrste. U slučaju smeše prahova Pt i WC, volframatne vrste najverovatnije se talože na Pt u obliku tankog sloja hidratisanih oksida volframa. Primećeno je povećanje interkalacije vodonika u sloju hidratisanih volframata i pretpostavlja se da prisustvo adatoma vodonika na površini Pt potpomaže proces vodonične interkalacije. Određivanje površine Pt u sloju Pt + WC desorpcijom monosloja Cu taloženog na potpotencijalima ukazuje da je čitava površina Pt dostupna za taloženje atoma Cu. Ispitivanje elektrohemijskih reakcija oksidacije metanola i mravlje kiseline na sloju smeše Pt + WC i sloju čiste Pt ukazuje da prisustvo praha WC ne utiče na elektrokatalitička svojstva Pt.
PB  - Serbian Chemical Society, Belgrade
T2  - Journal of the Serbian Chemical Society
T1  - Electrochemical properties of mixed WC and Pt-black powders
T1  - Elektrohemijska svojstva smeše prahova WC i Pt
EP  - 1209
IS  - 12
SP  - 1197
VL  - 73
UR  - https://hdl.handle.net/21.15107/rcub_technorep_1305
ER  - 
@article{
author = "Obradović, Maja and Babić, Biljana M. and Kowal, Andrzej and Panić, Vladimir and Gojković, Snežana Lj.",
year = "2008",
abstract = "The electrochemical characteristics of a mixture of Pt-black and WC powders and its catalytic activity for methanol and formic acid oxidation were investigated in acid solution. XRD and AFM measurements revealed that the WC powder employed for the investigation was a single-phase material consisting of crystallites/spherical particles of average size of about 50 nm, which were agglomerated into much larger particles. Cyclic voltammetry showed that the WC underwent electrochemical oxidation, producing tungstate species. In the case of the mixed Pt + WC powders, the tungstate species were deposited on the Pt as a thin film of hydrous tungsten oxide. Enhanced hydrogen intercalation in the hydrous tungsten oxide was observed and it was proposed to be promoted in mixed powders by the presence of hydrogen adatoms on bare Pt sites. The determination of Pt surface area in the Pt + WC layer by stripping of underpotentially deposited Cu revealed that the entire Pt surface was accessible for underpotential deposition of Cu. Investigation of the electrochemical oxidation of methanol and formic acid on Pt + WC and pure Pt layers did not indicate electrocatalytic promotion due to the presence of WC., U radu su ispitivane elektrohemijske karakteristike smeše prahova Pt i WC i njena katalitička aktivnost za reakcije oksidacije metanola i mravlje kiseline u kiselom rastvoru. Analiza rezultata difrakcije X-zraka (XRD) i mikroskopije atomskih sila (AFM) pokazuju da je prah WC jednofazni materijal sa prosečnom veličinom kristalita od oko 50 nm, koji su aglomerisani u mnogo veće čestice. Ciklična voltametrija ukazuje na to da WC podleže oksidaciji kojom nastaju volframatne vrste. U slučaju smeše prahova Pt i WC, volframatne vrste najverovatnije se talože na Pt u obliku tankog sloja hidratisanih oksida volframa. Primećeno je povećanje interkalacije vodonika u sloju hidratisanih volframata i pretpostavlja se da prisustvo adatoma vodonika na površini Pt potpomaže proces vodonične interkalacije. Određivanje površine Pt u sloju Pt + WC desorpcijom monosloja Cu taloženog na potpotencijalima ukazuje da je čitava površina Pt dostupna za taloženje atoma Cu. Ispitivanje elektrohemijskih reakcija oksidacije metanola i mravlje kiseline na sloju smeše Pt + WC i sloju čiste Pt ukazuje da prisustvo praha WC ne utiče na elektrokatalitička svojstva Pt.",
publisher = "Serbian Chemical Society, Belgrade",
journal = "Journal of the Serbian Chemical Society",
title = "Electrochemical properties of mixed WC and Pt-black powders, Elektrohemijska svojstva smeše prahova WC i Pt",
pages = "1209-1197",
number = "12",
volume = "73",
url = "https://hdl.handle.net/21.15107/rcub_technorep_1305"
}
Obradović, M., Babić, B. M., Kowal, A., Panić, V.,& Gojković, S. Lj.. (2008). Electrochemical properties of mixed WC and Pt-black powders. in Journal of the Serbian Chemical Society
Serbian Chemical Society, Belgrade., 73(12), 1197-1209.
https://hdl.handle.net/21.15107/rcub_technorep_1305
Obradović M, Babić BM, Kowal A, Panić V, Gojković SL. Electrochemical properties of mixed WC and Pt-black powders. in Journal of the Serbian Chemical Society. 2008;73(12):1197-1209.
https://hdl.handle.net/21.15107/rcub_technorep_1305 .
Obradović, Maja, Babić, Biljana M., Kowal, Andrzej, Panić, Vladimir, Gojković, Snežana Lj., "Electrochemical properties of mixed WC and Pt-black powders" in Journal of the Serbian Chemical Society, 73, no. 12 (2008):1197-1209,
https://hdl.handle.net/21.15107/rcub_technorep_1305 .
10
12

Enhancement of the electrochemical reduction of oxygen at platinum by nickel underpotential deposition

Obradović, Maja; Grgur, Branimir; Gojković, Snežana Lj.; Vračar, Ljiljana M.

(Springer, New York, 2006)

TY  - JOUR
AU  - Obradović, Maja
AU  - Grgur, Branimir
AU  - Gojković, Snežana Lj.
AU  - Vračar, Ljiljana M.
PY  - 2006
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/978
AB  - Polycrystalline Pt electrode was modified by underpotential deposition (upd) of nickel. The modification was performed by potential cycling in phosphate buffer pH 7. 0 containing NiSO4, in which hydrogen and nickel upd processes were well separated. The maximum Ni upd coverage was found to be 0.3. Oxygen reduction was studied at bare and nickel upd-modified Pt. It was found that the reaction rate increased with increasing Ni upd coverage. At theta(Ni)=0.3, the current density was a factor of 2 higher compared to bare Pt (at the potential of 0.85 V). The capacitance of the electrode interface was determined in potential-relaxation experiments following interruption of the polarization current. It was found that the pseudocapacitance owing to a coverage by the adsorbed reaction intermediates was higher on the Ni-modified Pt surface than on bare Pt, which resulted in higher reaction rate. The influence of Ni adatoms on the surface coverage by the reaction intermediates was attributed to the inhibition of OH adsorption on Pt by OH ligands attached on neighboring Ni atoms.
PB  - Springer, New York
T2  - Journal of Solid State Electrochemistry
T1  - Enhancement of the electrochemical reduction of oxygen at platinum by nickel underpotential deposition
EP  - 83
IS  - 1
SP  - 77
VL  - 11
DO  - 10.1007/s10008-005-0072-0
ER  - 
@article{
author = "Obradović, Maja and Grgur, Branimir and Gojković, Snežana Lj. and Vračar, Ljiljana M.",
year = "2006",
abstract = "Polycrystalline Pt electrode was modified by underpotential deposition (upd) of nickel. The modification was performed by potential cycling in phosphate buffer pH 7. 0 containing NiSO4, in which hydrogen and nickel upd processes were well separated. The maximum Ni upd coverage was found to be 0.3. Oxygen reduction was studied at bare and nickel upd-modified Pt. It was found that the reaction rate increased with increasing Ni upd coverage. At theta(Ni)=0.3, the current density was a factor of 2 higher compared to bare Pt (at the potential of 0.85 V). The capacitance of the electrode interface was determined in potential-relaxation experiments following interruption of the polarization current. It was found that the pseudocapacitance owing to a coverage by the adsorbed reaction intermediates was higher on the Ni-modified Pt surface than on bare Pt, which resulted in higher reaction rate. The influence of Ni adatoms on the surface coverage by the reaction intermediates was attributed to the inhibition of OH adsorption on Pt by OH ligands attached on neighboring Ni atoms.",
publisher = "Springer, New York",
journal = "Journal of Solid State Electrochemistry",
title = "Enhancement of the electrochemical reduction of oxygen at platinum by nickel underpotential deposition",
pages = "83-77",
number = "1",
volume = "11",
doi = "10.1007/s10008-005-0072-0"
}
Obradović, M., Grgur, B., Gojković, S. Lj.,& Vračar, L. M.. (2006). Enhancement of the electrochemical reduction of oxygen at platinum by nickel underpotential deposition. in Journal of Solid State Electrochemistry
Springer, New York., 11(1), 77-83.
https://doi.org/10.1007/s10008-005-0072-0
Obradović M, Grgur B, Gojković SL, Vračar LM. Enhancement of the electrochemical reduction of oxygen at platinum by nickel underpotential deposition. in Journal of Solid State Electrochemistry. 2006;11(1):77-83.
doi:10.1007/s10008-005-0072-0 .
Obradović, Maja, Grgur, Branimir, Gojković, Snežana Lj., Vračar, Ljiljana M., "Enhancement of the electrochemical reduction of oxygen at platinum by nickel underpotential deposition" in Journal of Solid State Electrochemistry, 11, no. 1 (2006):77-83,
https://doi.org/10.1007/s10008-005-0072-0 . .
4
4
3

Kinetic of corrosion reactions in acid and neutral solutions on electrochemically deposited Ni-W alloys

Obradović, Maja; Grgur, Branimir; Gojković, Snežana Lj.

(Engineering Society for Corrosion, Belgrade, Serbia, 2006)

TY  - JOUR
AU  - Obradović, Maja
AU  - Grgur, Branimir
AU  - Gojković, Snežana Lj.
PY  - 2006
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/982
AB  - Ni-W alloys were electrochemically deposited from an ammonia-citrate electrolyte on rotating disc electrode with a gold disc, by direct and pulsating current. The corrosion potential and kinetics of cathodic and anodic reaction were investigated on the alloys with molar fraction of tungsten from 0.11 to 0.25 in acid and neutral sulfate solutions of various pH. On the basis of kinetic equations resulting from these data, it was proposed that a barrier lazer of nickel and tungsten oxide was formed on the alloy surface preventing further alloy dissolution.
AB  - Prevlake legure Ni-W su elektrohemijski taložene iz amonijačno-citratnog elektrolita, na rotirajuću disk elektrodu od zlata, konstantnom i pulsirajućom strujom. Korozioni potencijal, kinetika katodne i anodne reakcije na elektrohemijski taloženim prevlakama legura Ni-W, sa udelom volframa od 0,11 do 0,25, su ispitivani u kiselim i neutralnim sulfatnim rastvorima, različitih pH vrednosti. Na osnovu dobijenih rezultata izvedene su kinetičke jednačine za katodnu i anodnu reakciju, koje ukazuju na formiranje barijernog sloja oksida volframa i nikla koji sprečava rastvaranje legure i delimično se redukuje pri katodnoj polarizaciji.
PB  - Engineering Society for Corrosion, Belgrade, Serbia
T2  - Zaštita materijala
T1  - Kinetic of corrosion reactions in acid and neutral solutions on electrochemically deposited Ni-W alloys
T1  - Kinetika korozionih reakcija u kiselim i neutralnim rastvorima na elektrohemijski taloženim legurama Ni-W
EP  - 10
IS  - 2
SP  - 3
VL  - 47
UR  - https://hdl.handle.net/21.15107/rcub_technorep_982
ER  - 
@article{
author = "Obradović, Maja and Grgur, Branimir and Gojković, Snežana Lj.",
year = "2006",
abstract = "Ni-W alloys were electrochemically deposited from an ammonia-citrate electrolyte on rotating disc electrode with a gold disc, by direct and pulsating current. The corrosion potential and kinetics of cathodic and anodic reaction were investigated on the alloys with molar fraction of tungsten from 0.11 to 0.25 in acid and neutral sulfate solutions of various pH. On the basis of kinetic equations resulting from these data, it was proposed that a barrier lazer of nickel and tungsten oxide was formed on the alloy surface preventing further alloy dissolution., Prevlake legure Ni-W su elektrohemijski taložene iz amonijačno-citratnog elektrolita, na rotirajuću disk elektrodu od zlata, konstantnom i pulsirajućom strujom. Korozioni potencijal, kinetika katodne i anodne reakcije na elektrohemijski taloženim prevlakama legura Ni-W, sa udelom volframa od 0,11 do 0,25, su ispitivani u kiselim i neutralnim sulfatnim rastvorima, različitih pH vrednosti. Na osnovu dobijenih rezultata izvedene su kinetičke jednačine za katodnu i anodnu reakciju, koje ukazuju na formiranje barijernog sloja oksida volframa i nikla koji sprečava rastvaranje legure i delimično se redukuje pri katodnoj polarizaciji.",
publisher = "Engineering Society for Corrosion, Belgrade, Serbia",
journal = "Zaštita materijala",
title = "Kinetic of corrosion reactions in acid and neutral solutions on electrochemically deposited Ni-W alloys, Kinetika korozionih reakcija u kiselim i neutralnim rastvorima na elektrohemijski taloženim legurama Ni-W",
pages = "10-3",
number = "2",
volume = "47",
url = "https://hdl.handle.net/21.15107/rcub_technorep_982"
}
Obradović, M., Grgur, B.,& Gojković, S. Lj.. (2006). Kinetic of corrosion reactions in acid and neutral solutions on electrochemically deposited Ni-W alloys. in Zaštita materijala
Engineering Society for Corrosion, Belgrade, Serbia., 47(2), 3-10.
https://hdl.handle.net/21.15107/rcub_technorep_982
Obradović M, Grgur B, Gojković SL. Kinetic of corrosion reactions in acid and neutral solutions on electrochemically deposited Ni-W alloys. in Zaštita materijala. 2006;47(2):3-10.
https://hdl.handle.net/21.15107/rcub_technorep_982 .
Obradović, Maja, Grgur, Branimir, Gojković, Snežana Lj., "Kinetic of corrosion reactions in acid and neutral solutions on electrochemically deposited Ni-W alloys" in Zaštita materijala, 47, no. 2 (2006):3-10,
https://hdl.handle.net/21.15107/rcub_technorep_982 .

Study of gold-platinum and platinum-gold surface modification and its influence on hydrogen evolution and oxygen reduction

Dešić, Maja N.; Popović, Milica M.; Obradović, Maja; Vračar, Ljiljana M.; Grgur, Branimir

(Serbian Chemical Society, Belgrade, 2005)

TY  - JOUR
AU  - Dešić, Maja N.
AU  - Popović, Milica M.
AU  - Obradović, Maja
AU  - Vračar, Ljiljana M.
AU  - Grgur, Branimir
PY  - 2005
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/775
AB  - Surface modification of the electrodes was conducted from sulfuric acid solutions containing the corresponding metal-chloride complexes using cyclic voltammeter. Comparing the charges of the hydrogen underpotential deposition region, and the corresponding oxide reduction regions, it is concluded that a platinum overlayer on gold forms 3D islands, while gold on platinum forms 2D islands. Foreign metals present in an amount of up to one monolayer exert an influence on the change in reaction rate with respect to both hydrogen evolution (HER) and oxygen reduction (ORR) reactions. Aplatinum overlayer on a gold substrate increases the activity for HER and for ORR, compared with pure gold. These results can be understood in terms of a simple model, in which the change in the H and OH binding energies are directly proportional to the shift of the d-bond center of the overlayer. On the contrary, a gold layer on platinum slightly decreases the activity for both reactions compared with pure platinum.
AB  - Površinska modifikacija platine zlatom i zlata platinom je izvršena iz rastvora sumporne kiseline i odgovarajućih hloridnih kompleksa metala primenom ciklične voltametrije. Poređenjem količine naelektrisanja u oblasti potpotencijalne depozicije vodonika i odgovarajućih oblasti redukcije oskida čistih i modifikovanih elektroda zaključeno je da platina na zlatu formira 3D, a zlato na platini 2D ostrva. Aktivnosti ovako modifikovanih površina za reakcije izdvajanja vodonika i redukcije kiseonika u rastvoru sumporne kiseline poređene sa aktivnostima čistih metala. Elektroda od zlata modifikovana platinom značajno uvećava aktivnost za obe ispitivane rekacije u poređenju sa čistim zlatom. Sa druge strane, elektroda od platine modifikovana zlatom ima neznatno manju aktivnost u poređenju sa čistom platinom. Zbog ograničenih resursa i visoke cene platine platina modifikovana zlatom može biti zamena za čistu platinu kao dobar katalizator za reakciju redukcije kiseonika, posebno u gorivim spregovima u oblasti niskih temperatura.
PB  - Serbian Chemical Society, Belgrade
T2  - Journal of the Serbian Chemical Society
T1  - Study of gold-platinum and platinum-gold surface modification and its influence on hydrogen evolution and oxygen reduction
T1  - Površinska modifikacija platine zlatom i zlata platinom i njen uticaj na reakcije izdvajanja vodonika i redukcije kiseonika
EP  - 242
IS  - 2
SP  - 231
VL  - 70
UR  - https://hdl.handle.net/21.15107/rcub_technorep_775
ER  - 
@article{
author = "Dešić, Maja N. and Popović, Milica M. and Obradović, Maja and Vračar, Ljiljana M. and Grgur, Branimir",
year = "2005",
abstract = "Surface modification of the electrodes was conducted from sulfuric acid solutions containing the corresponding metal-chloride complexes using cyclic voltammeter. Comparing the charges of the hydrogen underpotential deposition region, and the corresponding oxide reduction regions, it is concluded that a platinum overlayer on gold forms 3D islands, while gold on platinum forms 2D islands. Foreign metals present in an amount of up to one monolayer exert an influence on the change in reaction rate with respect to both hydrogen evolution (HER) and oxygen reduction (ORR) reactions. Aplatinum overlayer on a gold substrate increases the activity for HER and for ORR, compared with pure gold. These results can be understood in terms of a simple model, in which the change in the H and OH binding energies are directly proportional to the shift of the d-bond center of the overlayer. On the contrary, a gold layer on platinum slightly decreases the activity for both reactions compared with pure platinum., Površinska modifikacija platine zlatom i zlata platinom je izvršena iz rastvora sumporne kiseline i odgovarajućih hloridnih kompleksa metala primenom ciklične voltametrije. Poređenjem količine naelektrisanja u oblasti potpotencijalne depozicije vodonika i odgovarajućih oblasti redukcije oskida čistih i modifikovanih elektroda zaključeno je da platina na zlatu formira 3D, a zlato na platini 2D ostrva. Aktivnosti ovako modifikovanih površina za reakcije izdvajanja vodonika i redukcije kiseonika u rastvoru sumporne kiseline poređene sa aktivnostima čistih metala. Elektroda od zlata modifikovana platinom značajno uvećava aktivnost za obe ispitivane rekacije u poređenju sa čistim zlatom. Sa druge strane, elektroda od platine modifikovana zlatom ima neznatno manju aktivnost u poređenju sa čistom platinom. Zbog ograničenih resursa i visoke cene platine platina modifikovana zlatom može biti zamena za čistu platinu kao dobar katalizator za reakciju redukcije kiseonika, posebno u gorivim spregovima u oblasti niskih temperatura.",
publisher = "Serbian Chemical Society, Belgrade",
journal = "Journal of the Serbian Chemical Society",
title = "Study of gold-platinum and platinum-gold surface modification and its influence on hydrogen evolution and oxygen reduction, Površinska modifikacija platine zlatom i zlata platinom i njen uticaj na reakcije izdvajanja vodonika i redukcije kiseonika",
pages = "242-231",
number = "2",
volume = "70",
url = "https://hdl.handle.net/21.15107/rcub_technorep_775"
}
Dešić, M. N., Popović, M. M., Obradović, M., Vračar, L. M.,& Grgur, B.. (2005). Study of gold-platinum and platinum-gold surface modification and its influence on hydrogen evolution and oxygen reduction. in Journal of the Serbian Chemical Society
Serbian Chemical Society, Belgrade., 70(2), 231-242.
https://hdl.handle.net/21.15107/rcub_technorep_775
Dešić MN, Popović MM, Obradović M, Vračar LM, Grgur B. Study of gold-platinum and platinum-gold surface modification and its influence on hydrogen evolution and oxygen reduction. in Journal of the Serbian Chemical Society. 2005;70(2):231-242.
https://hdl.handle.net/21.15107/rcub_technorep_775 .
Dešić, Maja N., Popović, Milica M., Obradović, Maja, Vračar, Ljiljana M., Grgur, Branimir, "Study of gold-platinum and platinum-gold surface modification and its influence on hydrogen evolution and oxygen reduction" in Journal of the Serbian Chemical Society, 70, no. 2 (2005):231-242,
https://hdl.handle.net/21.15107/rcub_technorep_775 .
28
28

Comparative potentiodynamic study of nickel and hydrogen underpotential deposition at polycrystalline platinum electrode in weak acid and neutral solutions

Obradović, Maja; Grgur, Branimir; Vračar, Ljiljana M.

(6th Conference of the Yugoslav Materials Research Society, YUCOMAT VI: Current Research in Advanced Materials and Processes, 2005)

TY  - JOUR
AU  - Obradović, Maja
AU  - Grgur, Branimir
AU  - Vračar, Ljiljana M.
PY  - 2005
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/716
AB  - Underpotential deposition of nickel and hydrogen on polycrystalline platinum in weak acid and neutral solutions (3.5  lt = pH  lt = 7.0), with and without Ni2+-ions, has been examined using cyclic voltammetric technique in the range of temperature from 274 to 313 K. The nickel and hydrogen ad-atom surface coverages were calculated from the voltammetric adsorption and desorption charges. The Temkin isotherm was fitted for both underpotential depositions, and thermodynamic adsorption parameters were calculated for both atoms. The value of the bonding energy between hydrogen and surface in the presence of underpotentially deposited nickel was calculated and found to amount to 287 kJ mol(-1), which is 40 kJ mol(-1) stronger bond than the same of pure platinum. The presence of nickel on the surface facilitates interfacial transfer of hydrogen into the metal bulk and consequent hydride formation significant in design of hydrogen based fuel cells.
PB  - 6th Conference of the Yugoslav Materials Research Society, YUCOMAT VI: Current Research in Advanced Materials and Processes
T2  - Materials Science Forum
T1  - Comparative potentiodynamic study of nickel and hydrogen underpotential deposition at polycrystalline platinum electrode in weak acid and neutral solutions
EP  - 246
SP  - 241
VL  - 494
DO  - 10.4028/0-87849-971-7.241
ER  - 
@article{
author = "Obradović, Maja and Grgur, Branimir and Vračar, Ljiljana M.",
year = "2005",
abstract = "Underpotential deposition of nickel and hydrogen on polycrystalline platinum in weak acid and neutral solutions (3.5  lt = pH  lt = 7.0), with and without Ni2+-ions, has been examined using cyclic voltammetric technique in the range of temperature from 274 to 313 K. The nickel and hydrogen ad-atom surface coverages were calculated from the voltammetric adsorption and desorption charges. The Temkin isotherm was fitted for both underpotential depositions, and thermodynamic adsorption parameters were calculated for both atoms. The value of the bonding energy between hydrogen and surface in the presence of underpotentially deposited nickel was calculated and found to amount to 287 kJ mol(-1), which is 40 kJ mol(-1) stronger bond than the same of pure platinum. The presence of nickel on the surface facilitates interfacial transfer of hydrogen into the metal bulk and consequent hydride formation significant in design of hydrogen based fuel cells.",
publisher = "6th Conference of the Yugoslav Materials Research Society, YUCOMAT VI: Current Research in Advanced Materials and Processes",
journal = "Materials Science Forum",
title = "Comparative potentiodynamic study of nickel and hydrogen underpotential deposition at polycrystalline platinum electrode in weak acid and neutral solutions",
pages = "246-241",
volume = "494",
doi = "10.4028/0-87849-971-7.241"
}
Obradović, M., Grgur, B.,& Vračar, L. M.. (2005). Comparative potentiodynamic study of nickel and hydrogen underpotential deposition at polycrystalline platinum electrode in weak acid and neutral solutions. in Materials Science Forum
6th Conference of the Yugoslav Materials Research Society, YUCOMAT VI: Current Research in Advanced Materials and Processes., 494, 241-246.
https://doi.org/10.4028/0-87849-971-7.241
Obradović M, Grgur B, Vračar LM. Comparative potentiodynamic study of nickel and hydrogen underpotential deposition at polycrystalline platinum electrode in weak acid and neutral solutions. in Materials Science Forum. 2005;494:241-246.
doi:10.4028/0-87849-971-7.241 .
Obradović, Maja, Grgur, Branimir, Vračar, Ljiljana M., "Comparative potentiodynamic study of nickel and hydrogen underpotential deposition at polycrystalline platinum electrode in weak acid and neutral solutions" in Materials Science Forum, 494 (2005):241-246,
https://doi.org/10.4028/0-87849-971-7.241 . .
2
2

Apparent enthalpies of activation for oxygen reduction at Pt3Co electrode in alkaline solution

Obradović, Maja; Grgur, Branimir; Vračar, Ljiljana M.

(Progress in Advanced Materials and Processes: Proceedings of the Fifth Jugoslav Materials Research Society, YUCOMAT V, 2004)

TY  - JOUR
AU  - Obradović, Maja
AU  - Grgur, Branimir
AU  - Vračar, Ljiljana M.
PY  - 2004
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/596
AB  - Oxygen reduction (OR) at a Pt3Co alloy electrode has been examined in alkaline solutions of different pH's in the temperature range from 274 to 313 K. At all temperatures, two distinct E-log j rep-ions are observed. At low current densities (cd), Tafel slopes are close to -2.3 RT/F while at high current densities they are close to -2 x 2.3RT/F. The Tafel slopes at all pH values closely follow the kconventional temperature dependence with beta = 1/2. In addition, to confirm the mechanism in the two cd regions, the apparent enthalpies of activation at the selected potentials are calculated in both low and high cd regions at different pH. Although the relation DeltaH(a,J c.d)*  gt  DeltaH(a,h .c.d)(not equal) was found to be valid. it is concluded that at every pH, at the zero Galvani potential difference, the enthalples of activation are identical, and the rate determining step of OR reaction is the same in both cd regions. The changes in the Tafel slopes arise from different adsorption conditions of reaction intermediates in these regions as previously suggested [1].
PB  - Progress in Advanced Materials and Processes: Proceedings of the Fifth Jugoslav Materials Research Society, YUCOMAT V
T2  - Materials Science Forum
T1  - Apparent enthalpies of activation for oxygen reduction at Pt3Co electrode in alkaline solution
EP  - 114
SP  - 109
VL  - 453-454
UR  - https://hdl.handle.net/21.15107/rcub_technorep_596
ER  - 
@article{
author = "Obradović, Maja and Grgur, Branimir and Vračar, Ljiljana M.",
year = "2004",
abstract = "Oxygen reduction (OR) at a Pt3Co alloy electrode has been examined in alkaline solutions of different pH's in the temperature range from 274 to 313 K. At all temperatures, two distinct E-log j rep-ions are observed. At low current densities (cd), Tafel slopes are close to -2.3 RT/F while at high current densities they are close to -2 x 2.3RT/F. The Tafel slopes at all pH values closely follow the kconventional temperature dependence with beta = 1/2. In addition, to confirm the mechanism in the two cd regions, the apparent enthalpies of activation at the selected potentials are calculated in both low and high cd regions at different pH. Although the relation DeltaH(a,J c.d)*  gt  DeltaH(a,h .c.d)(not equal) was found to be valid. it is concluded that at every pH, at the zero Galvani potential difference, the enthalples of activation are identical, and the rate determining step of OR reaction is the same in both cd regions. The changes in the Tafel slopes arise from different adsorption conditions of reaction intermediates in these regions as previously suggested [1].",
publisher = "Progress in Advanced Materials and Processes: Proceedings of the Fifth Jugoslav Materials Research Society, YUCOMAT V",
journal = "Materials Science Forum",
title = "Apparent enthalpies of activation for oxygen reduction at Pt3Co electrode in alkaline solution",
pages = "114-109",
volume = "453-454",
url = "https://hdl.handle.net/21.15107/rcub_technorep_596"
}
Obradović, M., Grgur, B.,& Vračar, L. M.. (2004). Apparent enthalpies of activation for oxygen reduction at Pt3Co electrode in alkaline solution. in Materials Science Forum
Progress in Advanced Materials and Processes: Proceedings of the Fifth Jugoslav Materials Research Society, YUCOMAT V., 453-454, 109-114.
https://hdl.handle.net/21.15107/rcub_technorep_596
Obradović M, Grgur B, Vračar LM. Apparent enthalpies of activation for oxygen reduction at Pt3Co electrode in alkaline solution. in Materials Science Forum. 2004;453-454:109-114.
https://hdl.handle.net/21.15107/rcub_technorep_596 .
Obradović, Maja, Grgur, Branimir, Vračar, Ljiljana M., "Apparent enthalpies of activation for oxygen reduction at Pt3Co electrode in alkaline solution" in Materials Science Forum, 453-454 (2004):109-114,
https://hdl.handle.net/21.15107/rcub_technorep_596 .

Adsorption of oxygen containing species and their effect on oxygen reduction on Pt3Co electrode

Obradović, Maja; Grgur, Branimir; Vračar, Ljiljana M.

(Elsevier Science Sa, Lausanne, 2003)

TY  - JOUR
AU  - Obradović, Maja
AU  - Grgur, Branimir
AU  - Vračar, Ljiljana M.
PY  - 2003
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/516
AB  - A rotating Pt3Co, thermally prepared alloy disc is used to study electrochemical oxygen reduction in alkaline solutions of different pH. In all solutions two Tafel regions are found: at low current densities partial derivativeE/partial derivativelog j = -2.3RT/F and at high current densities partial derivativeE/log j = -2.3 x 2RT/F. The reaction order with respect to OH- is confirmed to be -1/2 and 0 for low and high current density regions, respectively. The coverage, theta, with oxygen intermediates, determined by a programmed potentiodynamic method, is found to be a function of potential and pH. In all solutions, substantial coverages are observed only at potentials in the low current density region. It is found that the fractional reaction order at low current densities is related through the adsorption of oxygen species under Temkin conditions and the dependence of activation energy on theta and pH.
PB  - Elsevier Science Sa, Lausanne
T2  - Journal of Electroanalytical Chemistry
T1  - Adsorption of oxygen containing species and their effect on oxygen reduction on Pt3Co electrode
EP  - 78
SP  - 69
VL  - 548
DO  - 10.1016/S0022-0728(03)00223-7
ER  - 
@article{
author = "Obradović, Maja and Grgur, Branimir and Vračar, Ljiljana M.",
year = "2003",
abstract = "A rotating Pt3Co, thermally prepared alloy disc is used to study electrochemical oxygen reduction in alkaline solutions of different pH. In all solutions two Tafel regions are found: at low current densities partial derivativeE/partial derivativelog j = -2.3RT/F and at high current densities partial derivativeE/log j = -2.3 x 2RT/F. The reaction order with respect to OH- is confirmed to be -1/2 and 0 for low and high current density regions, respectively. The coverage, theta, with oxygen intermediates, determined by a programmed potentiodynamic method, is found to be a function of potential and pH. In all solutions, substantial coverages are observed only at potentials in the low current density region. It is found that the fractional reaction order at low current densities is related through the adsorption of oxygen species under Temkin conditions and the dependence of activation energy on theta and pH.",
publisher = "Elsevier Science Sa, Lausanne",
journal = "Journal of Electroanalytical Chemistry",
title = "Adsorption of oxygen containing species and their effect on oxygen reduction on Pt3Co electrode",
pages = "78-69",
volume = "548",
doi = "10.1016/S0022-0728(03)00223-7"
}
Obradović, M., Grgur, B.,& Vračar, L. M.. (2003). Adsorption of oxygen containing species and their effect on oxygen reduction on Pt3Co electrode. in Journal of Electroanalytical Chemistry
Elsevier Science Sa, Lausanne., 548, 69-78.
https://doi.org/10.1016/S0022-0728(03)00223-7
Obradović M, Grgur B, Vračar LM. Adsorption of oxygen containing species and their effect on oxygen reduction on Pt3Co electrode. in Journal of Electroanalytical Chemistry. 2003;548:69-78.
doi:10.1016/S0022-0728(03)00223-7 .
Obradović, Maja, Grgur, Branimir, Vračar, Ljiljana M., "Adsorption of oxygen containing species and their effect on oxygen reduction on Pt3Co electrode" in Journal of Electroanalytical Chemistry, 548 (2003):69-78,
https://doi.org/10.1016/S0022-0728(03)00223-7 . .
40
39
42

Oxygen reduction on a duplex stainless steel

Gojković, Snežana Lj.; Zečević, S.K.; Obradović, Maja; Dražić, Dragutin M.

(Pergamon-Elsevier Science Ltd, Oxford, 1998)

TY  - JOUR
AU  - Gojković, Snežana Lj.
AU  - Zečević, S.K.
AU  - Obradović, Maja
AU  - Dražić, Dragutin M.
PY  - 1998
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/213
AB  - O-2 reduction on duplex stainless steel was investigated in neutral and alkaline solutions with and without the presence of chloride ions. All polarization curves showed hysteresis with higher reaction rate in positive going sweep than in the negative one. Tafel slopes of about -90 mV dec(-1) in neutral and alkaline solutions without chloride ions and about -150 mV dec(-1) in NaCl solution were obtained. Reaction rate is almost independent on pH in solutions of pH  lt  12 while in more alkaline solutions reaction order with respect to OH- ions of about -1 was obtained. Reaction rate and kinetic parameters for O-2 reduction on duplex stainless steel were compared to data for O-2 reduction on pure Fe and great similarity was found.
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - Corrosion Science
T1  - Oxygen reduction on a duplex stainless steel
EP  - 860
IS  - 6
SP  - 849
VL  - 40
DO  - 10.1016/S0010-938X(98)00004-3
ER  - 
@article{
author = "Gojković, Snežana Lj. and Zečević, S.K. and Obradović, Maja and Dražić, Dragutin M.",
year = "1998",
abstract = "O-2 reduction on duplex stainless steel was investigated in neutral and alkaline solutions with and without the presence of chloride ions. All polarization curves showed hysteresis with higher reaction rate in positive going sweep than in the negative one. Tafel slopes of about -90 mV dec(-1) in neutral and alkaline solutions without chloride ions and about -150 mV dec(-1) in NaCl solution were obtained. Reaction rate is almost independent on pH in solutions of pH  lt  12 while in more alkaline solutions reaction order with respect to OH- ions of about -1 was obtained. Reaction rate and kinetic parameters for O-2 reduction on duplex stainless steel were compared to data for O-2 reduction on pure Fe and great similarity was found.",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "Corrosion Science",
title = "Oxygen reduction on a duplex stainless steel",
pages = "860-849",
number = "6",
volume = "40",
doi = "10.1016/S0010-938X(98)00004-3"
}
Gojković, S. Lj., Zečević, S.K., Obradović, M.,& Dražić, D. M.. (1998). Oxygen reduction on a duplex stainless steel. in Corrosion Science
Pergamon-Elsevier Science Ltd, Oxford., 40(6), 849-860.
https://doi.org/10.1016/S0010-938X(98)00004-3
Gojković SL, Zečević S, Obradović M, Dražić DM. Oxygen reduction on a duplex stainless steel. in Corrosion Science. 1998;40(6):849-860.
doi:10.1016/S0010-938X(98)00004-3 .
Gojković, Snežana Lj., Zečević, S.K., Obradović, Maja, Dražić, Dragutin M., "Oxygen reduction on a duplex stainless steel" in Corrosion Science, 40, no. 6 (1998):849-860,
https://doi.org/10.1016/S0010-938X(98)00004-3 . .
37
27
35