Nb-doped TiO2 as a support of Pt and Pt-Ru anode catalyst for PEMFCs

Abstract

TiO2 doped by 0.5% Nb was synthesized by the acid-catalyzed sol-gel method. BET surface area was determined to be 72 m(2) g(-1). XRD measurements showed that TiO2 has structure of anatase with similar to 13 nm average crystallite size. Using Nb-TiO2 as a support, Pt/Nb-TiO2 and Pt-Ru/Nb-TiO2 were prepared by borohydride reduction method. TEM imaging of Pt-Ru/Nb-TiO2 revealed rather uniform distribution of the metallic particles on the support with a mean diameter of 3.8 nm. According to XRD analysis, Pt-Ru particles consist of the solid solution of Ru in Pt (40 at.% Ru) and a small amount of RuO2. Cyclic voltammetry of Pt/Nb-TiO2 and Pt-Ru/Nb-TiO2 indicated good conductivity of the supporting material. Oxidation of pre-adsorbed CO and methanol on Pt-Ru/Nb-TiO2 was faster than on Pt/Nb-TiO2. However, when the activities of Pt/Nb-TiO2 and Pt-Ru/Nb-TiO2 for methanol oxidation were compared to those of Pt/XC-72 and Pt-Ru/XC-72, no significant difference was observed. This means that Nb-TiO2 is a promising replacement for high area carbon supports in PEMFC anodes, but without the influence on the reaction kinetics.