Electrocatalysis by nanoparticles - Oxygen reduction on Ebonex/Pt electrode

Abstract

The oxygen reduction reaction was studied in 0.5 mol dm-3 HClO4 solution on an electrode based on Ebonex-supported platinum electrocatalyst applied on rotation Au disk electrode (Au/Ebonex/Pt). Pt catalyst was prepared by impregnation method from 2-propanol solution of Pt(NH3)2(NO2)2 and Ebonex powder. Ebonex support (non-stoichiometric mixture of titanium oxides) was characterized by: X-ray diffraction, energy dispersive X-ray spectroscopy and BET techniques. The synthesized catalyst was analysed by TEM technique. The kinetics of oxygen reduction reaction on the Ebonex/Pt catalyst shows a significant enhancement in comparison with the same on polycrystalline Pt. Only a single Tafel slope of -0.106 V dec-1 is observed and the first-rate determining step in direct four-electron reduction is proposed as a main partway in the whole range of potential. The absence of PtOH layer, that inhibits oxygen reduction on polycrystalline Pt, was discussed through synergetic effect into the catalyst as a consequence of the interactions of Pt nanoparticles with Ebonex, on one hand, and, through the d-band coupling model where the surface reactivity is given by the energy shift of the surface d-states with respect to the Fermi level, on the other hand.