A preliminary study of the electro-catalytic reduction of oxygen on Cu-Pd alloys in alkaline solution

Copper-palladium alloys of different compositions are electrodeposited on nickel from aqueous solutions. These alloys are characterized by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The catalytic activity of these alloys toward oxygen reduction reaction (ORR) in alkaline solution is investigated using rotating disk electrode (RDE). The number of electrons transferred per O-2 molecule (n) obtained at different potentials is close to 2 at low overpotential indicating HO2- formation and gradually increases to 4 at higher overpotentials indicating full reduction to OH-. It is shown that Cu-Pd alloys are better electrocatalysts than Pd with Pd-Cu-1 having 24.5% copper is the best in the series. The effect of Cu in modifying the electro-catalytic activity of Pd is rationalized by considering the theoretical and electrochemical results. Also, the resistance of the Cu-Pd electrocatalysts towards ethanol poisoning is investigated and it is found that the addition of Cu renders the alloys susceptible to alcohol poisoning in oxygen reduction reaction while pure Pd which has the least specific activity possesses the highest selectivity toward oxygen reduction. (C) 2010 Elsevier B.V. All rights reserved.