Kinetics and mechanism for the oxygen reduction reaction on polycrystalline cobalt–palladium electrocatalysts in acid media

Cobalt–palladium (CoPdx) bimetallic electrocatalysts of various compositions were prepared and their physical and electrochemical properties were examined. The nominal composition of the polycrystalline electrocatalysts was estimated by energy dispersive X-ray analysis (EDX) and the lattice parameters were evaluated using X-ray diffraction (XRD). Electrocatalytic activity of the CoPdx electrodes for the oxygen reduction reaction was compared using cyclic voltammograms obtained in oxygen saturated, 0.5 M H2SO4. CoPd3 was identified as having the highest activity, showing peak currents comparable to a polycrystalline Pt electrode under identical experimental conditions. The rotating disk electrode technique was used to collect kinetic data for the oxygen reduction on CoPd3 and the activity of the binary electrocatalysts was evaluated. Kinetic and mechanistic aspects of the oxygen reduction reaction on CoPd3 are discussed and specific ways in which the surface structures may be involved are proposed.