Catalytic activity-d-band center correlation for the O2 reduction reaction on platinum in alkaline solutions

We determined, by the rotating disk electrode technique, the kinetics of the oxygen-reduction reaction (ORR) on the surfaces of single crystals of Au( 111), Ag( 111), Pd( 111), Rh( 111), Ir( 111), and Ru( 0001), on Pt monolayers deposited on their surfaces, and also on nanoparticles of these metals dispersed on high-surface-area carbon. Plotting the correlation between the experimentally determined activities of these three types of electrocatalysts with the calculated metal d-band center energies, epsilon(d), revealed a volcano-type dependence. In all cases, the electronic properties of the metal electrocatalysts, represented by the epsilon(d) value, were used for elucidating the metal-dependent catalytic activities, and establishing their electronic propertiessthe ORR kinetics relationship. Pt( 111), Pt/C, and Pt/Pd( 111) were found to top their corresponding volcano plots. Pd in alkaline solutions showed particularly high activity, suggesting it may offer potential replacement for Pt in fuel cells.