DFT Study on Intermetallic Pd–Cu Alloy with Cover Layer Pd as Efficient Catalyst for Oxygen Reduction Reaction

Detailed density functional theory (DFT) calculations of the adsorption energies (E(ad)) for oxygen on monolayer Pd on top of the Pd–Cu face-centered cubic (FCC) alloy and intermetallic B2 structure revealed a linear correspondence between the adsorption energies and the d-band center position. The calculated barrier (E(barrier)) for oxygen dissociation depends linearly on the reaction energy difference (ΔE). The O(2) has a stronger adsorption strength and smaller barrier on the intermetallic Pd–Cu surface than on its FCC alloy surface. The room-temperature free energy (ΔG) analysis suggests the oxygen reduction reaction (ORR) pathways proceed by a direct dissociation mechanism instead of hydrogenation into OOH. These results might be of use in designing intermetallic Pd–Cu as ORR electrocatalysts.