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 O₂ 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.