High Performance Pseudo-Pt@Pt Core-Shell Electrocatalyst for Oxygen Reduction Reaction: A Density Functional Theory Study

The development of cost-effective Pt-based oxygen reduction reaction (ORR) electrocatalysts is crucial for the application of proton exchange membrane fuel cells (PEMFCs). In this work, by using density functional theory calculations, we show that the Pt-M@Pt core-shell alloy (M = Co, Ni, Cu, with Pt-M alloy as the pseudo-Pt core and Pt as the shell) gives significantly higher ORR activity than pure Pt and common Pt-M alloys. Through structural and electronic analyses, we suggest that this is mainly caused by the asymmetric strain modulation effect of the pseudo-Pt core on the Pt shell and the interfacial charge transfer, which leads to a significant downward shift of the d-band center (epsilon d) and alters the bonding mode between the metal d orbitals and the adsorbed oxygen (O) p orbitals from equal contributions of the five d orbitals to dominant contributions of d(xy) and d(x2-y2) orbitals, thereby weakening the adsorption strength of O. Notably, the PtCo@Pt(111) surface with a suitable compressive strain and appropriate interfacial charge transfer exhibits the highest ORR activity and the corresponding overpotential is 0.38 V lower than Pt(111).