Favorable Core/Shell Interface within Co2P/Pt Nanorods for Oxygen Reduction Electrocatalysis

Nanostructures with nonprecious metal cores and Pt ultrathin shells are recognized as promising catalysts for oxygen reduction reaction (ORR) to enhance Pt efficiency through core/shell interfacial strain and ligand effects. However, core/shell interaction within a real catalyst is complex and due to the presence of various interfaces in all three dimensions is often oversimply interpreted. Using Co2P/Pt core/shell structure as a model catalyst, we demonstrate, through density functional theory (DFT) calculations that forming Co2P(001)/Pt(111) interface can greatly improve Pt energetics for ORR, while Co2P(010)/Pt(111) is highly detrimental to ORR catalysis. We develop a seed-mediated approach to core/shell Co2P/Pt nanorods (NRs) within which Co2P(001)/Pt(111) interface is selectively expressed over the side facets and the undesired Co2P(010)/Pt(111) interface is minimized. The resultant Co2P/Pt NRs are highly efficient in catalyzing ORR in acid, superior to benchmark CoPt alloy and Pt nanoparticle catalyst. As the first example of one-dimensional (1D) core/shell nanostructure with an ultrathin Pt shell and a nonprecious element core, this strategy could be generalized to develop ultralow-loading precious-metal catalysts with favorable core/shell interactions for ORR and beyond.