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

Abstract

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.