Enhanced Oxygen Evolution Reaction Activity of a Co2P@NC-Fe2P Composite Boosted by Interfaces Between a N-Doped Carbon Matrix and Fe2P Microspheres.

Abstract

Constructing highly efficient and low-cost transition-metal-based electrocatalysts with a large number of interfaces to increase their active site densities constitutes a major advancement in the development of water-splitting technology. Herein, a bimetallic phosphide composite (Co2P@NC-Fe2P) is successfully synthesized from a ferric hydroxyphosphate-zeolitic imidazolate framework hybrid precursor (FeHP-ZIF-67). Benefitting from morphology and composition regulations, the FeHP-ZIF-67 precursor is prepared by a room-temperature solution synthesis method, which exhibits an optimal morphology, where FeHP microspheres are coated with excess ZIF-67 nanoparticles. During the annealing of FeHP-ZIF-67, FeHP serves as a source of phosphorus to form Fe2P and Co2P simultaneously, where Co2P nanoparticles coated with an N-doped carbon (NC) matrix derived from ZIF-67 are partially adsorbed onto the surface of Fe2P microspheres, thereby forming numerous NC-Fe2P interfaces. The optimal Co2P@NC-Fe2P composite has an overpotential of 260 mV at a current density of 10 mA cm-2, a small Tafel slope of 41 mV dec-1, and long-term stability of over 35 h in an alkaline medium for oxygen evolution reactions (OERs). Such a superior OER performance is attributed to the active NC-Fe2P interfaces in the Co2P@NC-Fe2P composite. This work provides a new strategy to optimize transition-metal phosphides with effective interfaces for OER electrocatalysis.