Enhanced Oxygen Evolution Reaction Activity of a Co 2 P@NC–Fe 2 P Composite Boosted by Interfaces Between a N-Doped Carbon Matrix and Fe 2 P Microspheres

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 (Co 2 P@NC–Fe 2 P) 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 Fe 2 P and Co 2 P simultaneously, where Co 2 P nanoparticles coated with an N-doped carbon (NC) matrix derived from ZIF-67 are partially adsorbed onto the surface of Fe 2 P microspheres, thereby forming numerous NC–Fe 2 P interfaces. The optimal Co 2 P@NC–Fe 2 P 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–Fe 2 P interfaces in the Co 2 P@NC–Fe 2 P composite. This work provides a new strategy to optimize transition-metal phosphides with effective interfaces for OER electrocatalysis.