Fe2P nanoparticles embedded on Ni2P nanosheets as highly efficient and stable bifunctional electrocatalysts for water splitting

Abstract It is urgent to develop highly efficient, stable and low-cost bifunctional electrocatalysts for overall water splitting. Herein, an iron-nickel phosphide (Fe2P/Ni2P) heterostructure, constructed by Fe2P nanoparticles embedded on Ni2P nanosheets, is strategically fabricated on nickel foam via a facile process. As a bifunctional electrocatalyst, the Fe2P/Ni2P heterostructure delivers a very low overpotential of 64 mV (or 185 mV) to reach current density of 10 mA cm−2 for hydrogen (or oxygen) evolution reaction. When simultaneously employed as both the anode and cathode electrodes, it demonstrates an ultralow cell voltage of 1.49 V@10 mA cm−2 for full water splitting with nearly 100% Faradaic efficiency, and superior long-term stability even over 100 h. Density functional theory calculations manifest that a strong heterointerface interaction could cause electron redistribution near the Fe2P/Ni2P heterointerface and optimize the ΔGH* of P sites, thus enhancing catalytic activity. Additionally, the 3D porous heterostructure is benefit to expose rich active sites and facilitate ion diffusion and gas bubble release, thus promoting the catalytic performance. This work opens up a new strategical approach for rational design of metal phosphide-based heterostructures as highly efficient and stable bifunctional electrocatalysts for water splitting.