Mo-Doped Ni 2 P/FeP 4 Heterostructure with Enhanced Interfacial Charge Transfer and Electron Availability for Efficient Water Electrolysis at Large Current Densities

Developing efficient and durable bifunctional electrocatalysts for overall water splitting (OWS) at high current densities and achieving a comprehensive understanding of the catalytic mechanism remains a critical challenge. Herein, we report a Mo-doped Ni 2 P/FeP 4 nanosheet array (Mo-Ni 2 P/FeP 4 ) grown in situ on a nickel foam as a model catalyst, which synergistically integrates the merits of Mo doping and a heterostructure. The optimized Mo-Ni 2 P/FeP 4 delivers high current densities of 500/1000 mA cm −2 at low overpotentials of 334/416 mV for the oxygen evolution reaction (OER) and 291/409 mV for the hydrogen evolution reaction (HER), respectively. Resultantly, the assembled alkaline electrolyzer achieved a low voltage of 1.85 V at 500 mA cm −2, outperforming most reported bifunctional electrocatalysts. Mechanistic studies reveal that the build-in electric field at the heterointerface promotes charge transfer from Mo-Ni 2 P to Mo-FeP 4, while Mo doping-induced work function modulation increases surface electron availability. This dual regulation simultaneously enhances HER kinetics by optimizing the hydrogen adsorption Gibbs free energy (Δ G H* ) at the Mo site and improves OER activity by lowering the energy barrier of the rate-determining step. This research provides an impressive “two-pronged” strategy by coupling heteroatom doping with heterostructure engineering to achieve efficient alkaline OWS performance at high current densities.