Ni ₂ P/CoSe Mott–Schottky Heterointerfaces with Electron Redistribution for Alkaline Hydrogen Evolution at Ampere-Level Current Densities

Electrolytic water splitting for hydrogen production remains a significant challenge, highlighting the urgent need for high-performance and economically viable electrocatalysts for the hydrogen evolution reaction (HER). In this study, a Ni 2 P/CoSe Mott–Schottky heterojunction was fabricated on carbon fiber paper (CFP), serving as an efficient HER electrocatalyst in alkaline media. The radially aligned CoSe hollow nanoneedles enable the uniform anchoring of Ni 2 P quantum dots, forming tightly coupled heterointerfaces between discrete quantum domains and the conductive scaffold, thereby increasing the density of interfacial active sites. Discretely dispersed semiconducting Ni 2 P on metallic CoSe induces interfacial charge polarization via quantum confinement effects, thereby generating a strong built-in electric field (BIEF) at the interface that drives electron transfer from Ni 2 P to CoSe. This field promotes interfacial charge redistribution and intrinsically activates the catalytic sites. Density functional theory (DFT) calculation reveals that interfacial charge redistribution between Ni 2 P and CoSe generates electron-deficient Ni sites and electron-rich Co sites, which respectively optimize H 2 O adsorption/dissociation and H* adsorption, thereby enhancing the HER activity. As a result, the 2-Ni 2 P/CoSe/CFP catalyst exhibits outstanding HER performance with a low overpotential of 186 mV at 1000 mA cm –2 and <1% loss after 300 h. Using 2-Ni 2 P/CoSe/CFP as the cathode, an AEM-WE device exhibits a low cell voltage of 1.74 V at 1000 mA cm –2 and a long-term stability for 500 h.