Multiphase NiMo with Spatially Separated Active Sites Enabled by Data-Assisted Synthesis for Spillover-Driven Alkaline Hydrogen Evolution Reaction

Abstract

Efficient hydrogen evolution in alkaline media requires electrocatalysts that couple rapid water dissociation with facile hydrogen desorption. Here, we report a binder-free nickel-molybdenum (NiMo) electrocatalyst grown directly on nickel foam, in which catalytic activity is governed by controlled formation of mixed amorphous-crystalline phases. By tuning hydrothermal synthesis duration and temperature and guided by a machine-learning cubic regression model, a kinetically favourable regime is identified around 24 h at 160 -180 °C, yielding an overpotential as low as 26.0 mV at 10 mA cm -2 .Structural analysis reveals intertwined Ni1Mo1 (313) and Ni4Mo1 (121) domains embedded within an amorphous matrix.Density functional theory calculations demonstrate that both phases are catalytically active, with site-resolved adsorption energetics showing preferential water adsorption and dissociation on Mo-rich sites, followed by hydrogen migration to Nirich sites for desorption. The coexistence of these phases shortens diffusion pathways and spatially separates reaction steps, thereby enhancing alkaline HER kinetics. When implemented as the cathode in an anion exchange membrane water electrolyser, the optimised NiMo electrode sustains stable operation at ~2.0 V for 100 h at 400 mA cm -2 . This work elucidates how phase cooperation in amorphous-crystalline NiMo alloys governs HER kinetics and provides a scalable route to durable, high-performance alkaline electrocatalysts.