Self-Adaptive Reaction Microenvironment via Charge Redistribution in Metastable Co3O4-CoN for Efficient Hydrogen Electrocatalysis

Regulating the reaction microenvironment at the catalyst-electrolyte interface is a key lever for accelerating alkaline hydrogen evolution reaction (HER) kinetics. However, most noble-metal-free oxide catalysts are limited by rigid electronic structures that impede dynamic charge redistribution. Here, we develop a metastable Co 3 O 4 -CoN catalyst that establishes a self-adaptive reaction microenvironment through charge redistribution at the oxide-nitride interface, enhancing alkaline HER kinetics. Nitrogen- and vanadium-codoped Co 3 O 4 -CoN hollow nanowires (HNV/Co 3 O 4 -CoN) were synthesized through a programmed reduction-annealing route, yielding mixed-valence cobalt surfaces with spatially confined defects and dopant gradients. This metastability-induced electronic flexibility, promotes water dissociation on oxide-derived sites while maintaining favorable hydrogen adsorption on nitride-modified regions, improving both elementary steps of alkaline HER. Ultraviolet and X-ray photoelectron spectroscopy indicate pronounced interfacial charge redistribution and work-function modulation induced by dopant incorporation and metastable phase coupling. The optimized HNV/Co 3 O 4 -CoN catalyst delivers an ultralow overpotential of 7 mV@10 mA cm -2 and 264 mV@1000 mA cm -2 high current density, while sustaining stable electrolysis at ≥500 mA cm -2 . Mechanistic analysis supports reduced barriers for water dissociation and near-thermoneutral hydrogen adsorption on the coupled interface. This work demonstrates a generalizable strategy to construct electronically adaptable surfaces for high-current-density, noble-metal-free hydrogen evolution.