Manipulation of Oxidation States on Phase Boundary via Surface Layer Modification for Enhanced Alkaline Hydrogen Electrocatalysis

Abstract In alkaline water electrolysis and anion exchange membrane water electrolysis technologies, the hydrogen evolution reaction (HER) at the cathode is significantly constrained by a high energy barrier during the water dissociation step. This study employs a phase engineering strategy to construct heterostructures composed of crystalline Ni₄W and amorphous WO_x aiming to enhance catalytic performance in the HER under alkaline conditions. This work systematically modulates the oxidation states of W within the amorphous WO_x of the heterostructure to adjust the electronic states of the phase boundary, the energy barriers associated with the water dissociation step, and the adsorption/desorption properties of intermediates during the alkaline HER process. The optimized catalyst, Ni₄W/WO_x‐2, with a quasi‐metallic state of W coordinated by a low oxygen content in amorphous WO_x, demonstrates exceptional catalytic performance (22 mV@10 mA cm⁻²), outperforming commercial Pt/C (30 mV@10 mA cm⁻²). Furthermore, the operando X‐ray absorption spectroscopy analysis and theoretical calculations reveal that the optimized W atoms in amorphous WO_x serve as active sites for water dissociation and the nearby Ni atoms in crystalline Ni₄W facilitated the release of H₂. These findings provide valuable insights into designing efficient heterostructured materials for energy conversion.