Phosphate Group Dependent Metallic Co(OH)2 toward Hydrogen Evolution in Alkali for the Industrial Current Density

Developing efficient and low-cost electrocatalysts is critical for hydrogen evolution by water splitting. Nonsubjective reconstruction is one of the main issues that induces difficulty to develop and understand the well-defined structure during the electrocatalysis. By studying the anion-exchange between phosphate and hydroxide, cobalt hydroxide nanosheets incorporated with phosphate inherited from cobalt phosphate are obtained, which provides a new case of metallic transition metal hydroxide. Benefiting from more exposed active sites, effective electron transport, and optimized electronic structure, the residual phosphate in two-dimensional Co(OH)2 gives rise to significant improvement in alkaline hydrogen evolution. Particularly, it can survive at 1600 mA cm–2 and maintain stability over 100 h under industrial conditions (6 M KOH at 60 °C). Density functional theory calculations and the confirmatory experiments of reverse anion-exchange from Co(OH)2 are investigated to confirm the successful engineering of metallic character and electronic structure. This work provides a facile modification of practical electrodes with phosphate groups for industrial water electrolysis as well as gaining insights into the reconstruction of cobalt-based electrocatalysts in alkali to become an effective catalyst.