Construction of Nitrogen‐Vacancy‐Rich Co ₄ N Nanosheet Electrocatalyst and Study on Its Performance for Hydrogen Evolution Reaction

ABSTRACT Developing sustainable energy sources to replace fossil fuels is crucial for addressing global energy and environmental challenges. Transition metal nitrides (TMNs) have proven to be excellent electrocatalysts due to their low cost, high stability, and excellent conductivity; however, conventional synthesis methods suffer from high energy consumption and lengthy processing times. In this work, we developed a nitrogen‐vacancy‐rich Co 4 N nanosheet catalyst (Co 4 N/NF) supported on nickel foam (NF) via a two‐step pyrolysis strategy (pre‐oxidation to Co 3 O 4 followed by nitridation in NH 3 ). This approach enables precise morphology control and efficient vacancy generation, overcoming structural collapse issues associated with direct nitridation. In alkaline media, the Co 4 N/NF electrode exhibits outstanding hydrogen evolution reaction (HER) activity with overpotentials of 60 mV at 10 mA/cm 2 and 205 mV at 100 mA/cm 2 , maintaining 12‐h stability in 1 M KOH. Density functional theory (DFT) indicates that the excellent electrochemical activity of Co 4 N/NF is attributed to the presence of nitrogen vacancies ( V N ), and the Gibbs free energy of Co sites adjacent to the nitrogen vacancies is closer to zero, thereby optimizing hydrogen adsorption. This work provides a viable approach for preparing structurally controllable, defect‐rich TMN electrocatalysts for sustainable energy applications.