Chemical Energy‐Driven Lithiation Preparation of Co@Mo Core–Shell Heterostructures for Highly Efficient Hydrogen Evolution

Developing efficient transition metal-based catalysts through interface and defect engineering is crucial for enhancing hydrogen production via water electrolysis at high current densities, though it remains a significant challenge. In this study, Co@Mo heterostructures are designed and synthesized using a chemical-energy-driven lithiation (CEDL) process on Co₉S₈@MoS₂. By taking advantage of the slow crystallization kinetics at room temperature, the original core-shell structure is preserved during the lithiation of Co₉S₈@MoS₂ heterostructures. Additionally, the electronic structure and adsorption-free energy are tuned as a result of the slow lithiation, which helped create and maintain more surface and boundary defects. These Co@Mo heterostructures demonstrate outstanding performance in the hydrogen evolution reaction (HER) due to the benefits of the heterojunction and the presence of metal defects. Specifically, the Co@Mo catalyst exhibits high catalytic activity in 1 m KOH solution, requiring only 87 and 200 mV to reach current densities of 100 and 400 mA cm^{- 2}, respectively. This work provides a novel strategy for designing robust transition metal-based hydrogen evolution catalysts with improved performance.