Abstract: Water electrolysis holds significant promise for hydrogen production, however, its commercial feasibility relies on the development of cost-effective and efficient catalysts. Molybdenum disulfide (MoS₂), an earth-abundant material with low hydrogen adsorption free energy, is a promising candidate, yet its performance is limited by the low density of active edge sites. In this work, a CoO-assisted mechanochemical ball-milling strategy is used to produce defect-rich, Co-dispersed, curved MoS₂ catalysts with significantly enhanced hydrogen evolution reaction (HER) activity. Co-milling commercial MoS₂ with CoO simultaneously exfoliates bulk MoS₂ into few-layer nanosheets, generates abundant structural defects (e.g., sulfur vacancies), incorporates Co atoms in situ into the MoS₂ lattice, and induces pronounced nanosheet curvature. This unique one-step process dramatically reduces MoS₂ particle size and activates otherwise inert basal planes; concurrently, the curvature-elongated Mo-Mo bonds and tuned local electronic structure facilitate rapid hydrogen adsorption/desorption kinetics. The optimized curved Co,O@MoS₂ electrocatalyst exhibits outstanding HER performance, requiring only a 94 mV overpotential to achieve a current density of 10 mA cm^-2 in alkaline electrolyte. These results establish CoO-assisted ball milling as a scalable and effective route to synthesize high-performance MoS₂-based electrocatalysts.

Key words: Mechanochemistry ball milling, Hydrogen evolution reaction, Curvature, Electronic structure regulation, Defects