Nano-Nickel Pinned Defective MoS₂ Heterostructures via Ball Milling for Improved Hydrogen Evolution

The development of cost-effective and scalable electrocatalysts remains a key challenge for the alkaline hydrogen evolution reaction (HER). Herein, we report a simple, solvent-free mechanochemical synthesis approach to fabricate Ni nanoparticle-pinned, defect-rich MoS₂ (Ni@MoS₂) heterojunction catalysts. This one-step ball-milling strategy enables simultaneous exfoliation of molybdenum disulfide (MoS₂) into the conductive 1T phase, generation of defects, and physical pinning of Ni nanoparticles without the need for high-temperature or solution-based processing. The resulting heterostructure forms a strong metal-support interaction and a Mott-Schottky interface, which facilitates water adsorption, accelerates Volmer step kinetics, and enhances the electron transfer from Ni to MoS₂. The catalyst exhibits remarkable catalytic activity and structural robustness, requiring only 301 mV to reach 500 mA cm^-2 while remaining stable at high current densities of 0.45 and 0.9 A cm^-2, owing to the defect-reinforced pin-type architecture. This work underscores the potential of defect and interface engineering via scalable mechanochemical methods to construct robust HER electrocatalysts for practical alkaline electrolysis.