Sulfur Vacancy-Induced Improved Hydrogen Evolution Reaction on 1T-MoS ₂

Metallic-phase MoS2 (1T-MoS2) is considered a promising catalyst for the hydrogen evolution reaction (HER) in acidic media, largely due to the abundant surface active sites induced by sulfur vacancies (SV). However, existing defect engineering approaches for MoS2 often involve corrosive chemicals or specialized equipment, hindering its practical scalability. In this work, 1T-MoS2 is synthesized via a facile one-step hydrothermal method, and defect engineering is achieved simply by modulating the sulfur-to-molybdenum (S/Mo) molar ratio in the precursor solution. The optimized catalyst exhibits a low HER overpotential of 266 mV at −10 mA cm–2 and a Tafel slope of 72 mV dec–1 in a 0.5 M H2SO4 electrolyte. It also shows outstanding operational stability, with only a 15 mV increase in overpotential at −10 mA cm–2 after 150 h of continuous HER testing under −0.7 V vs RHE (∼200 mA cm–2). The enhanced performance is attributed to multiple synergistic effects induced by SV defects, including reduced charge transfer resistance, accelerated reaction kinetics, and an enlarged electrochemically active surface area. Overall, this work offers a simple, scalable route to prepare SV-tuned 1T-MoS2, and it provides useful design insights for developing efficient and durable MoS2-based HER electrocatalysts.