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

Metallic-phase MoS 2 (1T-MoS 2 ) 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 (S V ). However, existing defect engineering approaches for MoS 2 often involve corrosive chemicals or specialized equipment, hindering its practical scalability. In this work, 1T-MoS 2 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 H 2 SO 4 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 S V 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 S V -tuned 1T-MoS 2, and it provides useful design insights for developing efficient and durable MoS 2 -based HER electrocatalysts.