Enhancing electrocatalytic hydrogen evolution of MoS₂ enabled by electrochemical cation implantation for simultaneous surface-defect and phase engineering

The increasing demand for energy-efficient and cost-effective water-splitting systems has prompted research on non-precious-metal-based electrocatalysts for the hydrogen evolution reaction (HER) over a wide pH range. Molybdenum sulfide (MoS₂) has received considerable attention owing to its excellent HER activity in acidic media. However, its competitive HER properties must be improved to achieve better performance in alkaline or neutral environments. In this study, we introduced an electrochemical cation implantation (ECI) process as a versatile method to enhance the electrocatalytic properties of MoS₂. By modifying the microstructure of MoS₂, the ECI process induced vacancies in Mo and S, primarily in the basal planes and facilitated a gradual transition from the semiconducting (2H) to metallic (1T) phase. The optimized ECI-processed MoS₂ catalysts exhibited improved HER activities and low overpotentials (η₁₀, 144 mV) over the entire pH range compared with bare MoS₂ catalysts, highlighting the potential application of the ECI process for enhanced electrocatalysts.