Ion Irradiation Activated Catalytic Activity of MoSe₂ Nanosheet for High‐Efficiency Hydrogen Evolution Reaction

Abstract Developing highly efficient, low cost, and stable electrocatalysts that work at a large current density is crucial for upgrading the current industrial electrochemical water splitting to produce H₂. Molybdenum selenide (MoSe₂) is a promising 2D transition metal dichalcogenide (TMD), however, its reported output is inadequate due to its inert basal plane. Herein, the catalytic activity of MoSe₂ nanosheet arrays is activated by a novel and controllable method of He⁺ ion irradiation to introduce multiple vacancies simultaneously into their inert basal planes. The vacancies activated MoSe₂ have improved electrocatalytic performance and stability with a minimum overpotential of 90 mV at 10 mA cm⁻², a Tafel slope of 49 mV dec⁻¹ and high stability of 650 h at the industry‐level large current density of 1000 mA cm⁻² compared to several hours for the pristine sample. The DFT results reveal that single Se and single Mo vacancies on the MoSe₂ basal plane can efficiently increase the electrical conductivity and reduce energy barriers for water dissociation and subsequent proton adsorption, thus improving the electrocatalytic capability. This finding proves the application of ion beam in defect engineering for effective hydrogen evolution in TMDs‐based catalysts.