Ar²⁺ Beam Irradiation-Induced Multivancancies in MoSe₂ Nanosheet for Enhanced Electrochemical Hydrogen Evolution

Poor electronic conductivity and an inert basal plane restrict the further enhancement of hydrogen evolution reaction (HER) in 2H-phase MoSe2. Herein, we synthesized MoSe2 nanosheet arrays on carbon cloth and induced multivacancies in their basal plane via high-energy Ar2+ beam irradiation, which are confirmed by Raman, electron spin resonance, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy analyses. Electrical measurement results indicate that these vacancies in the MoSe2 basal plane can effectively improve their electrocatalytic performance, where the lowest overpotential of −171 mV at the current density of −100 mA/cm2 and Tafel slope of 35 mV/dec were achieved in Ar2+-irradiated (dose of 5 × 1015 ions/cm2) MoSe2 nanosheets. First-principles calculation results reveal that different cases of native vacancies in the MoSe2 basal plane could effectively enhance the conductivity of MoSe2 and produce more catalytic active sites for hydrogen evolution, giving rise to the better electrocatalytic capacity in the HER process. This finding opens the strategy of vacancy engineering for efficient hydrogen evolution in other transition metal dichalcogenide-based electrocatalysts.