Boosting Hydrogen Evolution on MoS ₂ via Ion Irradiation: Synergistic Effect of Vacancy and Substitution

Ion irradiation is a powerful tool for tailoring the properties of materials. It has been recently demonstrated to be effective in enhancing the catalytic activity of two-dimensional (2D) transition metal dichalcogenides toward the hydrogen evolution reaction (HER), but the fundamental mechanism remains elusive. Here, by using first-principles calculations, ab initio molecular dynamics (AIMD) and Monte Carlo simulations, we investigate the atomic structure and catalytic activity of 2D MoS 2 under F irradiation. By systematically calculating the Gibbs free energy of hydrogen adsorption (Δ G H ) on MoS 2 with various point defects, we reveal that sulfur vacancies ( V S ) and substitutional fluorine atoms (F S ) are catalytically active sites, while other defects (e.g., interstitial atoms and adsorbed species) are chemically inert. Based on this, the optimal irradiation parameters are successfully identified with an incident ion energy range of 80–3000 eV and a fluence of 3 × 10 14 ions/cm 2, which can maximize the formation of V S and F S while suppressing other defects. Surprisingly, with the obtained atomic structure of irradiated MoS 2, we find that the combined defects involving both V S and F S exhibit even smaller Δ G H (∼−0.01 eV) compared to individual V S and F S (∼−0.06 eV), demonstrating their synergistic role in boosting HER. This work not only sheds light on the irradiation-enhanced catalytic performance of MoS 2 for water splitting but also provides crucial guidance for tuning the physicochemical properties of 2D materials/devices via defect engineering.