A theoretical study on ion irradiation engineered defect formation and hydrogen evolution on two-dimensional MoS₂

Via density functional theory, ab initio molecular dynamics and Monte Carlo simulations, we demonstrate the feasibility of ion irradiation for engineering defect formation and electrocatalytic activity of hydrogen evolution reaction (HER) on 2D MoS₂. Systematic ion irradiation simulations with different incident ions (C, O, Ne, and Ar), incident energies and ion fluences allow the identification of irradiation conditions for achieving a sulfur vacancy (V_S) of ∼9 %, an optimal defect concentration for HER activity. With the desired concentration, we reveal that lower incident energy or heavier ions require smaller ion fluence, attributed to the larger cross section for defect generation. Analyses on electronic properties reveal a metallic behavior of the irradiated structures, suggesting improved electrical conductivity. We further calculate the Gibbs free energies of H adsorption (ΔG_H), and find that the ΔG_H for irradiated structures are significantly reduced (∼ − 0.1 eV) as compared to the value for pristine MoS₂ (∼2.0 eV). Our findings not only provide a practical approach for rational design and optimization of MoS₂ electrocatalysts for efficient hydrogen production, but also pave an avenue for property modification of 2D nanodevices by ion beam irradiation.