Manipulating Hydrogen Evolution Reaction in Janus MoSSe Monolayer via Defect and Strain Engineering

Janus transition metal dichalcogenides (TMDs) exhibit exceptional electronic, optical, and catalytic properties due to their unique asymmetric structures. The article systematically investigates the stability of Janus MoSSe with typical vacancy defects using first‐principles calculations. The results reveal that the Gibbs free energy for the hydrogen evolution reaction (HER) is significantly reduced to ≈0.5 eV, lower than that of pristine MoSSe and conventional MoS 2 monolayers. Notably, the application of external strain further enhances the HER performance of defect‐engineered Janus MoSSe. This improvement is attributed to the adaptive release of concentrated strain by dangling bonds at the defect region, resulting in distinct tunable patterns. The findings elucidate the underlying mechanism behind the enhanced HER performance of MoSSe through strain engineering, providing theoretical support for the optimal design of efficient HER catalysts based on defective Janus TMDs.