Adsorption and gas-sensing performance of a ZnO-decorated WSe2 monolayer for toxic gas detection: a first-principles study

Abstract

The reliable detection of toxic and greenhouse gases is essential for environmental monitoring, industrial safety, and public health protection. In this work, a comprehensive first-principles density functional theory study was carried out to investigate the adsorption and gas-sensing performance of a ZnO-decorated WSe₂ monolayer toward CO₂, N₂O, CH₄, SF₆, CCl₂O and CH₃Cl gases. The results show that pristine WSe₂ exhibits weak adsorption due to limited gas–surface interaction, whereas ZnO decoration significantly enhances the adsorption behavior by increasing adsorption energies, reducing adsorption distances, and promoting charge transfer. Among the investigated gases, the ZnO–WSe₂ system exhibits the strongest interaction toward CCl₂O and CH₄, with adsorption energies of −0.566 eV and −0.542 eV, respectively. Electronic structure analysis, including band structure, density of states, differential charge density, and work function calculations, reveals pronounced gas-dependent electronic responses and confirms strong modulation of the electronic properties after gas adsorption. Sensitivity analysis indicates that the ZnO–WSe₂ monolayer exhibits excellent sensing performance, particularly toward CCl₂O, with appreciable responses also observed for CO₂ and CH₄, while recovery time calculations demonstrate that the desorption behavior can be effectively tuned by temperature. Furthermore, the strong binding interaction between ZnO and WSe₂ confirms the structural stability of the decorated monolayer under practical sensing conditions. These findings demonstrate that ZnO decoration is an effective strategy for activating the WSe₂ surface and improving its gas-sensing performance, highlighting ZnO–WSe₂ as a promising and selective sensing material for toxic gas detection and providing valuable theoretical guidance for the design of high-performance two-dimensional gas sensors.