First-principles study: enhancement of WS2 monolayer adsorption of toxic gases by doping with Cu atom

Abstract

Two-dimensional materials have the potential to be utilized as gas sensors, thereby facilitating the enhanced adsorption of toxic and hazardous gases. The adsorption properties of NO₂, N₂O, SO₂, and H₂S by WS₂ and Cu/WS₂ were investigated using first-principles calculations. In the doped system, the gases exhibit a tendency to adsorb above the Cu atoms, that is, above the S atoms that correspond to the intrinsic WS₂. The results demonstrate that during the adsorption process of Cu/WS₂, the gas molecules form chemical bonds with the Cu atom, thereby changing from physical adsorption to chemical adsorption. The doping of Cu atoms was observed to increase the adsorption energy, decrease the adsorption distance, increase the transferred charge, and decrease the band gap for the four gases. The dopant atoms facilitate the hybridization of the substrate with the orbitals of the gas molecules, resulting in a redistribution of charge within the adsorption system. This phenomenon is the underlying cause of the enhanced adsorption capacity observed in the doped system. The recovery times for Cu/WS₂-N₂O and Cu/WS₂-SO₂ are relatively short, which is suboptimal for a robust response to the detected signal. Compared with room temperature, the adsorption of NO₂ and H₂S by Cu/WS₂ can be effectively desorbed within a short time after heating. This study provides a theoretical basis for the design of WS₂-type high-performance gas sensing materials for NO₂ and H₂S.