First-principles study of WS2 monolayer decorated with noble metals (Pt, Rh, Ir) as the promising candidates to detect nitrogenous poisonous gases

Rapid identification of nitrogenous toxic gases (NPGs, including NO, NO₂, NH₃, and HCN) emitted from industrial processes is essential for environmental preservation. In this research, the first-principles calculations have been employed to systematically investigate the adsorption behavior and sensing characteristics of Pt, Rh, Ir-modified WS₂ monolayers (Pt-WS₂, Rh-WS₂, and Ir-WS₂) towards these NPGs, with the aim of assessing the potential of WS₂-based gas sensors for NPG detection. The results show that Pt, Rh, and Ir atoms can be stably anchored on the WS₂ surface, enhancing its chemical stability and the quantity of active sites. Additionally, the strong orbital hybridization between these noble metal atoms and gas molecules enhances the adsorption capacity of WS₂, markedly boosting the adsorption potency of these modified substances towards NPGs (E_ads≥−0.69 eV) while maintaining high selectivity toward NPGs in the presence of interfering gases (H₂O, N₂, CO₂). Analysis of the density of states, charge density distribution, and electron localization function indicates weak chemical adsorption of HCN on Pt-WS₂, Rh-WS₂, and Ir-WS₂, while strong chemical adsorption is observed for NO, NO₂, and NH₃. Furthermore, the adsorption of NO and NO₂ leads to significant band gap changes (∆E_g > 30 %) of Pt-WS₂, Rh-WS₂, and Ir-WS₂, and the response of work function to NH₃ and HCN adsorption is similarly pronounced (∆Φ > 15 %). Finally, analysis of recovery time indicates that Pt-WS₂ and Rh-WS₂ can serve as work function gas sensors for HCN and as adsorbents for NO, NO₂, and NH₃ at room temperature, whereas Ir-WS₂ can function as a reusable gas sensor for the effective detection of HCN at high temperature. This investigation establishes a robust theoretical framework for the development and manufacture of high-performance WS₂-based gas sensors.