Gas sensing properties of alkali metal decorated pristine and defect α-AsP monolayer toward acid SO2 and alkaline NH3 molecules

The sensing properties of Li and Na decorated pristine and defect α-AsP monolayer for acid SO2 and alkaline NH3 toxic gas molecules are systematically studied using first-principles calculations based on density functional theory (DFT-D2 method). The results suggest that the alkali metal atoms decorated defect α-AsP monolayer have moderate adsorption energies for SO2 and NH3 gas molecules, which is conducive to the desorption of gas molecules. In addition, a prominent increase in work function (WF) after SO2 and NH3 adsorption endow Li and Na decorated pristine and defect α-AsP monolayer with high sensitivity, and there is a clear relationship between the change of WF and the direction of charge transfer. The binding mechanism of SO2 and NH3 on different adsorbent models are explored by the electronic local function (ELF) and density of states (DOS) calculation. The results show that the adsorption of SO2 on substrates is mainly determined by electrostatic interaction and NH3 is bound to the substrates by a covalent bond. The adsorption of NH3 enhances the adsorption spectrum intensity of substrates around 150 and 200 nm. Additionally, thermodynamic analysis demonstrate that the Li and Na decorated pristine α-AsP monolayer may be a suitable material for the detection and storage of SO2 and NH3 toxic gas molecules. Therefore, these results can provide practical guidance for the research of promising novel two-dimensional V–V binary AsP-based gas sensors.