Theoretical research of toxic gases adsorbed by Mo-doped two-dimensional VS₂ structure

Abstract

As is well known, the leakage of four toxic gases, NO₂, NH₃, mustard gas and sarin greatly threaten the environment and human health. Among of them, mustard gas and sarin are two serious chemical and biological weapons agents, and exposure to a small amount can cause skin burns and immediate death. NO₂ and NH₃ are two common toxic pollutants produced by automobile exhaust, coal combustion and petrochemical industry. The presence of trace amounts of NO₂ and NH₃ gas in human tissues can cause serious respiratory diseases and damage human brain and other systems. Thus, it is very important to realize the rapid detection of NO₂, NH₃, mustard gas and sarin in academia and industry. In this study, we use density functional theory to investigate the ability of a transition metal Mo doped two-dimensional VS₂ structure to detect the four representative toxic gases. The results reveal that Mo atom doping has a significant effect on the stability and gas-sensitivity of the VS₂ structure. The Mo atom can be successfully doped on the S-vacancy in the two-dimensional VS₂ structure. Compared with the undoped structure VS₂, the doped structure Mo-VS₂ has strong interaction with NO₂, NH₃, sarin, and mustard gas, realizing effective adsorption of them. The presence of Mo atom in the VS₂ lattice changes the electronic structure of VS₂, also modifies its band gap and density of states. The interaction between the Mo-VS₂ structure and the target analytes depends strongly on the nature of the gas molecule. The binding energy values for NO₂, NH₃, mustard gas, and sarin on the Mo-VS₂ are significantly higher than those on the pristine VS₂, indicating stronger interaction between the Mo-VS₂ structure and these gases. Our calculations show that the Mo atom in VS₂ changes its electrical resistance after being exposed to the gases, which can be used to distinguish different gases. Moreover, differences in charge redistribution within the Mo-VS₂ structure upon being exposed to different gases can be used to explain their differential gas-sensitivity. Our results can provide sufficient theoretical basis for experimental researchers to design and optimize the performances of sensors in practical applications.