Effect of preadsorbing gas molecules on the adsorption of SO2 molecule on Hf2CO2 MXene by first-principles study

The sulfur dioxide (SO2) is one of the common polluting gases that can cause harm to human body. The adsorption of SO2 molecule on Hf2CO2 monolayer is investigated theoretically. The results show that Hf2CO2 monolayer cannot efficiently adsorb SO2 molecule. Preadsorbing gas molecules is an effective way to enhance the adsorption strength of the adsorption system. A series of gas molecules such as H2O, CO2, O2, NO2, CO, NO, N2, H2, CH4 are selected as preadsorbing molecules and possible adsorption positions for all preadsorbing gas are considered. It was found that preadsorbing H2O molecule can significantly enhance the adsorption of SO2 molecule on Hf2CO2 monolayer, and make the adsorption systems transform from physical to chemical adsorption. The three adsorption systems are potential reusable SO2 gas sensors due to the shorter recovery times. The electronic properties, charge distribution and effective mass of the three adsorption systems are further explored.