Effect of NH3 preadsorption on SO2 adsorption on Hf2CO2 MXene

Preadsorbing suitable gas molecule on the substrate can effectively improve the adsorption strength of the system. The adsorption properties of preadsorping NH 3 on SO 2 -adsorbed Hf 2 CO 2 monolayer are explored by first-principles calculation. All possible adsorption sites are considered. SO 2 molecule cannot be adsorbed by Hf 2 CO 2 monolayer, while preadsorbing NH 3 can increase the adsorption strength of SO 2 -adsorbed Hf 2 CO 2 monolayer. The adsorption system has the direct semiconductor character and is the reusable SO 2 gas sensor because of short recovery time and the appropriate adsorption strength. Preadsorbing NH 3 can decrease the carrier mobility in conduction band , but has little impact on the carrier mobility in valence band. The charge transfer of the co-adsorption system is also investigated. • Preadsorbing NH 3 can increase the adsorption strength of SO 2 -adsorbed Hf 2 CO 2 monolayer. • The co-adsorption system can be used as reusable SO 2 gas sensor. • Preadsorbing gas molecule can decrease the carrier mobility in conduction band.