Adsorption and sensing of CO and C2H2 by S-defected SnS2 monolayer for DGA in transformer oil: A DFT study

Chalcogen vacancies in transition metal dichalcogenides (TMDs) play an important role to tune the electronic property of the whole system. In this work, we using density functional theory studied the S-defected behavior on the SnS2 monolayer and related adsorption and sensing performances upon CO and C2H2 to explore the potential of S-defected SnS2 monolayer for DGA in transformer oil. Results indicated that S-vacancy could lead to strong ndoping for the pristine SnS2, which largely sways its electronic structure by inducing several novel states around the Fermi level. The vac-SnS2 performs desirable adsorption behavior towards two molecules, and gas adsorption in the S-vacancy can result in remarkable changes in the electronic property of vac-SnS2, including the greatly increased bandgap in C2H2 system while decreased bandgap in CO system, as well as the obviously raised work function. Based on these changes, we identified that vac-SnS(2 )monolayer could be a promising resistance-type sensing material for selective detection of CO and C2H2 in high electrical response. Our work would be meaningful to expound the S-vacancy behavior in SnS2 surface and to give a first insight into the exploration of vac-SnS(2 )monolayer as a new member of chemical resistance-type gas sensor to detect toxic gases.