Role of Cu Doping in SnO2 Sensing Properties Toward H2S

Adsorption properties of H 2 S on SnO 2 (110) surface and effects of Cu-doping on SnO 2 sensitivity toward H 2 S have been studied by means of the first-principles calculations based on the density functional theory. It has been found that H 2 S is dissociatively adsorbed on the SnO 2 (110) surface with one H atom converged to a bridging oxygen atom while the complex HS is bonded to a five-fold coordinated Sn atom. H 2 S adsorption has no change on the electrical conductivity of SnO 2, which indicates that SnO 2 has weak sensitivity toward H 2 S. Cu tends to be doped close to the surface region and prefers the five-fold coordinated Sn site. Cu-doping can directly improve the sensitivity of SnO 2 toward H 2 S because of the increase in surface electrical conductivity. In addition, Cu-doping can greatly improve the formation of surface oxygen vacancies in SnO 2, and the formation energy is in relation to Cu depth from surface. Molecular O 2 can be exothermically adsorbed on the reduced SnO 2 surface, which also underlies the mechanism of enhanced SnO 2 sensitivity toward H 2 S due to Cu-doping.