First-Principles Study of the Gas Sensing of Benzene and Formaldehyde by Ag2O- and CuO-Modified MoSe2 Nanosheets

C6H6 and HCHO are two types of hazardous indoor gasses that seriously threaten human health. Based on first-principles calculations, Ag2O- and CuO-modified MoSe2 nanosheets were selected as gas-sensing materials to study their adsorption and sensitivity to C6H6 and HCHO. The calculation results showed that Ag2O and CuO exhibit a stable modification structure on the MoSe2 nanosheets, which improves the gas adsorption activity of the MoSe2 surface. The adsorption structure, adsorption energy, charge transfer, energy band, and density of states were analyzed based on density functional theory. Gas molecules form stable structures on the surface of Ag2O–MoSe2 nanosheets by chemical adsorption and CuO–MoSe2 nanosheets by physical adsorption. The adsorption capacity of both Ag2O and CuO-modified MoSe2 nanosheets is HCHO > C6H6, and both gas adsorption processes are exothermic and occur spontaneously. In contrast, the gas adsorption on Ag2O–MoSe2 nanosheets is more stable than that on CuO–MoSe2 nanosheets.