Gas-Sensing Properties of Cu2S-MoSe2 Nanosheets to NO2 and NH3 Gases.

Cu2S-MoSe2 was selected as a gas-sensing material to detect NO2 and NH3. Based on density functional theory calculations, the adsorption structures, density of states, molecular orbit, and recovery time were studied to analyze the gas-sensing mechanism of Cu2S-MoSe2 to gases. Calculation results show that Cu2S clusters receive a stable doping structure on the MoSe2 surface. Compared with intrinsic MoSe2, Cu2S-MoSe2 shows more excellent adsorption performance to NO2 and NH3 due to the active feature of the Cu2S dopant. After NO2 and NH3 adsorption, the energy gap decreases, indicating an improvement of the conductivity, which is greatly significant for gas sensing. For double NH3 adsorption, the conductivity of the entire system increases more than that of a double NO2 adsorption system, signifying the sensitivity of Cu2S-MoSe2 is greater for NH3 than NO2. The results of theoretical recovery time show that Cu2S-MoSe2 is sensitive for NH3 detection at room temperature (298 K) and NO2 detection at high temperature (400 K).