Cu-decorated ZnO monolayer as a promising gas sensor in dry-type transformers: A first-principles study

In this work, we explore the Cu-decorating behavior on the geometric and electronic properties of the ZnO monolayer, and expound the sensing behavior of the Cu-decorated ZnO (Cu-ZnO) monolayer as a potential resistance-type gas sensor upon CO and HCHO. Our findings indicate that the Cu dopant prefers to be trapped on the T-O site of the ZnO surface with the binding energy (E-b) of -1.08 eV, and the n-doping could be inferred for Cu-decorating on the ZnO surface, leading to the zero bandgap for the Cu-ZnO system. Besides, the chemisorption is identified for two systems with E-ad of -2.04 and -1.66 eV, respectively, and the gas adsorptions exert no impact on the metallic property of the Cu-ZnO monolayer. From the frontier molecular orbital theory, the energy gap is increased from the 1.32 eV of the Cu-ZnO system to those of 1.68 and 1.72 eV for the CO and HCHO systems, which imply the detectable changing rate in the electrical conductivity of Cu-ZnO monolayer in the environmental CO and HCHO. This work would be meaningful to explore the sensing potential of ZnO-based gas sensors for application in the field of electrical engineering.