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

[Display omitted] •Cu-decorating behaviors on ZnO monolayer is studied.•Expound the sensing mechanism of Cu-ZnO monolayer upon CO and HCHO.•Explore the potential of Cu-ZnO monolayer for toxic gas detection in transformer substation. 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 TO site of the ZnO surface with the binding energy (Eb) 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 Ead 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.