Effects of Vacancy Defects and the Adsorption of Toxic Gas Molecules on Electronic, Magnetic, and Adsorptive Properties of g-ZnO: A First-Principles Study

Using first principles based on density functional theory (DFT), the CO, NH3, NO, and NO2 gas adsorbed on intrinsic Graphite-like ZnO (g-ZnO) and vacancy-deficient g-ZnO were systematically studied. For intrinsic g-ZnO, the adsorption energy of NH3, NO, and NO2 adsorption defective g-ZnO systems increased significantly due to the introduction of Zn vacancy (V-Zn). Especially, for NH3, NO, and NO2 adsorbed Zn-vacancy g-ZnO (V-Zn/g-ZnO) systems increased to 1.366 eV, 2.540 eV and 2.532 eV, respectively. In addition, with the introduction of vacancies, the adsorption height of the gases adsorbed on V-Zn/g-ZnO system is significantly reduced, especially the adsorption height of the NH3 adsorbed on V-Zn/g-ZnO system is reduced to 0.686 angstrom. It is worth mentioning that the introduction of O-vacancy (V-O) significantly enhances the charge transfer between NO or NO2 and V-O/g-ZnO. This suggest that the defective g-ZnO is more suitable for detecting NH3, NO and NO2 gas. It is interesting to note that the adsorption of NO and NO2 gases gives rise to magnetic moments of 1 mu(B) and 0.858 mu(B) for g-ZnO, and 1 mu(B) and 1 mu(B) for V-O/g-ZnO. In addition, V-Zn induced 1.996 mu(B) magnetic moments for intrinsic g-ZnO, and the CO, NH3, NO and NO2 change the magnetic of V-Zn/g-ZnO. The adsorption of NO2 causes the intrinsic g-ZnO to exhibit metallic properties, while the adsorption of NH3 gas molecules causes V-Zn/g-ZnO also to show metallic properties. The adsorption of NO and NO2 causes V-Zn/g-ZnO to display semi-metallic properties. These results facilitate the enrichment of defect detection means and the design of gas detection devices.

Automated summary

In this study, the adsorption of CO, NH3, NO, and NO2 gases on intrinsic and vacancy-deficient Graphite-like ZnO (g-ZnO) was systematically investigated using density functional theory (DFT). The results showed that the introduction of Zn vacancy (V-Zn) significantly increased the adsorption energy of NH3, NO, and NO2 on defective g-ZnO. Furthermore, vacancies also reduced the adsorption height of the gases on V-Zn/g-ZnO. These findings contribute to the enrichment of defect detection methods and the design of gas detection devices.