First principles study of the effect of (Mg, C) doping and Zn vacancies on the carrier activity, lifetime, visible light effect, and oxidation–reduction reaction of ZnO(0 0 1) monolayers

Abstract

At present, some progress has been made in the study of Mg doping on the photocatalytic performance of ZnO monolayers. However, few studies on the effects of C impurities, Mg doping, and Zn vacancy coexistence on the electronic structure and photocatalytic performance of ZnO monolayers have been conducted. The preparation of ZnO through metal organic chemical vapor deposition growth technology inevitably generates C impurities, which are difficult to remove. To solve such problems, we investigated the effects of Mg doping and the coexistence of C impurities and Zn vacancies on the electronic structure and the photocatalysis of ZnO monolayers with a generalized gradient approximation plane-wave ultrasoft pseudopotential method based on the framework of density-generalized functional theory. Results showed that all doped systems had negative formation energy under O-rich conditions, indicating that the systems easily formed. The cohesion energy of Zn33CiCZnMgO36(Ci1−/2+/3+/4+,CZn2+) monolayers was relatively large, and the systems were stable. The absorption spectra of the doped systems red-shifted in a wavelength range of 425–800 nm compared with the absorption spectrum of the undoped Zn36O36 monolayer system. All doped systems were able to react with water to produce H2 and O2 at pH of 0 or 7. The Zn34CiCOMgO35 (Ci1−,CO2−) monolayer exhibited the strongest activity, the best absorption spectrum red shift, the smallest work function, the longest carrier lifetime, and the best HER ability. The Zn34CiCOMgO35 (Ci1−,CO2−) monolayer was considered a strong candidate for photocatalytic hydrogen production. Overall, this study has a theoretical reference value for the design and preparation of novel photocatalytic functional materials.