Photoelectrocatalytic properties of defects (beryllium/magnesium/calcium doping, Zn vacancies, hydrogen interstitial) in ZnO monolayers determined via first-principles calculations

The first-principles method based on density functional theory was used to investigate the effect of different valence states of Zn vacancies, beryllium/magnesium/calcium doping, and hydrogen interstitial coexistence on the photocatalytic performance of the ZnO monolayer (001) using HSE06 hybrid functional calculations. Research has shown that all doped systems are stable. The stable charge states of the Zn34BeHiO36, Zn34MgHiO36, and Zn34CaHiO36 dopants are −1, 0, and +1, respectively. Compared with those of the pure ZnO monolayer, the Zn34BeHiO36 (VZn2−/1−/0), Zn34MgHiO36 (VZn2−/1−/0), and Zn34CaHiO36 (VZn2−/1−/0) systems exhibit a redshift in their absorption spectra in wavelength scale of 400–760 nm. The bandgap values of all the doped systems meet the potential requirements for generating H2 and O2. Comprehensive screening revealed that the Zn34MgHiO36 (VZn0) monolayer has the longest electron lifetime, fastest hole-to-electron separation, strongest photocatalytic reduction ability, strongest redshift of the absorption spectrum, and relatively strong carrier activity. The ΔGH* value of the Zn34MgHiO36 (VZn0) system is 0.48 eV, and the hydrogen evolution reaction has a relatively good reduction ability. The Zn34MgHiO36 (VZn0) system is a strong candidate for photocatalytic hydrogen production.