Visible-light-active ZnO via oxygen vacancy manipulation for efficient formaldehyde photodegradation

We developed a facile method for the synthesis of visible light responsive ZnO through the introduction of different concentrations of oxygen vacancy for efficient formaldehyde photodegradation under visible light irradiation. The visible light active ZnO was prepared using ZnO2 instead of traditional Zn(OH)2 as a precursor. According to the results of Raman and XPS, the concentrations of oxygen vacancy decreased with the increase of annealing temperatures. The effects of different concentrations of oxygen vacancy on the electronic structure of ZnO were investigated by density functional theory (DFT) simulation and the results were confirmed by UV-VIS spectra, which showed the oxygen vacancy narrowed the band gap of ZnO. ZnO with stable concentration of oxygen vacancy was used for formaldehyde photodegradation. The results of photocatalytic experiments reflected that oxygen vacancy can not only act as impurity levels in the band structure of ZnO but can also work as electron traps to accept the photogenerated electrons. The oxygen vacancy in ZnO effectively prohibited the recombination of electron-hole pairs, enhancing the photocatalytic activity of ZnO. The results of our study provide us useful information for the understanding of the mechanisms of the photocatalytic process of ZnO with oxygen vacancy.