Unveiling the photocorrosion mechanism of zinc oxide photocatalyst: Interplay between surface corrosion and regeneration

Photocorrosion of a photocatalyst's surface, leading to degradation of its catalytic efficiency/cyclability, is a major concern which must be tackled for designing efficient processes. Despite that the photocorrosion of ZnO has been widely explored, a deep understanding of the mechanism involved is still elusive. Here, a detailed investigation of the photocorrosion mechanism is presented. Controlled UV treatment of ZnO dispersions took place in the absence of pollutants. Employing advanced characterization techniques, we have elucidated the intricate pathways through which the photocorrosion takes place. Successive photocatalytic MB degradation cycles were performed using untreated ZnO nanocrystals to assess their photostability and reusability. It is shown that UV treatment up to 4 h, deteriorates the ZnO crystal which in turn diminishes its photocatalytic activity. For prolonged irradiation up to 8 h, an effective regeneration of the ZnO lattice takes place, reverting the photocatalytic activity to pristine levels. Understanding the photocorrosion mechanism could constitute the key in fabricating large-scale reusable photocatalysts that can be regenerated by UV light.