Modification of Structural and Photocatalytic Properties of Pure and Vanadium-Doped Sol–Gel Zinc Oxide Films by Adding Graphene Oxide Dispersion

The work explores the effect of modifying thin ZnO and ZnO:V sol–gel films with graphene oxide (GO) dispersions on their structural and photocatalytic properties. The study has, for the first time, detected the effect of selective phase separation in sols, characterized by the separate crystallization of zinc and vanadium oxides upon adding GO dispersion into a mixed sol. Increasing the GO concentration in ZnO-VO2 precursor sols improves the crystallinity of the material; films of the same composition without added GO are X-ray amorphous. Conversely, adding GO to unmodified ZnO sols causes a reduction in the crystallite size of the films, which increases with higher GO content. Notably, their photocatalytic activity varies non-monotonically: at 10 wt.% GO, it is minimal, while a further increase in the GO concentration leads to its improvement. An increase in the GO concentration in ZnO:V films causes a monotonically enhanced efficiency of photocatalysis. This may be related to the improved crystallinity and the formation of a percolation cluster from reduced graphene oxide.