Structural factors influencing photocatalytic and photoelectrochemical performance of low-dimensional ZnO nanostructures

In this study, low dimensional ZnO nanostructures at three levels of complexity (primary polycrystalline, secondary nanowires, and tertiary nanodendrites) were consecutively synthesized on FTO glass substrates, and the impact of their structure and morphology on photocatalysis and photoelectrochemical (PEC) properties was explored. XRD, SEM, and Raman corroborated with PL and UV–vis measurements revealed nanocrystallite wurtzite building blocks with shape anisotropy and defect concentration increasing with the level of complexity. Four estrogenic hormones, i.e., estrone (E1), estradiol (E2), ethinylestradiol (EE2), and estriol (E3), were evaluated as model endocrine disruptors to assess the relative photodegradation of each hormone. The same trend was observed for PEC water-splitting performance of these materials as photoanodes under AM 1.5 G illumination. On the contrary, the performance on photodegradation of diclofenac as a model drug and resazurin ink discoloration test revealed superiority of the polycrystalline sample followed by the nanodendrites sample. These reductive photocatalytic pathway processes are likely to be governed by the interfacial charge transfer efficiency at the solution/catalyst boundary, while the other factors may have more intriguing roles associated with the relatively weak reduction potential of ZnO in comparison to its large oxidation potential with respect to water splitting.