Zinc oxide (ZnO) nanomaterials have attracted widespread attention from researchers due to their morphology-dependent properties, eco-friendly characteristics, and potential as a sustainable photocatalyst with a broad range of applications. Therefore, in this study, three different ZnO nanostructures—nanosheets (NSs), nanoflowers (NFs), and nanorods (NBs)—were synthesized via a controlled precipitation method. Among these, NFs exhibited the highest photocatalytic efficiency. The obtained samples exhibited broad optical absorption edges extending into the visible region (corresponding to apparent energies of 1.81–2.09 eV), which is attributed to the sub-bandgap states induced by oxygen vacancies rather than intrinsic bandgap narrowing—far lower than the bandgap of bulk ZnO (3.37 eV). Their photocatalytic performance was evaluated by the degradation of Methyl Blue (MB), Methyl Orange (MO), and Rhodamine B (RhB) under UV or sunlight. Notably, the NFs achieved rapid degradation of MB and RhB within 90 min under UV irradiation without the addition of any H2O2, demonstrating their effectiveness and cost-effectiveness for practical applications. Although H2O2 inhibited the degradation of MB and RhB, it promoted the decomposition of MO. Furthermore, the ZnO NFs exhibited excellent recyclability in five consecutive degradation cycles. The self-synthesized ZnO nanomaterials in this study, with their broad-spectrum absorption, high stability, and eco-friendly properties, demonstrate their potential as an efficient and low-cost photocatalyst for large-scale wastewater treatment.
Zhou et al. (Tue,) studied this question.