Molten Salt Synthesis of Oxygen-Deficiency-Rich ZnO on Carbon Cloth for Efficient Photocatalytic Degradation of Antibiotics

Semiconductor-based photocatalysis using TiO₂, ZnO, and related materials offers a promising solution for efficient wastewater treatment through light-assisted advanced oxidation processes. In this study, oxygen vacancy (O_v)-rich ZnO micrometer-sized particles (ca. 0.5 μm) are grown on a conductive carbon cloth via a one-step molten salt method. The effects of different coordinating anions added into the molten salt on the morphological characteristics of the resultant ZnO crystallites are studied. The optimized photocatalyst (CC@ZnO-3 min) achieves near-complete degradation of 20 ppm ofloxacin within 2 h under UV irradiation and in the presence of 5 mM KHSO₅ (PMS). In the absence of PMS, it removes 26% of total organic carbon (TOC) after 8 h─a 6-fold improvement over commercial ZnO with an average particle size of ca. 0.2 μm, which is also immobilized on carbon cloth with a similar loading mass of ca. 7.0 mg·cm^-2. Radical trapping experiments reveal that superoxide (·O₂^-) and holes play dominant roles in the degradation process. The engineered oxygen vacancies not only enhance charge carrier separation but also significantly improve electron transfer efficiency. This work presents a strategy for developing high-efficiency photocatalysts to address pharmaceutical pollution.