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 (Ov)-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.