Z-scheme Ag₂O/ZnO heterostructure on carbon fibers for efficient photocatalysis of tetracycline

Antibiotics can be transferred from water bodies to soil environment through irrigation, and then enriched in agricultural products, causing larger scale pollution. Due to the ability of antibiotics to inhibit microbial activity, the use of traditional microbial methods is not suitable for treating wastewater containing antibiotics. In nowadays, photocatalytic technology has been widely studied to deeply mineralize low concentration water-soluble pollutants like antibiotics. However, the photocatalytic technology still faces two challenges, namely the difficulty of recovering and reusing powdered catalysts, and the insufficient activity of catalysts. In this work, we designed a Z-scheme Ag₂O/ZnO heterostructure in situ grown on large scaled carbon fiber (named CF/ZnO/Ag₂O) to enhance the efficiency of photocatalysis of tetracycline (TC) in water. The large-area carbon fiber cloth facilitates the recovery and industrial application of the catalyst, while the Z-scheme heterojunction structure significantly enhances the charge separation efficiency and catalytic performance. The results show that the interface formed by the close contact between ZnO and Ag₂O provides an effective channel for charge transfer between them. Compared with existing catalysts, the prepared Z-scheme Ag₂O/ZnO photocatalyst not only has higher activity, but also could solve the problem of easy loss and difficult recycling of powdered catalysts in water. Importantly, the efficiency for photocatalysis of tetracycline (TC) over CF/ZnO/Ag₂O is about 94.50%, and after sixth cycles, the degradation rate is still 81.32%. The catalyst grows in situ on the surface of carbon fibers and is not easily detached. The degradation pathways of TC, toxicity analysis of intermediates and mechanism of the photocatalysis over CF/ZnO/Ag₂O were explored. These characteristics make this catalyst have higher practical application potential and value, especially in improving the biodegradability of antibiotic wastewater and achieving deep purification of wastewater to improve effluent quality.