Facet-dependent CuO/{010}BiVO4 S-scheme photocatalyst enhanced peroxymonosulfate activation for efficient norfloxacin removal

Abstract

Rapid recombination of charge carriers and sluggish Cu²⁺/Cu⁺ conversion rate in Cu-based photocatalysts hinder the improvement of the peroxymonosulfate (PMS) activation efficiency. Herein, a novel S-scheme system was successfully built through hydrothermal and in-situ calcination methods to activate PMS for norfloxacin (NOR) degradation, which combined CuO with BiVO₄ (BVO) containing surface heterojunction. The UV–vis spectra manifested that BVO displayed excellent visible light absorption performance after compounding with CuO, and the light absorption threshold of CuO/BVO was about 600 nm. Thanks to the existence of surface heterojunction in BVO, the photoinduced electrons, and holes would transfer to {010} and {110} facets, respectively. The construction of S-scheme heterojunction further facilitated the accumulation of electrons on CuO, thus realizing the spatial separation of charge carriers. In addition, the electrons gathered on the CuO expedited the Cu²⁺/Cu⁺ cycle, thereby improving the activation efficiency of PMS. On this basis, the NOR removal capacity of 5CuO/BVO composites was obviously enhanced, which was 3.65 and 2.45 times that of CuO and BVO. Moreover, the influence of ambient pH and PMS dosage on the photocatalytic performance of CuO/BVO was investigated. Through the analysis of NOR degradation pathways and degradation products, it was found that the toxicity threat of NOR to the environment was reduced during the degradation process. According to the XPS results, forming the S-scheme heterojunction accelerated the Cu²⁺/Cu⁺ redox cycle during the PMS activating process. Meanwhile, photoluminescence (PL) and time-resolved photoluminescence (TRPL) analysis demonstrated that the CuO/BVO composites exhibited eminent ability for charge separation. The possible mechanism of charge transfer was assumed by exploring reactive species and the energy band structure of catalysts. To sum up, this research provides a new perspective on boosting PMS activation to purify antibiotics in water.