Engineering Z-scheme heterojunction via CuFe2O4-activated decahedral BiVO4 for tuned radical generation pathways in peroxymonosulfate activation for norfloxacin degradation

Constructing heterojunctions to activate peroxymonosulfate (PMS) addresses the challenge of poor photogenerated charge separation in individual materials, yet the effect of band alignment on reactive oxygen species (ROS) generation in composites is often overlooked. In this study, a novel Z-scheme system is successfully developed for PMS activation by integrating copper ferrite (CuFe₂O₄) with bismuth vanadate (BiVO₄) through hydrothermal and calcination methods. Notably, the production of hydroxyl radicals (HO•) and superoxide radicals (O₂⁻•) is significantly boosted by water oxidation via valence band holes of BiVO₄ and oxygen (O₂) reduction by conduction band electrons of CuFe₂O₄, respectively. Moreover, the non-radical pathways via PMS activation are enhanced by the additional active sites generated through bimetallic redox cycling of ≡Cu⁺/≡Cu²⁺ and ≡Fe²⁺/≡Fe³⁺, coupled with the formation of oxygen vacancies on the CFO/BVO surface. The CuFe₂O₄@BiVO₄/Vis/PMS system achieves 96.15 % norfloxacin (NOR) degradation efficiency within 30 min, significantly outperforming the individual CuFe₂O₄ and BiVO₄ catalysts by 6.39 and 1.38 times, respectively. In the CuFe₂O₄@BiVO₄/Vis/PMS system, the HO• content increases by 2.20 times, the O₂⁻• level by 1.49 times, and singlet oxygen (¹O₂) production by at least 3.55 times compared to the BiVO₄/Vis/PMS system. This system demonstrates excellent stability, recyclability, and broad pollutant degradation capability, offering a novel strategy for PMS activation and targeted ROS generation while advancing the design of visible-light-driven reusable photocatalysts for wastewater treatment.