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Difficult storage of hydrogen peroxide (H 2 O 2 ), low production of reactive oxygen species (ROS), and inefficient Fe(II)/Fe(III) recycling limit the application of the Fenton-like process. Calcium peroxide (CaO 2 ) based iron oxychloride (FeOCl) system was developed for solving these deficiencies, and ciprofloxacin (CIP) was effectively degraded within 20 min treatment. 0.33 mmol/L H 2 O 2 and 2.4 mg/L dissolved oxygen (DO) were produced via CaO 2 . Quenching experiments and electron paramagnetic resonance results confirmed that hydroxyl radicals (·OH) and superoxide anion (·O 2 - ) worked as the main ROS. Density functional theory (DFT) calculations and experimental results suggested that H atoms of H 2 O 2 adsorbed on FeOCl favored the activation of H 2 O 2 into ·OH and DO into ·O 2 - , and electrophilic Cl and O coordination in FeOCl contributed to the cycle of Fe(II)/Fe(III). ·OH and·O 2 - were responsible for CIP degradation, and toxicity assessments demonstrated that the developed system reduced the hazard of treated solution. Clarity of FeOCl/CaO 2 system triple roles, including H 2 O 2 and O 2 production, activation into ROS, and Fe(II)/Fe(III) recycling, facilitates the efficient utilization of O 2 in Fenton-like system., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Construction of Z-scheme heterostructure is an effective strategy to enhance the charge carriers' separation. However, successfully achieving this on the defect heterojunction to improve the photocatalytic activity remains challenging. This work successfully obtained sulfur vacancy in the ZnIn 2 S 4 /BiOBr (SZIS/BOB) heterojunction composites with S-O covalent bonding using a hydrothermal method. As a result, they exhibited superior photocatalytic and stability performance. The optimized SZIS/BOB-10 exhibited excellent rhodamine B degradation (95.2%) and chromium (VI) reduction (97.8%) within 100 min under visible light. The enhanced composites with S-vacancies, S-O bond, and internal electric field induced the Z-scheme charge transfer mechanism. We had verified this mechanism based on the surface photovoltage spectra, electron spin response spectra, and density functional theory calculations. This work not only provides valuable insights into designing photocatalysts with a direct Z scheme heterostructure but also delineates a promising strategy for developing efficient photocatalysts to degrade organic pollutants., (Copyright © 2022 Elsevier Ltd. All rights reserved.)