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The reactive oxygen species (ROS) generated by photoinduced molecular oxygen (O 2) activation has attracted great attention in environmental remediation and pollution control. Herein, we establish a facile sulfur doping strategy that promotes the activation of molecular oxygen over BiOCl for rapid and continuous degradation of organic pollutants. In this work, we demonstrate that the significantly enhanced built-in electric field (BIEF) induced by the heterogeneous introduction of S atoms not only multiplies the electron concentration in the BiOCl matrix, but also accelerates the rapid separation/transfer of charge carriers and inhibits recombination. Driven by this, the exciton behavior in the BOC undergoes a transformation. The electrons generated through exciton dissociation activate the adsorbed O 2 on the surface into superoxide radicals (•O 2 –). Benefited from the superior O 2 activation efficiency, the degradation rate constant of ciprofloxacin (CIP) the fabricated S-doped BiOCl increased by 8.8 times, under visible light. This work proposes a strategy to promote the photocatalytic O 2 activation via tuning BIEF and manipulating excitonic effects, which affords new perspective for understanding the reaction mechanisms related to charge transfer in photocatalytic systems. [Display omitted] • S doping dramatically alter morphology and physicochemical characteristics of BiOCl. • Enhanced built-in electric field induced by S doping promotes separation and migration of charge carriers in bulk BiOCl. • Remarkable efficiency of O 2 activation is achieved over S-doped BiOCl with abundant O vacancies. • Boosted dissociation of excitons into charge carriers transforms O 2 activation behavior. • S-doped BiOCl exhibits remarkable performance toward photocatalytic degradation of CIP and various antibiotics in water. [ABSTRACT FROM AUTHOR]

[Display omitted] • An in-situ etching method is developed to construct Sn-BiOBr/BiOIO 3 heterojunction. • Sn-doping magnifies the charge transfer channels at the interface. • The charge behaviors are quantified by experiments and DFT analysis. • Photocatalytic activities for pollutants removal and CO 2 reduction are enhanced. Fabrication of heterojunction photocatalysts is a promising strategy for achieving spatial charge separation, for which the interfacial electric field is the linchpin. However, the current density of interfacial electric field still have room for enhancement. In this study, we first demonstrated the regulation of interfacial electric field between bismuth semiconductors assisted by stannum (Sn) doping, raising the surface charge transfer efficiency from 27.25 % of BiOBr/BiOIO 3 to 38.08 % of Sn-BiOBr/BiOIO 3 composite. Correspondingly, the visible-light induced degradation rates towards tetracycline, 2, 4-chlorophenol and Rhodamine B exhibited 4.2-, 4.7- and 31.5-fold increase, respectively. Meanwhile, the CO 2 photoreduction activity was also improved. The density functional theory calculation results unveiled that the Sn2+/Sn4+ redox couple could cause charge redistribution at interface and a distinctly unidirectional interfacial electric field with the direction from BiOIO 3 to Sn-BiOBr was formed. This study provides a universal strategy for the design of bismuth-containing heterojunction with tunable interfacial electric field. [ABSTRACT FROM AUTHOR]