Zinc-doped C4N3/BiOBr S-scheme heterostructured hollow spheres for efficient photocatalytic degradation of tetracycline

Abstract

Photocatalytic degradation of organic pollutants in water is of great significance to the sustainable development of the environment, but encounters limited efficiency when a single compound is used. Thus, there have been enormous efforts to find novel photocatalytic heterostructured composites with high performance. In this work, a novel S-scheme heterostructure is constructed with BiOBr and Zn²⁺ doped C₄N₃ (Zn–C₄N₃) by a solvothermal method for efficient photodegradation of tetracycline (TC), a residual antibiotic difficult to be removed from the aquatic environment. Thanks to Zn²⁺-doping induced improvement in chemical affinity between Zn–C₄N₃ and BiOBr, well-formed Zn–C₄N₃/BiOBr heterostructured hollow spheres are formed. This structure can efficiently suppress fast recombination of photogenerated electron–hole pairs to enhance the photocatalytic activity of BiOBr dramatically. At a room temperature of 25 °C and neutral pH 7, the catalyst can degrade a significant portion of TC pollutants within 30 min under visible light. Also, the Zn–C₄N₃/BiOBr heterostructure displays good stability after recycling experiments. Free radical capture experiments and ESR tests show that ˙O₂⁻ is the main active substance for photocatalytic degradation of TC. This study provides new insights for constructing heterostructures with an intimate interface between the two phases for photocatalytic applications.