Spray-drying synthesis of Bi₂O₃/BiVO₄ composites with thin carbon coating for high performance photocatalytic degradation of organic pollutant

Background: To achieve efficient solar-to-chemical energy conversion in photocatalysis, it is crucial to develop visible-light-driven catalysts with excellent charge transport properties and superior activity. Methods: Here, p-n heterostructured Bi₂O₃/BiVO₄ (BO/BVO) composites were synthesized via a spray-drying method, incorporating synergistic effects of oxygen vacancies and asphaltene-derived carbon coating. Significant findings: The built-in electric field at the p−type BO and n-type BVO interface, combined with the electron sink effect of the coated graphitic carbon layer, enhances charge transfer while suppressing charge recombination. As a result, the carbon coated BO/BVO (C-BO/BVO) heterojunction reveals markedly improved efficiency for photodegradation of methylene blue (MB) in comparison with pure BO and BVO. Under visible light irradiation, the C-BO/BVO composite achieves an MB decomposition efficiency of 92.1 %, which is approximately 1.78, 2.23, and 2.98 times higher than that of BO/BVO, pure BVO, and pure BO, respectively. As a result, the C-BO/BVO composites exhibit superior degradation performance for MB and tetracycline (TC), achieving high rate constants of 6.51 × 10⁻² min⁻¹ and 7.55 × 10⁻³ min⁻¹, respectively. The C-BO/BVO photocatalysts also exhibit exceptional antibacterial activity against Escherichia coli (E. coli). Additionally, their biocompatibility has been assessed using an in vivo zebrafish embryo model, highlighting their potential for future biomedical applications.