Enhancing the Built-in Electric Field in Oxygen Vacancies-Enriched I-Doped Bi₃O₄Cl for Visible Light-Driven Photocatalytic Oxidation

In semiconductor catalysts, rational doping of nonmetallic elements holds significant scientific and technological importance for enhancing photocatalytic performance. Here, using a one-step hydrothermal technique, we synthesized iodine-doped Bi₃O₄Cl composite and evaluated the impact of iodine doping on its photocatalytic capability for organic dye degradation under visible light irradiation. In this study, we demonstrate that the introduction of iodide ions not only provides an ideal built-in electric field (BIEF) for Bi₃O₄Cl but also induces the generation of additional oxygen vacancies (OVs). The significantly enhanced BIEF, along with the collaborative effect of the OVs-induced narrow bandgap in Bi₃O₄Cl, effectively promotes the separation and transfer efficiency of photogenerated charges while suppressing recombination. Under this driving force, photogenerated electrons transfer to the surface OVs, facilitating the activation of surface oxygen, thereby forming highly active superoxide radicals (^•O₂). Simultaneously, oxygen vacancy engineering can reduce the reaction energy barrier, thereby facilitating the formation of singlet oxygen (¹O₂), which contributes significantly to photocatalytic processes. The results indicate that under visible light, the prepared iodine-doped Bi₃O₄Cl exhibits a 6.5-fold increase in the degradation rate constant for rhodamine B and demonstrates enhanced photocatalytic activity toward methyl orange and methylene blue. This study not only provides strong references for optimizing structural design to enhance photocatalytic performance but also offers profound insights into the synergistic effects of BIEF and OVs on charge transfer mechanisms in photocatalytic systems.