Construction of Dual-Defective Al2O3/Bi12O17Cl2 Heterojunctions for Enhanced Photocatalytic Molecular Oxygen Activation via Defect Coupling and Charge Separation

Adjusting the surface/interface of photocatalysts to promote molecular oxygen activation is a valid way to ameliorate photocatalytic performance. In this work, dual-defective Al2O3/Bi12O17Cl2 heterostructured photocatalysts are in situ constructed using the ionic liquid self-combustion method. The electron paramagnetic resonance (EPR) test confirms the existence of oxygen vacancies in both Al2O3 and Bi12O17Cl2, and there is defect coupling enhancement effect after their combination. X-ray photoelectron spectroscopy (XPS) further reveals defect signals of AlOx and oxygen vacancies. The O2-temperature-programmed desorption (TPD) experiment shows that defective Al2O3 greatly enhances the adsorption of molecular oxygen. Moreover, diffuse reflectance spectrum (DRS), electrochemical tests, and Kelvin probes are implemented to confirm that the introduction of Al2O3 into Bi12O17Cl2 not only significantly enhances the separation efficiency as an active support but also promotes the defect amounts and molecular oxygen adsorption. Moreover, 1.75 Al2O3/Bi12O17Cl2 (molar ratio of A12O3 to Bi12O17Cl2 is 1.75) exhibits the highest photocatalytic oxidation capability, and its degradation performance for tetracycline hydrochloride is 1.49 times that of Bi12O17Cl2. This work reports the one-step synthesis of Al2O3 and Bi12O17Cl2 with oxygen vacancies, discovers the synergetic enhancement of defects, and reveals the dual-functional roles of defective Al2O3 in strengthening molecular oxygen adsorption and charge separation.