Controllable construction of a three-dimensional spherical LaFeO₃/Bi₂O₃ heterojunction with enhanced photocatalytic ability for tetracycline degradation

A novel three-dimensional spherical LaFaO₃/Bi₂O₃ heterojunction was successfully constructed through a two-step synthesis, which included a biological template method and hydrothermal synthesis. Because of the addition of different quantities of LaFaO₃, the as-prepared LaFaO₃/Bi₂O₃ composite showed different morphological structures, excitation energies, charge separation efficiencies, and degrees of photocatalytic performance. With the change in the amount of LaFaO₃ added, the morphology of the LaFaO₃/Bi₂O₃ complex changed from irregular clusters to a regular spherical structure. When the molar doping ratio of LaFaO₃/Bi₂O₃ was 1:2, it exhibited a near-perfect 3D spherical structure with external pyknotic grooves. The results of electrochemical impedance spectroscopy indicated that the 1:2 LaFeO₃/Bi₂O₃ catalyst exhibited the optimal charge separation efficiency. The bandgap of the prepared LaFaO3/Bi₂O₃ composite changed from 1.95 eV (1:2) to 2.32 eV (3:4), which were lower than that of the Bi₂O₃ template (2.81 eV). The 3D-spherical LaFaO₃/Bi₂O₃ catalyst almost completely removed 50 mg L⁻¹ of tetracycline within 90 min. Electron spin resonance and radical trapping experiments revealed that radicals were the main oxidants in the photocatalytic reaction. The construction of a 3D floral spherically structured semiconductor composite photocatalyst improved the further degradation of tetracycline. Graphical abstract: [Figure not available: see fulltext.]