Mg-doped BiOCl/BiOIO3 Z-scheme heterojunction for efficient photocatalytic degradation of antibiotics

Photocatalyst-based degradation of antibiotic pollutants is recognized as a promising strategy for wastewater treatment and solar energy conversion and utilization. The hydrothermal-ultrasound synthesized Mg-doped BiOCl/BiOIO 3 heterojunction (MBB) exhibits superior light-driven tetracycline (TC) degradation, achieving 87.69% removal in 60 min and outperforming pristine BiOCl and BiOIO 3 by 2.1- and 1.5-fold, enabled by band matching that suppresses charge recombination and improves carrier separation. Radical-trapping experiments reveal •OH and •O 2 ⁻ as the dominant reactive species responsible for TC photodegradation. Photocurrent response, electrochemical impedance spectroscopy (EIS), and fluorescence spectroscopy (PL) tests confirm that the MBB heterostructure has a faster migration rate of photogenerated carriers and a lower charge recombination rate. DFT calculations reveal that Mg doping shrinks the bandgap of BiOCl and optimizes the energy band arrangement of the heterojunction, thereby enhancing the light absorption capability. After five cycles, the MBB-0.2 (Mg-BiOCl/BiOIO 3 mass ratio 1:0.2) sample retains 76% degradation efficiency, without significant changes in phase and morphology, highlighting its stability for practical water treatment. This study attains the optimization of various photocatalysts through strategic doping and the construction of heterojunction structures, thereby maximizing the utilization rate of solar energy, providing a new research approach for the development of efficient solar conversion systems.