CuBi₂O₄/Bi₂MoO₆ heterojunction photocatalyst for degradation of tetracycline and rhodamine B: preparation, characterization, and mechanism study

The efficiency of photocatalysts has historically been constrained by the suboptimal utilization of solar energy and the swift recombination of photogenerated charge carriers. To address this challenge, in situ growth of Bi₂MoO₆ nanosheets on CuBi₂O₄ surfaces to create a heterostructure has shown promising results. Our research focused on evaluating the degradation efficiency of pollutants by varying the proportions of CuBi₂O₄ and Bi₂MoO₆. The experiments determined that the 0.2CuBi₂O₄/Bi₂MoO₆ mixture exhibited the highest degradation efficiency. During the degradation of tetracycline and rhodamine B, the 0.2CuBi₂O₄/Bi₂MoO₆ composites achieved more than 90% effectiveness, significantly surpassing the efficiency of standalone CuBi₂O₄ and Bi₂MoO₆. This enhanced performance is primarily attributed to the heterojunction composition, which improves the migration efficiency of photon-generated carriers. In the degradation process, the most active species was identified as ^·O₂⁻, with h⁺ playing a supporting role. The 0.2CuBi₂O₄/Bi₂MoO₆ composites also demonstrated effective degradation in mixed solutions of TC and RhB. The material maintained its excellent degradation capability even after five degradation cycles, indicating its high stability. To elucidate the underlying mechanism of the CuBi₂O₄/Bi₂MoO₆ pn heterojunction photocatalyst, we conducted a comprehensive analysis using an energy band structure, free radical trapping, and electron spin resonance experiments. In addition, the degradation pathways and intermediates of TC were studied by LC–MS.