Construction of direct Z-scheme Sn3O4/WO3 heterostructure photocatalyst for enhanced Congo red degradation and Cr(Ⅵ) reduction performance

The development of well-designed architectures is crucial in accelerating the transport of photon-generated carriers in composite photocatalysts. In this study, a direct Z-scheme Sn₃O₄/WO₃ (SW) photocatalyst was successfully fabricated utilizing a straightforward hydro/solvothermal approach, where Sn₃O₄ nanosheets (NSs) grew in-situ onto WO₃ nanorods (NRs) uniformly. The optimal SW-2 composite exhibits a remarkable reduction rate of 93.5 % for Congo Red (CR) within 40 min, with a rate constant (k) of 0.075 min⁻¹. This performance surpasses that of pristine Sn₃O₄ and WO₃, which have rate constants of 0.027 min⁻¹ and 0.018 min⁻¹, respectively. Additionally, the SW-2 composite effectively removes 89.2 % of Cr(VI) over 100 min, achieving a k value of 0.019 min⁻¹, which is higher than that of Sn₃O₄ (0.013 min⁻¹) and WO₃ (0.001 min⁻¹). Furthermore, the photocatalytic degradation performance of the recovered samples retains their photocatalytic degradation performance after five consecutive experimental cycles, indicating excellent durability. The enhanced photocatalytic performance can be attributed to the construction of a direct Z-scheme heterostructure, which not only broadens the spectral response range, bur also ensures efficient separation of photoexcited carriers and fosters robust photo-redox capacity within the composite. This study is expected to provide some valuable insights into the design and synthesis of Z-scheme heterojunction photocatalysts, aimed at addressing pressing environmental pollution challenges.