Enhancing RhB photocatalytic degradation with ZnO/Sb₂MoO₆ Z-scheme photocatalyst: Evaluation of performance and mechanism

Integrating semiconductors to improve light absorption and promote efficient charge-carrier separation is widely regarded as a promising strategy for enhancing photocatalytic performance. Nevertheless, designing heterostructures that simultaneously possess optimal optical characteristics and favorable interfacial energy alignments remains a significant challenge. In this study, a Z-scheme ZnO/Sb₂MoO₆ photocatalyst was successfully fabricated via an efficient hydrothermal synthesis method and employed for photocatalytic RhB degradation for the first time. The XRD results confirmed the successful synthesis of pure bare ZnO, Sb₂MoO₆, and the ZnO/Sb₂MoO₆ composite, as evidenced by the characteristic peaks corresponding to these semiconductor materials. UV–Vis spectroscopy revealed that the nanocomposite exhibits a broader absorption range, suggesting its potential application as a visible-light-driven photocatalyst. Additionally, the composite demonstrated a smaller radius in the EIS Nyquist plot, a stronger photocurrent response, and a weaker PL emission intensity, all of which indicate reduced charge transfer resistance and more efficient separation of charge carriers. The ZnO/Sb₂MoO₆ composite demonstrated significantly enhanced and reliable photocatalytic degradation performance compared to individual ZnO and Sb₂MoO₆. Under optimal conditions (photocatalyst dosage: 1 g L^-1, dye concentration: 5 mg L^-1, and pH = 9), the composite achieved a degradation rate constant of 589.3 × 10^–4 min^-1 for RhB. The Z-scheme heterostructure enhances light absorption, effectively suppresses charge-carrier recombination, and enables the spatial separation of oxidation and reduction sites. Additionally, it preserves an optimal alignment of the valence and conduction bands, thereby sustaining the photocatalyst's robust redox activity. This study introduces an easy approach to developing photocatalysts by creating direct Z-scheme electron transfer pathways, enabling highly effective water purification.