2D/2D SnOx/TiO2 Z-scheme heterojunction with oxygen vacancies for boosted photocatalytic performance and mechanistic insight

A Z-Scheme heterojunction two-dimensional/two-dimensional (2D/2D) SnOx/TiO2 photocatalyst modified with oxygen vacancies (OVs) was successfully prepared using a hydrothermal method. Compared with SnOx and TiO2, the optimized SnOx/TiO2 heterojunction exhibited significantly higher photocatalytic activity for degrading methyl orange (MO). The apparent reaction rate of the SnOx/TiO2 heterostructure under visible light illumination reached 1.8355 min-1, approximately 15.74 times higher than that of SnOx alone. The results confirmed the presence of abundant oxygen vacancies on SnOx/TiO2, which acted as electron traps accelerating electron transfer. Furthermore, analyses including UPS, ESR, and reactive active species trapping experiments indicating a Z-scheme heterojunction were presented between SnOx and TiO2. According to density functional theory (DFT) calculations, the energy bands' alignment enabled the Z-scheme heterojunction formation, while the inherent electric field drove the reaction. The experimental and computational findings demonstrated that the combined influence of the Z-Scheme heterojunction and OVs enhanced the photocatalytic reaction mechanism, facilitating efficient electron transport and preserving charge carriers with excellent redox capability. And a possible mechanism degradation pathway of MO dye is proposed. This study serves as a source of inspiration for future endeavors in the design and development of Z-Scheme heterojunction photocatalysts incorporating oxygen vacancies, with the aim of achieving enhanced efficiency in environmental remediation processes.