A S-scheme heterojunction Fe-doped TiO2/SnO2 with rich oxygen vacancies for photo-Fenton degradation of Rhodamine B under visible light illumination

The photo-Fenton process serves as a highly efficient approach for removing contaminants from wastewater. In this study, we developed a Fe-doped TiO2/SnO2 heterojunction catalyst to enhance the efficiency of photo -Fenton catalytic activity under visible light. To investigate the physical properties of the catalysts, various characterization techniques were utilized, including XRD, SEM, TEM, HR-TEM, UV-VIS, PL, and XPS. The 7% mol Fe-doped TiO2/SnO2-OVs (TFS-7) heterostructure exhibited the highest rate constant of 17.03 x 10-3 min-1; 8.4 and 2.1 times higher than the individual components. This enhanced performance is mainly attributed to the rapid migration of photoinduced electrons to Fe3+ and the subsequent generation of Fe2+, which improved electron transfer capacity and facilitated the rapid production of hydroxyl radicals (center dot OH) through the reaction between Fe2+ and H2O2. We proposed a S-scheme mechanism for the Fe-doped TiO2/SnO2-OVs catalyst based on the analysis of reactive species trapping experiments, photoluminescence (PL) spectra, ultraviolet photoelectron spectroscopy (UPS), and density functional theory (DFT). These findings offer not only a straightforward approach for synthesizing highly active photocatalysts for the degradation of RhB dye, but also a framework for the construction of heterostructure photocatalysts.