Tuning the catalytic performance of CaSnO₃ by developing an S-scheme p-n heterojunction through Ag₆Si₂O₇ doping

Perovskites, especially alkaline earth stannates, have drawn enormous interest from the research community owing to their low chemical toxicity, environmental friendliness, excellent optical properties, and good thermal and chemical stabilities. However, poor conductivity, intense carrier recombination, and low absorption in the visible range prevent them from being practical. Herein, we took calcium tin oxide (CaSnO₃) as the target material and improved its photocatalytic performance by introducing different ratios of silver silicate (Ag₆Si₂O₇). The constitution of the heterostructure in CaSnO₃/Ag₆Si₂O₇ not only improved the separation of carriers but also promoted the absorption in the visible region owing to a reduction in the optical bandgap. The presence of Ag₆Si₂O₇ in the composite catalyst improved the conductivity and thereby helped carriers carry most of the energy to the surface of the catalyst. When the Ag₆Si₂O₇/CaSnO₃-H catalyst was tested against RhB degradation, it achieved a degradation efficiency of 95.24% in 60 minutes whilst showing a degradation rate constant of 0.04971 min⁻¹ which is 24.48 times greater than its counterparts. The quenching experiments showed that holes and OH radicals play a crucial role during the degradation process. The employed catalyst retained excellent recycling ability up to four cycles suggesting its excellent practicality in the field of catalysts. The facile and environmentally sustainable approach used for synthesizing Ag₆Si₂O₇/CaSnO₃ hybrids could be of great importance in the field of visible-light-driven catalysts and their subsequent applications.