Investigations on caesium-incorporated rubidium tin chloride-defect perovskite nanomaterial as highly efficient ultraviolet photocatalysts

Recently perovskites-based inorganic compounds have been researched incredibly for their photocatalytic applications. In this work, rubidium tin chloride [Rb₂SnCl₆] and caesium-incorporated rubidium [(Rb_XCs_1-X)₂SnCl₆]-defect perovskites were synthesized for photocatalytic applications. This material is very useful for the degradation of dyes under UV irradiation among other photocatalysts, because of its superior properties such as nontoxicity, low cost, simple preparation methods and long-term thermal stability. The crystal structure, morphology and elemental composition of synthesized defect perovskite materials have been analysed using XRD, FESEM and EDAX mapping analysis. The UV studies reveal that the band-gap values were tuned (from 2.71 eV in Rb₂SnCl₆ to 3.78 eV in (Rb_0.5Cs_0.5)₂SnCl₆), resulting in a blue shift of the PL emission peak (from 458 to 328 nm) due to the incorporation of caesium in rubidium site. The thermal stability of (Rb_0.5Cs_0.5)₂SnCl₆ is enhanced over other synthesized defect perovskite materials because 76% of samples remained at the highest temperature of 750 °C. Synthesized defect perovskite materials were used in the photocatalytic degradation of methylene blue dye under UV light radiation. Furthermore, an excellent photocatalytic degradation is observed for (Rb_0.5Cs_0.5)₂SnCl₆ (78% to 85%) compared to other defect perovskite materials even after 120 min irradiation. The increase in photocatalytic efficiency of (Rb_0.5Cs_0.5)₂SnCl₆ is due to strong absorption of light, large separation of electron–holes pairs and the size of the nanoparticles. Also, the radical trapping experiment showed that the super oxide radicals (^.O₂⁻) and photo-generated holes (h⁺) were the predominant active species in the photocatalytic degradation of methylene blue dye process. This study concludes that the defect perovskites are the potential materials for photocatalytic application.