Assessment of the superior photocatalytic properties of Sn2+-containing SnO2 microrods on the photodegradation of methyl orange

Abstract

Abstract A Sn2+-containing SnO2 material was synthesized via a simple hydrothermal route, and its characterization demonstrated that it presented a microrod morphology with rutile SnO2 crystalline structure. Sn2+ ions were detected in the interior of the material and no other impurities, such as Sn2+-containing tin oxide phases (Sn2O3, Sn3O4, SnO) were detected. The material’s optical properties have shown the absorption of a considerable fraction of visible light up to wavelengths of 671 cm-1, contrastingly to ordinary SnO2. The analysis of the internal crystalline structure of a single microrod was carried out with a Focused Ion beam microscope, confirming that the material was highly defective with strong polycrystalline nature down to the nanoscale. The results indicated that the constituent Sn2+ ions occupy intergranular sites in a rutile SnO2 mesocrystalline structure, and that Sn2+ states were responsible for the material’s superior photoactivity. The photocatalytic performance of the material was much higher than those of commercial TiO2 and SnO2 materials, and it decomposed nearly all methyl orange dye content in water (10 mg L‑1) in 6 min under UV irradiation for a photocatalyst dose of 5.33 g L‑1. The photodegradation of methyl orange was also verified under visible light.