Synthesis, Characterization And Photocatalysis Of SnO₂-Based Composites

SnO2 as a semiconductor has attracted considerable attention because of its geen synthesis, stable physicochemical properties as well as outstanding electrical and optical properties. These excellent properties offer it a wide range of applications in Li lion batteries, gas sensors, solar cells and photocatalysis fields.Using SiO2/SnO2 as precursor, the SiO2/SnO2/SnO2/Sn2+ composites with different Sn2+-doped ratio were prapered by self-doping method. The structures, compositions and morphologies of samples were characterized by X-ray diffraction (XRD), high transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectroscopy (Uv-vis). It was found that two layers of SnO2 and SnO2:Sn2+ nanocrystals with thickness of 13 nm and 8 nm were coated on SiO2 spheres showing monodispersed feature. The methyl orange (MO) was used as a model reaction to evaluate the photocatalytic performance of samples. As a result, the product with Sn2+-doped ratio of 50% exhibited the best photocatalytic activity, which could completely degrade the MO solution in 90min under vible light irradiation. Furthermore, the band gabs and lattice defects of SiO2/SnO2/SnO2/Sn2+composites could be regulated through changing the Sn2+-doped ratio.The p-n heterojunction BiOCl/SnO2 composites were synthesized through compounding of two wide-gab semiconductors, including n-type SnO2 and p-type BiOCl. The structures and properties were characterized by a range of techniques, including XRD, TEM, Uv-vis, Brunauer-Emmett-Teller (BET), XPS, photoluminescence spectroscopy (PL), surface photovoltage spectroscopy (SPC) and Mott-Schottky measurement (Mott-Schottky). The results indicated that SnO2 nanoparticles were uniformly dispersed on the facets of BiOCl, and the p-n heterojunction was formed at the interface. The photocatalytic activities of products were evaluated by decomposing rhodamine B (RhB) under visible light illumination. As a consequence, the sample with the mass ratio of BiOCl and SnO2 being 0.5 showed the best photocatalytic performance. Moreover, the enhanced photocatalytic properties of BiOCl/SnO2 were probably attributed to the formation of defect band energies and p-n heterojunction.The composites of SiO2/Ag/SnO2 and SiO2/SnO2/Ag were synthesized using SiO2 nanospheres as cores. The structures and morphologies of samples were identified by XRD, TEM, Uv-vis and scanning electron microscopy (SEM). Rhodamine B (RhB) was used to test the photocatalytic properties of the synthesized products. The results displayed that Si02/Ag/SnO2 exhibited the better catalytic performance than SiO2/SnO2/Ag, which could completely degrade RhB in 30min under UV light irradation. The surface plasmon resonance and the protective effect of SnO2 against Ag contributed to the higher catalytic activity of SiO2/Ag/SnO2. On the other hand, the catalyst SiO2/Ag/SnO2 showed excellent reusability, which catalytic efficiency could reach 90% even after 5 cycles.The photocatalytic activities of SnO2-based composites had been significantly improved through doping Sn2+, compounding BiOCl and loading Ag particles. This investigation could not only provide the technical basis for synthesizing related composites, but also offer the theoretical support for exploring SnO2 applications in more fields.