Photocatalytic decomposition of dyes using ZnO doped SnO2 nanoparticles prepared by solvothermal method

ZnO doped SnO₂ has been successfully synthesized by the solvothermal method using methanol as organic solvent. The effect of ZnO/SnO₂ molar ratios on the crystal structure, microstructure, optical and photocatalytic properties has been investigated. The synthesized samples are characterized by X-ray diffraction, transmission electron microscopy, N₂ physical adsorption, FT-IR spectroscopy and UV–Vis spectroscopy. XRD results revealed that all diffraction peaks positions agree well with the reflection of a tetragonal rutile structure of SnO₂ phase without extra peaks at 0.1ZnO:0.9SnO₂ and 0.2ZnO:0.8SnO₂ molar ratios. However, the secondary phase of ZnO at 0.3ZnO:0.7SnO₂ molar ratio was investigated. TEM images revealed that the shape of SnO₂ particles was spherical and the particle sizes of SnO₂ and 0.3ZnO:0.7SnO₂ molar ratio were 6.2 and 16.4 nm, respectively. The newly prepared samples have been tested by the determination of photocatalytic degradation of methylene blue (MB). The results indicated that Zn²⁺ doping at 0.3ZnO:0.7 SnO₂ molar ratio showed the highest photocatalytic activity for the MB photodegradation. The heightened photocatalytic activity of ZnO/SnO₂ could be ascribed to the enhanced charge separation derived from the coupling of ZnO with SnO₂ due to the potential energy differences between SnO₂ and ZnO. The recycling tests demonstrated that 0.3ZnO:0.7 SnO₂ photocatalysts were quite stable during that liquid–solid heterogeneous photocatalysis since no decrease in activity in the first four cycles was observed.