Sintering temperature effect on photocatalytic efficiencies of ZnO/TiO2 composite plates

Self-supporting ZnO/TiO2 composite plates were fabricated at a molar ratio of ZnO (wurtzite):TiO2 (anatase) = 1:1 by tape casting and lamination process. The laminated green plates were sintered in air at relatively low temperatures, ranging from 600 to 700 °C and finally characterized by TGA, BET, XRD and SEM-EDX analysis. Photocatalytic efficiencies of the plates were evaluated using a model aqueous dye solution (50 mg/L RR180). Decolorization effect of the photocatalyst plates was carried out in a laboratory scale quartz photo-reactor under UVA light irradiation. It was found that increasing sintering temperatures reduced the efficiencies of the plates. This is due not only to decrease in the surface area of the plates because of coarsening, but also to reactions between phase-pure ZnO and TiO2 leading to the formation of unwanted binary Zn2Ti3O8 and Zn2TiO4 compounds. Up to 76% color removal was successfully achieved for the plates sintered at 600 °C at the end of 90 min oxidation process.