Abstract
ZnO/TiO 2/SnO 2 mixture was prepared by mixing its component solid oxides ZnO, TiO 2 and SnO 2 in the molar ratio of 4ː1ː1, followed by calcining the solid mixture at 200–1300 °C. The products and solid-state reaction process during the calcinations were characterized with powder X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) and Brunauer–Emmett–Teller measurement of specific surface area. Neither solid-state reaction nor change of crystal phase composition took place among the ZnO, TiO 2 and SnO 2 powders on the calcinations up to 600 °C. However, formation of the inverse spinel Zn 2TiO 4 and Zn 2SnO 4 was detected at 700–900 and 1100–1200 °C, respectively. Further increase of the calcination temperature enabled the mixture to form a single-phase solid solution Zn 2Ti 0.5Sn 0.5O 4 with an inverse spinel structure in the space group of O h 7 - Fd 3 m . The ZnO/TiO 2/SnO 2 mixture was photocatalytically active for the degradation of methyl orange in water; its photocatalytic mass activity was 16.4 times that of SnO 2, 2.0 times that of TiO 2, and 0.92 times that of ZnO after calcination at 500 °C for 2 h. But, the mass activity of the mixture decreased with increasing the calcination temperature at above 700 °C because of the formation of the photoinactive Zn 2TiO 4, Zn 2SnO 4 and Zn 2Ti 0.5Sn 0.5O 4. The sample became completely inert for the photocatalysis after prolonged calcination at 1300 °C (42 h), since all of the active component oxides were reacted to form the solid solution Zn 2Ti 0.5Sn 0.5O 4 with no photocatalytic activity.
Published Version
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