Preparation of SnO2-TiO2/Fly Ash Cenospheres and its Application in Phenol Degradation

SnO2–TiO2/fly ash cenospheres (FAC) were prepared via hydrothermal method and used as an active photocatalyst in a photocatalytic system. Scanning electron microscopy, X‐ray diffraction analysis, UV–Vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy and N2 adsorption–desorption measurements were used to determine the structure and optical property of SnO2–TiO2/FAC. Phenol was selected as the model substance for photocatalytic reactions to evaluate catalytic ability. Results showed that the degradation efficiency of phenol by SnO2–TiO2/FAC was 90.7% higher than that decomposed by TiO2/FAC. Increased efficiency could be due to the enhanced synergistic effect of semiconductors and FAC could provide more adsorption sites for the pollutant in the photocatalytic reaction. Furthermore, SnO2–TiO2/FAC composites exhibited excellent photocatalytic stability in four reuse cycles. Radical‐trapping experiments further revealed the dominating functions of holes in the photocatalytic reaction. Under UV light irradiation, TiO2 and SnO2 are excited. The photo‐generated electrons of TiO2 transfer from the valence band to the conduction band and then injected into the conduction band of SnO2. Thus, electrons could be trapped by the absorbed O2 to produce ·O2− on the catalyst surface and then react with phenol. The photo‐generated holes are also transferred from the valence band of SnO2 to the valence band of TiO2; this transfer induces phenol degradation. The active species would decompose phenol to the final carbon dioxide or other intermediate products.