Zhengjiang Liu,Dan Zhou,Huiyan Ma,Lei Xing,Qiancheng Zhang,Juming Liu
SO 4 2− /CeO 2 /TiO 2 composite oxides are successfully fabricated via sol-gel method and impregnation process for photocatalytic H 2 production. The characterization results from XRD, FTIR and TEM revealed that the heterojunctions were formed by the formation of Ti-O-Ce bond across the SO 4 2− /CeO 2 /TiO 2 interface, which was contributed significantly to separation of photo-generated carriers. Py-FTIR spectra and XPS results indicated that Lewis acid and Brønsted acid sites were formed over the surface of SO 4 2− /CeO 2 /TiO 2 composite, which was owing to SO 4 2− coordinated to the metal on the sample surface. The induced Lewis acid sites could enhance the separation of photogenerated carriers, and Brønsted acid sites could provide protons for photocatalytic H 2 production. In addition, the Lewis acidity could facilitate the shift of conduction band minimum to a more negative value, which improves the photocatalytic H 2 production capacity of SO 4 2− /CeO 2 /TiO 2 . The results of photocatalytic H 2 production revealed that SO 4 2− /CeO 2 /TiO 2 composite exhibits superior photocatalytic activity compared to bare CeO 2 , TiO 2 and CeO 2 -TiO 2 composite. Notably, it achieves the average H 2 yield rate of 6295.2 μmol· g −1 h −1 over a period of 5 h. Combine the results of spectra analysis and photocatalytic activity H 2 evolution, it can be concluded that the synergetic effects of heterojunction structure of CeO 2 /TiO 2 composite and acid impregnation promoted the photocatalyst activity.
The novel nitrogen doped two-dimensional CeO 2 –TiO 2 nanosheets with a thickness of less than 5 nm were synthesized by a facile impregnation method using Chinese rose petals as biological templates. The detailed characterization by field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) exhibited that the CeO 2 –TiO 2 composites exactly duplicated the microstructure of Chinese rose petal and the self-owned nitrogen was successfully doped into the CeO 2 –TiO 2 composites, which could enhance the visible light absorption efficiency. UV–Vis diffuse reflection spectroscopy (DRS), photocurrent measurement (PM), electrochemical impedance spectroscopy(EIS) and photoluminescence spectroscopy (PL) were used to analyze the electrons and holes separation efficiency, which revealed that CeO 2 and TiO 2 formed well-defined hetero junctions promoting the effective separation of photogenerated electrons and holes. The photocatalytic activity of the samples was evaluated by photocatalytic degradation of dibenzothiophene (DBT) in model oil. The amount of hydrogenperoxide (H 2 O 2 ) and photocatalysts , the molar ratios of Ce and Ti in CeO 2 –TiO 2 composites as photocatalytic reaction conditions were investigated. Results showed that the removal rate of DBT could reach 93.7% under visible light irritation for 3 h, when the molar ratio of Ce/Ti was 1/1, the mass ratio of photocatalyst/DBT was 1/2 and the molar ratio of H 2 O 2 /DBT was 2/1. The trapping experiments confirmed that the photoinduced active species (•OH radical) was responsible for the degradation of DBT. Further studies demonstrated that DBT was converted to the corresponding sulfone, which could be extracted by the polar solvent. Moreover, a plausible mechanism for the photocatalytic oxidative desulfurization of this nanocomposite was proposed.
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