Photocatalytic hydrogen generation in the presence of glucose over ZnS-coated ZnIn_2S_4 under visible light irradiation

摘要

ZnS coated ZnIn_2S_4 (ZnS-ZnIn_2S_4) photocatalysts were prepared in methanol by a facile solvothermal process. The photocatalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), UV-Vis diffusive reflectance spectroscopy (DRS), BET, and electrochemistry measurements. ZnS-ZnIn_2S_4 photocatalysts have hexagonal crystal phase and complex morphology such as micro-spheres, micro-tubes and micro-ribbons. Using glucose as an electron donor, photocatalytic hydrogen generation over Pt/ZnS-ZnIn_2S_4 was investigated. The results show that photoactivity of hydrogen generation over Pt/ZnS-ZnIn_2S_4 was improved notably with simultaneous degradation of glucose. The factors which affect photocatalytic hydrogen generation, such as composition of ZnS-ZnIn_2S_4, initial concentration of glucose and concentration of NaOH, were investigated. The prepared ZnS-ZnIn_2S_4 photocatalysts exhibit better activity for hydrogen generation than pure ZnIn_2S_4, which may be attributed to enhancement of the adsorption of glucose by ZnS on the ZnIn_2S_4 surface. The effect of glucose concentration on the hydrogen generation rate is consistent with a Lang-muir model. The basic condition is favorable for the photocatalytic hydrogen generation. A large number of · OH radicals generated in ZnS-ZnIn_2S_4 system, have been tested by a TA-FL (terephthalic acid-fluorescence) method. A possible mechanism was discussed.