Photocatalytic hydrogen generation in the presence of glucose over ZnS-coated ZnIn 2S 4 under visible light irradiation

Abstract

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 Langmuir 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.