| In recent years, energy crisis and environmental pollution problems caused by fossil fuel combustion is always forcing people to seek alternative candidates of fossil fuel energy and feasible methods to control environmental pollution in order to achieve sustainable development in the future. Among different kinds of feasible schemes, profit from its unique mechanism of action, photocatalytic technology can play an important role both in solving the problem of energy crisis and environmental pollution control,which becomes one of the most promising high-tech in 21 th century. Photocatalytic performance is depends on the properties of semiconductor catalysts, so it is significance to development a novel catalyst with the properties of high efficiency,stable, multiple purposes and low cost. This thesis selected chalcogenide compounds,narrow band gap semiconductor as the research material, and improved the photocatalytic activity by modification.Graphene like Mo S2 is layered semiconductor, the more the layers, and the worse photocatalytic activity, Thus the preparation of single or few layer Mo S2 is the key to expand the application in the field of photocatalysis. This thesis explored a mixed solvent refluxing method to exfoliated bulk Mo S2 and a series of Mo S2 nanosheets were prepared, Through the photocatalytic hydrogen production rate test, the optimum conditions for preparation of Mo S2 nanosheets with highly photocatalytic activity was determined, that is refluxing in 30% ethanol-water solution under 80℃ for 3 h, Mo S2 nanosheets prepared by this method was then characterized by X ray powder diffraction(XRD), electron microscopy(FESEM, TEM, HRTEM), UV-vis diffuse reflectance spectroscopy(DRS), Raman spectroscopy, photocurrent and atomic force microscope(AFM) test. The results showed that bulk Mo S2 was successfully exfoliated by the method of mixed solvent refluxing treatment and the photocatalytic hydrogen production rate of exfoliated Mo S2 nanosheets has reached more than 8 times higher than bulk Mo S2.Cd S is a common visible light induced photocatalytic hydrogen production material. The combination with wide band gap semiconductor for the construction of heterojunction can not only improve the photocatalytic activity of the composite but also improve the stability of Cd S in a certain extent. This thesis selected Zn ions doping Sr2Nb2O7 and then combined with Cd S to prepared Cd S/Sr2(Nb17/18Zn1/18)2O7-δcomposite photocatalyst. The photocatalyst was then characterized by XRD powderdiffraction, FESEM, TEM, UV-vis diffuse reflectance, XPS, electrochemical and fluorescence spectra. The results showed that the doping of Zn and loading of Cd S does not change the crystal structure of the fertile material and improved the ability of light absorption in different extent. In addition, Cd S and Sr2(Nb17/18Zn1/18)2O7-δ combined closely and formed heterojunction structure. The results of photocatalytic hydrogen production rate test showed that the doping of Zn ion and the loading of Cd S can effectively improve the hydrogen production rate of materials. Among the photocatalysts, 30% Cd S/Sr2(Nb17/18Zn1/18)2O7-δ composite has the highest photocatalysis activity with a hydrogen production rate of 1669.1 mol/g·h. The results of contrast experiment with physical mixed 30% Cd S + Sr2(Nb17/18Zn1/18)2O7-δ validated Cd S and Sr2(Nb17/18Zn1/18)2O7-δ formed heterojunction effectively one more time. The results of photocatalytic oxidation of As(III) showed that, under the condition of p H = 9~ 11, 30% Cd S/Sr2(Nb17/18Zn1/18)2O7-δ composite photocatalyst can totally oxidized 10mg/L As(III) solution to As(V) in 20 min. And the results of mechanism experimental showed that, the main active species of photocatalytic oxidation of As(III) by 30%Cd S/Sr2(Nb17/18Zn1/18)2O7-δ composite photocatalyst is superoxide radical(·O2-). |
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