| Energy crisis and environmental pllution are two most serious issues that the world has to face at the present. The traditional non-renewable energy, as the main energy, not only results in serious environmental pollution while using, but also runs out in the foreseeable future because of the nonrenewable characteristics. As the most ideal clean energy, the development and use of hydrogen energy have been arousing great concern of many governments and researchers. H2 production from water splitting by decomposition of TiO2 electrodes under near UV radiation was reported by Fujishima and Honda In 1972, and the corresponding results were published in Nature. Photocatalytic water-splitting for hydrogen production using solar light has been considered as one of the optimal solutions for hydrogen production in this paper. Since then, semiconductor photocatalytic water-splitting for hydrogen production has been widely developed by many researchers. Up-conversion luminescence materials are being researched more due to their excellent chemical stability and thermal stability. However, the catalytic activity of these kind of materials in catalysis and hydrogen production still needs improvement.In recent years, our group has worked on the research about photocatalytic water-splitting for hydrogen production using composite catalyst, which consists of TiO2 and up-conversion luminescence materials. The results showed that the catalytic activity of the composite catalyst was obviously improved, chiefly because up-conversion luminescence materials could transform visible light into UV light, by which TiO2 can be excited. However, the relatively high reduction potential of TiO2 leads to lower photocatalytic reaction rate. Wide band-gap semiconductor with lower reduction potential, instead of TiO2, were chosen as the catalysis, and photocatalytic water-splitting for hydrogen production was developed by using the composite catalyst, which consisted of the wide band-gap semiconductor mentioned above and up-conversion luminescence materials. Besides, to resolve the problems about hard separation and hard recycle for the photocatalysis, the composite catalysis in a thin film was fixed on the substrate to take part in the catalytic process. The study includes the following contents:1. Photocatalysts Er:YAG/MoSe2-KTaO3 were successfully prepared by hydrothermal synthesis and ultrasonic dispersion methods, while KTaO3 nanoparticles were synthesized by hydrothermal method, and the up-conversion luminescence agent Er:YAG was synthesized by sol-gel and calcination methods. These new synthetic materials were characterized by the x-ray powder diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscopy (TEM), Uv-vis absorption spectroscopy (Uv-vis) and photoluminescence spectroscopy (PL) and so on, respectively. Firstly, the photocatalytic activity of Er:YAG/MoSe2-KTaO3 was examined through photocatalytic hydrogen evolution in aqueous methanol solution under visible-light irradiation. Besides, the influence factors such as mass ratio between Er:YAG and KTaO3, heat-treated temperature and initial pH value of solution, on the visible-light photocatalytic hydrogen evolution activity of Er:YAG/MoSe2-KTaO3 were also studied.2. Four corresponding photocatalysts Er:YAG/Pt-RuO/KTaO3 were successfully prepared by sol-gel, impregnation and hydrothermal methods. The properties of Er:YAG/Pt-RuO2/KTaO3 were characterized by XRD, SEM, TEM, and so on, the photocatalytic hydrogen evolution activity of Er:YAG/Pt-RuO2/KTaO3 were also studied. At the same time, the influence factors on the photocatalytic hydrogen evolution activity of Er:YAG/Pt-RuO2/KTaO3 were also studied.3. The nano-sized photocatalysts NaNbO3 was successfully synthesized by hydrothermal method, the high effective up-conversion luminescence agent, Er:YAP was synthesized by solegel method. New photocatalysts Er:YAP/MoS2-NaNbO3 were successfully prepared by heating boiling and ultrasonic dispersion methods, while NiGa2O4 nanoparticles were synthesized by hydrothermal method again. The prepared materials were characterized by XRD, SEM, TEM, XPS, EDX, UV-vis absorption and PL spectra. The visible-light photocatalytic hydrogen production activity of the prepared Er:YAP/MoS2-NaNbO3 was evaluated by using CH3OH as sacrificial reagents in an aqueous solution under visible-light irradiation. In addition, some influence factors on visible-light photocatalytic hydrogen production of Er:YAP/MoS2-NaNbO3 were investigated in detail, such as mass ratio between Er:YAP and NaNbO3, catalyst amount, irradiation intensity, and so on.4. The nanometer photocatalysts La2Ti2O7 was successfully synthesized by hydrothermal method. Three corresponding visible-light photocatalysts, Er:YAP/MoS2-La2Ti2O7 were successfully prepared using MoS2 as co-catalysts and La2Ti2O7 as bulk catalyst. The visible-light photocatalytic activities of all synthesized materials, which were characterized by XRD, XPS, EDX, and so on, Er:YAP/MoS2-La2Ti2O7 were simultaneously examined through photocatalytic hydrogen evolution from methanol aqueous solution under visible-light irradiation. Besides, the imfluence factors such as heat-treated temperature, initial pH value of solution, and so on were also studied.5. The photocatalysts NiGa2O4 was successfully prepared by hydrothermal method. Er:YAG, MoS2 and NiGa2O4 were mixed by ultrasonic dispersion method, and three corresponding photocatalysts Er:YAG/MoS2-NiGa2O4 were prepared by heating boiling method. The properties of Er:YAG/MoS2-NiGa2O4 were characterized, studied. At the same time, the influence factors on the photocatalytic hydrogen evolution activity of Er:YAG/MoS2-NiGa2O4 were also studied.6. BiVO4 and NiGa2O4 were synthesized by hydrothermal method Up-conversion luminescence agent Er:YAG and BiVO4-NiGa2O4 were compounded in advance, and four corresponding photocatalysts Er:YAG/MoS2-BiVO4/NiGa2O4 were prepared by ultrasonic dispersion and heating boiling methods, the prepared materials were also characterized. The visible-light photocatalytic activity of Er:YAG/MoS2-BiVO4/NiGa2O4 were examined through photocatalytic hydrogen evolution from methanol splitting under visible-light irradiation. Meanwhile, some influential factors such as mass ratio, catalyst amount, irradiation intensity, pre-treatment temperature and used times on visible-light photocatalytic H2 production of Er:YAG/MoS2-BiVO4/NiGa2O4 were investigated in detail. |
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