| Accompany with the rapid development of population and economy, energy becomes one of the most important problems facing human beings. Energy depletion severely restricts the development of human society. It is urgently desired to find a renewable and cleaning energy to solve the global environmental pollution crises and energy shortage.Solar energy is enormous and belongs to renewable energy. Hydrogen is an ideal energy carrier due to its high energy density, and the combustion of hydrogen is pollution-free for the environment.Photocatalysis is an advanced potential technique to convert solar energy into chemical energy and has many advantages in energy conversion. Photocatalytic water splitting to generate hydrogen has attracted much attention, and is developing rapidly.Nano metal oxides photocatalysts have many virtues such as strong oxidation,no selectivity to pollutants, no secondary pollution, low energy consumption, simple operation,reused several times and so on,which has attracted considerable attention due to its wide applications. The application of nano metal oxides photocatalysts in the fields of environmental treatment and clean energy conversion has become a research focus.Up to now, a lot of photocatalysts were discovered by researchers, but many of them only work under UV light, which occupy only 4% of solar energy. In order to sufficiently take advantage of solar energy, visible light-driven photocatalysts become more and more important. However, few photocatalysts can stoichiometrically split water into hydrogen and oxygen under visible light up to date. Many visible light-driven photocatalysts produce either hydrogen or oxygen from sacrificial reagent solution due to unsuitable conduction band or valence band.In this work, we have developed a one-pot method to prepare highly crystalline nano metal oxides photocatalysts by varying dosage of solvent, reaction temperature, time and so on.Firstly, In2O3 nanocrystals were achieved through a facile one-pot hydrothermal reaction using In(NO3)3 as raw maerial and ethylene glycol as solvent. The prepared In2O3 samples were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), high resolution TEM(HRTEM), X-ray photoelectron spectra(XPS) and diffuse reflectance spectrum(DRS). The results show that the prepared In2O3 nanocrystals are high purity nanoparticles with well spherical cubic structure, but its size distribution vary remarkably with different treatment. The UV-vis results indicate In2O3 prepared using hypophosphorous acid show visible absorption in a certain extent, suggesting that p-doped is effective on the narrowing of the In2O3 band gap.The photocatalytic activity of In2O3 nanocrystals were evaluated by the photocatalytic splitting of water to produce H2 under UV irradiation. The growth mechanism of In2O3 nanocrystals was also proposed.Secondly, Ti3+/P co-doped TiO2 nanocrystals with visible-light photocatalytic activity were prepared by a facile one-pot hydrothermal reaction strategy using tetrabutyl titanate as titanium source and hypophosphorous acid as reductant. The structure, crystallinity, morphology and other properties of the samples were characterized by transmission electron microscope(TEM), X-ray diffraction(XRD), X-ray photoelectron spectra(XPS), diffuse reflectance spectrum(DRS) and electron paramagnetic resonance(EPR). Under visible-light radiation, the samples exhibit excellent ability in the photocatalytic splitting of water to produce H2. The sample prepared by using 4 mL of hypophosphorousacid shows the highest visible-light photocatalytic activity. Moreover, the photocatalytic mechanism and growth mechanism of Ti3+/P co-doped TiO2 nanocrystals were also proposed. |
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