| With the depletion of fossil fuels, nuclear energy and hydrogen has been considered as the important energy in the future. The nuclear energy has great harm to human beings and environment because of its radioaction. Hydrogen, as a clean, renewable energy, becomes particularly important. It is known that the sea accounts for more than70%of the area on earth. If we convert the water in the sea into hydrogen, the energy released from hydrogen would be thousands of times higher than the energy released from all fossil fuels on earth. There is only water left after hydrogen burning. So it is harmless to the environment and the water left can be reused to product hydrogen again. Therefore, hydrogen is a truly clean and renewable energy which is very important for human beings. There are various ways to restore water into hydrogen. And hydrogen evolution from water under light irradiation is considered to be an environmentally friendly, energy saving, simple and efficient method. But there are still a number of key issues to be resolved, such as how to prepare efficient and inexpensive photocatalysts and find new methods to prepare the photocatalysts fast and simply.In this work, we designed several dye-CuO-MWNTs photocatalytic systems containing cheap organic dyes, and investigated their photocatalytic activities for hydrogen evolution from water. The effects of various factors on the photocatalytic activity of dye-CuO-MWNTs for hydrogen evolution were discussed. The photocatalytic mechanisms were investigated by using UV-visible spectroscopy, fluorescence spectroscopy et al. We also used a new method, which was much faster than the soakage and thermal decomposition processes to prepare the photocatalyst. The main results are as follows.CuO nanoparcitles were loaded onto multi-walled carbon nanotubes (CuO-MWNTs) by soakage and thermal decomposition processes. Eosin Y and Vitamin B12(VB12) as a mixing sensitizer were adsorbed on CuO-MWNTs by simple adsorption. The activity and photocatalytic mechanism of Eosin Y/VB12-CuO-MWNTs for hydrogen evolution from water under visible light was investigated. The effects of molar ratio of Eosin Y to VB12, mass ratio among dye mixture, MWNTs and CuO, concentration of triethanolamine (TEOA) and pH value of the solution on the photocatalytic activity were also explored. Finally, the life of the photocatalyst was examed for practical application. The results show that this photocatalytic system has a high activity of hydrogen evolution and long time life. VB12plays a very important role in this system. It significantly improves the performance of the photocatalyst. The introduction of VB12enhances the effective separation of photoinduced electrons, so that the photocatalytic activity of the system is improved.CuO-MWNTs was prepared by soakage and thermal decomposition processes. The mixture of Eosin Y and Rhodamine B (RhB) was selected as the sensitizer. The photocatalyst was prepared by simple adsorption method. The performance of this photocatalytic system was tested. The effects of various factors on the photocatalytic activity of Eosin Y/RhB-CuO-MWNTs for hydrogen evolution and its life were investigated. The mechanism was also discussed on the basis of these studies. The results show that this system has an excellent photocatalytic performance, its rate of hydrogen evolution reaches1170.5μumol·g-1·h-1. But the life is64h, which is much shorter than Eosin Y/VB12-CuO-MWNTs. The role of RhB is similar with VB12, RhB can enhance the effective separation of photoinduced electrons. RhB can also broaden the range of wavelength which is different from VB12.After MWNTs as the carrier were treated with H2SO4and HNO3, CuO nanoparticles were loaded on the MWNTs by mechanical grinding. The products were characterized with XRD, XPS, TEM et al. The photocatalytic system was prepared by simple adsorption of Eosin Y as sensitizer. The activity of hydrogen evolution was investigated in TEOA solution. The results show that a high efficient photocatalyst is obtained using the mechanical grinding method. Compared with soakage and thermal decomposition processes, the mechanical grinding method is much simpler, more moderate and faster. It can also enhance the photocatalytic activity of the system. |
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