| In the21st century, energy and environment are the two major global problems to be solved. Since Japanese scientists Fujishima and Honda found the photocatalytic splitting of water on titanium dioxide electrode in1972, sunlight induced photocatalytic reaction has been generally considered to be a way to convert solar energy into hydrogen energy, which can effectively solve the energy shortage; then, it has been found that the photocatalytic reaction also has many advantages like mild conditions, no secondary pollution, complete degradation of organic matters, and so on, which can become an ideal environment pollution control technology. Therefore, the semiconductor photocatalytic hydrogen production (energy photocatalysis) and photocatalytic pollutant degradation (environmental photocatalysis) are in a widespread concern. In this paper, the improvement of the photocatalytic activity of cadmium sulfide and titanium dioxide for energy and environmental photocatalysis, respectively, were studied.For energy photocatalysis, a graphene-CdS nanocomposite material was prepared by a solvothermal method, followed with the characterizations and tests such as X-ray diffraction analysis, transmission electron microscopy, N2adsorption-desorption, UV-Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, infrared spectroscopy and visible-light photocatalytic hydrogen production analysis. It was found that graphene nanosheets in the composite enhance the crystallinity and the specific surface areas of CdS clusters, and a low amount of graphene can dramatically improve the photocatalytic activity. The optimal weight percentage of graphene was found to be1.0wt%, which resulted in a high visible-light photocatalytic H2-production rate of1.12mmol-h-1and corresponding apparent quantum efficiency of22.5%at420nm with0.5wt%Pt as a cocatalyst. The results demonstrate that the unique features of graphene make it an excellent supporting material for semiconductor nanoparticles as well as an electron collector and transporter to separate photogene rated electron-hole pairs. This work not only demonstrates the potential of graphene as a support for CdS nanoparticles in photocatalytic hydrogen production, but also highlights more generally the potential application of graphene-based materials in the field of energy conversion.For energy photocatalysis, fluorinated B/C co-doped anatase TiO2nanoparticles were prepared by a hydrothermal method followed with a controlled calcination process. The characterizations and tests such as X-ray diffraction analysis, transmission electron microscopy, N2adsorption-desorption, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectroscopy, and visible-light photocatalytic RhB degradation analysis were carried out. It was found that the ionic liquid (IL) BMIM+BF4-played dual roles in the formation of the photocatalyst. One is to control the structure, making TiO2crystals grow uniformly with large specific surface area due to the "capping effect" of IL; the other is to behave as the F, B, and C dopant sources. In the doped TiO2, the surface fluorination favors the absoroption of RhB molecules in the TiO2/dye system, B doping induces the formation of Ti3+level and oxygen vacancies and improves the quantum efficiency, and C doping is responsible for the strong visible-light response of the photocatalyst. Thus, the modified mophology and synergic contributions of F, B and C dopants result in the excellent visible-light photocatalytic degradation rate of RhB, which is140%higher than that of commercial P25. The novel fluorinated B/C co-doped anatase TiO2nanoparticles with outstanding photocatalytic performance and the proposed contributions of specific active species involved in the dye degradation could provide new insights on the design of morphology-controlled multi-doped semiconductor materials, and be very promising for wide environmental applications. |
PDF Full Text Request