Translated Abstract
Photocatalytic technology which is based on the transformation of solar energy not only can degrade pollutants completely with no secondary pollution，but also has great economic and social benefit. Most of photocatalysts are semiconductor, such as TiO2, ZnO, SrTiO3, and so on. However, these semiconductor materials only response to UV-light which accounts for less than 5% for the solar energy. If the CuS and Cu2O semiconductors with narrow band gap are composited with ZnO, its photostability could be improved, at the same time, the absorbance range of ZnO would be expanded. Thus, the photocatalytic efficiency of ZnO is improved because of electronic-hole separated quickly and the lower recombination rate. The purpose of this work is to prepare high-performance semiconductor photocatalyst by the method of semiconductor composite.
Firstly, a two-step method for growing well-vertical ZnO nanorod arrays on ITO substrates was proposed. A zinc oxide seed layer formed on the ITO substrate by simple dip-coating combined with czochralski method firstly, and then the vertical ZnO nanorod arrays were obtained by a hydrothermal method. The results showed that the length and diameter of ZnO nanorod arrays increase with the increased precursor concentrations, sol aging time and hydrothermal reaction time. The well-vertical wurtzite structure ZnO nanorod arrays would be obtained under the optional growth condition of three times hydrothermal reaction for 150 minutes, three times of dip-coating, 0.5mol?L-1 precursor solution and 24h aging. This kind of nanorod arrays structure not only has great specific surface area, but also provides a quick transfer channel for electrons and makes for the separation of electronic-hole pair. All of those are advantageous to the generation and process of oxidation-reduction reaction. The photodegradation rate of of ZnO nanorod arrays is 84% when it photocatalytic methylene blue after 90 minutes.
Secondly, CuS micro-nano particles with various morphology were prepared by different methods. The results showed that the diameter of CuS nano particles increase with the increased precursor concentration by method of precipitation, and the well dispersive CuS nano particles with about 100 nm of average diameter would be obtained under the optional growth condition of 0.5mol?L-1 precursor solution. The diameter of about 10 nm nano particles gathered into a large diameter of the CuS micro spheres prepared by hydrothermal method, and diameter of CuS microspheres increase with the longer hydrothermal reaction time. On this basis, CuS particles and ZnO particles are composited using different methods. The CuS/ZnO composite composed of flower empty micro spheres with a lot of fins and channels in micro sphere surface. Photocatalytic degradation test results showed that the photodegradation rate of composite semiconductor is better than single semiconductor CuS or ZnO. Especially the photodegradation efficiency reached to 88% for CuS/ZnO composite semiconductor.
Finally, Cu2O nano hollow spheres were obtained by a hydrothermal method. The effects of the precursor concentration, reaction time, reaction temperature and reductant quantity on the structure and surface morphology of Cu2O hollow spheres were investigated. The well dispersive Cu2O nano hollow spheres with about 600 nm of average diameter were obtained under the optional growth condition of 0.4mol?L-1 precursor solution, 4 h reaction time, 140oC reaction temperature and 2.67ml reductant. The Cu2O/ZnO has good morphology that ZnO nano particles adhered on the surface of Cu2O nano hollow spheres. And the photodegradation efficiency of Cu2O/ZnO composite semiconductor improved significantly which has reached to 90% after 90 minutes.
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