Research On Design, Preparation And Properties Of Transitional Metal Oxides

With the quick development of social economy and the enhancement of living standard of people, environmental problem has increasingly become a focus in many countries of the world. More important, organic pollution in water is one of the most vexing problems to be resolved. Photocatalytic oxidation with semiconductors is proven to be a promising technology because the semiconductors are inexpensive and can easily mineralize various organic compounds. However, the electron and hole in the semiconductors easily recombine, which results in unsatisfactory photocatalytic efficiency in practical application. Therefore, how to enhance the photocatalytic performance of semiconductors is quite important.In this dissertation, the work was carried out centreing on the theme of design, preparation and properties of transitional metal oxide nanomaterials. The main researches are as following.1. Cubic cuprous oxide nanocubes were prepared by liquid phase method at room temperature. X-ray diffraction patterns, transmission electron microscopy and scanning electron microscopy images have verified that the products consists of uniform Cu2O nanocubes with edge length of170nm. Moreover, the photocatalytic performance of Cu2O nanocubes was investigated by photodegrading acid fuchsin. The results reveal that the phtotocatalytic activity of Cu2O nanocubes was greatly enhanced by adding moderate hydrogen peroxide in the system. Because moderate hydrogen peroxide can not only provide more·OH but also prohibit the recombination of electron and hole as oxidant. Therefore, the method to enhance photocatalytic activity of semiconductors is propagable.2. The Cu2O and CUCl/Cu2O films based on the copper substrate were respectively obtained by an easy hydrothermal method, in which hydrogen peroxide was used as reducing agent, cobalt chloride (CoCl2) as chlorine source as well as ethanol aqueous solution as solvent. The composition of CuCl/Cu2O films can be successful controlled by adjusting the concentration of cobalt chloride. The four films obtained with different concentration of cobalt chloride were used as photocatalyst degrading Rhodamin B solution, and it was discovered that the CuCl/Cu2O films exhibit higher photocatalytic performance than pure Cu2O film, which is attributed to the higher separation of electron and hole. Moreover, the initial concentration of cobalt chloride during preparation has a great effect on the photocatalytic performance of the CUCI/Cu2O films.3. The Ag/ZnO film based on the zinc substrate was synthsized in the Tollen’s reagent by a hydrothermal method via one step. The photocatalytic performance of the Ag/ZnO film was studied by photodegrading Rhodanmin B solution. The results demonstrate that in the degradation of Rhodamin B solution, the Ag/ZnO film exhibits ehancement of photocatalytic activity in comparsion with the pure ZnO film. In additon, the PL peformance and gas sensitivity to ammonia of the Ag/ZnO film were measured at room temperature. The Ag/ZnO film shows weaker PL intensity and better gas sensitivity than the pure ZnO film. The enhanced performance of the Ag/ZnO film was attributed to the more effective seperation of electron and hole resulting from the presence of metal silver.4. Cubic Ag dendritic nanostructure with ordered branches have been successfully prepared by soaking Zn plate into silver ammonia buffer solution and via a facile reduction reaction at room temperature. The overall length of the Ag nanodendrites is3-10μm, and the average diameter of the stems and the branches are100nm and50nm, respectively. A room temperature photoluminescence-type gas sensing device based on the pure Ag nanodendrites has been established to investigate their humidity sensing properties. Compared with Ag particles, the sensor based on the Ag nanodendrites presents better sensitivity, more excellent linearity, quicker recovery and reliable repeatability in a very wide humidity range at room temperature.