Synthesis And Mechanism Of High Activity Bismuth - Based Composite Oxide Visible Light Catalysts

Increasing environmental issues and renewable energy sources become exhausted had attracted our attention into searching for new technology to solve survive pressure in the future. In recent years, Photocatalytic technology has caught extensive attention due to cheapness, effectiveness and no secondary pollution. In order to utilize solar energy which is abundant in solar nergy effectively, preparing the visible-light photocatalyst become hot spot and key issues. Bismuth based materials were applied to electron device, medicine and catalyze field extensively. Among them BiVO4 is one of ideal, extremely potential, expecially in photocatalysis research. However, in a real world of application, BiVO4 has some defects such as poor carrier separation efficiency which is mianly because it has low conduction band. So it is significance to promote the charge separation efficiency of BiVO4. In this work, we use small nano-sized ZnO particles to couple with BiVO4 in order to enhance the electron-hole pairs separation also keep the energy level of photo-generated electron of BiVO4. Then through the methods of making some pores in the BiVO4, the resulting samples exhibit superior photoactivities. In addition, we have discussed the mechanism in detailed for the enhanced photoactivities.In this work, we select BiVO4 in the bismuth based materials as a model. We adopted wet-chemical method to prepare ZnO/BiVO4 nanocomposite photocatalyst. The results proved that the introducing of certain amount of nano-sized ZnO could promote the photoactivities of BiVO4. It is shown that the photogenerated charges of resulting nanocomposite display longer lifetime and higher separation than those of BiVO4 alone. This is attributed to the spatial transfer of visible-excited high-energy electrons from BiVO4 to ZnO on the basis of the ultra-low-temperature EPR measurements and the photocurrent action spectra. Then we prepared porous BiVO4 and composite, the reaearch results show that porous BiVO4 showed higher specific surface area. This is because it is favourable to absorb light and coulpled with ZnO.In order to overcome the problem lattice matching, we introducing silicate as a bridge to promote the link degree. We prepared silicate bridged ZnO/BiVO4 nanocomposite through wet-chemical method The results showed that silicate work as a bridge link with these two conductor and that silicate could further promote the electron-hole pairs separation efficiency and its photocatalytic activity as well as photoelectric conversion efficiency.