Synthesis Of BiVO₄-Based Semiconductors With Enhanced Photoelectric Activity

Environmental and energy are closely related to human life, environmental pollution and energy shortage for our production, living and health has brought many negative effects, especially the water pollution. Water is the source of life, in recent years, due to water pollution to human beings caused many painful lessons, handle and solve the water pollution become the priority. The current common methods are physical method, chemical method and biological method, these methods certain achievements have been obtained at the same time also brought a lot of problems, such as long cycle, low efficiency, serious second pollution makes these method cannot be widely used, such as, therefore, we should consider when choosing processing means to find more safe and effective way. At present, in many wastewater treatment technology, photocatalysis technology due to its advantages of the green, environmental protection, high efficiency, stable received universal attention. Photocatalytic technology mainly use solar radiation semiconductor materials, semiconductor materials can effectively degrade pollutants in wastewater. The main part of this technology is semiconductor catalyst materials. The Bi base semiconductor materials with special performance in the field of photocatalysis, has been widely applied. In this paper, we explore a series of Bi based compounds and composite material preparation and photoelectric performance of the research work, studies from the following several aspects:1. Facile formation of mesoporous BiVO4/Ag/AgCl heterostructured microspheres with enhanced visible-light photoactivityIn this study, we demonstrate a facile and novel dual-ion-exchange method together with subsequent visible-light induced reduction for synthesis of mesoporous BiVO4/Ag/AgCl ternary heterostructured microspheres (HSMSs) with uniform size distribution. Using flower-like BiOCl microspheres as the starting material.and introducing NaVO3 and AgNO3 by a facile impregnation method, mesoporous BiVO4/AgCl HSMSs have been obtained through solid-phase dual-ion-exchange reactions at 400℃ for 2 h. Interestingly, it has been found that Ag+ ions play an indispensable role on the dual-ion-exchange reactions, and then the BiVO4/AgCl HSMSs are converted into BiVO4/Ag/AgCl ternary HSMSs by a facile visible-light illumination for 2 h. The as-prepared mesoporous BiVO4/Ag/AgCl ternary HSMSs manifest high photocatalytic activity in degrading methyl orange (MO) and phenol under visible-light illumination, and a possible Z-scheme photocatalytic mechanism is proposed to understand the enhanced photochemical properties.2. Facile synthesis of mesoporous BiVO4-Bi2O3 direct Z-scheme composite microrod photocatalysts with superior photocatalytic degradation of phenolIn the present work, high-quality mesoporous BiVO4-Bi2O3 composite microrods (CMRs) with uniform size distribution have been successfully prepared through a facile solvothermal method followed by an annealing process. BiVO4-Bi(OH)C2O4 CMRs are first synthesized at the temperature of 180℃ by using Na2C2O4 and NaVO3 as the starting materials, and then thermally decomposed at 350℃to obtain mesoporous BiVO4-Bi2O3 CMRs. The as-prepared mesoporous BiVO4-Bi2O3 CMRs exhibit significantly enhanced photocatalytic activity in degrading colorless organic phenol under visible-light illumination, whose degradation efficiency is more than 48 times higher than that of the mechanical mixture of BiVO4 and Bi2O3, and 192 and 160 times higher than pure BiVO4 and Bi2O3, respectively. Furthermore, the as-prepared product also shows improved photoactivity in degrading color dye orange (MO). The mesoporous BiVO4-Bi2O3 CMR product is characterized by UV-vis diffuse reflectance spectroscopy (DRS) and valence-band X-ray photoelectron spectroscopy (XPS), and the enhanced photocatalytic activity is explained with a direct Z-scheme mechanism which is proposed to describe the transfer of photogenerated electrons and holes in the composite BiVO4-Bi2O3 system.3. Synthesis of BiVO4/CuWO4-x composite nanoparticles as an efficient photocatalyst with enhanced visible-light photoactivityIn this chapter, hierarchical BiVO4/CuWO4-x nanoparticles(NPs) were prepared by two steps. First, CuW04-x NPs were synthesis via a facile solvothermal approach followed by an annealing treatment, and then absorbingmetal Bi3+cation on the surface of CuWO4-x NPs in the presence of bismuth nitrate solution, after that, introducing NaVO3 by a facile impregnation method into the mixture which was placed at 140℃ for 12 hours to obtain BiVO4/CuWO4-x NPs. We choose the as-prepared BiVO4/CuWO4-x NPs as an example, which exhibits obviously photocatalytic activity for the photodegradation of phenol and waret splitting under visible-light irradiation. Therefore, the BiVO4/CuWO4-x NPs developed in this work may be a promising potential material for pollutant treatment.