Unconventional Technology Visible Catalyst For Synthesis Of Bismuth And Its Performance Study

Semiconductor photocatalysts have been widely applied in the field of energy and environment, which can transform the solar energy to other forms of energy. Among these catalysts, TiO2 has attracted much attention owing to its high stability, high activity and harmless for the healthy. However, the wide bandgap of TiO2 (3.1 eV) limits the absorption of solar light and the quantum efficiency is still very low. In order to solve this problem, many efforts have been devoted to develop the novel non-TiO2 catalyst besides the modified TiO2. Bismuth-based photocatalysts are sensitive in the visible light region since their band gap are narrow resulted from the hybrid of Bi Bi6s and O2p orbitals. However the traditional preparation methods including high-temperature synthesis generally lead to the low specific surface area and the poor stability, not favorable for the improvement of photoactivity. In this paper, non-conventional preparation methods have been developed to synthesize the novel photocatalysts with controllable morphologies and high surface area. Furthermore, the relationships between structure of catalyst and catalysis performance are discussed in detail. The main works are listed as following:1. Solvothermal Synthesis of flower-like BiOBr visible-light photocatalyst applied in photodegradation of organic compoundFlower-like BiOBr visible-light photocatalyst was synthesized via solvothermal method in two-component solvent of ethylene glycol and isopropanol, and the cetyltrimethylammonium bromide (CTAB) acted as both the bromine source and the template. The controllable structure was achieved via adjusting the ratio of ethylene glycol and isopropanol, and the mechanism of crystal growth was proposed through varying the reactants and preparation conditions. CTAB could lead to the growth of layer and the decreased content of isopropanol could result in the close aggregation. The characteristics of catalyst and the evaluation of photodegradation of RhB under visible light irradiations were carried out to determine the optimal conditions. When the ratio of ethylene glycol/isopropanol was 5:35, Bi/Br was 2:1 and the solvothermal time was 12 h, the BiOBr exhibited the highest degradation yield owing to the high crystallization, the large specific surface area and the enhanced visible light absorption resulted from the light multi-reflection. Meanwhile, the activity of BiOBr catalyst was much better than other catalysts.2. Based on BiOBr synergy effect of visible light photocatalysis and peroxide processUsing visible light/BiOBr/H2O2 system rearches the the effects of photocatalytic synergy peroxide mechanism. During the degradation of organic dye RhB, it is proved that the synergy effect can greatly speed up the degradation rate. The other study on the type of active species verifies the initial reaction mechanism.3. Synthesis of visible-light induced spheral BiVO4 and BiFeO3 by spray pyrolysis methodWe use soft-template agent with polyol structure method to produce novel catalysts BiVO4 and BiFeO3 by spray drying method. Changing the kind of soft templates, hollow BiVO4 and core-multilayer shell architecture are obtained. And with the increasing of the amount of glycerol, the shell of the hollow BiFeO3 becomes thicker and thicker. In the reaction of degrading RhB and 4-CP, it is proved the special morphology can absorb more light and improve the catalyst performance.