Study On BiVO₄ Ultrafine Powder Synthesized By Solution Combustion Method, Modification And Its Photocatalytic Performances

Bi-based composite oxide semiconductors have distinctive physical and chemical properties, including optical effects, optical and electrical properties, optical and catalytic properties, such as ferroelectricity.As a new photocatalytic materials with so many properties, more and more people are paying attention to it, because of its non-toxic, non-polluting and other characteristics.In this experiment,we used solution combustion method to synthesis BiVO4 powder with sucrose as fuel, bismuth nitrate as oxidizer/Bi source and finished its modification by Ag+ doped and ZnO coupled. The photocatalysts prepared was characterized by XRD, SEM, EDS, UV-vis spectrophotometer and other modern testing methods.This study investigated the effects of the fuel and oxidant molar ratio (φ value), ignition temperature, the content of nitrate, concentration of precursor solution, holding time to BiV04 phase composition morphology, and photocatalytic properties etc. In the experiment, the methylene blue dye was used as degradation, and BiV04 photocatalytic properties was investigated respectively in the visible and near-visible light.Finally,the results were obtained as follows:(1) With the increasing of φ value,the BiVO4 powder particle size first decreases and then increases.BiV04 powders can be synthesized between 300℃ 500℃.when the ignition temperature is 500℃,the synthesized BiVO4 power is all monoclinic phase, and when the ignition temperature is 300℃ and 400℃, the synthesized BiVO4 power has two phase, namely, monoclinic and tetragonal. The content of nitric acid only affects the morphology of the BiV℃4 powers. After the optimization process,BiVO4 powder synthesized has best performance.The best factors are as follows:ignition temperature is 500℃,φ value is 2.5, the content of nitric acid is 7 ml, the concentration of precursor solution was 0.1 mol/L, holding time is 240 min (500℃).The BiVO4 powder synthesized have the smallest average radial size of 200 nm. With stirring 240min under visible and near-visible light, the degradation efficiency of methylene blue solution (8 mg/L) reaches 72.3% and 19.5%, respectively.(2) Doping Ag+ to BiVO4 powder can significantly improve its performance. When Ag+ doping amount is 3wt%, concentration is 0.02 mol/L,and heat treatment temperature is 300 ℃.The prepared Ag+-BiVO4 powder is illuminated 240 min under near visible light, the degradation efficiency of methylene blue solution reaches 95.1%, and it creases 36.4% than that of pure BiVO4.(3) BiV04 power coupled with ZnO, the synthesized power exhibits good photocatalytic performance under visible light. When ZnO adding content is 1wt%, ignition temperature is 500℃, adding content of nitric acid is 7ml, concentration of the precursor solution is 0.1mol/L,and holding time is 10min, ZnO/BiVO4 power has best performance.Degradation of methylene blue reaches 58.3% under the visible light irradiation for 240min, which increases 2 times than that of pure BiVO4.