Study On Synthesis Of Bismuth-containing Photocatalysts And Their Applications

In the 21st century, the energy and environmental issues are the great problems and challenges for human, and the concept of using solar energy to solve the global energy and environmental problems has attracted considerable attention. Heterogeneous photocatalysis is a promising technology to solve global energy and environmental issues, since the photocatalysis materials can use the visible light response to transform solar light into chemical energy with high density, and use solar light to photocatalyze poisonous materials, decompose the harmful contaminations, purify the water, eliminate the air pollution and so on. As well known, the key problem of photocatalysis is photocatalyst.Among the reported photocatalysts up to now, Bismuth-containing semiconductor photocatalysts have attracted considerable attention due to their high catalytic activities towards the degradation of refractory organic materials under visible light irradiation.Based on good photocatalytic activities of Bismuth-containing semiconductor photocatalysts,in this paper, three types of Bismuth-containing composite materials (Bi2O3-MgO Bi2CuFe2Ox,BiVO4) were synthesized, and their photocatalytic activities were studied by the degradation of typical dyes (rhodamine B,methyl orange,crystal violet) under irradiation of visible light with wavelength(λ)>400 nm. The effects of preparation method and photodegradation condition on/the photocatalytic activity of the samples were studied.The prepared samples were characterized by XRD,SEM and UV-vis DRS techniques.The relationships between the structure and photocatalytic performance were also investigated.A series of Bi2O3-MgO composites were synthesized by solvent-thermal method. Compared with Bi2O3 and MgO, the Bi2O3-MgO composites are more active for the photocatalytic decolorization of RhB.The photocatalytic performance of Bi2O3-MgO was optimized through the adoption of R=2:1 and crystallization at 120℃(20h). The photodegradation efficiency of RhB can be significantly enhanced in the presence of HCl.It is plausible that HCl promotes the adsorption of RhB on the catalyst, enabling higher surface concentration of RhB for the catalytic action.Bi-Cu-Fe-Ox was synthesized by solvent-thermal method.SEM images revealed that the particles of the Bi-Cu-Fe-Ox exhibit spherical structure with the size ranging from 1～5μm.It was found that the photocatalytic activity of Bi-Cu-Fe-Ox was related to reaction conditions,initial concentration of MO, catalyst loading and H2O2 amount. The MO degradation over the photocatalyst is fitted for pseudo-first-order kinetics, and can be described by L-H kinetic equation.Monoclinic bismuth vanadate (BiVO4) samples with regular morphologies and narrow bandgaps were prepared by a facile hydrothermal process with the assistance of lysine.The photocatalytic activities of these BiV04 samples were evaluated for the degradation of crystal violet under visible-light irradiation (λ>400 nm).The best performance was observed over the BiVO4 sample synthesized by hydrothermal-treatment of the precursor suspensions in the presence of lysine at 200℃for 48 h. SEM images revealed that the particles of the BiVO4 has honeycomb structure with～2μm spheres in diameter, and its optical band gap is 1.81 eV estimated by UV-Vis diffuse reflectance spectroscopy, which is narrower than that of BiVO4 prepared by traditional hydrothermal method (2.06 eV).The photocatalytic performance of the as-prepared BiVO4 is much better than that of the BiVO4 prepared by traditional hydrothermal method.The improved optical absorption properties and photocatalytic activity of the BiVO4 sample is suggested to be related to the honeycomb structure with microspheres.