Preparation And Properties Of Bismuth Based Micro/Nano Materials

In recent years, environmental problems have attracted people’s attention, so people seek green, safe ways to solve the problem of environmental pollution and energy. Due to its high efficiency, low cost and environmentally friendly characteristics, nano semiconductor materials which have attracted extensive attention of researchers have been used in the photocatalytic degradation of organic pollutants and photocatalytic hydrogen production. Most of the catalysts have the disadvantages of wide band gap, high electron hole recombination rate, and low repetition rate. Therefore, it is of great significance to develop the catalyst with excellent performance. In this paper, we synthesize a novel adsorbent BiOBr/Bi2WO6, photocatalyst Ag/Bi2WO6 and BiOX (X=Cl, Br, I), and we also study their adsorption and photocatalytic properties.The specific contents of this paper are as follows:1. Synthesis of squamous and adsorption properties of BiOBr/Bi2WO6In this work, BiOBr/Bi2WO6 with squamous morphology was successfully prepared by one step hydrothermal method, and it was found that BiOBr/Bi2WO6 was an ideal material for adsorption. The structure of BiOBr/Bi2WO6 was characterized by powder X-ray diffraction (XRD), X ray photoelectron spectroscopy (XPS), FT-IR spectroscopy tenchniques and the morphology were detected with scanning electron microscopy (SEM). The specific surface of BiOBr/Bi2WO6 was tested by nitrogen adsorption/desorption surface area pore size distribution analyzer. According to the contrast of SEM photos of BiOBr/Bi2WO6, BiOBr and combine with the concentration of KBr experiment, The possible morphology formation mechanism of BiOBr/Bi2WO6 squamous was proposed. When the concentration of KBr is low, a large amount of bismuth tungstate is formed in the solution, and the morphology of the product showed the shape of class flower; when the KBr concentration is higher, BiOBr is mainly generated in the solution. As the reaction was carried out, WO42- was further reacted with BiOBr to replace one of the Br-, but the original crystal structure of BiOBr did not change. So the morphology of BiOBr/Bi2WO6 which was converted is very similar to that of BiOBr. We design a series of adsorption experiments and test the adsorption properties of the compounds with organic dyes as adsorbent and BiOBr/Bi2WO6 as adsorbent. The results showed that BiOBr/Bi2WO6 showed higher adsorption capacity for cationic dyes, especially the adsorption rate of MB; BiOBr/Bi2WO6 showed higher adsorption capacity compared with activated carbon. Adsorption behavior of BiOBr/Bi2WO6 is consistent with the Freundlich isotherm model and the adsorption process of MB follows a pseudo-second-order kinetic model.2. Synthesis and properties of Ag/Bi2WO6 nanoclustersWith water as solvent, Bi2WO6 with the morphology of cluster like was synthesized by hydrothermal method under mild and no template conditions, and the silver nanoparticles were loaded on the surface by in situ reduction method to prepare the composite catalyst Ag/Bi2WO6. The samples were characterized and tested by XRD, SEM, DRS UV-vis and other instruments. Only change the pH value of the solution, Bi2WO6 with different morphologies was obtained. According to the literature review and SEM pictures show, the H+ or OH- of solution impact the morphologies of Bi2WO6, and under the action of the Ostwald ripening mechanism, the final product morphology show some differences. The model reaction of reduction of nitro-phenol under the action of NaBH4 as a model was selected for the catalytic activity of Ag/Bi2WO6. The effects of NaBH4 concentration, the amount of catalyst and other factors on the reaction rate were discussed. The catalytic activity of the composite sample with Ag loading of 5% was the highest, and a certain concentration of 4-NP was fully catalyzed within 17 minutes. Under simulated solar light, the photocatalytic experiments were carried out to study the photocatalytic activity of the composite sample with organic dye crystal violet as pollutant model and Ag/Bi2WO6 as catalyst. The composite sample with a load of 5% showed the highest photocatalytic activity. This indicated that Ag/Bi2WO6 could be used as a new photocatalyst for photocatalytic degradation of organic pollutants.3. Preparation and properties of BiOX (X=Cl, Br, I) nanomaterialsThe photocatalysts BiOCl, BiOBr and BiOI were prepared by a simple and mild method, and their adsorption and photocatalytic properties were studied. The products were characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM), XPS ray diffraction (XPS), UV visible diffuse reflectance spectra (UV Vis DRS) etc. We design a series of adsorption experiments and test the adsorption properties of the nano material with organic dyes as adsorbent and BiOX as adsorbent. The results showed that BiOI have better adsorption performance. Three kinds of samples for adsorption of Rhodamine B (RhB) is superior to the other dyes. In addition, the photocatalytic performance of samples was studied under simulated sunlight, and the possible mechanism of photocatalytic degradation was discussed. The experimental results showed that the photocatalytic effect of BiOBr was the best. The degradation rate of RhB was 100% under simulated sunlight irradiation 10min. In addition, according to the activity free radical trapping experiment, we can know that the photo generated hole and. O2- jointly play a role in the process of photocatalytic reaction. Also, the photo generated hole plays a main role.