Preparation Of Bismuth Semiconductor And Its Composites And Photocatalytic Degradation Of Organic Pollutants

Along with the development of urban industrialization,the problem of environmental pollution is becoming more and more serious,especially the environmental pollution caused by organic pollutants.Today,we are striving to be green,harmless,energy-efficient and efficient when dealing with organic pollution problems.Photocatalytic technology refers to a photocatalytic material based on semiconductor materials that generates active radicals after being excited by sunlight of a certain wavelength,thereby achieving photohydrolysis,hydrogen production,degradation of organic macromolecules,reduction of heavy metal ions,sterilization and deodorization.Photocatalytic technology is a green,low-cost advanced oxidation technology that can effectively utilize solar energy in the natural world and convert solar energy into available resources such as electric energy or chemical energy,and achieve the purpose of deep oxidative degradation of pollutants,and It will not bring secondary pollution to the environment,and has already demonstrated its application value in the fields of energy conversion and environmental pollution control,thus greatly satisfying the needs of the current solution to environmental organic pollution.In this paper,a series of methods were used to modify and optimize the bismuth oxyhalide photocatalytic material to improve its photocatalytic performance.The microstructures and electronic structures were analyzed by X-ray diffraction analysis(XRD),X-ray photoelectron spectroscopy(XPS),scanning electron microscopy(SEM).transmission electron microscopy(TEM).UV-visible diffuse reflectance spectroscopy(DRS)and other characterization methods.The specific content is divided into three parts.(1)The composition of bismuth oxyhalide material was adjusted by simple chemical precipitation in deionized water and ethylene glycol mixture to form Bi4O5I2 ultra-thin nanosheet catalyst with rose petal shape.Compared with BiOI materials,Bi4O5I2 has a narrow band gap,strong redox ability,large specific surface area and permeability of rose nanostructures.In addition,as the content of Bi increases,the adsorption edge of the sample moving to shorter wavelengths,the valence band edge potential becomes more positive,which makes the separation of photogenerated electron-hole pairs higher.The final obtained Bi4O5I2 exhibits high visible light photocatalytic activity for degradation of RhB in aqueous solution compared to BiOI material.In the experiment of testing visible light photocatalytic degradation of rhodamine B,the degradation performance of Bi4O5I2 material is much higher than that of BiOI,and the degradation efficiency reaches 92.3%.Exploring its mechanism experiment,it can be seen that the h+ plays an important role in Bi4O5I2 photocatalytic degradation of rhodamine B by the mechanism experiment(2)On the basis of BiOI material,different ratios of g-C3N4/BiOI semiconductor heterojunction composites were synthesized with different amounts of thin nanosheets g-C3N4.The photocatalytic activity of g-C3N4/BiOI heterostructures was enhanced because of its strong absorption in the visible light region and the recombination rate of electron-hole pairs are greatly reduced,the g-C3N4/BiOI photocatalytic material combines the advantages of the nanosheet 2-C3N4 with high specific surface area.The high specific surface area can make the catalyst completely exposed to contaminants and also receive more light radiation,thereby generating enough reaction sites to produce active materials for photodegradation.According to the test results,when the doping ratio of g-C3N4/BiOI composite was 16:1,the maximum specific surface area of the composite was 140.58m2g-1.But the g-C3N4/BiOI(8:1)heterostructure exhibits the strongest visible light-driven photocatalytic activity in aqueous solution,and g-C3N4/BiOI(8:1)degraded Rhodamine B(RhB)with an efficiency of 99%within 2 hours(3)On the basis of BiOCl material,BiOCl does not have visible light photocatalytic properties due to the high band gap(3.5 eV).Therefore,under acidic conditions,the pH value is controlled by room temperature hydrolysis reaction,and Fe3+ is incorporated.In the BiOCl lattice.The substitution doping of Fe3+ at the Bi3+ site and then completed by a high temperature thermal annealing step,which prevents the formation of a BiFeO3 phase or phase segregation to form a uniform BiOCl and FeOCl phase to obtain a uniformly doped Fe3+ BiOCl nanosheet,is Bi0.7Fe0.3OCl.We have investigated the photocatalytic ability of Bi0.7Fe0.3OCl material synthesized by thermal annealing at different temperatures and Bi0.7Fe0.3OCl material synthesized at different pH values.The results show that the Bi0.7Fe0.3OCl is thermally annealed at 450 0C.has the best photocatalytic effect,the photocatalytic degradation efficiency is 70%,and the photocatalytic degradation rate is 1.3 times than that of Bi0.7Fe0.3OCl(400?)and 1.2 times than that of Bi0.7Fe0.3OCl(500?).It is also 1.8 times than that of Bi0.7Fe0.3OCl(550?).Compared with Bi0.7Fe0.3OCl synthesized at other thermal annealing temperatures,the Bi0.7Fe0.3OCl(450?)nanosheets are thinner and the nanosheets are more disorderly arranged.The gap between the nanosheets is much larger than other temperatures,which provides more active sites for photocatalytic degradation.Therefore.Bi0.7Fe0.3OCl(450?)has the best photocatalytic degradation efficiency.