Preparation And Photocatalytic Performance Of Bismuth Oxyiodide-based Composite Photocatalysts

As an emerging environmentally friendly technology,photocatalysis provides an effective solution to the current energy shortage and environmental pollution problems.Photocatalytic technology is inseparable from semiconductor materials,however,traditional semiconductor photocatalytic materials?such as TiO₂?have low utilization of sunlight and are difficult to meet practical application requirements.Therefore,it is of great practical significance to develop the new,efficient and pollution-free semiconductor materials.Bismuth iodide?BiOI?is a novel semiconductor photocatalytic material with narrow band gap energy?1.7¹.9 eV?,wide absorption range of light and unique layered structure,which making it with good catalytic properties and optical properties.However,the photogenerated electrons and holes of the BiOI are easily recombined,which affects its photocatalytic performance,and it limits the practical application of BiOI.Therefore,in order to ameliorate the performance of the BiOI,the paper uses it as the basis to construct different photocatalysts with composite structures,thereby promoting the separation efficiency of photo-generated charges in BiOI,improving the photocatalytic performance of it,also.The specific research contents are as follows:?1?CoWO₄ is prepared by hydrothermal method using Co?NO₃?₂·6H₂O and Na₂WO₄·2H₂O as raw materials.The CoWO₄/BiOI composite photocatalyst is prepared by precipitation method,which is adding the nanoparticle CoWO₄ to the BiOI,and determine the optimal ratio of them.Through a series of characterization analysis,confirming the p-type semiconductor CoWO₄ and the p-type semiconductor BiOI form the composite structure of p-p junction,which can effectively promote the separation of photogenerated electron-hole pairs in the photocatalyst.When the molar ratio of CoWO₄ to BiOI is 2:1,the best photocatalytic performance is exhibited.Under 120 min of visible light irradiation,the degradation efficiencies of RhB and TC are 99.3%and 81.8%,respectively.?2?Flower-like In₂O₃ is prepared hydrothermally by adding a certain amount of glucose and urea to the solution of InCl₃,then adding it to the preparing BiOI to obtain the In₂O₃/BiOI composite.The light absorption properties and composition of the prepared samples are analyzed by means of XRD,DRS,SEM,TEM and XPS.Moreover,in the electrochemical test method,the composite photocatalyst exhibits higher charge separation efficiency.The composite photocatalysts are applied to degrade RhB and TC,as the mass ratio of In₂O₃ is 5%,it shows the much higher photocatalytic performance.The degradation efficiency of RhB reaches 96%under the irradiation of visible light for 120 min,and the degradation efficiency of TC reached 83.1%within 80 min,the degradation efficiency is obviously higher than the others.?3?WO₃ is prepared by calcining tungstic acid,and then preparing the ternary composite photocatalysts of WO₃/BiOI/GO in one step by precipitation method.As doping the GO,the absorption intensity of visible light is improved and the absorption range of visible is widened in the experiment.The material of GO in the composite photocatalyst,greatly promotes the separation efficiency of photogenerated carriers as an electron conductor,thereby exhibiting excellent photocatalytic performance.In the degradation experiments of RhB and TC,the much higher photocatalytic efficiency is exhibited when the amount of GO introduced was 3%of the theoretical mass ratio of the composite.Under visible light irradiation for 120 min,the degradation efficiency of RhB and TC reached 96.5%and 84.0%,respectively.