Photocatalytic Performance Study Of BiVO₄,g-C₃N₄ And BiOCl Materials

BiVO4,g-C3N4 and BiOCl are three common n-type semiconductor photocatalysts.They are one of the hotspots in the field of environmental remediation because of their low cost,easy synthesis and environmental protection.BiVO4 has a suitable band gap(2.4-2.6 eV)position and good visible light absorption.It is a potential photocatalyst,but it is not optimal to degrade organic pollutants and reduce heavy metal ions under visible light.Therefore,by constructing a heterojunction or doping of the BiVO4 nanomaterial,it has good photocatalytic performance.The band gap position of g-C3N4 nanosheets is about 2.7 eV,which has the advantages of good light absorption and thermal stability,but the disadvantage is that the charge recombination is sernous,so by doping or finding the band gap matching semiconductor and composite to improve the separation efficiency of charge and thereby improve photocatalytic performance.BiOCl nanosheets inhibit the formation of photogenerated electrons and holes by the formation of dipole moments due to the layered structure itself.However,the band gap of BiOCl(3.19-3.5 eV)leads to poor light absorption in the visible region,so by doping or Finding a semiconductor compound that matches its band gap expands the absorption range of BiOCl for visible light and improves photocatalytic performance.This paper mainly includes the following three parts,the specific contents are as follows:1.Preparation and photocatalytic properties of BiVO4/Bi2S3 compositesBismuth sulphide(Bi2S3)is a promising photocatalyst for photocatalysis because of its unique electrical and optical properties.It is also an inorganic p-type semiconductor material and is widely used in the field of photocatalysis.We chose Bi2S3 to be combined with BiVO4,mainly based on Bi2S3 with better visible light absorption capacity.Firstly,we prepared a dumbbell-shaped BiVO4 precursor by hydrothermal method,and then added a certain concentration of sodium sulfide nonahydrate solution to prepare BiVO4/Bi2S3 composite by hydrothermal method by regulating BiVO4 precursor.The successful preparation of the material was confirmed by characterization of SEM,XRD,Raman spectra,UV-vis DRS and so on.Electrochemical tests on It-curve,EIS,etc.were also carried out,and it was found that the composite material has higher photocurrent and lower resistance,which proves that the photogenerated charge has a lower recombination probability.In addition,the experimental results of photocatalytic reduction of potassium dichromate are consistent with the characterization results of electrochemical tests,which proves the rationality of our analytical methods2.Preparation and photocatalytic properties of Fe2O3/g-C3N4 compositesDue to the high uniformity of the Fe2O3 quantum dots in the g-C3N4 nanosheet plane,the iron-based compound has close contact with the g-C3N4 nanosheet,thus accelerating the interface electron between the Fe2O3 quantum dot and the g-C3N4 nanosheet.Increased separation of photogenerated charges.In particular,the Fenton reagent system consisting of Fe2O3/g-G3N4 composite material and H2O2,wherein g-C3N4 nanosheets play a synergistic role in increasing the photocatalytic reaction rate Since the g-C3N4 nanosheet is excited by light to generate electrons and holes,in which electrons participate in and promote the redox cycle between Fe3+ and Fe2+,the overall photocatalytic reaction rate is increasedThe experiment first prepared ultrathin carbon nitride nanosheets by thermal polymerization.Then,adding ferric chloride hexahydrate solution,the Fe3+ is well adsorbed on the surface of the carbon nitride nanosheet by ultrasonication and stirring reaction,and then the ammonium hydrogencarbonate is added to adjust the pH of the solution.Finally,a composite of Fe2O3/g-C3N4 was obtained by different treatment of the above solution.The characterization of SEM,XRD,UV-Vis DRS and FT-IR,as well as the characterization of It-curve,IMPS and EIS,showed that the composites exhibited better optoelectronic properties.The data of the degradation test of p-nitrophenol by light-driven Fenton catalysis is consistent with the data obtained by the previous photocurrent test,indicating that the composite prepared by us has excellent photocatalytic activity.3.Preparation of Co-BiOCl composite nanosheets and their photocatalytic propertiesDue to its unique layered structure,bismuth oxychloride(BiOCl)nanosheets are typical photocatalysts,but their poor light absorption in the visible region is also very limited in their practical application in photocatalytic degradation of pollutants.In various methods of broadening the light absorbing region,doping modification is an effective method because it can customize the tape structure by forming a doping level without substantially changing the layer structure.In this case,the electrostaticfieldin the BiOCI crystal can be retained.Because cobalt(Co)has good photoelectric properties,it is an ideal element for doping modification,which not only enlarges the light absorption region but also improves the charge separation efficiency of the composite.In this work,cobalt-doped BiOCl nanosheets were prepared by a simple hydrothermal method.The composites were characterized by SEM,XRD,and FT-IR,and the photocurrent tests showed that the composites exhibited better optoelectronic properties.The experimental data of carbon dioxide reduction by composite materials prove that the composite has excellent photocatalytic performance.Finally,our experimental design is reasonable.