Construction And Photocatalytic Performance Of Visible Light Active BiVO₄-Based Composites

Photocatalytic technology is considered to be the most promising new generation of environmental remediation technology because of its advantages of using solar energy,environmental friendliness,mild reaction and thorough purification.It is of great significance to develop efficient photocatalytic material systems for environmental treatment.Among them,BiVO₄,as a visible light-responsive photocatalytic material,has a deep valence band energy level（2.7-3.0 eV）,which is higher than that of Cl₂,O₃,and H₂O₂,KMnO₄.The electrode potential of potassium permanganate has a strong oxidizing property.Nevertheless,the small specific surface area and low quantum efficiency of BiVO₄ limit its photocatalytic performance.In this paper,from the perspective of regulating the micro-nano structure of BiVO₄-based photocatalytic materials,through the construction of heterojunction,MOF（DUT-5）and semiconductor（AgIn₅S₈）are compounded with BiVO₄ respectively,and the reactive sites of the material are increased.The photoresponse ability is enhanced,and then the photocatalytic performance is improved.The specific research contents are as follows:（1）Using bismuth nitrate pentahydrate as the bismuth source,two kinds of BiVO₄ with different morphologies,leaf-like and needle-like,were synthesized by changing the ratio of morphology regulator and solvent.Then,two MOFs（NH2-MIL-101 and DUT-5）were compounded with the above two kinds of BiVO₄,respectively.From the obtained series of materials,it was found that only DUT-5 synthesized with aluminum nitrate nonahydrate as the aluminum source was loaded onto leaf-shaped BiVO₄ nanosheets,and the obtained DUT-5/BiVO₄ composite photocatalyst had enhanced Photocatalytic performance compared with the two monomers,and a series of composites with different mass ratios were prepared by changing the loading of DUT-5.（2）DUT-5/BiVO₄ was dye-sensitized with RhB with strong light-harvesting ability,and the effect of RhB sensitization on the performance of DUT-5/BiVO₄ composite photocatalytic material was explored.DUT-5 with large specific surface area has an effect,and the obtained RhB/DUT-5/BiVO₄ nanocomposite has better photocatalytic performance than DUT-5/BiVO₄.BET characterization and photoelectrochemical performance tests showed that the main reasons for the enhanced photocatalytic performance of the composites were the increase of active sites for adsorbing pollutants and the acceleration of charge transfer.Based on the trapping experiments and characterization test results,a possible type Ⅱheterojunction photocatalytic reaction mechanism is proposed.（3）Using silver nitrate as the silver source,two different AgInsSs nanomaterials were first synthesized in different solvents（water and anhydrous ethanol）,and then these two AgIn₅S₈ nanomaterials were added to the decahedral BiVO₄.A secondary hydrothermal process is performed in the precursor solution.Photocatalytic experiments show that the AgIn₅S₈/BiVO₄ composite photocatalytic material synthesized with anhydrous ethanol has enhanced photocatalytic performance.Finally,the material was photoreduced in a certain concentration of silver nitrate solution,and the reduced Ag acted as a bridge for electron transfer between AgIn₅S₈ and BiVO₄,and at the same time,the SPR effect produced by noble metal Ag broadened the visible light response range of the material.The UV-vis DRS characterization shows that the Ag/AgIn₅S₈/BiVO₄ composite photocatalytic material has enhanced light absorption capacity than the monomer,and the Mott-Schottky test results show that BiVO₄ and AgIn₅S₈ have lower oxidation potential and higher reduction potential,respectively,and combined with the trapping experiments,a possible Z-type heterojunction photocatalytic reaction mechanism is proposed.