Preparation And Piezo-Photocatalytic Properties Of Surface Modified Bi-Based Composite Materials

Photocatalytic reaction has shown great potential in solving the problems of environmental pollution and energy crisis.The level of catalytic activity is closely related to the separation and migration efficiency of photogenerated carriers.The improvement of the separation and transfer of charge carriers has become the key to prepare efficient catalysts.In recent years,the separation ability of photogenerated charge and hole can be improved by using the built-in piezoelectric field caused by the deformation of piezoelectric semiconductor,and the piezo-photocatalytic system can be constructed by coupling mechanical energy and light energy to further enhance the catalytic performance of the catalyst.Bi-based semiconductor has become a popular material for piezo-photocatalytic reaction system because of its piezoelectric properties and stable photoelectric properties.However,the coupling mechanism between piezoelectric effect and photocatalytic reaction in Bi-based piezo-photocatalytic system is not clear.The piezoelectric effect is concentrated in the edge region of the material,which can not fully activate the whole to participate in the piezo-photocatalytic reaction,limiting the further improvement of catalytic activity.By studying the structure,morphology,physicochemical properties and catalytic degradation experiments of typical Bi-based semiconductors bismuth oxybromide（Bi OBr）and bismuth tungstate（Bi₂WO₆）and their composites,the effects of the introduction of piezoelectric effect on the adjustment of semiconductor energy band structure and the improvement of photogenerated carrier transfer path are deeply analyzed.The synergistic mechanism of photocatalysis heterojunction theory and piezoelectric effect is revealed,and the advantages of surface modification strategy in the preparation of high-efficiency catalysts are expounded.The main contents of this paper are as follows:Ⅰ.Bi OBr photocatalytic thin films are prepared by hydrothermal method,black phosphorus quantum dots（BPQDs）are modified on the surface of Bi OBr by spin coating method,related technological parameters of heterostructure construction are explored,direct Z-type heterostructure are constructed,and degradation reaction of organic matter methyl purple（MV）and tetracycline hydrochloride（TC）are tested and characterized.The results show that the optimal kinetic rate constant of the composite film is more than 3 times that of the pure Bi OBr film.The main active species and cyclic degradation capacity of QDs are investigated,and the effect of QDs modification strategy on improving the catalytic activity is proved.Ⅱ.In view of the limitation of photocatalytic single energy source,Bi₂Mo O₆/Bi OBr piezo-photocatalyst is prepared by hydrothermal method.Bi₂Mo O₆nanoplates are deposited on the surface of Bi OBr microspheres.The Bi OBr deformation and piezoelectric potential distribution are simulated,and the edge piezoelectric effect is proposed.The kinetic rate constant of the optimal sample in the piezo-photocatalytic system is more than 10 times that of the pure Bi OBr in photocatalytic system.The results show that the piezoelectric photoelectron effect can more effectively promote the separation of photoelectrons and holes,and improve the catalytic activity,and the mechanism of carrier separation and transfer in the piezoelectric photocatalytic heterojunction is deeply discussed.Ⅲ.The edge piezoelectric effect of heterojunction piezo-photocatalytic system is extended to the whole,the titanium carbide layer/Bi OBr and titanium carbide quantum dots（TCQDs）/Bi OBr composites are successfully prepared.The crystal structure,physical properties,optical and piezoelectric properties are explored and the main active species of the system are studied.The advantages of high conductivity quantum dot particles in the modification of Bi-based nanosheets are compared and analyzed.TCQDs promotes the integral extension of edge piezoelectric effect,activates the whole nanosheet to participate in the degradation reaction.Ⅳ.The piezo-phototronic effect of Bi₂WO₆is extended to the whole with the help of quantum dots modified strategy,and the universality of Bi₂WO₆is studied.The kinetic rate constant of the optimal composite is about 7 times that of the pure Bi₂WO₆in the piezo-photocatalytic system.This results show that the catalytic degradation performance has been greatly improved,and TCQDs,as an excellent cocatalyst,is also universal in the modification of other layered bismuth based semiconductor.The heterojunction piezo-photocatalytic system modified with high conductivity quantum dots can further improve the separation and migration efficiency of photocarriers and construct more efficient catalysts.