Preparation And Photoelectrochemical Properties Of ZnO-Based Composites

Zinc oxide（ZnO）is considered as an ideal photocatalyst material because of its low manufacturing cost,rich morphology,easy synthesis and high carrier mobility(～155 cm²V^-1s-1).However,ZnO has a wide band gap（～3.3 e V）,which results in its photoactivity only in the UV region and the easy recombination of photogenerated electrons and hole pairs,thus hiding its practical application.In this paper,ZnO as the matrix,through the method of ion doping,construction of multidimensional structure and construction of heterogeneous structure to explore the synthesis of ZnO based composite,in order to improve the photoelectric chemical properties of ZnO.The main research results are as follows:（1）Orderly ZnO nanorods were grown on a-plane sapphire substrate coated with gold film by chemical vapor deposition method.The N-ZnO nanorod array photoanode was then prepared by annealing in ammonia（NH₃）atmosphere to achieve N doping.The study found that under suitable reaction pressure and NH₃ flow rate,the doping of N element and ZnO can be achieved.The photoelectrochemical（PEC）performance test and characterization of undoped ZnO nanorod arrays and N-ZnO nanorod arrays proves that N doping is beneficial to improve the PEC performance of ZnO.（2）Three-dimensional（3D）single-crystal cross-linked ZnO nano-networks were grown on gold-coated r-plane sapphire substrates by chemical vapor deposition using a counter-tilted epitaxial growth strategy.Compared with the one-dimensional ZnO nanostructure,the pure three-dimensional structure has improved photoelectrochemical properties.The N-doped 3D single-crystal cross-linked ZnO nanomaterials were also prepared by annealing in NH₃ atmosphere.The relationship between different annealing times and the photoelectrochemical performance of ZnO was investigated to obtain the most suitable conditions.Setting the same reaction pressure and NH₃gas flow rate as in the above experiments,when the doping time is 1 h,the photoelectrochemical properties of N-doped 3D single-crystal cross-linked ZnO nanomaterials are the best.The excellent PEC performance of N-doped 3D single-crystal cross-linked ZnO nanomaterials is explained by the charge transport kinetics and the semiconducting mechanism.（3）The 3D single crystal cross-linked ZnO nano-network structure described above is used as the matrix,bismuth nitrate（Bi（NO₃）₃.5H₂O）and vanadyl acetylacetonate(C₁₀H₁₄O₅V)are used as precursors,and ethylene glycol dimethyl ether is used as solvent.The 3D-ZnO/BiVO4 composite samples were prepared by metal organic decomposition method.The influence of the thickness of the BiVO4 shell wrapped on the surface of ZnO nanowires on the morphology,structure and optical properties of the samples was explored,and the reasons were analyzed.