Stduy On Preparation And Photoelectrochemical Properties Of Modified TiO₂ Nanotube Array Composite Material

Titanium dioxide(TiO₂)is widely used in photoelectrochemical water splitting due to its good chemical stability,high refractive index,low cost and non-toxicity.Among various TiO₂ nanomaterials,one-dimensional TiO₂ nanotubes have a higher specific surface area and excellent charge transport ability,which has attracted more and more attention.In order to further improve the performances of TiO₂ nanotubes,modification treatment is an indispensable step.In this thesis,a variety of modification methods are used to effectively improve the photoelectrochemical performance of TiO₂ nanotubes starting from the microstructure.The main research contents are as follows:(1)TiO₂ nanotubes were prepared on Ti foils by anodization,and ZnO nanorods were deposited on the TiO₂ nanotubes by the hydrothermal method.The results show that the ZnO/TiO₂ heterostructure has a higher photocurrent than the TiO₂ nanotubes prepared by anodization.After comparing the hydrothermal concentration of different ratios,the optimal hydrothermal concentration of Zn²⁺was determined to be 0.07mol/L.At this concentration,the photocurrent density of the ZnO/TiO₂ heterojunction reached 40.7?Acm^-2,which was 2-3 times that of pure TiO₂ nanotubes.(2)TiO₂ nanotubes were prepared by two-step anodization,black TiO₂ nanotubes were prepared by electrochemical reduction and ZnO/TiO₂ nanotubes were prepared by hydrothermal growth of ZnO.The results show that Ti³⁺and O_V produced by electrochemical reduction reduce the impedance of charge transport in TiO₂,and effectively increase the quantum efficiency and the range of visible light photoresponse.In addition,the recombination of ZnO further inhibits the recombination of light-excited electrons and holes,and accelerates the separation and transfer of charges.Under the coordination of the two,we got the highest photoelectric conversion efficiency of 0.078% under the bias voltage of 0.718V vs.RHE.The photocurrent density of ZnO/two-layer black TiO₂nanotubes also reached 121.8?Acm^-2,which was about 5 times that of the unmodified TiO₂ nanotubes.(3)SrTiO₃/B-TNTs heterojunction was prepared by hydrothermally depositing SrTiO₃nanocubes on black TiO₂ nanotubes prepared by two-step anodization and electrochemical reduction.Under the interface reflection of the SrTiO₃ nanocube 3-D structure and the polarizing electric field,the photoelectrochemical performances of SrTiO₃/black TiO₂nanotubes hve been greatly improved.The highest photocurrent density was obtained by hydrothermal deposition for 1h,which was about 61.4?Acm^-2.Combined with electrochemical reduction,under the synergistic optimization of the two,the photocurrent density reached 103.5?Acm^-2,which was 4 times that of pure TiO₂ nanotubes.The high photocurrent density reflects excellent photocatalytic activity,which provides favorable conditions for photoelectrochemical water splitting.