Study On Preparation And Modification Of TiO₂ Nanorod Arrays

In order to cope with the worldwide energy crisis and environmental pollution,human beings are gradually trying to develop and use solar energy,an inexhaustible new energy source.Solar cell is an important carrier for converting solar energy into electric energy,and plays a key role that cannot be ignored in this process.As a core part of solar cell,semiconductor materials are the basis for the rational design and application of solar cells by scholars from various countries.Semiconductor titanium dioxide（TiO₂）is a commonly photoanode material for solar cells,and has been widely used in many aspects such as photoelectric conversion,photocatalytic degradation（hydrogen production）,and light splitting water.Because of the unique energy level structure,good light stability,non-toxic and easy preparation,it has broad application prospects in the fields of biology,environment and energy.Among the various morphologies of TiO₂ nanomaterials,the highly ordered one-dimensional nanorod array structure has attracted people’s research and attention deeply due to its high electron transfer efficiency,good light scattering effect,and low interface resistance.In this thesis,a dense and ordered TiO₂ nanorod（TNR）arrays are prepared by hydrothermal method on fluorine-doped tin oxide（FTO）conductive glass.Noble metals and narrow band gap semiconductors were used to construct ternary system,at the same time,the morphological characterization and photoelectric performance of the obtained system were studied and discussed.The main research contents are as follows:Using FTO conductive glass as a substrate,single crystal TNR arrays were first prepared by hydrothermal reaction,and then Ag-Ag₂S quantum dots（QDs）co-modified TNR arrays were synthesized by wet chemical method.The size and content of Ag₂S quantum dots were controlled by changing the reaction time of the sample Ag/TNR in the N-N-dimethylformamide solution.The obtained samples were tested in structural and properties.The results show that the sample of Ag-Ag₂S（12 h）/TNR has the best photocurrent density（0.082 mA/cm²）and photocatalytic efficiency（62.2%）,which are 5.5 and 1.85 times that of the TNR.The reasons for the performance improvement can be summarized as the following two aspects:on the one hand,the local plasmon resonance（SPR）effect of the noble metal Ag broadens the light absorption range of the sample,and on the other hand,the synergistic effect between Ag-Ag₂S materials accelerates the transport and transfer of photo-generated carriers.Therefore,the synergistic effect between Ag-Ag₂S can inhibit the recombination of electron-hole pairs,and improve the overall photoelectrochemical and photocatalytic performance of Ag-Ag₂S/TNR materials.Highly ordered TNR arrays co-modified with In₂S₃ nanosheets and CdS quantum dots were successfully constructed through continuous hydrothermal reaction and in-situ cation exchange methods.The effect of the content and size of CdS quantum dots on the overall performance of sample was investigated by changing the reaction time of the samle TiO₂/In₂S₃ in Cd²⁺solution.The morphology and photoelectric properties of all samples were studied.The experimental results show that compared with unsensitized TiO₂ nanorod arrays,TiO₂/In₂S₃/CdS ternary heterostructure arrays can enhance the absorption of visible light and accelerate the transfer photogenerated electrons on the sample surface,thereby improving photoelectrochemical and photocatalytic performance.The photocurrent density（0.18mA/cm²）and photodegradation efficiency（58.8%）of TiO₂/In₂S₃/CdS（30 min）are about 18times and 6 times that of the unsensitized TNR,respectively.The enhancement of these properties is closely related to the synergistic effect between the components of the TiO₂/In₂S₃/CdS heterostructure arrays.Specifically,due to the relatively narrow band gaps of In₂S₃ and CdS,there are type II nano-heterojunctions at the interface of TiO₂/In₂S₃ and In₂S₃/CdS.This different electron transfer paths greatly improve the electron transmission efficiency.In addition,In₂S₃ nanosheets with a larger surface area can enhance the absorption of visible light.These synergistic effects improve the overall performance of the ternary system.