Fabrication, Characterization And Optoelectronic Performance Of TiO₂ Nanotube Arrays By Anodization

In the work, TiO₂ nanotube array films were assembled by anodization. Firstly, the fabricating process conditions were optimized and the growth mechanism of TiO₂ nanotube arrays was presented based on effect factors of fabricating TiO₂ nanotube array by anodization. Secondly, different-thick TiO₂ nanotube array films were prepared with controlling the anodic oxidation time, the photocatalytic reaction were analyzed and discussed after the films were characterized via FE-SEM, FE-TEM, XRD and XPS. Thirdly, FS-TNT(free-standing TiO₂ nanotube) array films were prepared by combined three-step anodization and heat treatment, the preparation mechanism of FS-TNT arrays were deeply, detailedly discussed and then presented based on FE-SEM, XRD analysis and the growth mechanism of TiO₂ nanotube arrays, the following mechanism were further confirmed by XPS and EDX. Lastly, the composite films were prepared by assembling FS-TNT and P25 paste film, namely FS-P25, FS-P25 as anode were used to fabricate dye-sensitized solar cells and the cells showed the biggestη% with FS2-P25, and the photocatalytic performances of FS-P25 were evaluated via degrade MB, the photocatalytic kinetics corresponded to first-order kinetics model and the reaction rate is the maximum when FS2-P25 were used for the photocatalyst.(1) Effect factors and growth mechanism of TiO₂ nanotube arrays by anodizationThe effect factors of fabrication TiO₂ nanotube arrays, including electrolyte, work voltage, cathode material and reaction time, were specifically analysed and discussed, then the preparing conditions of TiO₂ nanotube arrays were further optimized, the electrolyte for EG (polyethylene glycol, reference) +0.5wt%NH4F+3.0vol%H2O, work voltage for 60V, the distance between anode and cathode for 3cm, cathode for Pt electrode, the first anodic time for 0.5h. Subsequently, the growth mechanism of TiO₂ nanotube array films were discussed and summarized.(2) The photocatalytic performance of TiO₂ nanotube arrays were researchedThe removing deposit of TiO₂ nanotube mouth by anodization confirmed that these deposits were almost complete obliteration after these nanotubes had been soaked into 3.0wt% H2O₂ solution for 2h, and the morphology structure of nanotubes kept well. The effect of heat treatment on the nanotube morphology structure showed the nanotube antase(A) crystalline of TiO₂ annealed at 450℃had reached to perfect. Followingly, TiO₂ nanotube arrays with 1⁴h anodic time were used in resorption-desorption process and photocatalytic reaction, the results demonstrated that the nanotubes resorption ability for MB increased with heat temperature and the same-length nanotubes annealed at 450℃manifested the optimal performance, especially, the degradation efficiency of Rh.B was up to 93.40% with the nanotubes anodized for 2h, furthermore, the photocatalytic reaction during 0⁸0min corresponded to first-order kinetics model and the maximal reaction rate constant(k=0.03267min-1) was corresponding to the nanotubes with anodic time 2h.(3) The preparing mechanism of FS-TNT array filmsFS-TNT array films were prepared via adopting three-step anodization and heat treatment. FS-TNT array films with nanotube bottom open, nanotube bottom close, nanotube bottom close with thin TiO₂ compact layers were detected via FE-SEM and the preparation mechanisms were discussed and presented based on FE-SEM, FE-TEM, XRD ananlysis and the growth mechanism of TiO₂ nanotube arrays. Then XPS analysis checked the preparation mechanism of FS-TNT array films.(4) The photocatalysis and DSSCs based on FS-P25FS-P25 composite films were assembled based on FS-TNT array films and P25 paste films and then used as photoanode to fabricate DSSCs, and the cells performance showed that DSSCs with FS2-P25 exhibited the biggestη%. Meanwhile, FS-P25 were used to degrade MB and the degradation efficiency were 78.46% corresponding to the biggest first kinetic constant k=0.01822min-1.