Study On The Fabrication And Photoelectrochemical Properties Of TiO₂ Nanotube Films

The unique physical chemistry properties of TiO₂ nanotube films derived from high surface-to-volume ratios and specific architectures, making them of great applicable potential in the fields of photocatalysis, gas sensing, photoelectrolysis, and photovoltaics. Therefore, the fabrication of TiO₂ nanotube films and the exploration of their potential in practical application have been attracting more and more attention. In this dissertation, highly ordered TiO₂ nanotubes were prepared via LPD-template method and anodization, the microstructure and photoelectrochemical properties of TiO₂ nanotube films were characterized and analyzed through various methods. In addition, the photoelectrocatalytical performances of prepared TiO₂ nanotube films were investigated and the WO3/TiO₂ nanotube composite films with energy storage ability were prepared via electrodeposition method.The TiO₂ nanotube films were in-situ synthesized by liquid-phase deposition (LPD) on AAO template. The results indicate the clear nanotube structure can be obtained in macroporous AAO template but nanowire is inclined to be obtained by choosing AAO with small pore size. In addition, the method of LPD was also successfully applied to the fabrication of SnO2 nanotube films.The effects of different electrolytes in the fabrication of TiO₂ nanotube array films were investigated. The results showed TiO₂ nanotube arrays grew rapidly in ethylene glycol-based electrolytes, besides, the obtained nanotubes could reach 3μm in length within 30min and have optimal morphology with compact arrangement, uniform tube length, and smooth tube-wall. The photogenerated potential of the nanotube array electrode with the thickness of 2.0μm reached about 450mV under the illumination of simulated solar light, which was obviously higher than that of the nanotube films obtained in inorganic solution, and the saturated photocurrent density of the former exceeds 1mA·cm-2 when a bias potential was applied. The assosiated impedance analysis indicates the photoelectrochemical properties of TiO₂ nanotube films are largely influenced by their microstructures.The photoelectrocatalytic properties of various TiO₂ nanotube array films were investigated by their degradation efficiency of MB dye. The critical factors of photoelectrocatalysis, for instance, bias potential, electrolyte, initial pH value were analyzed. The results indicate the degradation efficiency of organic target is greatly enhanced by the synergetic effect of photoelctrocatalysis and the superior adsorbility of nanotubular structure. The TiO₂ nanotube array prepared in ethylene glycol-based electrolyte could degradate almost total MB by applying an electrical bias of +0.6V (vs. SCE) under simulated solar light illumination within 60min and exhibited the highest degradation efficiency to others.The energy storage materials were effectively loaded on TiO₂ nanotube arrays through electrodepostion and the influence of the technology conditions in the electrodeposition process towards the morphology of the composite films were studied in detail. The energy storage capabilities of the composite films were investigated through the evaluation of the recovery time of open-circuit potential and the results showed that the photogenerated electrons could be effectively stored during illumination and released slowly when illumination was ceased, the recovery time of the OCP exceeded 7h when illuminated for 30min. The specific property can be applied in solving photo-induced cathode protection for some metal materials in dark condition.