| The dissertation is aimed at developing ecological environment function material for environmental pollution prevention. We investigate environment-friendly functional compound nanomaterials which is capleble of efficiently reducing organic pollutants and heavy metal ions. Anodic titanium dioxide nanotube (TiO2 NT) arrays with highly orientation and controllable structure and its composite nanomaterials were used as media throughout the whole thesis. The research focuses on the methods to enhance the adsorption performance and photoelectrocatalytic activity of TiO2 NT. The photoelectric performance of nanomaterials and their applications in environmental pollution control were studied in depth.Titanium dioxide nanotube prepared by anodic oxidation method is an ideal and stable three-dimensional structure nanomaterial with highly ordered orientation, open ceiling, large specific surface area and uniform pore size. However, the utilization efficiency of visible light is very low due to its wide band gap. In addition, the efficiency of photocatalytic degradation is limited by the high recombination rate of photogenerated electron-hole pairs and low adsorbility to organic pollution. Therefore, the aims of our work are to enhance the charge separation of composite system and expand the spectral response range or improve the adsorbility to organic pollution using surface hydrophobic modification. The details are summarized as the following:(1) The effects of electrolyte and oxidation voltage in the fabrication of TiO2 NT through anodic oxidation on the surface topography and length of the resulted TiO2 NT arrays were studied. Moreover, the growth mechanism of TiO2 NT was investigated in detail.(Chapter Two)(2) TiO2 NT array was for the first time modified with inorganic semiconductor-imprinted film by molecular imprinting technique via sol-gel process. The resulting composites not only improve TiO2 NT adsorption ability, but also enhance the photocatalytic degradation efficiency to target molecule. It was found that the thickness of molecular imprinting film affected light absorption of the modified materials, and an obvious red-shift was observed in the light absorption of the thick molecular imprinting film. The photocurrent density and adsorption capacity of the thin molecular imprinting film modified TiO2 NT are 1.6 times and 5 times higher than that of the pure TiO2 NT, respectively. After 40 min, the removal efficiency of target molecule for the modified TiO2 NT is 100% while that for the pure TiO2 NT is only 57.4%. Its photocurrent density and photocatalytic activity of the thick printing film modified TiO2 NT are lower than that of the thin one due to thicker film obstructing the light absorption in the visible light range. Meanwhile, the inorganic imprinting film modified TiO2 NT show excellent photochemical stability and high reuse rate.(Chapter Three)(3) Two novel composites using surface modification of TiO2 NT with CuInS2 or CuInSe2 via pulse potential electrodeposition were prepared. The visible light response range of the TiO2 NT modified with CuInS2 nanoparticles expand to 730 nm, which strongly enhanced the absorbance to the visible light. We observed that the loading of CuInS2 can influence the photoelectric property, and the photocurrent density of the TiO2 NT modified with CuInS2 through 300-sequence deposition is 3 times higher than the pure TiO2 NT. The resulting composites significantly enhanced photocatalytic activity towards 2,4-dichlorophenoxyacetic acid (2,4-D). The absorption of CuInSe2-TiO2 NT composites in the visible light region also remarkablely increased. It was found that the response to the visible light and photocurrent density of CuInSe2 nanoparticles were variational under different concentrations of solutions and voltages. The higher the deposition voltage is, the larger photocurrent density shows; and the lower the solution concentration is, the smaller nanoparticles exists. Additionally, the efficiencies of simultaneous detoxification of 2,4-D and Cr(?) were also discussed, where the removal rates of pollutant using CuInSe2/TiO2 NT were lower than using CuInS2-TiO2 NT due to the relatively weak light absorption and photocurrent density.(Chapter Four)(4) A new ZnTe modified TiO2 NT catalyst was prepared by pulse potential electrodeposition of ZnTe nanoparticles (NPs) onto TiO2 NT arrays. The even distribution of ZnTe NPs was well-proportionedly grown on the top surface of the TiO2 NT without clogging the tube entrances. Compared with the unmodified TiO2 NT, the ZnTe modified TiO2 NT (ZnTe/TiO2 NT) showed significantly enhanced photocatalytic activity towards 9-AnCOOH under simulated solar light. After 70 min of irradiation, 9-AnCOOH was degraded with the removal ratio of 45% on the bare TiO2 NT, much lower than 80%,90%, and 100% on the ZnTe/TiO2 NT with the ZnTe NPs prepared under the pulsed "on" potentials of -0.8 V,-1.0 V, and -2.0 V, respectively. The increased photodegradation efficiency mainly results from the improved photocurrent density as results of enhanced visible-light absorption and decreased hole-electron recombination due to the presence of narrow-band-gap p-type semiconductor ZnTe. Additionally, ZnTe/TiO2 NT prepared under -2V can selectively detect dopamine in coexistence with ascorbic acid and uric acid, and the linear ranged from 1.0×10-6 mol/L to 6×10-5 mol/L and the detection limit was 1.0×10-6 mol/L.(Chapter Five)(5) Graphene films with high quality (large specific surface area, uniformity, continuity, and transparence) and small Ag nanoparticles, served as co-photogenerated electron transporters and acceptors, were decorated on TiO2 nanotube arrays via in situ electrodeposition and photodeposition, resulting in a novel ternary composites photocatalyst, which greatly facilitate photogenerated electron-hole pairs to separate. The cooperation between graphene and Ag nanoparticles significantly enhances light absorption in the visible range as well as photocatalytic ability of TiO2. It was found that the photoelectric properties of the ternary composites were influenced by different AgNO3 concentrations. The results show that the conductivity and the light response range of the ternary composites is the most excellent under 6 mM AgNO3, and the photocurrent density is 4 times higher than pure TiO2 NT. After 160 min,2,4-D can completely degrade, where the degradation efficiency is ten times higher than pure TiO2 NT. This strategy is expected to explore advanced TiO2-based photocatalysts in environmental remediation.(Chapter Six)... |
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