| Summary: | 博士 === 中原大學 === 化學研究所 === 98 === Part 1. Preparation and Characterization of Mesoporous TiO2
In this part, the mesoporous titanium dioxide (MTO) series, TP, TB, TO, TDM and TDB were prepared by the sol-gel polymerization using the water miscible imidazolium ionic liquids, 1-propyl-3-methylimidazolium tetrafluoroborate ([Pmim][BF4]), 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]), 1-octyl-3-methylimidazolium tetrafluoroborate ([Omim][BF4]), 1,1’-dimethyl-3,3’-methylene bisimidazolium dichloride ([Mmbi][Cl]2) and 1,1’-Dimethyl-3,3’-(1,4-tetramethylene) bisimidazoliumdichloride ([Mbbi][Cl]2) as the template, respectively. The imidazolium π-π stacking of the ionic liquids (ILs) in the titanium dioxide matrix was studied by FT-IR. It was found that the imidazolium π-π stacking interaction of IL was increased with decreasing the imidazolium cation chain length and enhancing the hydrogen bonding of the anion.
The pore and crystalline structure of all the MTO samples prepared above have been studied in detail by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) measurements. It was also found that the mesoporous morphology, including surface area, average pore size, wormhole-like structure, and thermal stability of the as-prepared MTO particle were varied with the chemical structure and content of the IL used due to the different extent of imidazolium π-π stacking.
In addition, it was also found that the titanium dioxide particles with better crystallinity and wormhole-like mesoporous structure as well as with anatase and brookite structure exhibited higher photodegradation efficiencies of methylene blue (MB) under 2 hour UV irradiation than the commercial product, P25.
Part 2. Application of MTO on DSSC
In this part, the mesoporous anatase TiO2, TB3, which was synthesized with [Bmim][BF4] is selected as the working electrode material for application on dye sensitized solar cell (DSSC).. The 450 C-calcined TB3 was found maintaining mesoporous structure with the morphology that benefits the dye adsorption and electrolyte diffusion. A series of dye-sensitized electrodes were prepared with a combination of the as-prepared TB3 and P25, a commercial TiO2. It was found that the short-circuit photocurrent (Jsc) and open-circuit photovoltage (Voc) of the TB3–containing electrodes were remarkably increased with increasing the content of TB3. The improvement was ascribed to increase of the amount of dye molecules adsorbed and prolongation of the electron lifetimes (τeff). The highest light-to-electricity conversion efficiency (η) of the dye-sensitized solar cell (DSSC) was obtained from that prepared with the pure TB3 electrode and was about 60% higher than that prepared with the pure P25 electrode under the same condition.
In addition, the effect of the surface area and pore size of the IL-templated TiO2, TB and TO, prepared with 4-carbon alkyl and 8-carbon alkyl IL template, respectively, on the performance of DSSCs were also studied. It was found that both the η values of the DSSCs fabricated with TB and TO electrodes were increasing with increase of the pore size of the TiO2 samples and the highest η and Isc of DSSC were obtained from the one fabricated with TB1, which was synthesized with [Bmim][BF4] as the template with a [Bmim][BF4]/TTIP molar ratio of 1.
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