本研究以胺基乙酸、尿素、硫脲等化合物當燃料(還原劑)，硝酸氧鈦為氧化劑使用溶液燃燒合成法製備TiO2粉體，探討TiO2粉體與薄膜特性與其在光觸媒及染料敏化太陽能電池之應用。改變燃料/氧化劑之比例，分析燃燒反應之機制與所合成之TiO2特性。本研究發現燃料/氧化劑比例將決定最高燃燒反應溫度，進而影響合成的TiO2之比表面積、結晶晶粒大小以及其anatase結晶相之含量。合成之TiO2含有含碳物，結晶結構為純antase相或是antase-rutile之混相。
TiO2之光觸媒光降解活性，與比表面積、結晶晶粒尺寸、antase相之含量與可見光-紅外光之吸收能力，有一定程度之相關性。結晶結構為混相且rutile相之含量＜25%之TiO2，比結構為純anatase相之TiO2，有較佳的光觸媒光降解能力；然而，當rutile相含量＞25%之TiO2，有較差之光觸媒光降解特性。本研究所合成之TiO2相較於商業化之Degussa P25 TiO2有較好的光觸媒光降解能力，其原因是因為含碳物種以及表面吸附之大量氫氧基。
本研究合成之TiO2應用在染料敏化太陽能電池之光電極時，因為其含碳或是硫之雜質，使其半導體能隙降低，展現可吸收可見光之良好特性。本研究所合成之TiO2擁有接近的開環電壓與填充因子，且對光電轉換效率只有些微影響。光電轉換效率不只與短路電流有特定關係，而且主要由短路電流決定，而當結晶顆粒較大時，因為光散射效應，會有較佳的短路電流；當有較多雜質將導致電流傳輸阻力增大，使短路電流降低。另外，粉體之比表面積也是影響短路電流與光電轉換效率之重要因素。

Titanium dioxide (TiO2) has demonstrated several potential applications, including photocatalysts, dye-sensitized solar cell (DSSC), pigment, and electronic data storage memory, etc. In this thesis, TiO2 powders were synthesized by a solution combustion synthesis method in which glycine, urea and thiourea were used as the fuel and titanyl nitrate was used as the oxidizer. Various fuel-to-oxidizer ratios were studied for their effects on the combustion phenomena and the properties of the synthesized TiO2. The fuel-to-oxidizer ratio was found to determine the maximum combustion temperature, which in turn affects the specific surface area, crystallite size, and weight fraction of anatase phase of the synthesized TiO2. The synthesized TiO2 all contain carbonaceous species and are either pure anatase or anatase–rutile mixed phase in crystalline structure.
The photocatalytic activity of the TiO2 was found to correlate to a certain degree with the specific surface area, crystallitesize, weight fraction of anatase phase, and visible and IR absorbances. The mixed phase TiO2 shows a higher photocatalytic activity than the pure anatase phase TiO2 when containing a small fraction (＜~25 wt%) of rutile phase but a lower phoyocatalytic activity when containing a large fraction (＞~25 wt%) of rutile phase. The synthesized TiO2 all show higher photocatalytic activity than Degussa P25 TiO2. The enhanced photocatalytic activity was attributed mainly to sensitization by the carbonaceous species and larger amounts of hydroxyl group adsorbed on the TiO2 surface.
These TiO2 nano powders were used to fabricate photoelectrodes for the DSSC and their performance was compared to that of the DSSC fabricated with Degussa P25 TiO2. The results showed that the TiO2 could work well as photoelectrode for DSSC. The solution combustion synthesis TiO2 contained impurities of C and/or S, thus exhibiting visible light absorption and reduced band gap. The open circuit voltage and the fill factor both varied little among the various TiO2 and thus both had little effect on the photoelectrical conversion efficiency (η). However, the variation of η was seen to be in quite a good agreement with that of the short circuit current (Isc), suggesting that η was dominated by Isc. Isc was found to be enhanced by light scattering effect due to the presence of large particles but reduced by high impurity content due to an increase in electron transfer resistance. In addition, the specific surface area of the powders was found to be an important factor affecting the Isc and thus the η.

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