光催化還原二氧化碳生成甲醇與甲烷之研究;Photocatalytic Reduction of Carbon Dioxide to Form Methane and Methanol

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題名:	光催化還原二氧化碳生成甲醇與甲烷之研究;Photocatalytic Reduction of Carbon Dioxide to Form Methane and Methanol
作者:	陳郁文
貢獻者:	中央大學化學工程與材料工程學系
關鍵詞:	化學工程類
日期:	2008-09-01
上傳時間:	2012-10-01 11:15:56 (UTC+8)
出版者:	行政院國家科學委員會
摘要:	一般而言，能障小於3eV的物質通稱為半導體，可以提供一個特定的能域，讓光催化產生的電子與電洞不會重新結合，傳導帶最低的能階大小可以視為光電子的還原能力，價電帶最高層的能階大小，可視為光電洞的氧化能力，當光線的能量（hν）比半導體能障高時，會能讓傳導帶的電子躍升到價電帶上，同時在價電帶產生一個電洞，激發的電子可以被半導體的添加物捕捉停留，或是跨越到觸媒的表面而與反應物進行氧化還原反應。二氧化鈦可耐強酸，在光化學反應中不會有自溶解的現象，加上礦物原料豐富，價格低廉，是非常適合的光觸媒選擇，銳鈦礦型（anatase）二氧化鈦的傳導帶電位比金紅石型（rutile）二氧化鈦的電位低，因此具有更高的還原力。縮小二氧化鈦的粒子，可以提升價電帶的電位，讓原本無法在半導體上進行的反應，可以在半導體量子顆粒上發生，另外，加入貴重金屬引起SMSI (strong metal support interaction)效應，可增加捕捉電子的機率以及幫助電子跟電洞的分離，因而提升光觸媒的活性，本研究目標在提升CO2以及H2O轉化成燃料分子的效率，提高可見光吸收量、反應物吸附量以及延長激發電子的壽命，探討不同貴重金屬擔載在二氧化鈦的效果、測試以TUD-1 為擔體之中孔觸媒，研究CO2還原反應中的速率決定步驟並設計光觸媒反應器。 ; In general, solids with band gap energies less than 3 eV are considered to be semiconductors which possess a void energy region where no energy levels are available to promote recombination of an electron and hole produced by photoactivation in the solid. The energy level at the bottom of the conduction band reflects the reduction potential of the photoelectrons, whereas the uppermost level of the valence band is a measure of the oxidizing ability of the photoholes. When a photon with energy of hn exceeds the energy of the band gap, an electron (e–) is promoted from the valence band to the conduction band leaving a hole (h+) behind. Either charge carriers may recombine or be trapped by impurities and dopants within the crystal or at its surface, or they may cross the particle surface and initiate redox reactions of the adsorbed molecules. TiO2 can stand strong acid and show no self-dissolution phenomenon in photo reactions. Besides, TiO2 is a suitable choice for photocatalysts due to its sufficiency of yield and cheap price. The conduction band energy of anatase is lower than rutile. So anatase has stronger reduction ability than rutile. By decreasing the particle size, it is possible to shift the conduction band to more negative potentials and the valence band to more positive potentials as a result of quantization effects. Hence, redox processes that cannot occur in bulk materials can be facilitated in quantized semiconductor particles. In addition, adding novel metal to induce SMSI effect can increase the possibility of trapping electrons and separating electrons and holes. The present proposal is aimed at an efficient use of photons to improve efficiency in the highly desired conversion of CO2 and H2O into fuel molecules, such as CH4, CH3OH, or even Fisher Tropsch-like products. The proposed research comprises catalyst development and practical reactor design, both aiming at highly efficient light harvesting. The photocatalysts should have well designed characteristics, such as large absorption of, preferably, visible light photons, a long lifetime of activated states, a good adsorption of reactants CO2 and H2O. Novel approaches include various other transition-metals loaded TiO2. Ti-based mesoporous catalysts based on TUD-1. Modification of various of nano-structured TiO2 with Cu2O might further enhance the visible light sensitivity and performance. Ti-based mesoporous materials will be test as well. Another challenge is to design an optimized photoreactor: illumination of the active sites and desorption of products need to be maximized. ; 研究期間 9708 ~ 9807
關聯:	財團法人國家實驗研究院科技政策研究與資訊中心
顯示於類別:	[化學工程與材料工程學系 ] 研究計畫

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