2009-10-012024-05-18https://scholars.lib.ntu.edu.tw/handle/123456789/702682摘要：光觸媒是異相觸媒重要的研究領域之一，有可能可以克服在選擇性氧化反應時，常見產物低選擇率的問題，例如烯類的環氧化。進行選擇性光催化氧化反應時，不僅須要特別的光觸媒，而且須要知曉反應物種結構之間的關係，因此必須從根本了解光催化的機理。但目前光催化的反應基本步驟及反應時的光觸媒狀態尚未被研究清楚，主要原因是這項研究須要結合有互補性專長的團隊才能達成。本計畫將由具有光觸媒研究經驗的台灣大學化工系觸媒實驗室，和具有光譜分析專長的西班牙高等科學委員會所屬觸媒與石油化學研究所，共同進行合作以達成以下目標。 本計畫將設計一個光譜式的光反應器，用原位(in situ)方式探測光催化反應，以揭發光觸媒反應機理，光譜分析包括使用近紅外光(NIR)-拉曼(Raman)光譜。截至目前為止，很少有用此原位方法探測光催化反應的報導，尤其是使用紅外光譜，原因是在光觸媒表面，水的強吸附覆蓋了大部分紅外光譜的信號。而在光照催化反應時，拉曼光譜則受限於原本就有瑩光(fluorescence)的強烈干擾。本計畫提出使用近紅外光雷射的拉曼光譜分析，可以有效避開瑩光的強烈干擾，同時拉曼光譜原本就沒有(或很弱)水的信號，將可順利以原位方式探測光催化反應。為了證實這個方法，初步將用TiO2/SiO2 和V5+/SiO2光觸媒，進行丙烯的光催化環氧化為測試反應。 <br> Abstract: The project 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. From the viewpoint of energy and environment, the conversion of CO2 to hydrocarbons by solar energy is the ultimate solution for CO2 emission and renewable energy. The reactions can be summarized as follows: CO2 + H2O → CH4 + O2 CO2 + H2O → CH3OH + O2 x CO2 + &#189; y H2O → CxHy + (x+ 2y) O2 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, and a relatively easy desorption of products (the fuel molecules). Various novel materials will be investigated including : i) Copper modified titanias, which have been demonstrated by the group of Prof. Wu to be promising candidates for further optimization, especially if made through sol-gel procedures. Novel approaches include various other transition-metals loaded TiO2, such as Pt and Ag, to further promote charge separation of photogenerated holes and electrons, as well as non-titania photo catalysts, such as Ta2O5 and Nb2O5 composite oxides. ii) Ti-based mesoporous catalysts based on TUD-1. Ti-based mesoporous materials (e.g. MCM-41) have been reported in the literature to be more efficient in the CO2 reduction reaction than dense phase TiO2 particles, while combinations of Cu and Zr, or Cu and Ti induce visible light sensitivity through a metal to metal charge transfer. The relatively easy synthesis procedure (one pot) of TUD-1 allows a combinatorial investigation of the potential combinations of metals to further optimize visible light sensitivity and CO2 reduction rates. The open 3-D structure of TUD-1 ensures mass transport limitations do not occur. iii) Various reports of nano-structured TiO2 have appeared in the literature recently, and appear to be interesting candidates for CO2 photoreduction due to their high surface area and open structure limiting transport phenomena. Modification of these structures with Cu2O might further enhance the visible light sensitivity and performance. Extensive screening is proposed to propel the discovery of novel formulations. The ultimate goal is to develop catalysts with an improved photon efficiency in the range of two orders of magnitude. At the same time, a rational approach will be followed by determination of the rate limiting step in the conversion of water and CO2 over the most promising catalysts, which leads to a rational further improvement of these candidates. The use of (ATR)-FT-IR spectroscopy and Raman spectroscopy is proposed to be used to analyze the dynamics of the surface composition of the catalysts as a function of reaction conditions. Another challenge is to design an optimized photoreactor: illumination of the active sites and desorption of products need to be maximized. Light transmitting reactor modules with parallel channels, combined with so-called Taylor flow operation (guaranteeing high mass transfer, and ideal plug flow reactor behavior, such as the absence of extended stagnant volumes close to the light source) might provide the optimal reaction environment in liquid phase (water) conversion of CO2. The application of a coating on the optical fibers is another approach that might lead to the optimum use of reactors for CO2 conversion.光催化CO2 還原碳氫燃料奈米結構材料光反應器PhotocatalysisCO2 reductionhydrocarbon fuelnanostructured materialsphoto reactors