太陽能及乙醇/氫氣轉換之量子化學計算模擬及實驗驗證（第三年）

Abstract

本計劃繼續結合於2004年5月由「國家高速網路與計算中心」協助組織的「台灣計算化學聯盟」(Taiwan Computational Chemistry Consortium, TCCC)中的兩組計算化學家，利用最先進的計算技術進行大尺度的理論計算，以瞭解製造InN/QD/TiO2奈米粒子薄膜和乙醇-氫氣轉化的機制。第一組專家將研究自組官能基加上拉電子或推電子的元素，如>BO-Ti, >PO-Ti或>Si=(OTi)2等對InN和TiO2的結合強度以及其對光電轉換效率的影響。這些界面物質可以利用氫氧化的TiO2, (HO-Ti)x或Ti(OH)4與BCl3, PCl3或SiCl4反應，脫去HCl而形成。也可以B(OH)3, P(OH)3或Si(OH)4水溶液直接浸附在多孔的TiO2奈米薄膜，去水後產生HOB(O)O, HOP(O)O及(HO)2Si(O)O等聯鍵。利用量子化學計算可以來研究這些反應在TiO2上之產物結構。官能化的表面也可與三甲基銦, (CH3)3In, NHx (x=1, 2)或SiHx(x=1-3)反應以產生量子點(quantum dots, QDs) 及/或InN和Si的奈米粒子薄膜，以增進InN/QDs/TiO2系統中的光電流。實驗上，活化的NHx和SiHx可以利用熟知的NH3和SiH4利用微波或催化分解來產生。吾人將與核能研究所密切合作進行相輔相成的理論和實驗工作，以對製程的改進和提昇太陽能的轉換效率作出貢獻。第二組專家將以Schmidt等人[Science, 2004, 303, 993]所使用之技術作為依據，對燃料電池所應用到的乙醇轉化為氫氣的過程加以研究。實驗的工作也將和理論計算工作同時進行，以一個小的反應器來鑑測各種催化劑對於乙醇的部份氧化之效果。實驗的結果可以和理論計算結果相互比對並相輔相成。吾人將先進行Rh/CeO2系統的研究以瞭解Rh/CeO2將乙醇轉化為氫氣的機制並找出為何它可以有如此高的轉化效率的原因。所得的數據將可與其他有可能較具經濟效益的奈米粒子催化劑，如CuO/Al2O3、Cu2O/Al2O3 (以CuxO/Al2O3代表之)等之研究相比較，再者，ZnO及ZrO2的功能也要研究，取代CeO2。實驗與理論的密切結合將可以很有效地產生有用的數據以供實際設計及製造較具經濟效益且具相似轉化效率的燃料電池參考。 此計劃亦將訓練一批優秀的計算化學家以及博、碩士班學生，為台灣相關的材料化學之理論研究作出貢獻。

The proposed large scale computational simulation studies, to be carried out by two teams of computational chemists associated with Taiwan Computational Chemistry Consortium (TCCC) established in May 2004 in collaboration with National Center for High-performance Computing (NCHC), employing state-of-the-art computational techniques to elucidate the mechanisms for the fabrication of In(Ga)N/TiO2 and In(Ga)N/QD/TiO2 nanoparticle films and the ethanol to hydrogen conversion processes. The first team will examine the effects of self-assembled interface functional groups attached with electron withdrawing and donating elements, such as >BO-Ti, >PO-Ti, or >Si=(OTi)2, etc., on the device’s photo-conversion efficiency and on the strength of the contact between the InN and TiO2. These interfacial species can be generated readily by reactions of hydroxylated TiO2, (HO-Ti)x or Ti(OH)4 covered TiO2, for example, with BCl3, PCl3 or SiCl4 by dehydrochlorination (- HCl). These linking groups can also be formed by dipping TiO2 nanoparticle films in the solutions of B(OH)3, P(OH)3 or Si(OH)4. After appropriate drying and dehydration process, the InN and TiO2 interfacing species such as HOB(O)O, HOP(O)O and (HO)2Si(O)O can be produced on TiO2 substrate surfaces for subsequent deposition of InN or In(Ga)N quantum dots or nanoparticles. These reactions will be studied quantum chemically for their product configurations on TiO2. The functionalized surface species will also be reacted with trimethyl indium, NHx (x=1,2) and SiHx (x=1-3) to produce quantum dots (QDs) and/or nanoparticle films of InN and Si, which are expected to enhance the photocurrent of the InN/QDs/TiO2 system. Experimentally, the activated NHx and SiHx can be produced by the well-known microwave discharge or catalytic decomposition of NH3 and SiH4. Both experimental and computational studies will be carried out hand in hand at NCTU and INER for an expected synergistic improvement in the fabrication processes and the ultimate solar energy conversion efficiencies. The second team associated with the TCCC will conduct computational studies of the ethanol to hydrogen conversion processes for fuel cell applications according to the technique of Schmidt et al. [Science, 2004, 303, 993]. These studies will be carried out in parallel with an experimental study to be performed at NCTU under the direction of the PI using a small reactor to characterize a variety of catalysts for the autothermal partial oxidation of ethanol; the experimental data will be used to validate the computational simulation results, or vice versa. These tandem studies will begin with the Rh/CeO2 system to elucidate the mechanism for the conversion of ethanol to H2 by the catalyst as well as the under-pinning reason of its superior efficiency reported by Schmidt. The bench-mark data will be compared with other potentially cheaper nanoparticle catalyst such as CuxO/Al2O3 (x=1, 2) with and without CeO2 among others. In addition, we will study experimentally and computationally the effects of ZnO and ZrO2 in place of CeO2.The tandem experimental and computational studies are expected to produce very efficiently a set of data valuable for a practical design of a cheaper but equally effective catalyst for fuel cell applications. We expect that more than a dozen PhD and MS students can be trained in this project with several SCI papers generated from the project in addition to the useful data on both solar cell and the ethanol to hydrogen conversion processes.