官能化中孔碳材負載鉑(Pt)金屬觸媒材料之製備、特性鑑定與燃料電池應用

Synthesis, Characterization, Functionalized and application of mesoporous materials supported Pt catalyst

吳旻聰(Min-Tsung WU)

指導教授 ： 劉尚斌博士

國立臺灣師範大學/理學院/化學系/碩士(2007年)

摘要

面對石化能源的逐漸短缺、高油價時代的來臨及日趨嚴重的大氣環境污染問題，人類正積極地尋求替代能源。其中，燃料電池、太陽能、氫能源、核能、風力等均是尋求開發的重點能源。有鑒於近年來有序規則性奈米結構孔洞性氧化矽分子篩及孔洞性碳材之蓬勃發展，這些材料大都具有可調控孔徑、高比表面積、高結構、水熱及機械穩定性，以及獨特的吸附、電化學及催化特性，是能源相關尖端應用的理想素材，如做為燃料儲存吸附載體或燃料電池電極觸媒擔體等。本研究的主要目的在於尋求新穎的合成方法來製備負載貴重金屬鉑(Pt)的表面修飾奈米孔洞性碳材(PtCNxM)，並評估其在被應用做為燃料電池陰極觸媒之可行性，吾人尤致力於提昇貴重金屬的分散度、減少其使用量、表面修飾氨官能基的作用等之系統性探討。
在材料合成與觸媒製備方面，吾人首先利用共凝聚(co-condensation)法及後修飾(post-synthesis)法，使用不同含有二氨基及三氨?官能基的矽烷類合成具有胺基的SBA-15中孔洞氧化矽模板(SNxM)。隨後並以貴重金屬乙醯丙酮化合物，如Pt[CH(COCH3)2]2等，做為觸媒金屬主要來源及次要碳源，將之與主要碳源，如furfuryl alcohol等，混合成勻相溶液後，同時以濕式含浸法注入具有胺基的中孔洞氧化矽模板，以複製(replication)法在真空狀態下進行高溫(600-800 oC)石墨化，再以氫氟酸去除氧化矽模板，經清洗、過慮及乾燥後，合成出負載鉑金屬的含氮中孔碳材(PtCNxM)。吾人透過不同光譜及分析實驗技術，如粉末X-光繞射(XRD)、氮氣等溫吸附/脫附(N2 adsorption/desorption isotherm)、元素分析(EA)、穿透式電子顯微鏡(TEM)、感應耦合電漿質譜分析(ICP-MS)、傅立葉紅外線(FTIR)吸收光譜等，對各類合成樣品之物化特性詳以鑑定。並利用此類PtCNxM複合材料為燃料電池陰極觸媒，以循環伏安(CV)法量測其電化學特性，並探討比較其對氧氣還原反應之催化效能。
本研究所得之實驗結果，除期能增進吾人對負載金屬觸媒的官能化孔洞性碳材的製備方法、物化特性鑑定及其在質子交換膜燃料電池(PEMFC)或直接甲醇燃料電池(DMFC)電池極的觸媒應用的進一步瞭解外，並期能提昇其陰極氧氣還原催化效能，進而降低觸媒之製備成本，增加商業化的競爭力。故本研究兼具學術研究及工業應用之重要性。

關鍵字

官能化 ； 孔洞碳材 ； 燃料電池 ； 碳材表面修飾

並列摘要

In view of the continuing shortages and increasing costs in fossil fuels and the increasing demands in environmental protection issues, such as suppression of greenhouse gases (CO2, chlorofluorocarbons, etc.), R&D of more economical and renewable energy resources are of great demands. Among them, fuel cells and solar, wind, nuclear, and hydrogen energies have drawn much R&D attentions. In particular, recent research and development of novel nanostructured porous silicate and porous carbon materials, which possess tunable pores in the mesoporous range, high specific surface area, high structural, hydrothermal and mechanical stabilities and unique adsorptive, electrochemical and catalytic properties, are the most promising candidates for advanced applications in energy-related sectors, for examples, as carriers for fuel storage and as catalytic supports for fuel cell electrodes. The objectives of this research are aiming at developing novel synthesis routes to fabricate novel metal (Pt) catalyst supported on amine-functionalized porous carbons (PtCNxM), and to evaluate their applications as fuel cell cathode electrodecatalysts. In particular, the dispersion of the novel metal catalyst, reduction of it loading, and the effects of surface modification by amine-functionalization, are of special interests and have been comprehensively investigated.
In terms of the material synthesis, various amine-functionalized mesoporous SBA-15 slilica templates (SNxM) were prepared via using different di- and tri-aminosilanes through two different routes, namely by co-condensation and post-synthesis methods. Subsequently, fabrication of PtCNxM catalysts were replicated by co-feeding primary carbon sorces (e.g., furfuryl alcohol) and primary metal precursors (i.e., platinum acetylacetonate, which also served as secondary carbon source) into the SNxM template by incipient wetness method, followed by carbonization under vacuum at high temperatures (600-800 oC), silica template removal by hydrofluoric acid, and finally by washing, filtering and drying processes. A variety of different spectroscopic and analytical techniques, such as X-ray diffraction (XRD), N2 adsorption/desoption isotherm, elemental analysis (EA), transmission electron microscopy (TEM), induced coupled plasma mass spectroscopy (ICP-MS), Fourier-transformed infrared (FTIR) absorption spectroscopy etc., have been used to characterize the physicochemical properties of various materials. The electrochemical properties and catalytic performance of the fuel cell cathode electrocatalysts (PtCNxM) during oxygen reduction reaction were also evaluated by cyclic voltammetry (CV).
The results obtained from this study should not only enhance our knowledge on the fabrication of metal catalysts supported on surface-functionalized porous carbon materials and their fundamental physicochemical properties, but also their applications as electrocatalysts for proton exchange membrane fuel cell (PEMFC) and direct methanol fuel cell (DMFC) as well as their catalytic performances during oxygen reduction reaction. Aiming at improving the catalytic activity of the cathode electrocatalysts, reduction of the catalyst fabrication costs, and applicability for commercialization, it is anticipated that the outcomes of this research should have some impact to academic research as well as industrial applications.

並列關鍵字

mesoporous materials ； Functionalized ； fuel cell

參考文獻

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