自組裝合成中孔碳材之表面修飾及負載鉑（Pt）金屬觸媒之製備、特性鑑定及其在DMFC/PEMFC燃料電池之應用

Synthesis and Characterization of Self-assembly, Surface-Modified, and Platinum Catalyst Supported Mesoporous Carbons and Their Application as Electrodecatalysts for DMFC/PEMFC Cathode

江建章(Chien-Chang Chiang)

指導教授 ： 劉尚斌

國立臺灣師範大學/理學院/化學系/碩士(2007年)

摘要

由於目前全球正面臨石化燃料短缺，油價持續高漲；能源短缺的危機迫在眉睫以及日趨嚴重之大氣環境污染等問題，因而相關綠色能源議題也逐漸被訴求且受到重視，其中，風力、潮汐能、太陽能、氫能源、燃料電池等相關研究與發展，近幾年都是世界各國積極尋求替代性能源創新開發之重點方針。本研究主要目的，在於研發新穎之奈米結構孔洞碳材與負載鉑（Pt）等貴重金屬之一步合成奈米中孔洞碳材（Pt-SCMs），並應用於燃料儲存與燃料電池等能源相關領域。
在材料方面，本研究主要利用奈米結構之孔洞性碳材的高比表面積、高結構、水熱及機械穩定性，以及獨特的吸附、電化學及催化等特性作為燃料電池材料，例如：燃料儲存吸附載體或燃料電池電極觸媒擔體。但由於目前許多奈米中孔結構碳材都是利用中孔矽模板（例如：SBA-15）填入碳源經高溫石墨化後，再使用氫氟酸（HF）將模板移除，合成複製而來，其中除需使用高成本之矽烷（silanes）材料外，複製合成中孔碳材的步驟亦十分繁瑣，因而大幅降低其實際應用之可能行性。因此，吾人提出利用低成本之有機化合物一步合成直接製備奈米中孔洞碳材的策略，期能節省合成之時間與成本，更符合商業化應用趨勢。
吾人首先利用一介面活性劑做為軟模版，有機化合物當做碳源，應用有機-有機自組裝（organic-organic self-assembly）方式合成，再使用不同溫度（350℃、550℃、850℃）石墨化，獲得奈米中孔洞碳材(SCMs)，隨後，再以有機矽烷類3-[2-(2-Aminoethylamino)ethyl amino]propyltrimethoxysilane（C10H27N3O3Si）進行表面胺基官能化修飾，並透過各種光譜及分析實驗技術，鑑定並探討其物化特性。吾人再於SCMs碳材上負載貴重金屬鉑（Pt），再利用化學方法將金屬鉑還原，最後合成出負載鉑金屬之中孔洞碳材（Pt-SCMs）。隨後，再利用Pt-SCMs複合材料作為燃料電池陰極觸媒，以循環伏特（CV）法測量其電化學特性，並探討比較其對氧氣還原反應(oxygen reduction reaction; ORR)之催化效能。
本研究所獲得之結果，不僅可望增進吾人對一步合成製備奈米中孔洞碳材SCMs及負載金屬的方法與物化特性及其在質子交換膜燃料電池(PEMFC)或直接甲醇燃料電池(DMFC)之電極觸媒應用之瞭解外，並期望能提昇其在燃料電池陰極之氧氣還原催化效能，進而降低觸媒與碳材之製備成本，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

燃料電池 ； 中孔碳材 ； 自組裝合成

並列摘要

Facing the global crisis in shortage of fossil fuels and increasing environmental pollutions mainly from combustions of carbon-based fuels and abused emission of greenhouse gases, renewable energy-related R&D have becoming a demanding and challenging tasks. Among them, hydrogen fuel cells have received much attention and being considered as the ideal eco-friendly electrical energy conversion devices. The objectives of this research are to develop novel one-step synthesis route to fabricate nanostructured porous carbon materials and to utilize them as supports for noble metal (Pt) catalyst aiming at their practical applications in energy-related issues, such as hydrogen fuel storage and fuel cells.
Owing to the high surface area, structural, thermal/hydrothermal, and mechanical stabilities, and adsorptive, electrical, and catalytic properties, carbon mesoporous materials (CMMs) represent ideal electrodecatalyst supports for fuel cells and adsorption carriers for fuel storage devices. However, in view of the sophisticated procedures invoked for fabrication of CMMs, which were mostly synthesized by replication method using ordered mesoporous silica’s as templates, infiltrated by appropriate carbon precursors followed by thermal polymerization, carbonization, and subsequent removal of the silica framework with acid or base solution. Such a complex synthesis procedure not only is cost ineffective but also limits practical commercial applications of CMMs.
A facile method to fabricate CMMs is by crosslinking phenolic resins in the presence of a self-assembled block-copolymer surfactant template, followed by pyrolysis of the organic precursors (carbon source) and carbonization to obtain the self-assembled carbon materials (SCMs). The SCMs so fabricated were found to possess high surface area, good electrical conductivity, and aboundant hydroxyl groups on the pore-wall surfaces, which facilitates surface functionalization and dispersion of metal catalysts in a controllable fashion.
In this work, SCMs were first synthesized by organic-organic self-assembly at different carbonization temperatures (350-850 oC), then, subjected to surface modification by organic silane reagent, 3-[2-(2-Aminoethylamino)ethylamino]propyltrimethoxysilane (TA), or by chemical treatments (H2O2 and H2SO4/HNO3). Subsequently, carbon-supported Pt catalysts (Pt-SCMs) were prepared via chemical reduction of H2PtCl6 by NaBH4 at room temperature. Related samples were characterized by a variety of different analytical and spectroscopic techniques. Furthermore, using the surface-functionalized Pt-SCMs as cathode electrodecatalyst, their electrocataytic activities during oxygen reduction reaction (ORR) were evaluated by cyclic voltammetry (CV) and compared to Pt-SCMs prepared by one-pot synthesis.
The results obtained from this research should enhance not only our knowledge on direct fabrication and physicochemical properties of SCMs but also their practical applications as cathode electrocatalysts for proton exchange membrane fuel cell (PEMFC) and direct methanol fuel cell (DMFC). Thus, the outcomes of this research should have some importance in academic as well as industrial R&D and applications.

並列關鍵字

Fuel Cell ； Mesoporous Carbon ； Self-assembly ； DMFC ； Cathode

參考文獻

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