Improvement of PEMFC Performance by Coating Reduced Graphene Oxide on the Anode Gas Diffusion Layer

質子交換膜燃料電池具有高轉換效率、能量密度很高、操作快速容易、零污染等優點。但一般燃料電池的製作仍須要克服很多挑戰，如觸媒分散性不佳、白金價格昂貴、水管理不容易掌握等都是造成PEMFC效能無法提升的問題之一，因此研究第一部分主要探討如何增加Pt在碳黑載體上的分散性，本研究使用雙氧水對碳黑表面進行表面改質，使碳黑表面佈滿含氧官能基，增加碳黑在水中的分散性，由XRD圖可以看到Pt晶粒尺寸從6.56 nm減小到4.26 nm，TEM圖則證實確實有助於減少Pt團聚現象的發生，因而提高了電池的輸出功率。 第二部分會將一維的碳黑結構與二維的石墨烯混合形成新的3D複合結構，期望藉由石墨烯高比表面積的特性來增加碳黑的分散性，使Pt在還原時分佈更均勻，粒徑更小，但從SEM及TEM結果發現還是有團聚現象的發生，造成電流密度及輸出功率會隨著石墨烯的添加量增加而下降，主要是由於製作的石墨烯無法達到理論比表面積，且與Pt交互作用不佳所導致。 第三部分主要會去探討在陽極氣體擴散層上塗佈石墨烯來改善水管理，且利用石墨烯高導電率的特性來降低極化現象的發生，由接觸角分析結果發現隨還原氧化石墨烯塗佈量增加接觸角有下降的趨勢，表示親水性增加，能達到潤濕的效果幫助氫離子傳遞，在65 ℃操作溫度下，塗佈2.52mg/cm2還原氧化石墨烯的電流密度由0.395 W/cm2增加為0.538 W/cm2，證實塗佈還原氧化石墨烯於氣體擴散層上，確實有助於效率的提升。Proton exchange membrane fuel cells have the advantages of high conversion efficiency, high energy density, fast and easy operation, and zero pollution. However, the production of fuel cells still needs to overcome many challenges. The poor dispersion of catalysts, the high price of platinum, and the difficulty in mastering water management are all problems that cannot improve the performance of PEMFC. Therefore, the first part of the experiment will mainly discuss how to increase the dispersibility of Pt particles on the carbon black carrier. In this study, the surface of carbon black was surface-modified with hydrogen peroxide, and the surface of carbon black was filled with oxygen-containing functional groups to increase the dispersibility of carbon black in water. From the XRD pattern, the Pt particle size decreases from 6.56 nm to 4.26 nm.It was confirmed that the surface treatment of carbon black by hydrogen peroxide really reduce the occurrence of Pt agglomeration. The second part will combine the one-dimensional carbon black structure with two-dimensional graphene to form a new 3D composite structure. It is expected that the high specific surface area of graphene will increase the dispersion of carbon black and make Pt more distributed during reduction. However, it was found by SEM and TEM that agglomeration occurred, and the current density decreased with the increase of graphene addition, mainly due to the poor interaction between graphene and Pt. The third part will mainly discuss the coating of graphene on the anode gas diffusion layer to improve water management and use the high conductivity of graphene to reduce the occurrence of polarization. From the contact angle analysis results, it is found that the contact angle decreases with the increase of the amount of reduced graphene oxide coating, indicating that the hydrophilicity is increased, and the wetting effect can be achieved to help the hydrogen ion transfer. At 65°C operating temperature, the power density of coating 2.52mg/cm2 reduced graphene oxide increased from 0.395 W/cm2 to 0.538 W/cm2. It was confirmed that coating graphene oxide on anode gas diffusion layer can really increase efficiency.摘要 i Abstract ii 總目錄 iii 圖 目 錄 vi 表 目 錄 viii 第一章 序論 1 1.1 前言 1 1.2 研究動機 1 第二章 基礎原理與文獻探討 3 2.1 燃料電池簡介 3 2.1.1 燃料電池發展歷史 4 2.1.2 燃料電池的種類 4 2.1.3 質子交換膜燃料工作原理 5 2.1.4 質子交換膜燃料電池關鍵材料與元件 6 2.2 燃料電池水管理 10 2.3 電極反應動力學 12 2.3.1 極化曲線 12 2.3.2 活化極化 13 2.3.3 歐姆極化 13 2.3.4 濃度極化 13 2.4 載體之分散 13 2.5 觸媒製作方法 16 2.6 石墨烯簡介 18 2.7 石墨烯製備 19 第三章 研究方法 22 3.1 藥品與材料 22 3.2 實驗儀器 23 3.3 實驗流程 23 3.3.1 氧化石墨烯製備 23 3.3.2 還原氧化石墨烯製備 25 3.3.3 碳載體前處理 27 3.3.4 鉑/碳黑(Pt/C)觸媒製備 27 3.3.5 Nafion的前處理 28 3.3.6 膜電極(MEA)的製備 29 3.3.7 塗佈還原氧化石墨烯的MEA製備 30 3.4 實驗儀器分析原理 30 第四章 結果與討論 36 4.1 碳黑表面處理之特性 36 4.1.1 晶體結構分析 36 4.1.2 微結構與表面形貌分析 38 4.1.3 表面官能基分析 43 4.1.4 電化學分析 44 4.1.5 單電池測試系統 45 4.2 石墨烯之特性 46 4.2.1 晶體結構分析 47 4.2.2 拉曼分析 48 4.2.3 表面官能基分析 49 4.3 不同含量RGO用於觸媒載體之特性 50 4.3.1 微結構與表面形貌分析 50 4.3.2 電化學分析 53 4.4 不同含量RGO塗佈於氣體擴散層之特性 55 4.4.1 表面形貌分析 55 4.4.2 表面電阻分析 56 4.4.3 接觸角分析 57 4.4.4 單電池測試系統 59 4.4.5 單電池內電阻分析 64 第五章 結論 66 參考文獻 6