為提高質子交換膜燃料電池(Proton Exchange Membrane Fuel Cell, PEMFC)之陰極氧氣還原反應(Oxygen Reduction Reaction, ORR)，本實驗利用電化學共沉積法直接還原鉑鎳合金觸媒於碳基材表面，有別於傳統化學還原法，還原鉑於碳黑顆粒上再塗佈於電極表面，電化學沉積法具有製備快速、低沉積量、低成本等優點。在本研究中，更選用高還原電位來沉積具有特殊花狀結構的觸媒，透過3D結構來增加觸媒的電化學活性表面(ECSA)，藉此提升全電池測試的功率密度。
氧氣還原反應在燃料電池中為速率決定步驟(Rate-Determining Step, RDS)，是造成觸媒活性不佳及低耐久度的主因，因此本實驗嘗試添加過渡金屬鎳於貴重金屬鉑的晶格中，形成鉑鎳合金結構。電化學沉積過程中，將鎳還原於鉑的晶格內，鎳將在晶格內部產生壓縮應力，縮短鉑的原子間距(d-spacing)，可以改變d-band的能帶位置來改善合金觸媒的催化活性，加快氧氣在觸媒表面的吸附及脫附機制，有效提升氧氣在燃料電池中陰極的ORR速率。不僅如此，在鉑觸媒中添加非貴重金屬，可以讓觸媒顆粒的表面變得粗糙，增加觸媒的電化學活性表面積，並且藉由伽凡尼效應，以過渡金屬鎳來保護活性較穩定之貴重金屬鉑，提升燃料電池的耐久度，不易發生團聚現象。整體而言，鉑鎳合金觸媒的優點除了大幅提升陰極的氧氣還原速率外，也減少了鉑的用量。這些對於提升單位面積效能卻能夠降低成本的技術，皆使燃料電池在未來的商業化之路向前邁進了一大步。本實驗利用恆電位沉積法以硫酸作為輔助電解質並搭配乙二醇作為分散劑及還原劑，成功製備出具有特殊花狀形貌的鉑鎳合金觸媒，透過掃描式電子顯微鏡(scanning electron microscopy, SEM)、高解像能電子顯微鏡(High Resolution Transmission Electron Microscope, HR-TEM)、能量色散X射線譜(Energy Dispersive X-ray Spectroscopy, EDS)、高解析光電子能譜儀(High Resolution X-ray Photoelectron Spectrometer, HR-XPS、X光吸收光譜(X-ray Absorption Spectroscopy, XAS)、X光繞射分析儀(X-ray Diffraction, XRD)及感應耦合電漿質譜分析儀 (Inductively Coupled Plasma-Mass Spectrometer, ICP-MS)確認觸媒形貌分佈、合金化程度及觸媒乘載量。觸媒微結構具有100奈米以下的微觀結構和良好的均勻性，並在XRD圖譜中可以觀察到2 theta位移程度及無明顯的純鎳金屬訊號來佐證本實驗成功製備出的花狀鉑鎳合金觸媒。
在本篇實驗中，將比較電鍍液配方中以硫酸作為輔助電解質及乙二醇作為分散劑之最佳比例，試圖優化觸媒製程參數。搭配循環伏安法(cyclic voltammetry, CV)及旋轉盤電極(rotating disk electrode, RDE)的線性掃描伏安法(linear sweep voltammetry, LSV)等半電池電化學分析，經優化參數後之觸媒分析結果皆顯示本實驗製備之花狀鉑鎳合金觸媒比較商用觸媒具有較高的氧氣還原反應速率及比活性。最終，將自製花狀鉑鎳合金作為陰極，商用觸媒作為陽極組成全電池，最高功率密度可達到1031 mW/cm2，相比以商用觸媒都作為陰陽極的實驗對照組(920 mW/cm2)提高了約12%的功率密度。

The hydrogen economy plays an important role in the low-carbon economy, and fuel cell technology is an essential part of the hydrogen economy. The proton exchange membrane fuel cell (PEMFC) is one kind of electrochemical reaction device with the advantages of low working temperature, high conversion efficiency and noiseless, which is expected to widely utilizes in public transportations. The oxygen reduction reaction (ORR) at the cathode is the rate-determining step in a PEMFC. To enhance the ORR efficiency at the cathode, the unique flower-like platinum-nickel binary alloy catalysts were deposited on the carbon cloth by potentiostatic electrodeposition, effectively improve the oxygen absorption and desorption paths on the surface. The Pt-Ni binary alloy catalysts with the shorter lattice spacings and the effect of high-index facets would increase the electrochemical surface areas (ECSA) of the catalysts and power density. The samples with the pure platinum and commercial Pt catalyst were also prepared as comparison. Morphology, particle size and elemental composition are characterized by SEM, TEM, XRD, XPS, XAS and ICP-MS. In addition, the electrochemical characteristics of the PtNi catalysts were investigated via cyclic voltammetry (CV) and linear sweep voltammetry (LSV) analysis in 0.1 M perchloric acid solution with rotating disk electrode (RDE). In single cell test, the maximum peak power density of PEMFC with homemade PtNi alloy catalyst as the cathode reached to 1031 mW/cm2, enhancing about 12% power density, compared to the commercial Pt/C.

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