碳支撐鉑金錫奈米棒應用於乙醇氧化反應之研究;The Ethanol Oxidation Reaction Performance of Carbon-Supported PtAuSn Nanorods

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題名:	碳支撐鉑金錫奈米棒應用於乙醇氧化反應之研究;The Ethanol Oxidation Reaction Performance of Carbon-Supported PtAuSn Nanorods
作者:	林鄭安;Ling, Cheng-An
貢獻者:	材料科學與工程研究所
關鍵詞:	鉑/金/錫;乙醇氧化反應;奈米棒;雙功能機制;穩定度;PtAuSn;ethanol oxidation reaction;nanorods;bi-functional mechanism;stability
日期:	2018-07-20
上傳時間:	2018-08-31 13:11:27 (UTC+8)
出版者:	國立中央大學
摘要:	近年來，由於乙醇可由生質能源包含發酵反應產生，而使直接乙醇燃料電池(direct ethanol fuel cell, DEFC)的收到廣泛注意。然而，由於COad和CHxad等中間產物會吸附在白金觸媒表面使得反應速率下降，使得乙醇氧化反應(ethanol oxidation reaction, EOR)效能不佳，。為了要增益白金觸媒之EOR活性，本研究透過甲酸還原法(formic acid method, FAM)製備具有不同程度親氧性之碳支撐鉑基二元與三元包含鉑金、鉑錫、鉑鈀錫和鉑金錫奈米棒(nanorods, NRs)。所製備觸媒之結構、表面組成、化學組成、形貌和電化學性質分析可藉由X光繞射儀(X-ray diffraction, XRD)，光電子能譜儀(X-ray photoelectron spectroscopy, XPS)，感應耦合電漿原子發射光譜分析儀(inductively coupled plasma-atomic emission spectrometer, ICP-OES)，高解析度穿透式電子顯微鏡(high resolution transmission electron microscopy， HRTEM)，電化學量測系統等儀器鑑定。研究結果分為兩個部分，第一部分以FAM製備碳支撐鉑金、鉑錫二元和鉑鈀錫和鉑金錫三元奈米棒。經過電化學量測後，EOR的活性和耐久度測試結果相同，優劣如下: PtAuSn20 > PtPdSn > PtSn > PtAu。PtAuSn20在添加第三元素後，不但具有較高的親氧性，能夠增強Pt表面乙醇的解離吸附反應，而且通過電子修飾效應和雙功能機制具有較佳的協同效應。此外，PtAuSn20也因具有鉑核/ 金次層/ 錫殼結構而有著絕佳的穩定度。在第二部分中，製備出不同鉑/金/錫(70/5/25、70/10/20和70/20/10)組成的三元合金觸媒並命名為PtAuSn25、PtAuSn20與PtAuSn10，利用XPS，可以得到表面金/錫比例，依序為1/4、1/2和1/5，金會導致表面鉑原子產生拉伸應變，PtAuSn20因有著較多的表面金比例而擁有較佳的EOR活性。在穩定度方面，則是和表面錫與二氧化錫含量相同，依序為PtAuSn25 (50%錫) > PtAuSn10 (43%錫)> PtAuSn20¬¬(38%錫)。根據以上研究顯示，可以利用控制金/錫比例來有效提升三元鉑金錫奈米棒觸媒之EOR性能。 ;Direct ethanol fuel cells (DEFCs) have been attracted much attention recently because ethanol can be produced from biomass through various methods including fermentations. However, owing to poisoning by adsorbed intermediates such as COad and CHxad, the electro-oxidation of ethanol is sluggish. In order to enhance the ethanol oxidation reaction (EOR) performance, carbon-supported Pt-based nanorods (NRs) catalysts, including PtAu, PtSn, PtPdSn and PtAuSn have been prepared via formic acid method (FAM). The lattice structures, surface compositions, chemical compositions, morphologies and electrochemical properties of prepared catalysts are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectrometer (ICP-OES), high resolution transmission electron microscopy (HRTEM), and electrochemical measurements, respectively. This study is divided into two parts. In the first part, carbon-supported Pt-based binary and ternary NRs are prepared and their activity and durability performance have the same order PtAuSn20 > PtPdSn > PtSn > PtAu. With the third elements addition, PtAuSn20 NRs not only have the high oxophilicity that can activate the dissociative adsorption of ethanol on Pt surface, but also have synergies effect through electronic modification effect and bi-functional mechanism. Besides, PtAuSn20 with the Pt core/Au sublayer/Sn shell structure has the best stability. In the second part, the effect of compositions on the EOR performance of PtAuSn NRs has been investigated. PtAuSn NRs with Pt/Au/Sn ratios of 70/5/25, 70/10/20 and 70/20/10 have been prepared (named as PtAuSn25, PtAuSn20 and PtAuSn10, respectively). According to XPS results, Au/Sn ratios of PtAuSn25, PtAuSn20 and PtAuSn10 are closed to 1/4, 1/2 and 1/5, respectively. The EOR activity of PtAuSn20 with the largest Au/Sn ratios is the highest, which can be contributed to the tensile strain provided by Au. Otherwise, CA tests have the same order of Sn and SnO2 contents, which is PtAuSn25 (50%) > PtAuSn10 (43%) > PtAuSn20 (38%). Based on the above results, we have demonstrated that by tuning the Sn and Au ratio, the EOR performance can be promoted effectively.
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