| 摘要: | 乙醇在低溫燃料電池中是很具吸引力的再生能源之一，因為其可以從農作物中大量取得。為了更有效的提升乙醇能量轉換效率，各式觸媒被開發以應用於乙醇燃料電池。在本研究中，探討了鉑基二元和三元催化劑（鉑錫、鉑釕和鉑錫釕）在酸性介質中乙醇氧化反應（ethanol oxidation reaction, EOR）的性能。另外，其結構/表面特性與電化學行為之間的關係則利用X光繞射儀，感應耦合電漿放射光譜儀，X射線光電子能譜儀，高解析度穿透式電子顯微鏡和電化學循環伏安法，線性掃描伏安法和計時電流法分析。
本研究分成兩部分，第一部分，分別製備長寬比為5.2、7.2和7.4的碳支撐鉑釕、鉑錫和鉑錫釕奈米棒應用於乙醇氧化反應。研究發現通過添加釕和/或錫到鉑中，可以改變鉑的晶格與化學狀態。電化學結果顯示，藉由釕和/或錫修飾的鉑可以進一步通過配體效應和雙功能機制有效促進乙醇氧化反應的性能，包括在標準電位為0.6伏特下的電流(I06)以及最高電流值(Imax)。另一方面，鉑錫在所有催化劑中顯示出最低的衰減值，即最佳的耐久度，這可歸因於表面上二氧化錫的保護，進而防止鉑在乙醇氧化反應期間溶解。
第二部分中，研究了三元觸媒鉑錫釕組成比例與乙醇氧化反應性能之間的關係。觸媒之鉑/錫/釕原子比為60/35/5、60/30/10、60/20/20和60/10/30。在乙醇氧化反應中，金屬態釕(錫)和二氧化釕(錫)藉由與水的高度活性化可促進一氧化碳氧化，提升了觸媒的電催化活性，而適度的二氧化錫含量(Pt60Sn20Ru20) 則有利於吸附在鉑表面上的乙醇解離，進而提升觸媒在低電位區域的電催化活性。經過2小時的計時電流法（CA）測試後，Pt60Sn20Ru20在初始和最終的測試結果都表現出較高的鉑質量活性，但其衰退量則遠高於Pt60Sn35Ru5的，這是由於表面二氧化錫提供了穩定性。因此最佳的乙醇氧化反應觸媒為錫/釕比例為1/1的Pt60Sn20Ru20。
;Ethanol is one of the most attractive renewable energies in low temperature fuel cells because it can be produced in large quantities from agricultural products. In order to improve the energy conversion efficiency of ethanol, various catalysts have been developed for direct ethanol fuel cells (DEFCs). In this study, the ethanol oxidation reaction (EOR) performance of Pt-based binary and ternary catalysts (PtSn/C, PtRu/C, and PtSnRu/C) in an acidic media is systematically elucidated. The relationship between their structural/ surface properties and electrochemical behavior is investigated. The obtained nanorods (NRs) were characterized by X-ray diffraction (XRD), inductively coupled plasma-optical emission spectrometer (ICP-OES), X-ray photoelectron spectroscopy (XPS), and high resolution transmission electron microscopy (HRTEM). Electrochemical characterization was accomplished by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry (CA).
This study is divided into two parts. In the first part, carbon-supported PtSn, PtRu and PtSnRu NRs with an aspect ratio of 7.2, 5.2, and 7.4, respectively, are applied as electrocatalysts for EOR. Through Sn and /or Ru addition, the lattice and the chemical state of Pt can be modified. The electrochemical results show that Pt-decorated by Sn and Ru can effectively promote the EOR performance of Pt, both at I06 and Imax, by the ligand effect and bifunctional mechanism. On the other hand, PtSn displays the lowest decay in all catalysts, because the stable structure of SnO2 on the surface can prevent Pt from dissociation during the EOR.
In the second part, the relationship between Pt/Sn/Ru compositions and EOR performance of PtSnRu has been explored. Catalysts were prepared with Pt/Sn/Ru atomic ratios of 60/35/5, 60/30/10, 60/20/20, and 60/10/30. Ru(Sn) and Ru(Sn)O2 enhance the electrocatalytic activity due to the high activation of H2O and promotion of CO oxidation, while SnO2 can promote dissociative adsorption of ethanol on Pt surface, thus the electrocatalytic activity increases. After the 2-hour chronoamperometric (CA) tests, although higher Ru content catalyst presents higher mass activity both before and after CA test, its decay (61%) is far larger than that of lower Ru one (31%), owing to the stability effect of SnO2. The best EOR catalyst is found in the Pt60Sn20Ru20 with the Sn/Ru ratio of 1/1. |
