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研究生: 顏劭晏
Yan, Shao-Yan
論文名稱: 以計算探討鉑錫基催化劑在直接乙醇燃料電池陽極和陰極反應中的研究
Computational study of PtSn-based catalysts for anodic and cathodic reactions in direct ethanol fuel cells
指導教授: 王禎翰
Wang, Jeng-Han
學位類別: 碩士
Master
系所名稱: 化學系
Department of Chemistry
論文出版年: 2018
畢業學年度: 106
語文別: 中文
論文頁數: 58
中文關鍵詞: 鉑錫催化劑鉑錫銀催化劑奈米線氧氣還原反應乙醇氧化反應偏析能態密度
英文關鍵詞: PtSn catalyst, PtSnAg catalyst, nanowires, oxygen reduction reaction(ORR), ethanol oxidation reaction(EOR), segregation energy, density of states(DOS)
DOI URL: http://doi.org/10.6345/THE.NTNU.DC.014.2018.B05
論文種類: 學術論文
相關次數: 點閱:116下載:6
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  • 本研究分陰極觸媒和陽極觸媒兩部分: PtSn雙金屬催化劑上的陰極氧還原反應(ORR)和陽極乙醇氧化反應(EOR)。在ORR的研究中,使用Pt(111)表面取代不同Sn比例來模擬PtSn催化劑。我們的計算發現,Sn取代越多,活性越高,這歸因於其較低的親氧性和相鄰Pt的d-band center;然而,越多的Sn由於結構扭曲降低穩定性。穩定性可以藉由錫氧化物修飾Pt表面進一步改善,在ORR過程中,這些氧化物對Pt表面吸附適中及強的斥力以保持結構。而在EOR的研究中,通過在PtSn中添加Ag形成三元PtSnAg催化劑來修飾PtSn雙金屬。Ag上的氧化物由於可以吸引解離的氫以及與OH有排斥效應可以有效改進關鍵步驟CH3CHO氧化成CH3COOH而促進了EOR。此外,氧化物可以增強乙醇在鄰近的Pt上的吸附以降低初始脫氫反應。

    The present study includes two main parts: the cathodic oxygen reduction reaction (ORR) and anodic ethanol oxidation reaction (EOR) on PtSn bimetallic catalysts. In the study of ORR, PtSn catalyst was modeled by Pt (111)surface with varied Sn substitution of surface Pt. Our calculations found that the more Sn substitution results the higher activity, attributable to their lower oxophilicity and d-band center of adjacent Pt; however, the more Sn substitution demotes the stability due to the structural distortion. The durability can be further improved by separating and lifting the oxide phase of Sn on Pt surface. The oxide has moderate adsorption on Pt surface and strong repulsion among them to retain the structure during ORR. In the study of EOR, we modified PtSn bimetal with the addition of Ag forming ternary PtSnAg catalyst. The oxide phase of Ag can effectively enhance CH3CHO oxidize to CH3COOH, the key step, and promote EOR activity due to its attraction of dissociated H and repulsion of OH. Additionally, the oxide can assist ethanol adsorption on the neighboring Pt that can lower the initial dehydrogenation step.

    摘要 I Abstract II 致謝 III 目錄 IV 圖目錄 VI 表目錄 VIII 第一章 緒論 1 1-1 質子交換膜燃料電池(PEMFC) 1 1-1-1 陰極氧氣還原反應: 1 1-1-2 文獻回顧: 2 1-2 直接乙醇燃料電池(DEFCs): 6 1-2-1 陽極乙醇氧化反應: 7 1-2-2 文獻回顧: 7 1-3 研究目的: 9 第二章 理論原理與計算方法 10 2-1 密度泛函理論(Density functional theory,DFT) 10 2-1-1 Born-Oppenheimer近似 10 2-1-2 The Kohn-Sham equation 10 2-1-3 交換相關函數(Exchange-Correlation Functions) 12 2-1-4 布洛赫定理與平面波基組(Bloch theorem and plane wave basis sets) 12 2-1-5 有效核勢(Pseudopotential or Effective core potential,ECP) 13 2-2 系統與軟體 14 2-2-1 國家高速網路與計算中心 14 2-2-2 操作軟體 VASP(Vienna Ab-initio simulation Package) 14 2-2-3 檔案參數設定 15 2-3 本篇計算相關參數設定及表面model的建立 19 2-3-1 本篇計算參數設定 19 2-3-2 表面模型 20 2-3-3 計算流程 21 第三章 結果與討論 22 3-1 氧氣在不同比例PtSn合金的還原 22 3-1-1 中間物的吸附能 23 3-1-2 態密度分析(DOS) 26 3-1-3 電荷分析 28 3-1-4 反應能和活化能 29 3-1-5 Sn上的OH對Pt原子的吸附 30 3-1-6 實驗結果 31 3-1-7 小結 31 3-2 PtSn的穩定性 32 3-2-1 金屬原子與表層Pt的交換能 33 3-2-2 金屬氧化物的吸附能與排斥能 33 3-2-3 金屬氧化物和Pt的態密度分析 35 3-2-4 氧和氫氧化物的吸附能 38 3-2-5 實驗結果 39 3-2-6 小結 40 3-3 乙醇在PtSnAg和PtSn合金上的氧化反應 41 3-3-1 乙醇的吸附能 41 3-3-2 乙醇吸附位置的態密度分析 42 3-3-3 乙醇吸附不同位置的電荷分析 43 3-3-4 反應能和活化能 43 3-3-5 以態密度分析PtSnAg和PtSn表面上的氧化物 47 3-3-6 以電荷分析PtSnAg和PtSn表面上的氧化物 48 3-3-7 實驗結果 49 3-3-8 小結 49 第四章 結論 51 第五章 參考文獻 52

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