第四章 結果與討論
4.4 XRD 圖譜分析
圖4.13 不同比例Pdx-Mny/C 之XRD圖，掃瞄區間為20~90◦，掃瞄速率為 2◦/min，不同方向特徵峰角度整理為表4.3，由圖4.13 可觀察到Pd/C的五支 繞射峰之位置分別 40.12◦，46.26◦，68.14◦，82.30◦， 86.72◦為Pd (1 1 1)，
(2 0 0)，(2 2 0)，(3 1 1) ，(2 2 2) 的主要特徵峰。Pd金屬微粒在Pd/C 觸媒中是以 fcc (face centered cubic)結構存在，再看不同比例Pdx-Mny與Pd/C 的特徵峰比較，如圖4.13之中並不存在單獨的Mn繞射峰，且可見Pd-Mn/C其 特徵峰2θ值為39.87◦，46.07◦，67.76◦，81.55◦，86.33◦ 均比Pd/C之特徵峰角 度小，呈現負向平移，此現象與J.B. Xu之研究符合，J.B. Xu 【48】所作之Pt-Au 合金觸媒與Pt觸媒比較發現其XRD之繞射峰2θ值有平移的現象，指出此現象 為Au固溶於Pt中之依據，由此說明其觸媒有形成合金。Lingling Zhang 【15】、
Xin Wang 【5】都以此判斷其第二金屬是否固融入於另一金屬中，故可判斷 本實驗Mn已固溶於Pd中，可見透過化學還原法製備奈米金屬粒子可呈現固溶 合金相，是不錯的製程。
利用Scherrer Formula方程式可估算待測晶體之粒徑大小【49】，以Pd (220) 與Pd(111)估算待測不同比例Pdx-Mny/C 之粒徑，整理為表4.4，圖4.13可觀 察到隨著Mn的量增加，更多的Mn原子進入Pd晶格，Pd的繞射峰強度逐漸減 少，Pd-Mn合金金屬微粒粒徑也縮小，再度驗證 Mn可以避免Pd金屬微粒團聚
【5】。
不同比例Pdx-Mny/C合金結構，可用Vegards Law relation 方程式去計算 其晶格常數【50】，估算待測不同比例Pdx- Mny/C 晶格参數整理於表4.5，
表4.4為Pd (220)與Pd(111)估算待測不同比例Pdx-Mny/C之粒徑，從表4.4、
4.5可以觀察到Pd-Mn合金觸媒隨著Mn金屬含量的增加，造成Pd繞射峰負向偏 移，其晶格参數會越大，所以Pd5-Mn/C的Pd-Mn晶格2θ值會小於Pd/C的Pd晶
格2θ值，其Pd5-Mn/C晶格参數就大於Pd/C晶格参數。由表4.5可觀察到，不管 哪個方向的晶格参數只有些微的變化，因不同比例Pdx-Mny/C觸媒中，Mn金屬 的含量只有些微的差別，所以晶格参數變異不大。
圖4.13 不同組成Pdx-Mny/C 之XRD圖譜 。 (a)Mn/C (b)Pd-Mn/C (c)Pd3-Mn/C (d) Pd5-Mn/C (e)Pd/C
表 4.3 XRD測得之觸媒不同方向特徵峰之角度。
樣品 Pd (1 1 1) Pd (2 0 0) Pd (2 2 0) Pd (3 1 1) Pd (2 2 2)
Pd/C 40.12 46.26 68.14 82.30 86.72
Pd-Mn/C 39.87 46.07 67.76 81.55 86.33
Pd3-Mn/C 40.03 46.11 67.92 81.72 86.45
Pd5-Mn /C 40.08 46.18 68.08 82.13 86.56
表 4.4 XRD測得之觸媒粒徑 樣品 characteristic
peak values for (111)
(2θ)
Average size for (111)
(nm)
characteristic peak values
for (220) (2θ)
Average size for (220)
(nm)
Pd/C 40.12 8.23 68.14 10.11
Pd-Mn/C 39.87 4.86 67.76 5.56
Pd3-Mn/C 40.03 5.63 67.92 6.78
Pd5-Mn /C 40.08 8.06 68.08 8.69
表 4.5 XRD 測得之觸媒不同方向晶格参數。
樣品 Pd (1 1 1) Pd (2 0 0) Pd (2 2 0) Pd (3 1 1) Pd (2 2 2) Pd/C 0.6390 nm 0.5515 nm 0.3902 nm 0.3379nm 0.3201nm
Pd-Mn/C 0.6417nm 0.5529nm 0.3923nm 0.3393nm 0.3216nm
Pd3-Mn/C 0.6411nm 0.5523nm 0.3916nm 0.3389nm 0.3210nm
Pd5-Mn /C 0.6398nm 0.5518nm 0.3914nm 0.3385nm 0.3207nm
第五章 結論
其中最好的辦法是研究特殊的Pd雙金屬合金觸媒，一方面降低Pd使甲酸分解 的速率，同時又能提高Pd催化劑對甲酸氧化的電催化穩定性，初步的工作證 明這種想法是可能實現的。如能解決這兩個重大的問題，DFAFC基本上就能開 始商業化。
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