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摘要: 離子交換樹脂（Ionomer）是質子交換膜燃料電池催化層的重要組成部分，它在催化層中的主要作用是作為質子傳導相傳導質子。本文采用旋轉圓盤電極法（RDE），在模擬燃料電池真實的運行環境（模式一）和模擬燃料電池啟停環境（模式二）兩種模式下，研究了Ionomer對鉑碳催化劑電壓循環耐久性的影響。通過相同位置透射電鏡分析法（IL-TEM），分析了鉑碳催化劑經歷模式二耐久性測試后的結構變化。研究發現Ionomer的存在可以提高鉑碳催化劑的耐久性。在模式一的測試中：添加Ionomer后，其氧還原半波電位下降值?E從23 mV下降至11 mV；沒有發生碳的腐蝕，Pt顆粒的長大是催化劑性能下降的主要原因；Ionomer的存在延緩了Pt電化學比表面積（ECSA）的降低從而有利于保持Pt的活性。在模式二的測試中：添加Ionomer后，其氧還原半波電位下降值?E從25 mV下降至5 mV，除了鉑顆粒長大外還發生了載體碳的腐蝕；Ionomer的存在同樣可以保持Pt的活性；IL-TEM分析可以看到明顯的鉑顆粒長大和碳腐蝕，碳載體的腐蝕造成鉑的嚴重流失和團聚。含Nafion的催化劑中鉑顆粒平均粒徑從2.7 nm增加到了3.76 nm，不含Nafion的催化劑中的鉑顆粒平均粒徑從2.44 nm增加到了4.19 nm。
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關鍵詞:
- 質子交換膜燃料電池 /
- 離子交換樹脂 /
- Pt/C催化劑 /
- 耐久性 /
- 相同位置透射電鏡(IL-TEM)
Abstract: Ionomer is an important part of the catalytic layer in proton exchange membrane fuel cell. Its main role is to conduct protons. We investigated the effect of ionomer on the durability of Pt/C catalyst using rotating disk electrode (RDE) under two modes: the real operating conditions (mode 1) and startup/shutdown conditions (mode 2). The structural changes of Pt/C catalyst after the durability test were analyzed by identical location transmission electron microscopy (IL-TEM). Results show that the addition of ionomer improved the durability of Pt/C catalysts. After the durability test of mode 1, the addition of ionomer reduced the change of half-wave potential (?E1/2) of oxygen reduction reaction from 23 to 11 mV, which is attributed to the growth of Pt particles rather than carbon corrosion. Ionomer delayed the decrease of electrochemical specific surface area (ECSA) of Pt/C catalyst, which is beneficial to the maintenance of Pt activity. After the durability test of mode 2, in addition to the growth of platinum particles, carbon corrosion occurred in the catalyst layer, and the growth of platinum particles was mainly due to carbon corrosion. The addition of ionomer reduced the ?E1/2 of oxygen reduction reaction from 25 to 5 mV. Furthermore, the growth of platinum particles and carbon corrosion can be clearly seen by IL-TEM, and the corrosion of the carbon support resulted in the loss and agglomeration of platinum. The average particle size of platinum in Nafion-containing catalyst increased from 2.7 to 3.76 nm, while that of Nafion-free catalyst increased from 2.44 nm to 4.19 nm. -
圖 1 模擬燃料電池真實的運行環境的加速模式圖（a）和模擬燃料電池啟停環境的加速模式圖（b）
Figure 1. Acceleration mode diagram that simulates the real operating environment of the fuel cell (a) and acceleration mode diagram that simulates the start-stop environment of the fuel cell (b)
圖 2 金色TEM網格和PTFE（聚四氟乙烯）蓋固定在GC尖端上
Figure 2. Golden TEM grid and PTFE cap are fixed on the GC tip
圖 3 樣品一（a）和樣品二（b）按模式一經歷0、3×103、6×103和104次循環后的CV曲線和ECSA的變化情況（c）
Figure 3. CV curves of sample 1 (a) and sample 2 (b) after 0, 3×103, 6×103和104 cycles in mode 1, and changes in ECSA (c)
圖 4 樣品一（a）和樣品二（b）在0、3×103、6×103和104次循環后的LSV曲線
Figure 4. LSV curves of sample 1 (a) and sample 2 (b) after 0, 3×103, 6×103 and 104 cycles
圖 5 樣品一（a）和樣品二（b）按模式二經歷0、3×103、9×103和2.7×104次循環后的CV曲線和ECSA的變化情況（c）
Figure 5. CV curves of sample 1 (a) and sample 2 (b) after 0, 3×103, 9×103, and 2.7×104 cycles in mode 2, and changes in ECSA (c)
圖 6 樣品一(a)和樣品二（b）經歷0、3×103、9×103和2.7×104次循環后的LSV曲線
Figure 6. LSV curves of sample 1(a) and sample 2 (b) after 0, 3×103, 9×103, and 2.7×104 cycles
圖 7 樣品一在耐久性測試前（a, c）和2.7×104次耐久性循環測試后（b, d）相同位置的TEM電鏡圖（a, b）和催化劑粒徑分布圖（c, d）
Figure 7. TEM electron microscope image of the same position of the catalyst (a, b) and catalyst particle size distribution diagram (c, d) in sample 1 before the durability test (a, c), and after the 2.7×104 durability cycle test (b, d)
圖 8 樣品二在耐久性測試前（a, c）和2.7×104次耐久性循環測試后（b, d）相同位置的TEM電鏡圖（a, b）和催化劑粒徑分布圖（c, d）
Figure 8. TEM electron microscope image of the same position of the catalyst (a, b) and catalyst particle size distribution diagram (c, d) in sample 2 before the durability test (a, c), and after the 2.7×104 durability cycle test (b, d)
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