アルカリ,固体ポリマー電解質フィルムにおける溶解酸素の電気化学的還元
David Novitski1, Aslan Kosakian2, Thomas Weissbach1
1Department of Chemistry, Simon Fraser University , Burnaby, British Columbia V5A 1S6, Canada.
Journal of the American Chemical Society
|November 3, 2016
まとめ
アニオン交換膜燃料電池における酸素輸送は極めて重要であるが,十分に研究されていない. イオノマーの水分濃度を下げると酸素の拡散が大きく減り,燃料電池の性能に影響する.
科学分野:
- 電気化学
- 材料科学
- 化学工学
背景:
- アニオン交換膜燃料電池 (AEMFC) では,イオノマーを通過した酸素輸送が不可欠である.
- 水は,アルカリ媒体の酸素還元反応 (ORR) の反応物質であり,十分な水供給が必要である.
- カトド触媒層における質量輸送の制限は,AEMFCの性能にとって重要な課題です.
研究 の 目的:
- AEMFCのイオノマーにおける酸素還元反応 (ORR) の質量輸送行動を調査する.
- 酸素の拡散と濃度に対するイオノマー水分の影響を決定する.
- 薄いイオノマーフィルムでの質量輸送パラメータ抽出のためのショップ-シャボ方程式の精度を評価する.
主な方法:
- Ptマイクロディスク電極を用いた電気化学的ポテンシャルステップクロノアンペロメトリー
- メチル化ヘクサメチル-p-テルフェニルポリメチルベンジミダゾール (HMT-PMBI) とフーマテックFAA-3膜の試験
- 60 °Cで相対湿度を70%から98%まで制御する.
- Shoup-Szabo方程式による電流変数の非線形曲線フィッティング
- Shoup-Szabo方程式の限界を評価するための数値モデリング.
主要な成果:
- 酸素拡散係数 (DbO2) は,相対湿度 (水分含量) の減少に伴い2つの量位で減少した.
- 酸素の浸透性 (DbO2·cbO2) は,イオノマーの水分量に強く依存していることが判明した.
- Shoup-Szabo方程式を用いた数値モデリングでは,水分量が高い膜の 29%までの不一致が明らかになった.
結論:
- イオノマー含有量は,AEMFCにおける酸素質量輸送に大きく影響する.
- 減少した水分は酸素の拡散を大幅に減少させ,ORRを潜在的に制限します.
- Shoup-Szabo方程式は,高度に水分化された膜の質量輸送パラメータを過大評価する可能性があります.
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