局所的静電相互作用を用いた非対称なコバルトポルフィリンの酸素減少選択性の制御
1Simon Fraser University, Department of Chemistry, 8888 University Drive, Burnaby BC V5A 1S6 Canada.
Journal of the American Chemical Society
|July 25, 2020
まとめ
酸素還元反応 (ORR) のための新しい電気触媒の開発は極めて重要です. この研究では,カチオンの補助群を用いたコバルト・ポルフィリンORR触媒を強化し,広範囲のpHで水生成のための高い選択性を達成した.
科学分野:
- 電気化学
- 材料科学
- カタリシス
背景:
- 酸素還元反応 (ORR) のための電気触媒は,エネルギー変換技術にとって不可欠です.
- ORRの選択性および運動性の改善,特にO2をH2Oに減らす4H+/4e-は重要な課題である.
- 活性部位付近の補助群は,触媒の性能を高めることができるが,コバルトポルフィリンに対する戦略は,鉄ポルフィリンに対する戦略とは異なる.
研究 の 目的:
- コバルトポルフィリン触媒の改善のために,鉄ポルフィリンORR触媒のために開発された補助グループのための戦略を適応させる.
- コバルト・ポルフィリンを合成し,さまざまな補助グループを持つ一連の電気触媒を研究する.
- これらの改変がpH値の範囲におけるORRの選択性および動力学に与える影響を決定する.
主な方法:
- -NH2, -N(CH3) 2,および -N(CH3) 3の補助群を持つコ[5,10,15,20-テトラフェニルポルフィリン]誘導体の合成
- サイクル電圧測定と水力動力電気化学を用いた電気化学的調査.
- 反応メカニズムを解明するための量子化学計算.
主要な成果:
- カチオンの補助群 (-N(CH3) 3+) は,幅広いpH範囲 (0−7) でO2をH2Oに変換する催化剤を選択した.
- 他の触媒は,カチオンの変種とは異なり,より高いpH値でH2O2を生成した.
- -N(CH3) 3+改変した触媒は,安定したORR率106M-1s-1とpH0から7までの選択性を示した.
結論:
- O2をH2に完全に還元するためにコバルトポルフィリン電解剤の選択性を高めるのに非常に効果的です.
- Co-porphyrinsのメカニズムは,アニオン,過酸化結合中間物質を含む可能性があり,静電安定化が重要なことを示唆しています.
- O2結合中介物の静電安定化は,鉄ポルフィリンで使用されるプロティック補助基よりもコバルトポルフィリンORR触媒にとってより重要である.
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