H/Dイソトープ効果は,水酸化のためのコベース酸化物における触媒活動を制御する要因を明らかにする
Chiara Pasquini1, Ivelina Zaharieva1, Diego González-Flores1
1Department of Physics , Freie Universität Berlin , Arnimallee 14 , 14195 Berlin , Germany.
Journal of the American Chemical Society
|January 18, 2019
まとめ
デュテリウム置換はコバルト酸化物の触媒における水酸化触媒を著しく低下させ,陽子結合電子の移転が速度決定的ではないことを示した. 酸素-酸素結合の形成は,重要なステップとして提案されています.
科学分野:
- カタリシス
- 電気化学
- 人工光合成
背景:
- 電気化学的な水酸化は 人工光合成に不可欠です
- 陽子結合電子移転 (PCET) は,水の酸化メカニズムにおける重要なステップです.
- PCETメカニズムを理解することは 効率的な触媒の設計に不可欠です
研究 の 目的:
- コ基の無形酸化物触媒による電気化学的水酸化のメカニズムを解明する.
- 触媒サイクルのプロトン結合電子移転の役割を調査する.
- 水酸化過程における速度決定のステップを特定する.
主な方法:
- 同位体置換試験 (水素に対するデュテリウム,16Oに対する18O)
- インサイトおよび準インサイトX線吸収光譜 (XAS)
- 時間分解のスペクトル電気化学測定
主要な成果:
- デュテリウム置換は触媒活性が87%低下し,18O置換は10%減少した.
- 同位体効果は,CO 還酸化過程における酸化ポテンシャルの正のシフトを示した.
- 運動同位体効果の欠如は,電子移転が速度決定的ではないことを示唆している.
- 触媒速度は平均のコバルト酸化状態と指数関数的に相関する.
結論:
- 陽子や電子の移転は,この水酸化メカニズムで速度を決定するステップではありません.
- 速度決定のステップとして,隣接する Co ((IV) 種と O-O 結合形成を含むメカニズムが提案されています.
- この発見は 人工光合成のための高度な触媒の設計に 洞察を与えてくれます
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