期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 133, 期 14, 页码 5174-5177出版社
AMER CHEMICAL SOC
DOI: 10.1021/ja110908v
关键词
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资金
- NSF
- Jane Coffin Childs Memorial Fund for Medicinal Research
- AFOSR [FA9550-09-1-0689]
The oxidation of water to molecular oxygen is a kinetically demanding reaction that requires efficient coupling of proton and electron transfer. The key proton-coupled electron transfer (PCET) event in water oxidation mediated by a cobalt-phosphate-based heterogeneous catalyst is the one-electron, one-proton conversion of Co-III-OH to Co-IV-O. We now isolate the kinetics of this PCET step in a molecular Co4O4 cubane model compound. Detailed electrochemical, stopped-flow, and NMR studies of the CoIII-OH to Co-IV-O reaction reveal distinct mechanisms for the unidirectional PCET self-exchange reaction and the corresponding bidirectional PCET. A stepwise mechanism, with rate-limiting electron transfer is observed for the bidirectional PCET at an electrode surface and in solution, whereas a concerted proton electron transfer displaying a moderate KIE (4.3 +/- 0.2), is observed for the unidirectional self-exchange reaction.
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