文章基本信息
- 标题：In situ characterization of cofacial Co(IV) centers in Co4O4 cubane: Modeling the high-valent active site in oxygen-evolving catalysts
- 本地全文：下载
- 作者：Casey N. Brodsky ; Ryan G. Hadt ; Dugan Hayes 等
- 期刊名称：Proceedings of the National Academy of Sciences
- 印刷版ISSN：0027-8424
- 电子版ISSN：1091-6490
- 出版年度：2017
- 卷号：114
- 期号：15
- 页码：3855-3860
- DOI：10.1073/pnas.1701816114
- 语种：English
- 出版社：The National Academy of Sciences of the United States of America
- 摘要：The Co4O4 cubane is a representative structural model of oxidic cobalt oxygen-evolving catalysts (Co-OECs). The Co-OECs are active when residing at two oxidation levels above an all-Co(III) resting state. This doubly oxidized Co(IV)2 state may be captured in a Co(III)2(IV)2 cubane. We demonstrate that the Co(III)2(IV)2 cubane may be electrochemically generated and the electronic properties of this unique high-valent state may be probed by in situ spectroscopy. Intervalence charge-transfer (IVCT) bands in the near-IR are observed for the Co(III)2(IV)2 cubane, and spectroscopic analysis together with electrochemical kinetics measurements reveal a larger reorganization energy and a smaller electron transfer rate constant for the doubly versus singly oxidized cubane. Spectroelectrochemical X-ray absorption data further reveal systematic spectral changes with successive oxidations from the cubane resting state. Electronic structure calculations correlated to experimental data suggest that this state is best represented as a localized, antiferromagnetically coupled Co(IV)2 dimer. The exchange coupling in the cofacial Co(IV)2 site allows for parallels to be drawn between the electronic structure of the Co4O4 cubane model system and the high-valent active site of the Co-OEC, with specific emphasis on the manifestation of a doubly oxidized Co(IV)2 center on O–O bond formation.
- 关键词：water splitting ; renewable energy ; solar-to-fuels ; electrocatalysis ; oxygen evolution reaction
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