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Title: Synthetic control and empirical prediction of redox potentials for Co 4O 4 cubanes over a 1.4 V range: implications for catalyst design and evaluation of high-valent intermediates in water oxidation

Abstract

The oxo-cobalt cubane unit [Co 4O 4] is of interest as a homogeneous oxygen-evolution reaction (OER) catalyst, and as a functional mimic of heterogeneous cobalt oxide OER catalysts. The synthesis of several new cubanes allows evaluation of redox potentials for the [Co 4O 4] cluster, which are highly sensitive to the ligand environment and span a remarkable range of 1.42 V. The [Co III 4O 4] 4+/[Co III 3Co IVO 4 ]5+ and [Co III 3Co IVO 4] 5+/[Co III 2Co IV 2O 4] 6+ redox potentials are reliably predicted by the pKas of the ligands. Hydrogen bonding is also shown to significantly raise the redox potentials, by ~500 mV. The potential-p K a correlation is used to evaluate the feasibility of various proposed OER catalytic intermediates, including high-valent Co-oxo species. The synthetic methods and structure–reactivity relationships developed by these studies should better guide the design of new cubane-based OER catalysts.

Authors:
ORCiD logo [1];  [2]; ORCiD logo [2]; ORCiD logo [1];  [1]
  1. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Univ. of California, Berkeley, CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1379637
Grant/Contract Number:
AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Chemical Science
Additional Journal Information:
Journal Volume: 8; Journal Issue: 6; Journal ID: ISSN 2041-6520
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Nguyen, Andy I., Wang, Jianing, Levine, Daniel S., Ziegler, Micah S., and Tilley, T. Don. Synthetic control and empirical prediction of redox potentials for Co4O4 cubanes over a 1.4 V range: implications for catalyst design and evaluation of high-valent intermediates in water oxidation. United States: N. p., 2017. Web. doi:10.1039/c7sc00627f.
Nguyen, Andy I., Wang, Jianing, Levine, Daniel S., Ziegler, Micah S., & Tilley, T. Don. Synthetic control and empirical prediction of redox potentials for Co4O4 cubanes over a 1.4 V range: implications for catalyst design and evaluation of high-valent intermediates in water oxidation. United States. doi:10.1039/c7sc00627f.
Nguyen, Andy I., Wang, Jianing, Levine, Daniel S., Ziegler, Micah S., and Tilley, T. Don. Fri . "Synthetic control and empirical prediction of redox potentials for Co4O4 cubanes over a 1.4 V range: implications for catalyst design and evaluation of high-valent intermediates in water oxidation". United States. doi:10.1039/c7sc00627f. https://www.osti.gov/servlets/purl/1379637.
@article{osti_1379637,
title = {Synthetic control and empirical prediction of redox potentials for Co4O4 cubanes over a 1.4 V range: implications for catalyst design and evaluation of high-valent intermediates in water oxidation},
author = {Nguyen, Andy I. and Wang, Jianing and Levine, Daniel S. and Ziegler, Micah S. and Tilley, T. Don},
abstractNote = {The oxo-cobalt cubane unit [Co4O4] is of interest as a homogeneous oxygen-evolution reaction (OER) catalyst, and as a functional mimic of heterogeneous cobalt oxide OER catalysts. The synthesis of several new cubanes allows evaluation of redox potentials for the [Co4O4] cluster, which are highly sensitive to the ligand environment and span a remarkable range of 1.42 V. The [CoIII4O4]4+/[CoIII3CoIVO4]5+ and [CoIII3CoIVO4]5+/[CoIII2CoIV2O4]6+ redox potentials are reliably predicted by the pKas of the ligands. Hydrogen bonding is also shown to significantly raise the redox potentials, by ~500 mV. The potential-pKa correlation is used to evaluate the feasibility of various proposed OER catalytic intermediates, including high-valent Co-oxo species. The synthetic methods and structure–reactivity relationships developed by these studies should better guide the design of new cubane-based OER catalysts.},
doi = {10.1039/c7sc00627f},
journal = {Chemical Science},
number = 6,
volume = 8,
place = {United States},
year = {Fri Apr 07 00:00:00 EDT 2017},
month = {Fri Apr 07 00:00:00 EDT 2017}
}

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