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The FeIV-O● oxyl unit as a key intermediate in water oxidation on the FeIII-hydroxide: DFT predictions
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  • Alexander Shubin,
  • Viktor Kovalskii,
  • Sergey Ruzankin,
  • Igor Zilberberg,
  • Valentin Parmon,
  • Felix Tomilin,
  • Paul Avramov
Alexander Shubin
Boreskov Institute of Catalysis SB RAS
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Viktor Kovalskii
Boreskov Institute of Catalysis SB RAS
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Sergey Ruzankin
Boreskov Institute of Catalysis SB RAS
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Igor Zilberberg
Boreskov Institute of Catalysis SB RAS
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Valentin Parmon
Boreskov Institute of Catalysis SB RAS
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Felix Tomilin
Kirensky Institute of Physics SB RAS
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Paul Avramov
Kyungpook National University
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Abstract

The O-O coupling process in water oxidation on the gamma FeOOH hydroxide catalyst is simulated by means of density functional theory using model iron cubane cluster Fe4O4(OH)4. A key reactive intermediate is proposed to be the HO-FeIV-O• oxyl unit with terminal oxo radical formed from vertex HO-FeIV-OH moiety by withdrawal of proton-electron pair. The O-O coupling goes via water nucleophilic attack on the oxyl oxygen to form the O-O bond with a remarkably low barrier of 11 kcal/mol. This process is far more effective than alternative scenario based on direct interaction of two ferryl FeIV=O sites (with estimated barrier of 36 kcal/mol) and is comparable with the coupling between terminal oxo center and three-coordinated lattice oxo center (12 kcal/mol barrier). The process of hydroxylation of terminal oxygen inhibits the O-O coupling. Nevertheless, being more effective for ferryl oxygen, the hydroxylation in fact enhances selectivity of the O-O coupling initiated by the oxyl oxygen.

Peer review status:ACCEPTED

01 Jun 2020Submitted to International Journal of Quantum Chemistry
02 Jun 2020Submission Checks Completed
02 Jun 2020Assigned to Editor
24 Jun 2020Reviewer(s) Assigned
21 Jul 2020Review(s) Completed, Editorial Evaluation Pending
21 Jul 2020Editorial Decision: Revise Major
14 Oct 20201st Revision Received
14 Oct 2020Assigned to Editor
14 Oct 2020Submission Checks Completed
29 Oct 2020Reviewer(s) Assigned
05 Nov 2020Review(s) Completed, Editorial Evaluation Pending
05 Nov 2020Editorial Decision: Revise Major
06 Jan 20212nd Revision Received
09 Jan 2021Submission Checks Completed
09 Jan 2021Assigned to Editor
09 Jan 2021Reviewer(s) Assigned
14 Jan 2021Review(s) Completed, Editorial Evaluation Pending
14 Jan 2021Editorial Decision: Accept