Titel
Activation by oxidation and ligand exchange in a molecular manganese vanadium oxide water oxidation catalyst
Autor*in
Ivan Trentin
Institute of Inorganic Chemistry I, Ulm University
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Abstract
Despite their technological importance for water splitting, the reaction mechanisms of most water oxidation catalysts (WOCs) are poorly understood. This paper combines theoretical and experimental methods to reveal mechanistic insights into the reactivity of the highly active molecular manganese vanadium oxide WOC [Mn4V4O17(OAc)3]3− in aqueous acetonitrile solutions. Using density functional theory together with electrochemistry and IR-spectroscopy, we propose a sequential three-step activation mechanism including a one-electron oxidation of the catalyst from [Mn23+Mn24+] to [Mn3+Mn34+], acetate-to-water ligand exchange, and a second one-electron oxidation from [Mn3+Mn34+] to [Mn44+]. Analysis of several plausible ligand exchange pathways shows that nucleophilic attack of water molecules along the Jahn–Teller axis of the Mn3+ centers leads to significantly lower activation barriers compared with attack at Mn4+ centers. Deprotonation of one water ligand by the leaving acetate group leads to the formation of the activated species [Mn4V4O17(OAc)2(H2O)(OH)]− featuring one H2O and one OH ligand. Redox potentials based on the computed intermediates are in excellent agreement with electrochemical measurements at various solvent compositions. This intricate interplay between redox chemistry and ligand exchange controls the formation of the catalytically active species. These results provide key reactivity information essential to further study bio-inspired molecular WOCs and solid-state manganese oxide catalysts.
Stichwort
General Chemistry
Objekt-Typ
Sprache
Englisch [eng]
Persistent identifier
Erschienen in
Titel
Chemical Science
Band
12
Ausgabe
39
ISSN
2041-6520
Erscheinungsdatum
2021
Seitenanfang
12918
Seitenende
12927
Publication
Royal Society of Chemistry (RSC)
Projekt
Kod / Identifikator
I3987-N28
Fördergeber
Erscheinungsdatum
2021
Zugänglichkeit
Rechte
Rechteangabe
© 2021 The Author(s)
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