Issue 39, 2021

Activation by oxidation and ligand exchange in a molecular manganese vanadium oxide water oxidation catalyst

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.

Graphical abstract: Activation by oxidation and ligand exchange in a molecular manganese vanadium oxide water oxidation catalyst

Supplementary files

Article information

Article type
Edge Article
Submitted
14 Jun 2021
Accepted
30 Aug 2021
First published
30 Aug 2021
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2021,12, 12918-12927

Activation by oxidation and ligand exchange in a molecular manganese vanadium oxide water oxidation catalyst

G. Cárdenas, I. Trentin, L. Schwiedrzik, D. Hernández-Castillo, G. A. Lowe, J. Kund, C. Kranz, S. Klingler, R. Stach, B. Mizaikoff, P. Marquetand, J. J. Nogueira, C. Streb and L. González, Chem. Sci., 2021, 12, 12918 DOI: 10.1039/D1SC03239A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements