Issue 22, 2022

Water oxidation at low potential exploiting a nitroxide/oxoammonium ion redox couple as mediator

Abstract

The oxoammonium cation (OAC) of 3-carboxy proxyl, a nitroxide radical (NitR), could be produced either by chemical or by electrochemical oxidation (0.8–1.0 V vs. NHE) of the radical. We have determined that in dilute aqueous basic solutions (pH ≥ 9), OAC is reduced quantitatively to the original radical with concomitant formation of molecular oxygen in a ratio ca. 4 : 1 (4 moles of OAC reduced per 1 mole of O2), and the redox cycle can be repeated. The low electrolysis potential (0.8 V) contrasts with the high redox potential of the bare OH anion (2–2.6 V vs. NHE for the first outer-sphere electron transfer). This apparent thermodynamic paradox was solved by a careful study of its possible mechanism. In our opinion, OAC/NitR's may represent a new class of redox mediators for a novel approach to water oxidation (and generation of molecular oxygen) at a low potential.

Graphical abstract: Water oxidation at low potential exploiting a nitroxide/oxoammonium ion redox couple as mediator

Supplementary files

Article information

Article type
Paper
Submitted
10 Jun 2022
Accepted
26 Sep 2022
First published
27 Sep 2022
This article is Open Access
Creative Commons BY-NC license

Mater. Adv., 2022,3, 8149-8156

Water oxidation at low potential exploiting a nitroxide/oxoammonium ion redox couple as mediator

A. Barbon, A. A. Isse, A. Gennaro, R. Carmieli, I. Bilkis and L. Weiner, Mater. Adv., 2022, 3, 8149 DOI: 10.1039/D2MA00668E

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