Issue 6, 2023

Aqueous solutions of super reduced polyoxotungstates as electron storage systems

Abstract

Due to the increasing energy density demands of battery technology, it is vital to develop electrolytes with high electron storage capacity. Polyoxometalate (POM) clusters can act as electron sponges, storing and releasing multiple electrons and have potential as electron storage electrolytes for flow batteries. Despite this rational design of clusters for high storage ability can not yet be achieved as little is known about the features influencing storage ability. Here we report that the large POM clusters, {P5W30} and {P8W48}, can store up to 23 e and 28 e per cluster in acidic aqueous solution, respectively. Our investigations reveal key structural and speciation factors influencing the improved behaviour of these POMs over those previously reported (P2W18). We show, using NMR and MS, that for these polyoxotungstates hydrolysis equilibria for the different tungstate salts is key to explaining unexpected storage trends while the performance limit for {P5W30} and {P8W48}, can be attributed to unavoidable hydrogen generation, evidenced by GC. NMR spectroscopy, in combination with the MS analysis, provided experimental evidence for a cation/proton exchange process during the reduction/reoxidation process of {P5W30} which likely occurs due to this hydrogen generation. Our study offers a deeper understanding of the factors affecting the electron storage ability of POMs and provides insights allowing for further development of these materials for energy storage.

Graphical abstract: Aqueous solutions of super reduced polyoxotungstates as electron storage systems

Supplementary files

Article information

Article type
Paper
Submitted
22 Feb 2023
Accepted
20 Apr 2023
First published
21 Apr 2023
This article is Open Access
Creative Commons BY license

Energy Environ. Sci., 2023,16, 2603-2610

Aqueous solutions of super reduced polyoxotungstates as electron storage systems

T. Zhao, N. L. Bell, G. Chisholm, B. Kandasamy, D. Long and L. Cronin, Energy Environ. Sci., 2023, 16, 2603 DOI: 10.1039/D3EE00569K

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.

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