The unique properties of aqueous polyoxometalate (POM) mixtures and their role in the design of molecular coatings for electrochemical energy storage

•PMo12O403− (PMo12) and PW12O403− (PW12) react spontaneously in aqueous solutions.•This reaction synthesizes combinations of mixed addenda polyoxometalates (POMs).•This facile mixed addenda reaction can be replicated with various POM molecules.•The mixed addenda combinations show novel, unique and c...

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Bibliographic Details
Published in:Electrochimica acta 2016-05, Vol.199, p.261-269
Main Authors: Genovese, Matthew, Foong, Yee Wei, Lian, Keryn
Format: Article
Language:English
Subjects:
Acetal resins
Carbon nanotubes
Charge
Coatings
Design engineering
Electrodes
Hydrolysis
layer-by-layer deposition
Nanostructure
NMR
polyoxometalates (POMs)
Polyoxometallates
Pseudocapacitive
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Summary:•PMo12O403− (PMo12) and PW12O403− (PW12) react spontaneously in aqueous solutions.•This reaction synthesizes combinations of mixed addenda polyoxometalates (POMs).•This facile mixed addenda reaction can be replicated with various POM molecules.•The mixed addenda combinations show novel, unique and controllable redox properties.•Controllable redox properties enable the custom design of energy storage electrodes. A facile method to combine Keggin polyoxometalates (POMs) e.g. PMo12O403− (PMo12) and PW12O403− (PW12) in aqueous solutions has led to a unique electrochemical phenomenon, in which the POM mixtures demonstrate their own tunable redox activity, far different from the pure components. Through electrochemical and NMR analyses we have confirmed that this interesting behaviour arises from the spontaneous hydrolysis and recombination of PMo12 and PW12 ions forming complex blends of PMo12-xWx mixed addenda chemistries. While this process occurs spontaneously for the PMo12-PW12 system due to the ready hydrolysis, it can be induced in other POM mixtures such as SiMo12-SiW12 by adjusting the pH to stimulate hydrolysis. The highly tunable redox properties of the mixtures can be leveraged to design molecular coatings for a variety of applications. When deposited on nanocarbon, the overlapping redox features of the POM mixtures result in cyclic voltammograms with substantial pseudocapacitive currents which maintain relatively smooth charge/discharge profiles, ideal for supercapacitor electrodes.
ISSN:0013-4686
1873-3859
DOI:10.1016/j.electacta.2016.01.145