Driving Electrochemical Membrane Processes with Coupled Ionic Diodes

Victor Li, Klaus Mathwig, O.A. Arotiba, Luthando Tshwenya, Evaldo Batista Carneiro Neto, Ernesto Chaves Pereira, Frank Marken

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Ionic diodes have emerged repeatedly in the literature for gel interfaces, for nanopores and channels, for nano-/micro-fluidic systems, and for asymmetrically ionomer-covered microholes. Concentration polarisation is likely to be the key to understanding the diode function and the diode time constant diode, i.e. the time for approaching steady state following a potential/polarity switch. For frequencies higher than diode = 2f = (diode)-1, the polarization mechanism is too slow for ion current rectification. Below the frequency associated with the diode time constant, irreversibility in ion flow is induced and the diode switches between two resistive states at opposite potentials (“open” and “closed”). The irreversible flow of ions allows energy conversion from electrical to electrochemical. For energy conversion, two coupled ionic diodes are necessary driven by alternating current (AC) electricity to minimise driver electrode electrolysis and energy losses. Opportunities for AC-desalination and for electroosmotic water harvesting with coupled ionic diodes are discussed.
Original languageEnglish
Article number101280
JournalCurrent Opinion in Electrochemistry
Early online date24 Mar 2023
Publication statusE-pub ahead of print - 24 Mar 2023


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