Driving electrochemical membrane processes with coupled ionic diodes

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

Research output: Contribution to journalReview articlepeer-review

3 Citations (SciVal)
32 Downloads (Pure)


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 τdiode, i.e. the time for approaching steady state following a potential/polarity switch. For frequencies higher than ωdiode = 2πf = (τdiode)−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 statusPublished - 30 Jun 2023

Bibliographical note

Funding Information:
F.M. thanks for the initial financial support by the EPSRC (EP/K004956/1). K.M. acknowledges financial support by Provincie Gelderland. E.B.C.N. and E.C.P. acknowledge support from FAPESP (São Paulo Research Foundation, Grant Numbers 2013/07296-2 , 2021/03592-2 , 2022/06229-9 ), Shell, and the strategic importance of the support given by ANP (Brazil's National Oil, Natural Gas and Biofuels Agency) through the R\&D levy regulation, CNPq (Grant Number 407878/2022 ), and CAPES (Code 001 ).

Publisher Copyright:
© 2023 The Author(s)


  • Desalination
  • Impedance
  • Microfluidic
  • Voltammetry
  • Water harvesting

ASJC Scopus subject areas

  • Analytical Chemistry
  • Electrochemistry


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