pH-induced reversal of ionic diode polarity in 300 nm thin membranes based on a polymer of intrinsic microporosity

Yuanyang Rong, Qilei Song, Klaus Mathwig, Elena Madrid, Daping He, Ralf G. Niemann, Petra J. Cameron, Sara E C Dale, Simon Bending, Mariolino Carta, Richard Malpass-Evans, Neil B. McKeown, Frank Marken

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Abstract

"Ionic diode" (or current rectification) effects are potentially important for a range of applications including water purification. In this preliminary report, we observe novel ionic diode behaviour of thin (300 nm) membranes based on a polymer of intrinsic microporosity (PIM-EA-TB) supported on a poly-ethylene-terephthalate (PET) film with a 20 μm diameter microhole, and immersed in aqueous electrolyte media. Current rectification effects are observed for half-cells with the same electrolyte solution on both sides of the membrane for cases where cation and anion mobility differ (HCl, other acids, NaOH, etc.) but not for cases where cation and anion mobility are more alike (LiCl, NaCl, KCl, etc.). A pH-dependent reversal of the ionic diode effect is observed and discussed in terms of tentatively assigned mechanisms based on both (i) ion mobility within the PIM-EA-TB nano-membrane and (ii) a possible "mechanical valve effect" linked to membrane potential and electrokinetic movement of the membrane as well as hydrostatic pressure effects.

Original languageEnglish
Pages (from-to)41-45
Number of pages5
JournalElectrochemistry Communications
Volume69
Early online date27 May 2016
DOIs
Publication statusPublished - 1 Aug 2016

Keywords

  • Electrokinetic effects
  • Electrophysiology
  • Iontronics
  • Membrane potential
  • Nanofluidics
  • Salt separation

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