Chemical physics insight of PPy-based modified ion exchange membranes: A fundamental approach

https://doi.org/10.1016/j.memsci.2021.120020Get rights and content
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Highlights

  • Ion exchange membranes were chemically modified for preventing crossover.

  • The electrical properties differ considering the nature of exchange membranes.

  • Polypyrrole-based membranes prevents crossover of electroactive compounds while keeping out the characteristics of a good semiconductor.

  • Modified membranes show excellent mechanical properties.

Abstract

Four commercially available, cost-effective ion exchange membranes (two cationic and two anionic exchange membranes, CEMs and AEMs, respectively) were modified to mitigate crossover phenomena of the redox active species typically observed in Aqueous Organic Redox Flow Batteries (AORFB) systems. The modification strategy was carried out using a pyrrole(Py)-based polymer which successfully reduced the permeation of two redox active organic molecules, a viologen derivative (named BP7 throughout this study) and TEMPOL, by an order of magnitude. Additionally, modified membranes showed not significant changes in ion conductivity, with negligible effect on the electrical conductivity of the membranes at a given conditions. The morphology, physicochemical, mechanical, and electrochemical properties of the membranes were determined to evaluate the impact of these modifications. AEMs modified in this manner were found to have optimal properties, showing an increase in ion exchange capacity while maintaining excellent mechanical stability and unaltered permselectivity. Additionally, the diffusion boundary layer of these AEMs was slightly extended, which suggests a greater double layer stability for ion exchange processes than in the case of CEMs. Our work shows that these modified membranes could be an appealing approach for AORFB applications.

Keywords

Ion exchange membrane
Membrane modification
Permeability
Permselectivity
Mechanical properties

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