Open AccessCyclic Voltammetry as a Probe of Selective Ion Transport within Layered, Electrode-Supported Ion-Exchange Membrane Materials
Author(s) -
Jiahe Xu,
Johna Leddy,
Carol Korzeniewski
Publication year - 2022
Publication title -
journal of the electrochemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.258
H-Index - 271
eISSN - 1945-7111
pISSN - 0013-4651
DOI - 10.1149/1945-7111/ac51fd
Subject(s) - nafion , cyclic voltammetry , ionomer , chemistry , counterion , membrane , inorganic chemistry , ion exchange , electrode , overlayer , redox , analytical chemistry (journal) , ion , polymer , electrochemistry , organic chemistry , biochemistry , copolymer
Cyclic voltammetry was applied to investigate the permselective properties of electrode-supported ion-exchange polymer films intended for use in future molecular-scale spectroscopic studies of bipolar membranes. The ability of thin ionomer film assemblies to exclude mobile ions charged similarly to the polymer (co-ions) and accumulate ions charged opposite to the polymer (counterions) was scrutinized through use of the diffusible redox probe molecules [Ru(NH 3 ) 6 ] 3+ and [IrCl 6 ] 2− . With the anion exchange membrane (AEM) phase supported on a carbon disk electrode, bipolar junctions formed by addition of a cation exchange membrane (CEM) overlayer demonstrated high selectivity toward redox ion extraction and exclusion. For junctions formed using a Fumion ® AEM phase and a Nafion ® overlayer, [IrCl 6 ] 2− ions exchanged into Fumion ® prior to Nafion ® overcoating remained entrapped and the Fumion ® excluded [Ru(NH 3 ) 6 ] 3+ ions for durability testing periods of more than 20 h under conditions of interest for eventual in situ spectral measurements. Experiments with the Sustainion ® anion exchange ionomer uncovered evidence for [IrCl 6 ] 2− ion coordination to pendant imidazolium groups on the polymer. A cyclic voltammetric method for estimation of the effective diffusion coefficient and equilibrium extraction constant for redox active probe ions within inert, uniform density electrode-supported thin films was applied to examine charge transport mechanisms.