Impact of Formulation of Photocurable Precursor Mixtures on the Performance and Dimensional Stability of Hierarchical Cation Exchange Membranes

Abstract

This work presents a systematic approach to formulating UV curable ionomer coatings that can be used as ion-exchange membranes when they are applied on porous substrates. Ion-exchange membranes fabricated in this way can be a cost-effective alternative to perfluorosulfonic acid membranes, such as Nafion and similar thin ionomer film membranes. Hierarchically structured coated membranes find applications for energy storage and conversion (organic redox flow batteries and artificial photosynthesis cells) and separation processes (electrodialysis). Designing the ionomer precursor for membrane formulation requires the introduction of compounds with drastically different properties into a liquid mixture. Hansen solubility theory was used to find the solvents to compatibilize main formulation components: acrylic sulfone salt (3-sulfopropyl methacrylate potassium salt) and hexafunctional polyester acrylate cross-linker (Ebecryl 830), otherwise nonmiscible or mutely soluble. Among the identified suitable solvents, acrylic acid and acetic acid allowed for optimal mixing of the components and reaching the highest levels of sulfonic group content, providing the desired ion-exchange capacity. Interestingly, they represented a case of a reactive and nonreactive solvent since acrylic acid was built into the ionomer during the UV curing step. Properties of the two membrane variants were compared. Samples fabricated with acetic acid exhibit improved handleability compared with the case of acrylic acid. Acetic acid yielded a lower area-specific resistance (6.4 ± 0.17 Ohm•cm 2 ) compared to acrylic acid (12.1 ± 0.16 Ohm•cm 2 in 0.5 M NaCl). This was achieved without severely suppressing the selectivity of the membrane, which was standing at 93.4 and 96.4% for preparation with acetic and acrylic acid, respectively.

Overcoming the Trade-Off between Methanol Rejection and Proton Conductivity via Facile Synthesis of Crosslinked Sulfonated PEEK Proton Exchange Membranes

“…In addition, the presence of DCX creates hydrophobic parts, rejecting methanol. Those effects were also consistent with the lower water and methanol uptake values [34].…”

“…In addition, the presence of DCX creates hydrophobic parts, rejecting methanol. Those effects were also consistent with the lower water and methanol uptake values [34]. The shortcoming of the methodology of how the data are represented in Figure 11 is that it gives the impression that the membrane performance can easily be tuned by the thickness.…”

“…The cation/anion permeation of the membranes was determined following the same procedure as reported by Deboli et al and Firganek et al [33,34]. First, the membrane was immersed in a 0.1 M KCl solution for 24 h. To perform the experiment, the membrane (active area 19.63 cm 2 ) was positioned in a two-compartment cell equipped with two saturated calomel electrodes.…”

Green Synthesis of Cation Exchange Membranes: A Review

“…They both put effort in making their synthesis procedure greener by eliminating the solvent or by using a greener solvent, however, the production of sulfopropyl methacrylate is not environmently friendly. It is synthesized by a reaction between the corresponding methacrylic salt and 1,3-propane sultone or 1,4 butane sultone, both of which can cause cancer [ 73 , 74 , 75 ].…”