Improved Structural Stability of Charged Hydrogels under Organic CO₂ Reduction Products: Effect of Acrylate and Methacrylate Backbone Linkages

Abstract

Understanding the mixed solute transport behavior of CO 2 reduction products (methanol and formate) in ion exchange membranes (IEMs) is of interest for CO 2 reduction cells (CO 2 RCs). The role of an IEM in a typical CO 2 RC is to suppress the crossover of all CO 2 reduction products while allowing the transport of electrolytes. Tuning the polymer rigidity of the membrane is a key contributor to such highly controlled transport of organic solutes in a dense hydrated membrane. Here, we investigate the mixed solute transport behavior of methanol and formate in a series of tough phenyl acrylate-based cross-linked IEMs. We then investigate the effects of a structural modification on mixed solute transport behavior by introducing quaternary carbons within the membrane. We measured the relative permittivity properties of swollen films to determine if the water hydrogen bonding environment within the IEMs, which is related to maintaining selective ion transport within the membrane (electrolytes over CO 2 reduction products), was impacted by various organic solutes. We observed films with methacrylate backbone linkages have effectively constant relative permittivities when exposed to solutions containing methanol, formate, and a mix thereof. These findings may assist in designing membranes for applications, including CO 2 reduction cells and water−organic separation.

Development of Structure–Property Relationships for Ammonium Transport through Charged Organogels

“…While the general structure of Nafion ® is known, the complex morphology of the polymer makes it difficult to develop structure–property relationships, which are needed to guide the development of new membranes [ 22 , 23 ]. Previous work has demonstrated the use of readily tunable (meth)acrylate gels as a platform to understand structure–property relationships in ion exchange membranes [ 24 , 25 , 26 ], with some gels demonstrating improved performance compared to commercial membranes [ 27 ]. Based on these reports, we decided to adopt this tunable chemistry to study the impact of network structure on the transport of ammonium to guide the development of new membranes for NRR cells.…”