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 CO2 reduction products (methanol and formate) in ion exchange membranes (IEMs) is of interest for CO2 reduction cells (CO2RCs). The role of an IEM in a typical CO2RC is to suppress the crossover of all CO2 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 CO2 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 CO2 reduction cells and water–organic separation.