Fuel cell devices such as photoelectrochemical CO2 reduction cells (PEC-CRC) convert CO2 into chemicals such as alcohol (methanol) and carboxylate ions (formate and acetate). These devices require ion exchange membranes that prevent crossover (transport) of chemical species along with sufficient ionic conductivity. Additionally, the transport of a particular chemical is affected due to the presence of other products. Therefore, understanding the relationship between membrane structures towards chemical (solute) transport is essential. Previously, our group observed increased acetate transport when it is in co-transport with fast diffusing methanol to poly(ethylene glycol) diacrylate (PEGDA) based crosslinked membranes. The addition of uncharged monoacrylate poly(ethylene glycol) phenyl ether acrylate (PEGPEA) monomer suppressed acetate transport. Furthermore, the inclusion of charged monoacrylate 3-sulfopropyl methacrylate potassium salt (SPMAK) enhanced ionic conductivity with an undesirable increase in acetate and methanol transport. At certain compositions of SPMAK and PEGPEA, acetate transport decreases in co-transport with methanol, which is desirable to PEC-CRC. The two main factors that affect the solute transport in these crosslinked membranes are membrane water uptake and fixed charge concentration, and it is pertinent to isolate and investigate their individual impact on solute transport. Therefore, tunable crosslinked membranes with varying SPMAK content and three different uncharged monomers of increasing chain length, namely phenyl acrylate (PA), ethylene glycol phenyl ether acrylate (EGPEA) and PEGPEA are utilized. Membranes with (i) constant water uptake, varying charge concentration, and (ii) varying water uptake, constant charge concentration were prepared as a result. Currently, membrane transport experiments are carried out to better understand the underlying transport-physiochemical property relationships.
