Ion exchange membranes (IEMs) are crucial for various energy devices, including direct urea fuel cells (DUFCs) and flow batteries. A major role of IEMs in such devices is to permit counterion and suppress co-ion transport. While commercially available IEMs (Fumasep® and Nafion®) exhibit decent power and energy densities in these devices, they often experience swelling over time (leading to a reduction in device performance because of crossover). Therefore, the design of IEMs that can suppress crossover is important for device performance. Here, we report a new class of stand-alone crosslinked ion exchange membranes with favorable mechanical toughness. These materials are based on a hydrophobic monomer (phenyl acrylate, PA) and a charged monomer (methacroylcholine chloride, MACC, or 2-acrylamido-2-methyl-1-propanesulfonic acid, AMPS). These membranes (PA/MACC and PA/AMPS) were evaluated in DUFC and flow battery devices. We observed competitive device performance relative to measurements made using Fumasep® and Nafion® IEMs. Transport properties (permeability and sorption coefficient) were measured to understand the solute (e.g., urea and redox shuttle) crossover and to further analyze device performance.
