Highly charged and stable cross-linked polysulfone alkaline membrane for fuel cell applications: 4,4′-((3,3′-bis(chloromethyl)-(1,1′-biphenyl)-4,4-diyl) bis(oxy))dianiline (BCBD) a novel cross-linker

Alkaline membrane (AM) shows fast transport of OH- towards the anode, separates both electrodes, and prevents fuel cross-over. To achieve good membrane conductivity and performance, high concentration of positively charged groups (quaternary ammonium) is an essential requirement, which also leads excessive swelling and mechanical instability of the AMs. Further, directly grafted quaternary ammonium (QA) with main polymer chain substitution and/or elimination reactions under strong alkaline environment. To avoid above-mentioned problems, we report preparation of cross-linked chloromethylated polysulfone based AM using (4,4,-((3,3'-bis(chloromethyl)-[1.1'-biphenyl]-4,4-diyl)bis(oxy))dianiline) (BCBD), a multi-functional novel cross-linking agent. Reported strategy compensates 2 mol of chloromethyl groups consumed during cross-linking, but additional functional groups (4 mol) with cross-linking agent. These AMs are designed to avoid the nucleophilic substitution (S-N(2)) (grafting quaternary ammonium (QA) groups at benzylic position), and Hofmann elimination (E-2) reactions (unavailability of beta-H), under strong alkaline environment. Effective cross-linking has been confirmed by spectral analysis, and improves membrane stabilities and fuel cell performance. Single-cell alkaline membrane fuel cell (AEMFC) performance of most suitable (CR-QPS-03) membrane, showed comparatively high performance (open circuit voltage (OCV): 0.813 V, maximum power density: 103.6 mW/cm(2) at 260.0 mA/cm(2)) in compare with Nafion 117 membrane (OCV: 0.682 V, maximum power density: 63.36 mW/cm(2) at 220.0 mA/cm(2)) under similar experimental conditions. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.