Investigation On Preparation Of Free-radical Functionlized Controllable Alkaline Anion Exchange Membranes

Alkaline anion exchange membrane fuel cell (AEMFC) is a new fuel cell system, which iscomposed of an anode, a cathode, an electrolyte membrane and an external circuit. Usinghydrogen or lower aliphatic alcohol as a fuel and oxygen as the oxidant, it can transform thechemical energy into electrical energy. Alkaline anion exchange membrane (AEM) is one ofthe key parts of the AEMFC and plays the roles of separating anode and cathode, as well asconducting hydroxide ions. In this paper, our work have started with the molecular design anddevoted to the preparation and characterization of new AEMs.1. A series of functionalized quaternary ammonium poly(arylene ether)s (QBMPAEs)containing tetramethyl triphenyl methane moieties are synthesized via polycondensation,benzylic bromination, quaternization, and alkalization. The IECs of the QBMPAEsmembranes varies from0.90mmol g-1to1.73mmol g-1. The hydroxide ion transportactivation energy (Ea) of the QBMPAE-a is8.01kJ mol-1. The QBMPAE-d membrane withan IEC value of1.73mmol g-1bears a sulfone/ketone structure and demonstrates the highestconductivity (46.6mS cm-1) at80°C. The QBMPAE-d membrane conditioned in1~10MNaOH at room temperature for30days display conductivity higher than that of the parentmembrane. An H2/air single fuel cell with a membrane electrode assembly (MEA) madeentirely in-house from QBMPAE-d achieves a peak power density of20.1mW cm-2at70°C.2. A series of AEMs based on conductive multiblock copolymers, which have sequentialhydrophobic/hydrophilic structures with quaternary ammonium basic groups functionedtetramethyl triphenyl methane moiety, are fabricated via prepolycondensation, blockcopolycondensation, benzylic bromination, quaternization, and alkalization. The multiblockQMCPAEs have low water uptake and swelling ratio, good thermal stability, high ionicconductivities. The water uptake, swelling ratio, and ionic conductivity are increased with anincreasing oligmer length of the hydrophilic segments. The mechanical properties arestrengthened with the increasing length of the hydrophobic blocks. The obtained multiblockQMCPAE-X12Y11membrane demonstrated the best comprehensive properties.QMCPAE-X12Y11(IEC=1.80mmol g-1) shows the highest hydroxide conductivities of24.4 mS cm-1and44.3mS cm-1at20oC and80oC respectively.