Composite Membrane of Zirconium Sulfate -Poly(Ether Sulfone Quinoxalines) for Hydrogen and Direct Methanol Fuel Cells

Abstract

The synthesis of aromatic polymers containing quinoxalines and preparation of composite proton exchange membranes with zirconium sulfate is described. Poly(ether sulfone quinoxalines) was synthesized via condensation polymerization from dihydroxyquinoxaline, bis(4-fluorophenyl)sulfone, and bisphenol monomers in N-methylpyrrolidone at 175-180oC. The synthesized polymer has a molecular weight of ~32,000 Daltons and glass transition temperature of ~176±2oC. The polymers were sulfonated using chlorosulfonic acid in concentrated sulfuric acid. The composite membranes were prepared from zirconium sulfate and blend of sulfonated poly(ether sulfone quinoxalines) and sulfonated polyethersulfone. Membrane electrode assemblies containing 25cm2 of active area were prepared with a catalyst loading of 3mg/cm2. The performance of the MEAs was characterized using a single fuel cell tester with hydrogen and methanol as the fuel sources. The methanol concentration was investigated from 3 v/v% to 20 v/v%. The peak power of the fuel cell was 108 mW for 20 v/v% methanol and a power of 750mW fueled with hydrogen at 5psi backpressure.