3, University of Arizona, Tucson, Arizona, United States
2, University of Arizona, Tucson, Arizona, United States
Direct methanol fuel cells (DMFC) typically use low concentrations of methanol (1-2 M) in water as fuel so as to reduce methanol cross-over and consequent losses in efficiency. Here we report successfully using methanol-polymer gels coated with a non-porous polysulfone coating to deliver methanol to the DMFC a concentrations low enough to reduce methanol crossover and significantly reduce the amount of water required for DMFC operation. After finding that many polymeric hydrogels were not compatible with pure methanol, we discovered that gels could be made from 2-hydroxylethyl methacrylate (HEMA) cross-linked with 5-20 mol% ethylene glycol dimethacrylate (EGDMA) in methanol (75wt%). The monomers in methanol were polymerized with AIBN (0.05 mol%) at 65 °C. The un-modified, cross-linked gels released methanol over 5-10 hours; not slowly enough to replace traditional aqueous methanol. Release rates were dramatically reduced by coating the gels with a nonporous polysulfone membrane. Subsequently we showed DMFC fuel cells operated significantly longer using methanol from the polysulfone-modified methanol gels than from a comparable mass of 1-2 M solutions of methanol in water.