ABSTRACT
Sulfonated hydrocarbon polymers like polyether ether ketone (SPEEK) and poly(phthalalizinone ether ketone) (SPPEK) are widely studied as electrolytes for DMFCs. Narrow and branched channels of these polymers mitigate/restrict methanol crossover in direct methanol fuel cells (DMFCs). However, stability and ionic conductivity are major concerns in these polymers when used as electrolytes, and overcoming this carbon-based additive is explored as an option to form nanocomposite membranes with better stability and proton conductivity. Carbon nanostructures are functionalized through different routes for the surface enrichment of sulfonic acid groups and for better dispersion in the polymer matrix. This influences the restriction in methanol crossover without affecting the ionic conductivity of the host matrix in DMFC. This chapter explains the impact of functionalized carbon nanostructures, like fullerene, multi-walled carbon nanotubes, and graphite nanofibers dispersed in aromatic polymers, like sulfonated poly(ether ether ketone) and poly(phthalalizinone ether ketone) for better electrochemical selectivity in DMFC. The properties of these composite membranes are highly dependent on its structural orientation in the polymer matrix, sulfonation routes and the dispersion content in relation to the polymer. This chapter will cover all of the above parameters and their impact on DMFC performance.
