Alternatively chitosan sulfate blending membrane as methanol-blocking polymer electrolyte membrane for direct methanol fuel cell

A series of blending chitosan sulfate membranes have been developed by grafting the chitosan monomers with sulfonic groups, then cross-linking the polymers from the bond reactions between the sulfonic groups in the chitosan sulfate and the amido groups in the pure chitosan monomers. Mechanical characterizations demonstrated that the dimensional swelling as well as the methanol crossover of the chitosan membranes were suppressed successfully by the polymer blending, with area swelling value decreased from 55.1% to 39.3% and methanol diffusion coefficient decreased from 1.0 × 10^-6 cm² s^-1 of pure chitosan to 4.7 × 10^-7 cm² s^-1 of the membrane with chitosan sulfate content of ∼9.1 wt% (CCSM 110). The thermal analysis indicated that the blending chitosan sulfate membranes were structure stable below 100 °C. The blending membrane showed the best conductivity (0.03 S cm^-1 at 80 °C). The methanol permeability of CCSM 110 was much lower compared with that of Nafion 112 (1.9 × 10^-6 cm² s^-1).