2009 Volume 66 Issue 9 Pages 373-380
We have investigated the ion exchange capacity (IEC), water uptake, thermal and chemical stability, mechanical strength, proton conductivity, and the methanol permeability coefficient (PM) in aqueous methanol solutions for cross-linked sulfoethylcellulose (CL-SEC) membranes. The highly swollen CL-SEC membranes exhibit a high proton conductivity (σ) which is comparable to that of Nafion® 112. The CL-SEC membranes also show low methanol permeability (PM) in methanol aqueous solutions. The selectivity (σ/PM)-which is a measure of the performance of polymer electrolyte membranes for direct methanol fuel cells- of the CL-SEC membranes increases with increasing the degree of cross-linking as well as the concentration of methanol solution. The value of σ/PM for the highly cross-linked membranes is at least 5 times higher than that of Nafion® 112 for the methanol solutions with the concentrations of more than 1 M. The results suggest that the CL-SEC membranes are potentially applicable to polymer electrolyte membranes for direct methanol fuel cells utilizing a high concentration methanol solution as a fuel.
