Effects of membrane preparation and treatment on transport properties in recast Nafion membranes
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abstract
Membrane preparation techniques and post-treatments have important roles in suppressing methanol crossover and increasing proton conductivity, thereby affecting the performance of direct methanol fuel cell (DMFC). Solvent choice, casting environment, annealing temperature, and post-acidification are parameters that affect the transport properties (proton conductivity and methanol permeability) and fuel cell performances of polymer electrolyte membranes. The same polymer cast from different solvents with varying thermodynamic properties (i.e., boiling point, viscosity) exhibits differences in proton conductivity, methanol permeability, and DMFC performance. Inert and ambient casting environments showed significant differences in both proton conductivity and methanol permeability experiments. Annealing at different temperatures enhanced selectivity, while post-acidification increased proton conductivity. Dilute solutions of Nafion in different solvents yielded varying aggregate sizes (micelles), which can be due to the differences in solubility parameters of the solvent and the hydrophobic (backbone) and hydrophilic (side chain) portions of Nafion. This is an abstract of a paper presented at the AIChE Annual Meeting (Salt Lake, UT 11/4-9/2007).
