Optimal ion-conducting membranes are critical to the desired electrochemical devices for a clean energy future. Although perfluorinated sulfonic-acid ionomers (e.g., Nafion�) are widely used due to outstanding ionic conductivity and chemical/mechanical stability upon hydration, understanding water uptake and transport in them has been slow due to limited experimental accessibility into the internal water profiles. Herein the elucidated water behaviors are discussed by visualizing the internal water profile using X-ray micro-tomography with high resolution (~1 �m, ~10 min). The results demonstrate the nonlinear water profile including a continuous transition from dynamic to steady-state transport coefficients with the requisite water-uptake dependence under different water boundary conditions. The importance of the interfacial condition in controlling the water profile and the absence of Schroeder's paradox within the membrane will also be discussed. The technique and obtained results yield new understandings into fundamental polymer physical properties, and allow for device-operation optimization and novel material development.

Understanding water uptake and transport in polymer electrolyte membrane of fuel cells using X-ray microtomography

245th National Meeting (2013)

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