Aligned Proton Transport Highway of Hierarchically Structured Proton-Exchange Membranes Constructed via Capillary Force Lithography

The aligned nanostructure of perfluorinated polymer electrolytes is successfully achieved by capillary force lithography to allow increased proton conductivity through the proton highway. The hierarchical structure is realized from topographic line patterns to achieve the phase-separated architectures of the Nafion membranes via soft lithography using a prepatterned poly(dimethylsiloxane) mold. The controlled structures of proton-transporting channels are investigated by atomic force microscopy and small-angle X-ray scattering. The line-patterned membranes exhibit increased proton conductivities according to electrochemical impedance analysis. Furthermore, the increased interfacial contact area between the patterned membrane and cathode catalyst layer was observed, which enhances the power generation by the membrane-electrode assembly of proton-exchange membrane fuel cells.