A Nafion‐filled Polycarbonate Track‐Etched Composite Membrane with Enhanced Selectivity for Direct Methanol Fuel Cells

Abstract

The high proton conductivity of Nafion© membranes in direct methanol fuel cells is attributed to a random three dimensional 3D network of elongated ion channels formed by bundles of rod‐like inverted micelles. However, this network is also responsible for high methanol crossover. In addition, its conductivity is impaired at temperatures 120 °C and above due to ion channel rearrangement, thus limiting the operational temperature to 60–80 °C. Here we report a composite proton exchange membrane prepared by filling the pores of polycarbonate track‐etched membrane with Nafion, which promote channel orientation roughly normal to the surface. The proton conductivity of this geometry is significantly enhanced, presumably due to the restricted swelling, resulting in a better ion channel connectivity and realignment in the axial pore direction upon hydration. The permeability of sodium chloride and methanol, though, is suppressed, presumably due to formation of regions of closely packed sulfonic groups, which facilitate proton transfer but strongly exclude other solutes. Composite membranes with improved conductivity and selectivity based on the principle presented here are expected to allow operating direct methanol fuel cells at higher temperatures and with higher methanol concentrations, thus reducing costs and increasing the efficiency.

Understanding methods of preparation and characterization of pore-filling polymer composites for proton exchange membranes: a beginner’s guide

“…Through-plane σ and η NaCl of the pore-filling Nafion were two and four times higher, respectively, than for bulk recast Nafion. Later, the same group also reported on Nafion impregnation into PCTE (pore diameter, 600-1000 nm) membranes ( Gloukhovski et al 2017). The pore-filling Nafion demonstrated increased proton conductivity, presumably due to the lower tortuosity and better connectivity of water channels aligned by the pore walls.…”

“…The advantage of this method is that it requires only a simple real-time monitoring of cell conductivity or impedance, and thus, it is faster and simpler compared to P H2 and P MeOH measurements. Thereby, it can be used in combination with σ measurements for the initial screening of numerous experimental membranes, before more technically demanding characterization techniques are applied (Gloukhovski et al 2017). …”

Experimental Studies on the Performances of a Direct Methanol Fuel Cell with a Novel Integrated Ultrasonic Atomization Fuel Feeder

“…However, the complicated system makes it difficult to operate. In addition, many researches employ pervaporation membrane to realize the phase change of methanol . The performance of vapor feed DMFC is proved to be greatly improved when supplying with concentrated methanol.…”

A Limiting Case of Constant Counterion Electrochemical Potentials in the Membrane for Examining Ion Transfer at Ion-Exchange Membranes and Patches

“…Selective ion transport through ion-exchange membranes is vital in traditional applications such as the chloralkali process, desalination of brackish water, and fuel cells, as well as emerging processes including power generation from salinity gradients and ion preconcentration in microfluidic applications. − In all of these areas, the defining characteristic of such membranes is their perm-selectivity, that is, selective passage of cations or anions. However, the rates of ion transport through these membranes depend on both the unstirred boundary layers adjacent to the membrane and the membrane itself.…”