Reinforced Poly(ether ether ketone)/Nafion Composite Membrane with Highly Improved Proton Conductivity for High Concentration Direct Methanol Fuel Cells

Abstract

The composite membranes that combine pore-filling with a matrix having precisely assembled sulfonated groups are designed here for use in the applications of direct methanol fuel cells. A porous crystalline poly­(ether ether ketone)/sulfonated poly­(ether ether ketone) blended matrix with continuous pore structures is first fabricated using a phase inversion process. Solvent treatment of the porous matrix is then employed to induce the enrichment of sulfonated groups at the pore surfaces, based on the interaction between the solvent and functional groups in polymer chains. This strategy effectively shortens the proton transport path, accelerating the proton transfer rate. The pores of the matrix are then filled with Nafion ionomers, resulting in a reinforced composite membrane consisting of interconnected hydrophilic domains in a fuel-insulating rigid matrix. A single cell made using the novel composite membrane exhibits a relatively high power density of 91.7 mW/cm2 and an open circuit voltage of 0.67 V at 70 °C using 10 M methanol, significantly higher than a test device made using Nafion 117. This work supplies a simple and highly efficient strategy to address the low proton conductivity that is normally seen in composite membranes made using pore-filling technology.

Facile Fabrication of Amphiphilic and Asymmetric Films with Excellent Deformability for Efficient and Stable Adsorption Applications

“…Generally, strong interactions between the polymer and solvent can promote the movement of molecular chains and thus improve the cell morphology. [ 34 ] But, these filled CNTs cause significantly increased solution viscosity, meanwhile, they can delay the demixing process during the liquid–liquid phase inversion procedure, resulting in the suppression of the macrovoid formation and porous structure. [ 35–37 ] Figure shows the density of these as‐prepared films.…”

A Critical Assessment on Functional Attributes and Degradation Mechanism of Membrane Electrode Assembly Components in Direct Methanol Fuel Cells

“…The bonding force supplied by the direct pressing approach of CCM cannot withstand the swelling of the membrane during the operation of the DMFC, resulting in delamination [164]. A study reported that the isotropic membrane swelling (i.e., expansion coefficient difference between the CL and membrane) enhances the variance in swelling ratio with catalyst encompasses a Nafion binder, which would most likely increase electrode layer delamination [165].…”

Design and development of nucleobase modified sulfonated poly(ether ether ketone) membranes for high-performance direct methanol fuel cells

“…With the increase of DS, the proton conductivity increases, which will also increase the swelling of the membranes, reduce their mechanical properties and dimensional stability, and dramatically decrease the lifetime of the fuel cell. [14][15][16] In order to overcome these disadvantages, two kinds of polymer modication methods have been used to modify SPEEK membranes by researchers including polymer blending [17][18][19] and crosslinking. [20][21][22][23] SPEEK membranes crosslinked to a certain extent via chemical or ionic crosslinking can not only overcome the membrane swelling problem caused by high DS, but also inhibit methanol crossover due to the dense network structure formed by crosslinking.…”