Nafion-layered silicate nanocomposite membrane for fuel cell application

Abstract

Direct methanol fuel cells (DMFCs) using a proton exchange membrane as electrolyte is an attractive option for electricity generation. The most widely used membrane in the DMFC system is based on a perfluorinated polymer bearing sulfonic acid functions like Nafion ® . The latter combines chemical, mechanical and thermal stability and high protonic conductivity but shows elevated methanol permeability. We propose the preparation of a novel type of hybrid membranes to tentatively solve this problem. This innovative material results from the homogeneous dispersion of a nano-scaled inorganic filler within Nafion. The filler consists of stacks of negatively charged alumino-silicate layers (Cloisite), with a positive counter-ion in the interlamellar space. The purpose of the addition of this filler is to decrease methanol diffusion through the polymer membrane without decreasing too much the ionic conductivity.

Contribution of nanoclays to the barrier properties of a model proton exchange membrane for fuel cell application

“…Because polymers commonly used as fuel cell membranes are not able to disperse the native nanoclay properly [14], poly(vinyl alcohol), in which the nanofiller is easily exfoliated, has been chosen as a model membrane. However, the ionic conductivity of this type of membraneisintrinsically low and doping by phosphotungstic acid is required.…”

“…L/W is the anisotropy factor. In a previous study, we have shown that although nanoclays resist complete exfoliation within Nafion ® [14,15], the methanol permeability of this polymer is decreased by the multi-layered alumino-silicate. This preliminary observation is a strong incentive to model a situation in which the alumino-silicate would be completely delaminated within a polymer usable as a fuel cell membrane.…”

Polymer-Layered Silicate Nanocomposite Membranes for Fuel Cell Application

“…This trend remains unchanged even upon UV irradiation of the , and ammonium counter ions) showed a highest conductivity with the acid-activated MMT (H + counter ion) compared to MMT having Na + and ammonium counter ions due to the ease in mobility of the smaller counter ions (H + ion) (Fig. 22.16) [113]. Sulfonation of the nanoclay surface was also noted to increase the proton conductivity of the resulting membrane compared to the virgin Nafion and Nafion ® -unmodified Laponite nanocomposite due to the presence of the highly proton-conducting -SO 3 H group on the clay surface [94].…”

“…Addition of sulfonated MMT and Cloisite 30B to Nafion reduced the methanol and water permeability relative to the virgin Nafion due nm m to their well-dispersed morphology in Nafion [89,113]. However, poor polymer-filler interactions resulting in the void formation in the polymer-filler interface and inferior dispersion of unmodified MMT in Nafion reduced the barrier effect of Nafion-based composite towards methanol compared to the virgin Nafion ( Fig.…”

“…However, poor polymer-filler interactions resulting in the void formation in the polymer-filler interface and inferior dispersion of unmodified MMT in Nafion reduced the barrier effect of Nafion-based composite towards methanol compared to the virgin Nafion ( Fig. 22.8) [113].…”