On the proton conductivity of Nafion–Faujasite composite membranes for low temperature direct methanol fuel cells

Abstract

a b s t r a c tAlthough zeolites are introduced to decrease methanol crossover of Nafion membranes for direct methanol fuel cells (DMFCs), little is known about the effect of their intrinsic properties and the interaction with the ionomer. In this work, Nafion-Faujasite composite membranes prepared by solution casting were characterized by extensive physicochemical and electrochemical techniques. Faujasite was found to undergo severe dealumination during the membrane activation, but its structure remained intact. The zeolite interacts with Nafion probably through hydrogen bonding between Si-OH and SO 3 H groups, which combined with the increase of the water uptake and the water mobility, and the addition of a less conductive phase (the zeolite) leads to an optimum proton conductivity between 0.98 and 2 wt% of zeolite. Hot pressing the membranes before their assembling with the electrodes enhanced the DMFC performance by reducing the methanol crossover and the serial resistance.

Mordenite/Nafion and analcime/Nafion composite membranes prepared by spray method for improved direct methanol fuel cell performance

“…2SiOH >>> Si-O-Si + H2O (6) For MPTES modified MOR (MOR-MPTES), the 15% weight loss observed in the temperature range 25 -250 ºC was due to the evaporation of weakly adsorbed water, whereas the additional loss of 9% between 250 ºC and 650 ºC was due to the decomposition of the organic species attached to MOR surface after modification. The data from TGA was used to calculate % silane treatment.…”

“…This is due to their high proton conductivity, chemical and thermal stability, and mechanical strength [5][6][7][8]. Nevertheless, DMFC has some severe problems.…”

Enhancement of PEM fuel cell performance at higher temperatures and lower humidities by high performance membrane electrode assembly based on Nafion/zeolite membrane

“…We obtained comparable proton conductivity values with literature. Zhang et al [17] prepared Nafion/zeolite composite membranes and showed that conductivity was higher than Nafion membrane. The maximum proton conductivity was found to be 0.11 S/cm as compared to bare Nafion, which is 110% lower than composite membrane.…”

“…Zeolites can potentially be a candidate for novel ion-conducting materials, since the cation is mobile in the framework structure, which has been materialized as ion exchangers in an aqueous phase. Zeolites are highly hydrophilic solids and have a high water sorption capacity because of the charged anionic framework and the extra-framework cations in addition to their open structure, high pore volume and surface area [17,18]. They are widely used as ion-exchangers and can hydrate with high amount of water.…”

Transport Properties of Zeolite Na‐X–Nafion Membranes: Effect of Zeolite Loadings and Particle Size

“…However, for a better understanding of what controls the properties of composite membranes further investigations, mainly focused on the effect of Na-X zeolite with different Al contents and zeolite in its acid form, are argument of undergoing researches. Although, Na-X zeolite undergo to extensive dealumination in acidic conditions (i.e., in the hydrated Nafion membrane or during the acidic activation treatment), this is not considered an issue for the study reported here since it modifies only the zeolite surface chemistry and does not destroy the zeolite structure [24].…”