Impact of acid containing montmorillonite on the properties of Nafion® membranes

Abstract

The counter-ions of montmorillonite have been exchanged for ammonium cations containing either a sulfonic acid or a carboxylic acid in order to improve the performances of sulfonated membranes in direct methanol fuel cell. These layered silicates have been dispersed within Nafion ® by solution mixing. Comparison with conventional organo-modified montmorillonite (Cloisite 30B) shows that the incorporation of carboxylic acid in the clay galleries improves the filler dispersion and, consequently, the methanol barrier properties. Moreover, the negative impact of Cloisite 30B on the ionic conductivity is restricted.

Beneficial effect of carbon nanotubes on the performances of Nafion membranes in fuel cell applications

“…The same effect was observed upon the polymer addition by organomodified montmorillonite (MMT 30B, Fig. 4) [24].…”

“…This decrease is very small compared to the effect observed upon addition of montmorillonite (5% versus 25% at 2 wt% filler content) [24]. It is however erased by the grafting of carboxylic acid onto the surface of the MWCNTs.…”

“…PBI membranes are remarkable because they do not need to be humidified for exhibiting high ionic conductivity, which allows for operation at temperature higher than 100°C. The second strategy relies on the modification of ion-conducting polymers by inorganic fillers, such as silica [11,12], heteropolyacid [13,14], zirconium phosphate [15][16][17] and multi-layered silicates (montmorillonite) [18][19][20][21][22][23][24]. The main reason for the addition of these inorganic fillers is to reduce the methanol permeability while keeping the ionic conductivity as high as possible.…”

Nafion–clay nanocomposite membranes: Morphology and properties

“…Several papers describe the synthesis and characterization of Nafion membranes based on sulfonated [23][24][25][26][27][28], fluoro-modified [29,30] conventional organo-modified [31][32][33] or native clays [33]. Other approaches for synthesizing Nafionclay hybrids have also been reported [34,35].…”

Nafion–clay hybrids with a network structure

“…[17][18][19][20] Inorganic additives include silica, heteropolyacids, metal oxides or solid state ionic conductors, and they are incorporated in the membrane by physical mixing or they are generated in-situ using sol-gel reactions. [21][22][23][24][25][26][27][28][29][30][31] The expectation was that incorporation of hydrophilic inorganic particles will improve water retention and the overall performance of the composite membranes. Despite the better water retention at higher temperatures, however, the performance of cells based on heteropolyacid based hybrid membranes deteriorates over time due to acid leaching out of the membranes.…”