hide
Free keywords:
proton conductor; phosphonic acid; siloxane; membrane material; PEM fuel cell
Abstract:
Fully immobilized phosphonic acid based proton conductors, where
phosphonic acid groups are tethered to cyclic siloxanes via flexible
alkane spacers, are synthesized. Unlike conventional hydrated ionomers
containing sulfonic acid groups, which are commonly used as separator
material in PEM fuel cells, the proton conductivity of these materials
occurs within a dynamical hydrogen bond network formed by the
protogenic groups (phosphonic acid), which are present at very high
concentrations. Conductivities of up to 2 (.) 10(-3) S cm(-1) are
obtained at T approximate to 130 degrees C and RH approximate to 37%.
This is only slightly higher than the conductivity of similar imidazole
based systems although neat phosphonic acid has a much higher proton
conductivity compared to neat imidazole. The proton conductivity of
phosphonic acid is more sensitive towards immobilization at cyclic
siloxanes and the corresponding restrictions for hydrogen bond
formation (aggregation). (c) 2006 Elsevier B.V. All rights reserved.