Chemistry
Design of triazole bearing sol-gel membranes as water free proton exchange membranes for hydrogen fuel cells, effect of crosslink density, and heterocycle content on membrane performance
Abstract
Free-standing, water free, proton conducting, membranes were synthesized by incorporating triazole containing tetracyclosiloxanes into a PEG-TEOS based sol-gel matrix. The crosslinked films showed proton conductivities higher or comparable to those observed for the linear, liquid, polysiloxane analogs. An increase in the molecular weight of the PEG chains used to create the sol-gel matrix produced membranes with increased flexibility and higher proton conductivities at temperatures below 100 °C. PFGE-NMR studies show an increase in the apparent diffusion coefficient of the sol-gel threaded cyclosiloxane motifs compared to the linear polysiloxanes, suggesting a significant reduction on the coupling between mechanical strength and ion transport capability. The influence of crosslink density and the concentration of ionizable groups on membrane performance will be discussed, along with some preliminary data on the possibility of extending this approach to other ion transporting systems.
