Speaker
Description
In the last years, enzymatic fuel cells (EFCs) were developed as an alternative to classical fuel cells and recently promising performance improvements were reported. EFCs work mostly with liquid electrolytes, but for the miniaturization of the devices, an ion exchange membrane separator is necessary. The membrane should be biocompatible, not alter the enzymatic activity, and its swelling behavior and conductivity need to be optimized in buffer solutions that are essential for the enzyme catalyst.
This work presents the study of the gravimetric and volumetric water uptake and ionic conductivity of two ionomers, sulfonated poly(ether ether ketone) (SPEEK) and polysulfone-trimethylammonium chloride (PSU-TMA), after immersion in phosphate, acetate and citrate buffer solutions at different pHs and concentrations.
The swelling and the hydration data can be interpreted using the osmotic pressure dependence on the ion exchange capacity of the ionomers and the concentration of the buffer. Anisotropic swelling is observed for SPEEK in diluted buffers. A large water uptake is observed for citrate ions, due to their large hydration. The ionic conductivity is related to the conducting ions and, in the case of SPEEK, to sorbed excess electrolyte. The highest value is observed after immersion in phosphate buffers. Ionic cross-linking is for the first time observed in the case of PSU-TMA in presence of divalent citrate ions, limiting the volumetric swelling and the ionic conductivity.
Furthermore, membranes based on sulfonated poly(ether ether ketone) (SPEEK) and sulfonated poly(phenyl sulfone) (SPPSU) are optimized in phosphate buffer in terms of hydrolytic stability, conductivity and mechanical behavior. The hydrolytic stability can be adapted by changing the casting solvent (DMSO, water or ethanol) and procedures, including a crosslinking heat treatment, or by blending the two ionomers.
| Speaker Country | France |
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