For AEMFC OH^- form of membrane reacts with CO₂ when exposed to air leading to loss in conductivity. The data published by Yanagi et.al.^[1] suggest that OH species reacts to form Carbonate/bicarbonate in few minutes and after 2 h the membrane only consists of carbonate and bicarbonate. Although this is an important data to consider the reaction kinetics, morphological properties and equilibrium concentrations are still unknown at different environmental conditions. We have attempted to study the CO₂ kinetics and its transient effect on conductivity, water-uptake (or lambda) and morphology when the OH^- form of PFAEM membrane is exposed to air which has approx. 400 ppm of CO₂. The kinetics was studied by exposing the membrane to controlled environment and titrating it using Warder and Winkler titration methods. We have studied transient change in small angle x-ray scattering patterns when the films are exposed to air at different conditions to study the change in d-spacing of the ionic domains. From SAXS analysis it can be concluded that the intensity of spectrum drops over time and the time of equilibration is higher at higher humidity. It takes few hours for the conductivity to drop to carbonate/bicarbonate level. Ultimately we want to understand the effect of CO₂ on membrane from every aspect and possibly help us think about strategies to mitigate the problem.

Keywords: Anionic exchange membrane, Carbonate,bicarbonate,carbon-dioxide, small angle x-ray scattering

Ref:

[1]Yanagi and Fukuta, ECS transactions,16(2008).