A Study of Carbonate Formation Kinetics and Morphological Effects Observed on OH^-Form of Pfaem When Exposed to Air Containing CO₂

Abstract

For AEMFC, OHform of membrane reacts with CO2 when exposed to air leading to loss in conductivity. Very few attempts have been made to understand the reaction kinetics, morphological properties and equilibrium concentrations at different environmental conditions. We have attempted to study the CO2 kinetics and its effect on water-uptake (or lambda) and morphology(SAXS) when the OHform of 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. From transient SAXS analysis we observe the intensity of ionomer feature of membrane spectrum dropping over time. Also the d-spacing at equilibrium is lower than the initial value. 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.

The Effect of Ambient Carbon Dioxide on Anion‐Exchange Membrane Fuel Cells

“…It is widely understood that these reactions occur quickly . It can be problematic to accurately calculate their intrinsic rate because, in relevant systems, the transformation may be limited by CO 2 mass transport.…”

“…It is widely understood that these reactions occur quickly. [10,[17][18][19][20] It can be problematic to accurately calculate their intrinsic rate because, in relevant systems, the transformation may be limited by CO 2 mass transport. Yanagi and Fukuta found that, for an A201 AEM (Tokuyama Corp.,Japan), the OH À concentrationd ecreased by about 90 %i nt he first 10 min of exposure to air,f orming CO 3 2À .…”

The impact of alkyl tri‐methyl ammonium side chains on perfluorinated ionic membranes for electrochemical applications

“…OH − water uptake was only measured for the PFAEM_CH3_C6 polymer because it was the only material stable enough to survive this measurement. In this polymer, the λ values for the OH − form are higher than in the Cl − form . We also notice that the λ value is almost half of the Nafion®‐117 .…”

“…The temperature was increased from 30 to 80 °C and relative humidity of the chamber was kept constant at a 95% RH value. For the OH − conductivity, the AEM samples were soaked in aqueous 1M KOH solution in a N 2 environment glove box, which is CO 2 free as the OH − in AEM reacts with CO 2 in air to form carbonate/bicarbonate . The samples were soaked for 24 h and washed with degassed DI water four times in 24 h after alkali treatment still in the CO 2 free glove box.…”

“…For obtaining the SAXS data of OH − form of the PFAEM_CH3_C6, the samples need to be loaded in CO 2 free condition as the OH − reacts with CO 2 from air and forms HCO 3 − and CO 3 2− . We have explained the procedure in our previous work . The PFAEM_CH3_C6 samples were prepared in a CO 2 free N 2 environment glove box in the beamline.…”