Kinetic Equilibrium Study of CO2 poisoning Observed in Anion Exchange Membranes When Exposed to Ambient Air and Varying Levels of CO2 ppm

Abstract

One of the hurdles in Anion exchange membrane fuel cell technology is weaker understanding of CO2 poisoning observed when they are exposed to air. Our previous work suggests that OH- ions depletes in approximately 15 min to form CO3 2- and HCO3 - ions when exposed to ambient air at 30 °C and 95%RH[1]. However, an actual fuel cell device is operated at a much higher temperature. In this study we have obtained the CO2 absorption data at different temperatures and different CO2 concentration environment. Our data suggest that the air equilibrated AEM concentration of CO3 2- increases at higher temperatures whereas HCO3 - concentration follows a decreasing trend. The OH- ion has a very insignificant change at higher temperatures but we observe that the equilibrium OH- concentration is higher at lower ppm level of CO2 environment. This indicates that the CO2 reaction is dependent on CO2 concentration in air. We have also studied the transient change in ionic conductivity of OH- AEM films in ambient air. Here, we observe the nature of drop in conductivity when exposed to air. We have attempted to fit the conductivity data to mathematical models that will give us more insights into absorption phenomenon of CO2. Acknowledgements: This research was funded by the Department of energy through NREL. The AEM samples were supplied by Dr. Bryan Pivovar’s group at NREL. Reference A.G. Divekar, A. M. Park, Z. R. Owczarczyk, S. Seifert, B. S. Pivovar and A. M. Herring, ECS Transactions, 80, 1005 (2017). Figure 1