Anion Exchange Membrane Fuel Cell Performance in the Presence of Carbon Dioxide

Anion Exchange Membrane Fuel Cells (AEMFCs) offer some possible advantages over their Proton Exchange Membrane (PEM) counterparts due to more facile oxygen reduction reaction kinetics (enabling cheaper catalysts), easier water management & balance of plant, cheaper membrane materials, and improved stability of fuel cell stack materials. However, AEMFCs perform significantly worse when exposed to carbon dioxide (CO2), which is present in most applications. Furthermore, because CO2 is so pervasive inside the AEMFC system, its effects are difficult to isolate experimentally. Therefore, a modeling approach was developed which can offer independent control of membrane properties and operating conditions, as well as the contextual freedom to isolate specific aspects of operation. For instance, AEMFCs exhibit a phenomenon known as “self-purging”, whereby CO2 is removed from the system during normal operation. Due to self-purging, AEMFCs approach their CO2-free performance as the current density is increased. Without this effect, it would be impractical to use AEMFCs. Despite its importance, the mechanism behind the self-purging phenomenon is still relatively obscure, which makes it difficult to design these devices with this effect in mind. In this modeling approach, existing ex situ AEM models are built up to include operating effects such as current density and gas stream conditions. A morphology model is also developed to investigate the effects of CO2 on electrospun AEMs, which are a class of AEMs with unique morphologies. Finally, we present a study that implements and evaluates the two leading explanations for self-purging, and discuss their relative merits