Study of Transport Behavior in an Anion Exchange Membrane Fuel Cell

Abstract

Currently, anion exchange membrane fuel cells (AEMFC) are gaining strong interests from researchers because it provides great potential for applying non-precious metal in comparison to the proton exchange membrane fuel cells (PEMFC). The alkaline oxygen reduction reaction (ORR) has lower cathodic activation overpotential than ORR in a PEMFC. In addition, low-cost stainless steel can be used as flowfield material, instead of more expensive metals or high-purity graphite because corrosion of the bipolar plate is less of an issue in the alkaline environment. However, there are still many technical challenges existed in AEMFC research. One key challenge is related to the transport of reactants and product in and out of the catalyst layer. Different from a PEMFC, water is actively participating in anodic hydrogen oxidation reaction (HOR) as a product and cathodic ORR as a reactant. Therefore, anode flooding and cathode drying are concerns for operating an AEMFC under high current density conditions. This complicates the study of transport behavior in an AEMFC because transport limitation may occur due to one or a combination of hydrogen, oxygen, hydroxide, and water. Additionally, hydroxide transport in the membrane strongly relies on proper hydration, which may induce severe polarization losses due to membrane and ionomer conductivity caused by drying. Therefore, adequate water balance combined with effective reactant/product transportation are essential in achieving good performance for an AEMFC. In this work, we focus on studying the effect of operating conditions on fuel cell performance experimentally. Key parameters include relative humidity, temperature, pressure, and inlet gas concentration. An in-situ diagnostic tool, limiting current method1, is employed to analyze transport behaviors in an AEMFC. Differential conditions are achieved by using a straight parallel flowfield with 2 cm2 active area as shown in Figure 1. Our aim is to identify sources of transport limitations and quantify their effect under various operating conditions. Detail experimental and analytical results will be shared at the conference.