Understanding and optimizing water transport phenomena in the catalyst layer for anion exchange membrane fuel cells

Abstract

Anion exchange membrane fuel cells (AEMFCs) are a promising power source due to zero emissions and high efficiency, and low precious metal loading. However, water management remains a significant issue affecting cell performance and durability. In this study, we develop a multi-physics model to investigate and optimize transport phenomena under various operational conditions and microstructure parameters. The agglomerate model is optimized to consider the influence of anode flooding and cathode drying in electrochemical reactions, and the simulation is validated with experimental results. Our findings indicate that an optimal anode inlet gas relative humidity of 80% achieved a tradeoff between anode flooding and ionic conductivity, resulting in a maximal power density of 758.9 mW/cm2. To alleviate anode flooding, we optimize the microstructure of the anode gas diffusion layer, significantly improving maximal power density to 833.4 mW/cm2 by increasing the contact angle to 130°. The optimal porosity achieves a balance between the transport of liquid water and electron. Large pore diameter and small thickness lead to a slighter anode flooding and higher maximal power density. In summary, our study provides insights into the transport behavior of multi-phase water, reactant gas, ion, and electron to guide the design of high-performance AEMFCs.