Numerical investigation of anisotropic gas diffusion layers with graded porosity and wettability in anion exchange membrane fuel cells

Alkaline anion-exchange membrane fuel cells (AEMFCs) have been regarded as a promising alternative of proton exchange membrane fuel cells (PEMFCs) due to their high oxygen reduction reaction activity in the cathode side, which allow the usage of non-noble metal catalyst. Unlike PEMFCs, water is generated on the anode side of AEMFCs, and the electro-osmotic drag effect exacerbates the flooding phenomenon on the anode side and the dry-out on the cathode side. Therefore, water management plays a crucial role in the performance of AEMFC. In this study, we develop a multiphase flow multi-physics AEMFC model considering the anisotropy of gas diffusion layer (GDL). The study examines the impact of varying porosity gradients in GDLs, as well as changes in wettability, on cell performance. We find that in GDLs with varying porosity gradients, reducing porosity near the interface between the anode GDL and the catalyst layer (CL) promotes even distribution of reactive gases, enhancing cell performance. Under the operating conditions of this paper, the maximum power density can be increased by 1.27 %. Regarding wettability changes, optimal cell performance was observed with a higher contact angle on the anode GDL and a lower contact angle on the cathode GDL. The maximum power density can be increased by 1.59 %. Moreover, a higher contact angle near the anode GDL/CL interface maintained high membrane hydration levels, resulting in improved cell performance. The maximum power density can be increased by 2.68 %.