Ionomer dispersion solvent influence on the microstructure of Co–N–C catalyst layers for anion exchange membrane fuel cell

Abstract

The controllable fabrication of non-precious metal cathode catalyst layer (CCL) to improve the water management is crucial to the performance of anion exchange membrane fuel cells (AEMFCs). Due to the higher porosity and larger particle size of M-N-C (M = Co, Fe) catalysts, compared with commercial Pt/C catalysts, the M-N-C layer is more complex. Here, we study the influence of solvent dispersion on the microstructure of Co–N–C CCLs. The solvent dielectric constants determine the aggregate size, while the relative volatilization rate dominates the final pore structure. The Co–N–C aggregate size in methanol is approximately two times larger than that in tetrahydrofuran or isopropanol. An interesting phenomenon is that ionomer tends to migrate and coalesce because of height differences in the CCL, demonstrating the importance of fast consolidation for achieving a homogenous ionomer distribution. By using ink containing tetrahydrofuran, the membrane electrode assembly from the Co–N–C CCL exhibits higher water adsorption ability in comparison with those using methanol, propanol, or isopropanol solvents, leading to a power density of 181.7 mW cm−2 at 50 °C, assembled with a commercial FAA-3-20 membrane. We anticipate our results can guide the design of Co–N–C CCLs with improved microstructure to achieve high performance AEMFCs.