Optimizing the Mass-Transfer Efficiency of a Microporous Layer for High-Performance Proton Exchange Membrane Fuel Cells

To facilitate mass transfer in proton exchange membrane fuel cells (PEMFCs), carbon-based gel was used to fabricate micron-scale ordered indentations on the surface of the microporous layer (MPL). The high viscosity of carbon-based gel prevented the intrusion of slurry into the pores of macroporous substrate (MPS), providing more space for rapid mass transfer in the gas diffusion layer (GDL). The direction of ordered indentations was perpendicular to the direction of gas channels, working as an additional flow field at the interface of the catalyst layer and MPL. Besides, the indentations reduced the distance for water removal, providing an excellent water management efficiency. From measurements, the maximum power density of membrane electrode assembly (MEA) containing homemade GDL was 8.5% higher than that of MEA containing commercial GDL. Cyclic compressive loading on MEAs was carried out to in situ evaluate the correlation between mechanical degradation and mass-transfer efficiency. After being compressed five times, the mass-transfer efficiency of MEA containing homemade GDL was stable, but the MEA containing commercial GDL degraded seriously. From the structure and composition analysis, it is that commercial GDL revealed deformation of structure and a serious loss of hydrophobic materials after cyclic compressive loading. In contrast, the homemade GDL revealed high mechanical stability. In summary, this structural design of GDL is a promising strategy to improve the property of MEA for high-performance PEMFCs.