Boosting Reactant Transport in Low-Pt-Loaded Proton Exchange Membrane Fuel Cells via a Tailored Ionomer Assembly Strategy

Reducing the Pt loading of proton exchange membrane fuel cells (PEMFCs) is a crucial research focus to advance their commercial application. In conventional membrane electrode assemblies (MEAs), the random and inhomogeneous ionomer distribution significantly restricts both proton conduction and oxygen transport kinetics, hindering the fuel cells from approaching the theoretical performance upper bound. Therefore, optimizing the ionomer distribution in MEAs with low Pt loading is of great significance. In this work, the structure–function relationship between heterogeneous ionomer distribution and high reactant accessibility in the cathode catalyst layer (CL) was investigated. The deposited ionomer coated on carbon particles served as a high-speed channel for long-range proton conduction. A thinner and more homogeneous ionomer film on the catalyst surface facilitated the formation of an ideal catalyst/ionomer interface, achieving high proton accessibility and low oxygen transport resistance. The peak power density of the optimized MEA was increased by 5.8%. Specifically, it achieved a 55% increase in dry proton accessibility and a 14.4% reduction in oxygen transport resistance. This structure provides a tailored ionomer assembly strategy for boosting reactant transport in low Pt-loaded MEAs.