Integrated MEA for polymer electrolyte membrane fuel cells enabled by freeze–casting and direct membrane deposition

Abstract

Polymer electrolyte membrane fuel cells require electrode architectures that promote efficient gas and proton transport, while minimizing platinum usage. However, conventional catalyst-coated membranes, which employ thin and planar catalyst layers, form a two-dimensional triple-phase boundary (TPB), limiting further improvements in the power output and mass transport. To overcome these limitations, herein, an integrated membrane electrode assembly (MEA) was fabricated by combining freeze-casting and direct membrane deposition (FC + DMD). The freeze-cast catalyst layer was 30.9 μm thick, with high porosity and an open-pore structure, facilitating oxygen diffusion. Simultaneously, DMD formed a membrane that infiltrated the porous structure, establishing an interdigitated interface that enhanced proton conduction. Structural analysis confirmed 49 % porosity and 0.273 mL/g of pore volume, which was 2.6 times higher than GDE + DMD MEA. Simultaneously, the integrated FC + DMD MEA exhibited up to 50 % reductions in proton diffusion resistance (5.6 mΩ·cm2) and charge transfer resistance (526 mΩ·cm2) compared with Nafion laminated (GDE + N211) MEA. Finally, the electrochemical performance of the integrated FC + DMD MEA revealed a peak power density of 1.62 W/cm2 in oxygen. This is higher than that of the GDE + DMD (1.424 W/cm2) and at least threefold higher than FC + N211 (< 0.5 W/cm2) MEAs, evidencing the synergistic formation of 3D TPB and reduced ionic/ohmic losses. © 2025 Elsevier B.V.