Nanotrap Architectures for Mitigating Interfacial Transport Limitations in Cathode Catalyst Layers of Proton Exchange Membrane Fuel Cells.

Efficient gas transport and abundant triple-phase boundaries (TPBs) are vital for thick cathode catalyst layers (CCLs) in proton exchange membrane fuel cells (PEMFCs), yet remain challenging to realize. In this work, we introduce a carbon-based nanotrap architecture functionalized with pyrrolic-N groups, which reorganizes the Pt-carbon-ionomer interface to enhance local oxygen supply. These nanotraps simultaneously confine Pt nanoparticles and ionomer, forming continuous pathways for oxygen, protons, and electrons, thereby significantly increasing active TPB density. The underlying enhancement mechanism is validated by x-ray tomography and 3D two-phase flow simulations. Using a 15.5 µm-thick CCL, the optimized electrode achieves peak power densities of 1940 mW cm-2 in H2/O2 and 1410 mW cm-2 in H2/Air-improvements of ∼30% and ∼80%, respectively. Moreover, it exhibits a good stability, with a voltage decay rate of only 43.8 µV h-1 at 1.5 A cm-2 over 1000 h. This nanotrap concept offers a versatile interfacial design strategy for advanced gas-diffusion electrodes in energy conversion technologies.