Enhancing Oxygen Transport in Proton Exchange Membrane Fuel Cell Through Nanoconfined Triple Phase Interface Engineering

In proton exchange membrane fuel cells (PEMFCs), ionomer aggregation on Pt/C catalysts leads to increased oxygen transport resistance of conventional catalyst layers. This behavior significantly influences oxygen transport in the microenvironment at the triple-phase interface of Pt/C catalysts. To address this challenge, triazine-based covalent organic frameworks (COFs) were incorporated into the cathode catalyst layer, so that their well-defined pore structure and proton eligible triazine sites interact with terminal sulfonate groups of the Nafion ionomer. This interaction regulates the triple-phase microenvironment, enhances Pt utilization, and establishes directed oxygen-enriched transport channels. Under low-platinum loading conditions (−0.05 mg_Pt cm⁻²) in a H₂─O₂ PEMFC, the COF-modified system achieved a peak power density of 1.55 W cm⁻², 1.3 times of conventional PEMFCs, with a 38% reduction in local oxygen transport resistance. This work presents a new design principle for high-performance low-platinum PEMFCs, as a new approach to further advance their commercialization.