Decoupled Proton and Oxygen Transport at Cathode Triple-Phase Interfaces via Noncovalently Cross-Linked Biomimetic Nanochannels

The performance of proton exchange membrane fuel cells (PEMFCs) is critically governed by the cathodic triple-phase interface, where platinum catalyst poisoning and inefficient proton/oxygen transport severely impede the oxygen reduction reaction. Inspired by the selective transport of biological membranes, we herein develop a porphyrin-based organic network (H-PorBz) as a multifunctional ionomer modifier to reconfigure the catalyst/ionomer/gas triple-phase interface. In situ noncovalent cross-linking between the H-PorBz and Nafion via NH+-H···SO3– interactions forms an interfacial layer that decouples proton and oxygen transport while suppressing sulfonate-induced Pt poisoning. Spectroscopic and computational studies reveal that H-PorBz simultaneously enhances proton conduction and oxygen transport by establishing a low-barrier proton-transfer network and tuning nanopore polarity. This membrane-mimetic design reduces sulfonate coverage on Pt by 28% and oxygen-transport resistance by 39.4%, delivering a mass-specific power density of 15.8 W mgPt–1 under H2/air conditions, 1.7-fold that of a conventional Pt/C@Nafion cathode. The composite ionomer also demonstrates excellent durability (>120 h at 0.6 V), with a voltage decay rate below 50 μV h–1. This work presents a bioinspired interfacial engineering strategy that reconfigures the three-phase region to mitigate catalyst poisoning and transport losses, offering a viable route to high-performance low-Pt PEMFCs.