Balanced Oxygen‐Proton Transport via Dual‐Functional Binders for High‐Performance Low‐Pt Fuel Cells

Abstract Mass transport resistance is a major bottleneck for high‐temperature proton exchange membrane fuel cells (HT‐PEMFCs), particularly at the low Pt loadings required for commercial viability. Although rational binder design is proposed as a potential solution, few binder systems have demonstrated the capability to simultaneously mitigate both proton and oxygen transport resistances. Herein, this work engineers a dual‐functional binder system incorporating covalent triazine frameworks‐4,4′‐biphenyldicarbonitrile (CTFs‐DCBP) and polyaniline (PANI) that successfully addresses this critical issue. The phosphoric acid‐doped PANI enables dual proton/electron conduction, while the Knudsen‐optimized straight pores in CTFs‐DCBP significantly reduce oxygen transport resistance by 22% compared to the commercial polytetrafluoroethylene (PTFE) binder. The optimized membrane electrode assembly (MEA) achieves a record‐breaking Pt mass‐specific power density of 8.5 W mg Pt −1 at 2 atm with a low Pt loading of 0.1 mg Pt cm −2 , demonstrating 5.4 times greater performance than commercial PTFE‐based systems and surpassing all reported HT‐PEMFCs under comparable Pt loadings. This study further reveals that reducing oxygen transport resistance is pivotal to achieving high fuel cell performance with low Pt loading‐a crucial aspect frequently overlooked in prior studies, thereby establishing new design principles for next‐generation electrodes.