A Novel Cyclized Polyacrylonitrile Binder Strategy for Efficient Oxygen Evolution Reaction Catalysts

In alkaline water electrolysis, conventional polymer binders like Nafion suffer from poor hydroxide conductivity and inadequate interfacial properties. Herein, a thermally cyclized polyacrylonitrile (CPAN) binder system with a conjugated ladder structure is introduced. The CPAN binders are synthesized by controlled thermal treatment under various temperatures, among which CPAN-400 demonstrates the optimal 57.03% pyridinic N content, provides π-conjugated pathways for enhanced electronic conductivity, and indicates hierarchically porous electrode architectures. The NiFe/CPAN-400 electrode achieves enhanced oxygen evolution performance with an overpotential of 354 mV at 100 mA cm^-2, which is 153 mV and 103 mV lower than NiFe-Nafion and NiFe-PAN, respectively. This enhancement results from synergistic effects, including an electrochemically active surface area increased 2.3-fold, improved electrolyte wettability, and optimized charge transfer kinetics. The pyridinic nitrogen-enriched structure also facilitates a rate-determining step transition from charge transfer to *OOH formation, with a Tafel slope of 59.9 mV dec^-1. This work establishes thermally induced polymer cyclization as a versatile strategy for advanced binder developments.