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

Abstract

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.