Utilize rather than create: transforming phthalonitrile resin into N-rich hierarchical porous carbon for supercapacitor materials

Abstract

Phthalonitrile (PN) resins, renowned for their highly conjugated heteroaromatic N-rich structures, are exemplary precursors for the fabrication of porous materials. However, the conventional synthesis of PN is marred by the generation of the hazardous KNO₂ by-product that poses significant environmental, safety, and health hazards. In this study, we introduce an innovative approach to PN synthesis, utilizing 4-chlorophthalonitrile as the starting material. This “utilize rather than create” strategy employs the reaction product (RPH) as the precursor and the by-product (KCl) as the template for the synthesis of porous carbon (RKC). The formation mechanism of RKC is elucidated through TGA/FTIR and TGA/MS analysis. The resultant RKCs exhibit exceptional characteristics suitable for supercapacitor applications, including hierarchical micro-/meso-/macropores, an extensive specific surface area, a high N-doping level, and diverse N species (N-6, N-5, N-Q). RKC@600 achieves a remarkable specific capacitance of 300 F g⁻¹ at 1 A g⁻¹ and demonstrates impressive cycling stability with a retention of 96.1% capacitance after 10 000 cycles at 10 A g⁻¹. This research promotes the advancement of green and sustainable PN chemistry, driving forward the evolution of PN-based functional materials.