Hierarchically Porous and Nitrogen-Rich Carbon Materials Derived from Polyimide Waste for High-Performance Supercapacitor Applications

High-performance and eco-friendly carbon electrode material for supercapacitors is still a challenge for both academia and industry. In this work, polyimide waste (PI)-derived, hierarchically porous, and nitrogen-rich carbon materials were prepared by simple hydrothermal treatment and carbonization using potassium hydroxide (KOH) as an activator. The effects of KOH/preoxidized PI mass ratio and hydrothermal treatment time on the morphology, chemical and crystalline structure, and electrochemical performance were systematically investigated. Interestingly, it is noticed that hydrothermal treatment with KOH solution can promote the infiltration and destruction of preoxidized PI, thereby enhancing the activation effect and forming a hierarchically porous structure. The specific surface area (SSA) of porous carbon with hydrothermal treatment (e.g., PIC2-24h) was as high as 2593 m2 g–1, which is much larger than that of porous carbon without hydrothermal treatment (PIC2). The as-prepared PIC2-24h presented a high specific capacitance of 229 F g–1 at 1 A g–1, superb rate performance (205 F g–1 at 10 A g–1), and excellent cycle stability (94% capacity retention after 20,000 cycles at 1 A g–1), revealing that these PI-derived porous carbon materials can not only alleviate the environmental stress caused by the disposal of PI waste but also provide an ideal candidate electrode for high-performance supercapacitor applications.