Template-Free N-Doped Hierarchical Porous Carbon from Azobenzene-Interconnected Polyimide for Ultra-Stable Supercapacitor Electrodes

Abstract

Facile preparation of N-doped hierarchical porous carbon (NHPC) materials with controllable composition and porosity is crucial for advancing the development of high-performance supercapacitors. In this study, a new NHPC has been created by first using the one-pot synthesis of in-situ dual-crosslinking azobenzene-interconnected polyimide precursors from ingeniously designed three monomers, followed by carbonization activation. We have found that during the polymer precursor synthesis stage, the incorporation of azobenzene into the polyimide network is the key, as it not only functions as an in-situ N-rich source but also enables the template-free formation of a multi-scale micro/nanoporous carbon structure, which is critical for enhancing electrical performance and stability. The resulting N-doped carbon material with a specific surface area of 900.1 m² g⁻¹ exhibits a maximum capacitance of 179.2 F g⁻¹ in a three-electrode configuration. The assembled symmetric supercapacitor using NHPC as the electrode delivers a good energy density (18.0 Wh kg⁻¹) and power density (799.51 W kg⁻¹) at a current density of 1 A g⁻¹. Most notably, the NHPC electrode retains an efficiency of 113.5 % without decrease, demonstrating impressive cycling stability, even after 5000 charge-discharge cycles at 10 A g⁻¹. This study offers a new and universal molecular design methodology for advancing supercapacitor materials with outstanding cycling stabilities.