Three-dimensional Zn-MOF-derived nitrogen-doped porous carbon: unlocking high capacitance and long-term stability in supercapacitors

Abstract

Highly activated porous carbon materials with a unique architecture, heteroatom incorporation, substantial specific surface area, and promising electrochemical properties are regarded as superior electrode materials for supercapacitor applications. In this study, we synthesized activated porous nitrogen-doped carbon (APNC) using a nitrogen-containing isonicotinic acid organic ligand within a Zn-based metal-organic framework (Zn-MOF) as both a source and template through a facile pyrolysis process with KOH activation. The resulting APNC material with the optimized synthesis conditions exhibited uniform polyhedral morphology, a large specific surface area (1947.9 m2 g-1), and nitrogen heteroatom doping in the carbon framework. These features collectively enhanced its electrochemical performance and ensured exceptional electrochemical stability in a 6 M KOH electrolyte. Electrochemical measurements in a three-electrode setup revealed that the synthesized APNC electrode material accomplished a specific capacitance of 360 F g-1 at 1 A g-1. In addition, APNC provided excellent cycling stability, retaining 95.5% of its capacitance after 50 000 cycles at a high current density of 20 A g-1. Moreover, a coin-cell-type symmetric supercapacitor fabricated from APNC delivered a brilliant energy density of 18.2 Wh kg-1 at a power density of 400 W kg-1. Density functional theory (DFT) calculations further revealed that nitrogen doping, in conjunction with high porosity, markedly improves the electronic characteristics of N-doped porous carbon, thereby enhancing its energy storage capability in supercapacitors. This study highlights the ability of APNC to serve as an inexpensive and highly effective electrode material, establishing its potential for practical applications in high-performance supercapacitors.