One-step fabrication of N/O self-doped porous carbon derived from 2-MeIM for high-performance supercapacitor electrode

Abstract

Doping engineering is a high-efficiency strategy to introduce heteroatom species and modify the surface electronic structures of porous carbon materials. However, the conventional doping strategies for porous carbons usually involve with either complicated fabrication processes or difficulty in quality control. Herein, nitrogen‑oxygen self-doped porous carbons (NOPCs) with adjustable structure are prepared by a facile one-step process of direct carbonization/activation the mixture of 2-methylimidazole (2-MeIM) and KOH. The as-prepared NOPCs possess hierarchical porous structure with interconnected micro-/meso-/macropores, high specific surface area (2900 m2 g−1), large pore volume (1.2 cm3 g−1) and high N,O heteroatoms level (26.8 at.% in total), which exhibit ultra-high specific capacitance of 424.2 F g−1 at 1.0 A g−1 in a three-electrode system in 2 M KOH electrolyte and 173.4 F g−1 at 1.0 A g−1 in a two-electrode system in EMIMBF4 ionic liquid electrolyte. Impressively, the symmetric supercapacitor based on NOPC exhibits a wide operating voltage window up to 3 V, a high energy density of 56.4 Wh kg−1 at a power density of 373.6 W kg−1, excellent rate performance with the retention of ~76.2 % from 1.0 to 100 A g−1, and splendid cycling stability with only 0.0011 % capacity fading per cycle within 10,000 loops. Consequently, the one-step carbonization/activation strategy with commercial-available 2-MeIM as raw material is promising for mass production of high performance NOPC materials.