N-enriched multilayered porous carbon derived from natural casings for high-performance supercapacitors

In this study, N-enriched multilayered porous activated carbon (LPAC), using natural casings as precursor, was fabricated by a facile carbonization and subsequent KOH activation procedure. The influence of the mass ratio of KOH to carbonized material on pore-structure and surface element composition of LPACs was investigated by a variety of means, such as SEM, HRTEM, BET, Raman, XRD, XPS and XAS. Owing to the unique multilayered texture and nitrogen (N) and oxygen (O) rich feature of natural casings, the resulting LPACs possess interconnected and developed porous structure with N- and O-enriched functional groups, contributing to larger pseudocapacitance. With the rise of mass ratio, the specific surface area (SSA) and average pore size of LPACs increased. The final materials were endowed with a desirable SSA (3100 m(2) g(-1)) and high N content (6.34 at.%). Meanwhile, N- and O-enriched LPAC-4 exhibited a high specific capacitance (307.5 F g(-1) at a current density of 0.5 A g(-1) in 6 M KOH aqueous solution), excellent rate performance (63.4% capacitance retention at 20 A g(-1)) and good cycling stability (7.1% capacitance loss after 5000 cycles). Furthermore, the assembled symmetrical supercapacitor (LPAC-4//LPAC-4) with a wide voltage window of 1.4 V delivered a remarkable energy density of 11.6 Wh kg(-1) at a power density of 297Wkg(-1). These results suggested that unique LPACs derived from natural casings are a promising material for supercapacitors. (C) 2018 Elsevier B.V. All rights reserved.