Hydrothermal nitrogen doping of anthracene oil-derived activated carbons for wide voltage asymmetric capacitors

Abstract

This work focused on the development of doping procedures to introduce nitrogen functionalities on an activated carbon derived from anthracene oil to be subsequently used on wide voltage asymmetric capacitors. For that, ammonia solution was used and different hydrothermal conditions applied. Tailoring the temperature treatment (120 and 180 °C), nitrogen-doped activated carbons (N-ACs) with different nitrogen content (5.6 and 4.1 at. %) and diverse speciation were obtained. N-ACs exhibited excellent capacitive behavior and long-life cycle in a three-electrode cell using KOH aqueous solution as electrolyte. The significant capacitance value of 291 F g−1 at 0.2 A g−1 was achieved by the N-AC obtained at 180 °C. Furthermore, full carbon asymmetric supercapacitors incorporating N-ACs as negative electrodes were assembled, and an operating voltage window of 1.3 V in 6 M KOH solution established. As a result, high energy densities were achieved in the devices, particularly in that including N-AC-180. Electrochemical tests revealed that pyridinic and quaternary nitrogen species of N-ACs play a critical role in the excellent asymmetric supercapacitor electrochemical performance, including improvement of conductivity and specific capacitance.