Effect of nitrogen and sulphur co-doping on the surface and diffusion characteristics of date seed-derived porous carbon for asymmetric supercapacitors

Abstract

Date seeds are the by-product of date fruits, which are abundant all over the world mainly in Middle East. Herein, we report a facile transformation of waste date seeds into highly porous activated carbon (D-800) via simple one-pot hydrothermal carbonization followed by KOH activation route. The resultant date seeds derived activated carbon was then co-doped with nitrogen and sulphur (NSD-800) via effective binary heteroatom doping method. The NSD-800 material has interconnected pores like framework, which facilitate significant ion storage and fast ion transport. Heteroatom doping produces a faradaic contribution in addition to the EDLC (electric double layer capacitor) characteristics of the carbon which facilitates the faster diffusion process. Hence, NSD-800 demonstrate promising electrochemical performance achieving a high specific capacitance of 298.5 F/g at 0.5 A/g using 1 M H2SO4 electrolyte. Furthermore, symmetrical and asymmetrical supercapacitor (SC) devices were fabricated using these electrode materials for comparison purpose. It is found that D-800//NSD-800 asymmetric SC device shows superior electrochemical performance delivering high energy density of ~30 Wh/kg at a power density of 394 W/kg along with extraordinary cyclic stability of 92.7 % after 10,000 charge-discharge cycles. This intriguing performance notably bestows NSD-800 with promising prospects as electrode material for supercapacitor application.