Activated carbon from nitrogen rich watermelon rind for high-performance supercapacitors

Abstract

Watermelon rind (WR) is proposed as a nitrogen rich precursor of nitrogen-doped activated carbon (WRAC) for possible energy storage applications in supercapacitors. The WRAC gives rise to a large surface area of up to 2277 m² g⁻¹ and provides an efficient pathway for ions to diffuse into the interior surfaces of bulk electrodes. The nitrogen-doped WRAC electrode gives a high gravimetric specific capacitance (333.42 F g⁻¹) in 6 M KOH at a current density of 1 A g⁻¹ with an adequate nitrogen content of 2.48%, in which the specific capacitance is higher than most previously reported synthetic nitrogen-doped carbon materials. It also exhibits excellent high rate performance, low impedance and good cycle stability (96.82% capacitance reserved after 10 000 cycles). These excellent electrochemical performances are attributed to the high surface area, unique pore size distribution and appropriate nitrogen content.