Sequential doping of nitrogen and oxygen in single-walled carbon nanohorns for use as supercapacitor electrodes

Abstract

To store more energy in limited spaces, the volumetric performance of energy storage devices used in electric vehicles and portable electronics has attracted more research attention than their gravimetric performance. Herein, we describe the preparation of N/O co-doped single-walled carbon nanohorns (SWCNH) using chemical vapor deposition with pyridine followed by acid treatment to obtain a supercapacitor electrode material with high specific volumetric capacitance. The synthesized N/O co-doped SWCNH (N and O contents of 6.1 and 9.1 at%, respectively) electrode had a higher bulk density (1.05 g cm−3) than that of the pristine SWCNH electrode (0.86 g cm−3). Moreover, the N/O co-doped SWCNH supercapacitor electrode exhibited drastically increased specific volumetric, gravimetric, and areal capacitances (123 F cm−3, 117 F g−1, and 91.4 μF cm−2, respectively) in 1 M H2SO4 electrolyte, compared with those of a pristine SWCNH electrode (36 F cm−3, 42 F g−1, and 11.4 μF cm−2, respectively). The superior electrochemical performances are associated with enhanced pseudocapacitive contribution and high bulk density of electrode upon N/O co-doping. The simple method described herein for producing SWCNH electrodes with high bulk density and high specific volumetric capacitance should contribute to the development of supercapacitors with high volumetric performance.