Influence of S doping on cobalt hydroxide and nitrogen-doped carbon dots of supercapacitor electrode materials

Abstract

Recently, the supercapacitor has been used as a type of energy storage application. In this work, cobalt hydroxide adorned with nitrogen-doped carbon dots (NC) is synthesized by a hydrothermal approach. Then Co(OH)2/NC is modified by sodium sulfide to obtain S-Co(OH)2/NC, which shows an excellent specific capacitance of 730 F g− 1 at 1 A g− 1 (much higher than that of pristine Co(OH)2/NC (592 F g− 1 at 1 A g− 1)). An asymmetric supercapacitor (ASC) is assembled by S-Co(OH)2/NC (as a positive electrode) and GA/NC (as a negative electrode), which presents a specific energy density as high as 39.59 Wh kg− 1 with a power density of 639 W kg− 1. Also, the ACS manifests extraordinary cycle stability (75% capacitance retention after 8500 cycles). According to the electrochemical performance, it can be inferred that S-Co(OH)2/NC has a great practical application value in supercapacitor devices.