Coupling of chrysanthemum-shaped cobalt hydroxide and nitrogen-doped carbon dots for high-performance hybrid supercapacitors

Abstract

• Due to the negative potential of NQDS, it can generate electrostatic reaction with Co 2+ . NQDs directed Co(OH) 2 growth, the amount of NQDs determines the density of rod-shaped cobalt hydroxide. • Fabrication of Cobalt hydroxide/N doped graphene quantum dots (Co(OH) 2 /NQDs) composites with chrysanthemum-shaped by an in-situ reaction. • the strong coupling between NQDs and Co(OH) 2 creates new electron transfer channels (Co-N), the Co(OH) 2 /NQDs composites delivers enhanced specific capacitance of about 593 F g −1 at 1 A/g. • The hybrid supercapacitor device based on Co(OH) 2 /NQDs composite and graphene aerogel exhibits a high energy density of about 33 Wh kg −1 at power density of 800 Wkg −1 and it retain about 137% specific capacitances after 8000 cycle test. NQDs can stabilize cobalt hydroxide after long cycles. Cobalt hydroxide is expecting electrode material for high-performance supercapacitors, however, it is still a challenge to improve its lack of transmission track and active sites. An effective method to improve the electrochemistry performance of cobalt hydroxide is to couple it with graphene quantum dots. Herein, we report the preparation of Cobalt hydroxide/N doped graphene quantum dots (Co(OH) 2 /NQDs) composites and study the electrochemistry performance of Co(OH)2/NQDs composites as supercapacitors electrode materials. Benefit from the strong coupling between NQDs and Co(OH) 2 creates new electron transfer channels (Co-N). The hybrid supercapacitor device based on Co(OH) 2 /NQDs composite and GA shows a high energy density of about 33.6 Wh kg −1 at a power density of 800 Wk g −1 , and it retains about 137% specific capacitances after 8000 cycle test. Due to the negative potential of NQDS, it can generate an electrostatic reaction with Co 2+ , which can stabilize cobalt hydroxide after long cycles.