Metal-organic-frameworks-derived Co(OH)2/nitrogen-doped carbon graphene nanocomposites for high-performance supercapacitors

An effective method to prepare beta-Co(OH)(2)/nitrogen-doped carbon graphene (Co(OH)(2)/C-N@GP) nanocomposites is presented in this work. First, we synthesized a composite of ZIF-67 and polystyrene by reacting Co(NO3)(2)center dot 6H(2)O with 2-methylimidazole in a polystyrene-COOH ethanol dispersion. The ZIF-67/polystyrene composite was carbonized and subsequently reacted with thioacetamide and graphene to produce Co(SO4)(2)/C-N@GP. Finally, Co(SO4)(2)/C-N@GP was soaked in KOH aqueous solution to obtain Co(OH)(2)/C-N@GP nanocomposites. The scanning electron microscope image of obtained Co(OH)(2)/C-N@GP showed Co(OH)(2) with sizes of 10-20 nm well dispersed on the graphene. Electrochemical analysis indicated that Co(OH)(2)/C-N as an electrode material exhibits typical Faraday charge-transfer behavior for supercapacitors. The specific capacitance of Co(OH)(2)/C-N can be enhanced when graphene is present. The Co(OH)(2)/C-N@GP exhibited a high specific capacitance of 985.4 F center dot g(-1) at 2 A center dot g(-1) in 3 mol center dot L-1 KOH with a specific capacitance retention rate of 76.6% after 1 000 cycles.