Sodium Carboxymethylcellulose as Versatile Biotemplates of Zeolitic Imidazolate Frameworks for Reduced Graphene Oxide-/N-Doped Porous Carbon Hydrogel Electrodes for Supercapacitors

A novel self-assembling reduced graphene oxide-/N-doped porous carbon (rGO/NPC) hydrogel electrode was successfully synthesized by in situ growth of zeolitic imidazolate framework (ZIF-67) nanoparticles on sodium carboxymethylcellulose (CMC) and a subsequent carbonization, followed by self-assembly with rGO through a simple hydrothermal process. The CMC serving as the biotemplate of ZIF-67 nanoparticles could effectively prevent their serious aggregation for fabricating NPC, which is efficiently doped with abundant nitrogen content that originates in ZIF-67. The introduction of rGO could improve the conductivity of the composite and directly used as a binder-free electrode for supercapacitors. The results show that the hydrogel electrode exhibited excellent electrochemical performance; it presented an improved capacitance of 190 F/g at 0.5 A/g. Further, a symmetric supercapacitor based on the hydrogel electrode was constructed, which possessed a superior energy density of 17.4 W h/kg at a power density of 338 W/kg and 12 W h/kg at 3375 W/kg and long cycling stability (a retention of 87.1% after 10 000 cycles). This facile and effective preparation method of rGO/NPC electrodes possesses great potential in the fabrication of next-generation electrochemical capacitors with excellent capacitance performance.