Graphene-based supercapacitors can achieve high power density due to its high conductivity and large surface area. The critical limitations of graphene electrodes are the low electrochemical double layers capacitance and limited ion accessible active surface due to restacking. Herein, hierarchical hollow frameworks composed of interconnected carbon nanotubes bridged by nitrogen-doped graphene are designed and fabricated by a framework-preserved thermal transformation from metal-organic frameworks. The performance of hierarchical frameworks as supercapacitor electrode demonstrates that such composite can produce higher capacitance than those of nitrogen-doped graphene or carbon nanotubes. The remarkable enhanced electrochemical performance is mainly attributed to the synergistic effect of the hierarchical frameworks resulted more accessible active surface and higher efficient conducting paths, and pseudocapacitance from nitrogen doping. Moreover, this approach of controlling synthesis of hierarchical nitrogen-doped graphene-bridged carbon nanotubes can be scaled up to the industrial level.

Graphene-based supercapacitors can achieve high power density due to its high conductivity and large surface area. The critical limitations of graphene electrodes are the low electrochemical double layers capacitance and limited ion accessible active surface due to restacking. Herein, hierarchical hollow frameworks composed of interconnected carbon nanotubes bridged by nitrogen-doped graphene are designed and fabricated by a framework-preserved thermal transformation from metal-organic frameworks. The performance of hierarchical frameworks as supercapacitor electrode demonstrates that such composite can produce higher capacitance than those of nitrogen-doped graphene or carbon nanotubes. The remarkable enhanced electrochemical performance is mainly attributed to the synergistic effect of the hierarchical frameworks resulted more accessible active surface and higher efficient conducting paths, and pseudocapacitance from nitrogen doping. Moreover, this approach of controlling synthesis of hierarchical nitrogen-doped graphene-bridged carbon nanotubes can be scaled up to the industrial level.