A facile self-template strategy to fabricate three-dimensional nitrogen-doped hierarchical porous carbon/graphene for conductive agent-free supercapacitors with excellent electrochemical performance

Carbon materials with large surface area, high conductivity and suitable pore distribution are highly desirable for high-performance supercapacitors. The paper reported a self-template strategy for the fabrication of three-dimensional nitrogen-doped hierarchical porous carbon/graphene (3D-NHPC/G). The mixture of beer yeast cells, graphite oxide, urea, potassium hydroxide and phytic acid was dispersed in water by ultrasonication to form homogeneous slurry, which was then dried by spray drying and finally heated at 850 degrees C in Ar/H-2 environment. The study shows that such a new strategy creates a 3D carbon framework, hierarchical pore distribution, moderate graphitization and appropriate nitrogen doping. The as-prepared 3D-NHPC/G offers excellent dispersion, specific surface area of 3108.7 m(2) g(-1) and electronic conductivity of 3096 S m(-1), which is more than six-fold that of 3D-NHPC (494 S m(-1)). Owing to the greatly enchanced electron transfer and mass transport, the 3D-NHPC/G electrode displays the largely enhanced electrochemical performance. In 6 mol l(-1) potassium hydroxide aqueous electrolyte, its specific capacitance is 318 F g(-1) at the current density of I A g(-1) 277 F g(-1) at the current density of 10 A g(-1), and 155 F g(-1) at the current density of 100 A g(-1) that can remain at least 96.5% after 10000 cycles. In 1 mol I-1 tetraethylammonium tetrafluoroborate organic electrolyte, the specific capacitance is 138 F g(-1) at the current density of 1 A g(-1) and 109 F g(-1) at the current density of 10 A g(-1). The study also provides an approach for design and synthesis of carbon-based materials with high supercapacitor behaviors. (C) 2014 Published by Elsevier Ltd.