Flexible free-standing 3D porous N-doped graphene-carbon nanotube hybrid paper for high-performance supercapacitors

The nanoarchitecture of carbon with assembled building blocks on diverse scales is of great importance for energy storage. Herein, we demonstrate high-performance supercapacitors by building a three-dimensional (3D) porous structure that consists of a N-doped graphene-carbon nanotube (CNT) hybrid. The 3D porous nitrogen-doped graphene-CNT (p-N-GC) hybrid paper was fabricated by using polystyrene (PS) colloidal particles as a sacrificial template, followed by calcination to remove PS to generate macropores, to reduce graphene oxide (GO) into graphene, and to realize N-doping simultaneously by one step. The as-prepared p-N-GC paper with high porosity, conductivity and flexibility has a high specific capacitance of 294 F g(-1) at a current density of 1 A g(-1) in 6 M KOH electrolyte solution, as well as good rate capability and cycle stability. The greatly enhanced electrochemical performance can be ascribed to the synergistic effect of the 3D porous nanostructure, effective CNT intercalation, and nitrogen-doping, suggesting that p-N-GC as novel electrode materials may have potential applications in high-performance energy storage devices.