Three-dimensional hierarchical porous carbon/graphene composites derived from graphene oxide-chitosan hydrogels for high performance supercapacitors

•Chitosan was used as a low fabrication cost precursor to prepare electrode materials.•This new type of nitrogen-containing porous carbon composites provide pseudocapacitance and strengthen supercapacitive performance.•The three-dimensional structure benefit fast diffusion and transport of electrolyte ions.•The capacitance of 3DHCG composites is 50% higher than that of the 3DHC.

Graphene-based material, featured with high electrical conductivity, large surface area and good cycling performance, has been considered as one of the most promising materials for supercapacitor. In this work, three-dimensional hierarchical porous carbon/graphene composites (3DHCG) have been synthesized from lyophilized graphene oxide-chitosan (GO-CS) composite hydrogels by the combination of direct carbonization and chemical activation processes. The resulting graphene-based composite has been able to construct a hierarchical pore network with randomly opened macropores and micropores, facilitating fast diffusion to the interior surfaces during rapid charge/discharge process. When compared with the pure carbon, the synthesized 3DHCG composite exhibits remarkably enhanced specific capacitance of 320 F g−1 at a current density of 1 A g−1 in 6 M KOH solution, meanwhile maintaining excellent rate performance (with the capacity retention of 70% at 20 A/g) and outstanding cycling stability (96% retention after 2000 cycles). The improved electrochemical performances of graphene-based materials represent an alternative promising candidate for the application as supercapacitor electrodes.