Design and tailoring of a hierarchical graphene-carbon nanotube architecture for supercapacitors

Stacking of individual graphene sheets (GS) is effectively inhibited by introducing one-dimensional carbon nanotubes (CNTs) to form a 3-D hierarchical structure which significantly enhances the electrochemical capacitive performances of GS-based composites. From SEM images, inserting proper quantity of CNTs as nanospacers can effectively impede the stacking of GS and enlarge the space between GS sheets, leading to obtain a highly porous nanostructure. The specific capacitance of GS-CNTs-9-1 (∼326.5 F g−1 at 20 mV s−1) is much higher than that of GS material (∼83 F g−1). Furthermore, the energy and power densities of GS-CNTs-9-1 are respectively as high as 21.74 Wh kg−1 and 78.29 kW kg−1, revealing that the hierarchical graphene-CNT architecture provides remarkable effects on enhancing the capacitive performance of GS-based composites. Therefore, the GS-CNT composites are promising carbon materials for supercapacitors.