Nanoporous graphene/single wall carbon nanohorn heterostructures with enhanced capacitance

This is the first report on the synthesis of nanoporous graphene/single wall carbon nanohorns (G/SWCNHs), a novel multicomponent of nanocarbons, using a facile hydrothermal method. Heterostructures were formed with interconnected graphene to support single wall carbon nanohorns (SWCNHs); meanwhile, SWCNHs prevented graphene nanosheets from stacking face-to-face. The samples were thoroughly characterized to illustrate their nanostructures and electrochemical properties. G/SWCNHs showed xerogel-like structures having ultra-micropores of ca. 0.6 nm and mesopores of 2–12 nm with the total nanopore volume of 0.20 cm3 g−1. The heterostructures of G/SWCNHs had an enhanced capacitance of 244 F g−1 in 1 M KOH with ultra fast charge–discharge and excellent rate capability, superior to reduced graphene oxide, SWCNHs and SWCNH composites. The nanohybrid achieved a capacitance retention of 99% after 1000 cycles at a current density of 10 A g−1, promising for practical high power density applications. This study also provides an environmentally friendly process for the preparation of better nanostructured carbons for electrochemical energy storage devices of high-performance.