Correlation in structure and properties of highly-porous graphene monoliths studied with a thermal treatment method

We prepared high surface area nanoporous graphene by reduction and KOH activation of graphene oxides and then heat-treated the nanoporous graphene up to 3073 K in Ar. The surface area of thus-prepared samples decreased remarkably from 1560 m2 g−1 to 10 m2 g−1 according to the subtracting pore effect (SPE) method. The transmission electron microscopic (TEM), X-ray diffraction (XRD), Raman spectroscopy and N2 adsorption isotherms at 77.4 K clearly illustrate the evolution of morphology, crystallinity and porosity during the graphitization process with increasing the heating temperature. The high temperature treatment shows a clear segregation of the disordered sp3 carbon frames in addition to the growth of graphitic structure in the porous graphene monoliths, although overall changes in properties and structure of porous graphene monoliths with high temperature treatment are similar to those of other porous carbons. The electrical conductivity measurements indicate that heat-treated samples have an imperfect semimetallic property due to the crystallite boundaries. The cyclic voltammograms measurements indicate that the optimized pore size range of nanoporous graphene for specific capacitance with 2 M KCl aqueous solution as electrolyte is of 0.7 nm < w < 2 nm.