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The Ar (87.3 K) and N2 (77.4 K) adsorption isotherms of six non-graphitized carbon blacks are compared to choose the best reference material for an accurate determination of surface area of porous carbons with subtracting pore effect (SPE) method using high resolution αs-plot. Microporous carbon blacks cannot be used as references for SPE method since they underestimate the surface area. On the other hand, reference carbon blacks exhibiting capillary condensation underestimate external surface areas. The total surface area from SPE method using Ar adsorption at 87.3 K has a stronger dependence on the microporosity of reference carbon blacks than that using N2 adsorption at 77.4 K. The surface area of carbons whose pore widths are >1 nm result more affected by the reference carbon black than those with widths https://osf.io/zjg8a ) for quick and easy use of the SPE method to characterize the porous carbons precisely.

The composites consisting of graphene oxides (GOs) and carbon spheres (CSs), which were hydrothermally derived from the aqueous solution of glucose with average diameter of 200 nm, were mechanically mixed, and the GOs/CSs (GCSs) were thermally treated at high temperatures in the range of 700–900 °C. In the GCS composites, the CSs as spacers located between the GO sheets prevent the aggregation and restacking of graphene sheets. The GCS composites (GO/CS = 1) treated at 800 °C (GCS@800) have the high specific capacitances of 272.8 and 197.5 F g−1 in a three-electrode cell at the current density of 0.2 and 10 A g−1, respectively, in 6 M KOH aqueous solution, and demonstrated high rate capability and good cycling stability. The excellent electrochemical performance of the GCS@800 electrode is attributed to its structure with hierarchical porous structures including overwhelming micropores and a few of macropores. This work provides an effective and simple technique by integrating CSs and graphene sheets into composite structures for high-performance energy storage devices.

Electrically-conductive graphene colloids with tuned nanoporosity are promising materials for numerous applications. As charge-transfer interaction enhances electrical conductivity of polyaromatic hydrocarbon crystals, we intercalated water-soluble pyrene derivatives such as pyrene-boronic acid in nanoporous graphene by reduction of a mixture of graphene oxides and pyrene derivatives. The pyrene derivative intercalation increases more than twice both microporosity and mesoporosity. The N2 adsorption isotherms at 77 K of all samples have low-pressure adsorption hysteresis due to inaccessible small microporosity; the total porosity evaluated by water adsorption at 298 K is almost twice that of N2 adsorption. These adsorption measurements together with X-ray diffraction suggest the presence of a pore mouth structure whose width is about 0.4 nm. The charge-transfer interaction between the pyrene derivative and porous graphene is evidenced by a high frequency shift of the G band of Raman spectrum, appearance of a new optical absorption band, and the increase in electrical conductivity. The intercalation of pyrene-boronic acid through charge-transfer interaction increases the voltammetric charge of cyclic voltammogram for nanoporous graphene owing to an enhanced ion-accessibility from 3% to 54%, which indicates their high application potential for electrochemical studies.

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 m 2 g −1 to 10 m 2 g −1 according to the subtracting pore effect (SPE) method. The transmission electron microscopic (TEM), X-ray diffraction (XRD), Raman spectroscopy and N 2 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 sp 3 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

Graphite oxide (GO) and graphene monoliths were prepared using the unidirectional freezing of GO water suspension. These materials were saturated with a poly(ammonium-4-styrene sulfonate) water soluble polymer and then carbonized at 1123 K. This process increases significantly the materials strength and density. A uniform deposition of the polymer-derived carbon on the external layers of the graphene sheets of the monolith was found. The carbon from polymer not only provided more contact between the graphene sheets but also apparently increased the overall graphitization level (based on Raman spectra). The modification decreased the electrical resistance by one order of magnitude compared to that of the graphene monolith. N-2 adsorption at 77 K showed that the thus-treated graphene monoliths have quite homogenous pores with the pore width of 0.7 nm. These pores, combined with large transport pores, and conductive properties make the monoliths tested the promising materials for separation, energy storage, and/or gas sensing. The tunability of the properties and pore structure of the robust graphene ultramicroporous monolith through the control of chemistry of the initial GO monolith was shown. (C) 2015 Elsevier Ltd. All rights reserved., Article, CARBON. 87:87-97 (2015)

In this work, we describe a new type of activation method of carbon materials using pressure swing of CO2. The porosity development markedly depends on the pressure swinging frequency. The porous carbon obtained from pressure-swing activation shows an additional porosity development without pitting corrosion on the surface, which occurs on CO2 activation without pressure-swing. This phenomenon is ascribed to the enhancement of Knudsen diffusion and/or configurational diffusion of CO2 which is caused by an exterior stimulus from the pressure swing. (C) 2015 Elsevier Ltd. All rights reserved., Article, CARBON. 85:245-248 (2015)