Electrochemical capacitors, also called supercapacitors, store energy in two closely spaced layers with opposing charges, and are used to power hybrid electric vehicles, portable electronic equipment and other devices¹. By offering fast charging and discharging rates, and the ability to sustain millions of ²⁻⁵, electrochemical capacitors bridge the gap between batteries, which offer high energy densities but are slow, and conventional electrolytic capacitors, which are fast but have low energy densities. Here, we demonstrate microsupercapacitors with powers per volume that are comparable to electrolytic capacitors, capacitances that are four orders of magnitude higher, and energies per volume that are an order of magnitude higher. We also measured discharge rates of up to 200 V s⁻¹, which is three orders of magnitude higher than conventional supercapacitors. The microsupercapacitors are produced by the electrophoretic deposition of a several micrometre-thick layer of nanostructured carbon onions⁶‚⁷ with diameters of 6-7 nm. Integration of these nanoparticles in a microdevice with a high surface-to-volume ratio, without the use of organic binders and polymer separators, improves performance because of the ease with which ions can access the active material. Increasing the energy density and discharge rates of supercapacitors will enable them to compete with batteries and conventional electrolytic capacitors in a number of applications.

/pdf/ultrahigh-power-micrometre-sized-supercapacitors-based-on-28alaqlic6.pdf

Ultrahigh-power micrometre-sized supercapacitors based on onion-like carbon

and Applications of Fullerenes, Carbon Dots, Nanotubes, Graphene, Nanodiamonds, and Combined Superstructures Vasilios Georgakilas,† Jason A. Perman,‡ Jiri Tucek,‡ and Radek Zboril*,‡ †Material Science Department, University of Patras, 26504 Rio Patras, Greece ‡Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University in Olomouc, 17 listopadu 1192/12, 771 46 Olomouc, Czech Republic

Broad family of carbon nanoallotropes: classification, chemistry, and applications of fullerenes, carbon dots, nanotubes, graphene, nanodiamonds, and combined superstructures.

Graphene oxide and reduced graphene oxide studied by the XRD, TEM and electron spectroscopy methods

Porous carbons that are three-dimensionally periodic on the scale of optical wavelengths were made by a synthesis route resembling the geological formation of natural opal. Porous silica opal crystals were sintered to form an intersphere interface through which the silica was removed after infiltration with carbon or a carbon precursor. The resulting porous carbons had different structures depending on synthesis conditions. Both diamond and glassy carbon inverse opals resulted from volume filling. Graphite inverse opals, comprising 40-angstrom-thick layers of graphite sheets tiled on spherical surfaces, were produced by surface templating. The carbon inverse opals provide examples of both dielectric and metallic optical photonic crystals. They strongly diffract light and may provide a route toward photonic band-gap materials.

https://science.sciencemag.org/content/sci/282/5390/897.full.pdf

Carbon Structures with Three-Dimensional Periodicity at Optical Wavelengths

A common misconception is that the irradiation of solids with energetic electrons and ions has exclusively detrimental effects on the properties of target materials. In addition to the well-known cases of doping of bulk semiconductors and ion beam nitriding of steels, recent experiments show that irradiation can also have beneficial effects on nanostructured systems. Electron or ion beams may serve as tools to synthesize nanoclusters and nanowires, change their morphology in a controllable manner, and tailor their mechanical, electronic, and even magnetic properties. Harnessing irradiation as a tool for modifying material properties at the nanoscale requires having the full microscopic picture of defect production and annealing in nanotargets. In this article, we review recent progress in the understanding of effects of irradiation on various zero-dimensional and one-dimensional nanoscale systems, such as semiconductor and metal nanoclusters and nanowires, nanotubes, and fullerenes. We also consider the t...

Ion and electron irradiation-induced effects in nanostructured materials

Raman identification of onion-like carbon

Effect of explosion conditions on the structure of detonation soots: Ultradisperse diamond and onion carbon

In recent high resolution transmission electron microscopic studies we have found that high temperature vacuum annealing (1200–1800 K) of ultradispersed (2–5 nm) and micron size diamond produces fullerene-like graphitic species, namely, onion-like carbon and closed curved graphite structures (multilayer nanotubes and nanofolds), respectively. Here we undertake theoretical studies to help in the understanding of the experimental data for these systems. (1) Calculations of cluster models by a standard semiempirical method (MNDO a software package) are used to explain the preferential exfoliation of {111} planes over other low index diamond planes. (2) The same approach suggests the likelihood that the graphitization is initiated by a significant thermal displacement of a single carbon atom at temperatures close to the Debye temperature. (3) At the diamond–graphite interface we have observed the formation of two curved graphitic sheets from three diamond {111} planes. We suggest that the evolution of this in...

Theoretical study of the formation of closed curved graphite-like structures during annealing of diamond surface

The bulk density of graphitized ultradisperse diamond (UDD) was measured by a gamma-ray attenuation method at 1370–1870 K. These data combined with small angle x-ray scattering and true density measurements of the samples heated at various fixed temperatures were used to study the graphitization kinetics of the UDD. The reaction rate was modeled as a migration rate of the interface between the developing graphite-like carbon and the remaining diamond phase. A “reducing sphere” model was used to obtain the rates from the changes in densities. The estimated kinetic parameters in an Arrhenius expression, namely the activation energy, E=45±4 kcal/mol, and the pre-exponential factor, A=74±5 nm/s, allow quantitative calculations of the diamond graphitization rates in and around the indicated temperature range. The calculated graphitization rates agree well with the graphitization rates of diamonds with different dispersity estimated from high-resolution transmission electron microscopy data. The large differenc...

Kinetics of the graphitization of dispersed diamonds at “low” temperatures

Photoelectron spectroscopy has been used to study the products resulting from high temperature phase transformation of nanodiamonds (ND). Depending on the temperature of annealing various particles with a diamond core covered by nanometer sized fullerene-like shells, and onionlike carbon (OLC) were formed. Analysis of the $\mathrm{C}1s$ photoemission lines of the intermediates of ND transformation, prepared at temperatures of 1420 and 1600 K and then exposed to atmosphere, reveals the presence of oxygen-containing groups and both ${\mathit{sp}}^{\mathit{2}}$ and ${\mathit{sp}}^{\mathit{3}}$ carbon. The ${\mathit{sp}}^{\mathit{2}}$ component for these samples has binding energies of $284.70\ifmmode\pm\else\textpm\fi{}0.05\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ (for the sample prepared at 1420 K) and $284.50\ifmmode\pm\else\textpm\fi{}0.05\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ (for the sample prepared at 1600 K). A difference of $1.3\ifmmode\pm\else\textpm\fi{}0.1\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ in the binding energy of the ${\mathit{sp}}^{\mathit{3}}$ and ${\mathit{sp}}^{\mathit{2}}$ components was observed. The ${\mathit{sp}}^{\mathit{2}}$ component for OLC prepared at 1800, 1900, and 2140 K has a binding energy of $284.45\ifmmode\pm\else\textpm\fi{}0.05\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. The shift towards higher binding energies of the ${\mathit{sp}}^{\mathit{2}}$ component of the samples prepared at lower temperatures is explained by significant curvature of graphite layers formed in the initial stages of graphitization. The observed increase in density of states at the Fermi level for the samples prepared at 1600, 1800, and 1900 K is associated with an accumulation of different types of defects in the curved graphite layers during graphitization of diamond. The Lorentzian widths of $\mathrm{C}1s$ photoemission lines from OLC are large compared with those of HOPG. The possible reasons for this broadening are discussed.

/pdf/photoemission-study-of-onionlike-carbons-produced-by-1sv4dkfx92.pdf

Yu. V. Butenko

Papers

Raman identification of onion-like carbon

Effect of explosion conditions on the structure of detonation soots: Ultradisperse diamond and onion carbon

Theoretical study of the formation of closed curved graphite-like structures during annealing of diamond surface

Kinetics of the graphitization of dispersed diamonds at “low” temperatures

Photoemission study of onionlike carbons produced by annealing nanodiamonds