Evgeny Shkolnikov

Characterization of the pore structure of nanoporous activated carbons produced from wood waste

Abstract Highly developed nanoporous carbon materials have been prepared by a two-stage thermocatalytic process. In the first step, alder (Alnus rhombifolia) and birchwood (Betula pendula) were carbonized with and without a dehydration catalyst (H3PO4); in the second step, the material was activated by means of NaOH. The dependence of the porous structure of activated carbons from process parameters was characterized by the novel limited evaporation technique. Specific surface areas, pore volumes, and radii were calculated according to the Derjaguin-Broekhoff-de Boer theory. The tests of activated carbons as electrodes in supercapacitors demonstrated their high potential for this application.

Wood-based activated carbons for supercapacitors with organic electrolyte

Abstract The thermocatalytical synthesis conditions required for the activation of wood charcoal with NaOH in terms of the formation of pores in its structure were investigated. The present study was conducted to explore the potential application of activated carbons as electrodes in supercapacitors with organic electrolyte. The total pore volume and micro- and mesopore ratio were controlled by the activation temperature and alkali addition rate. The working characteristics of carbon electrodes (e.g., specific capacity and ohmic losses) in supercapacitors are strongly influenced by the properties of the pores in their structures. Herein, the optimal ratio of raw material to activator and activation temperature are established: an increase in the ratio of NaOH to carbonizate rate by a factor of 2 and setting the synthesis temperature at 700°C positively influence the electrochemical characteristics of supercapacitors and provide them with specific capacities of up to 160 F g-1.

Structure of nanoporous carbon materials for supercapacitors

Activated carbons with highly developed porous structure and nanosized pores (8 - 11 A) were prepared from alder wood using thermochemical activation method with sodium hydroxide. Properties of the obtained activated carbons were examined by benzene and nitrogen sorption, X-Ray diffraction and Raman spectroscopy. Tests of activated carbons as electrodes in supercapacitors were performed as well. It was found that specific surface area of above mentioned activated carbons was 1800 m 2 /g (Dubinin - Radushkevich). Raman spectroscopy demonstrated the presence of ordered and disordered structures of graphite origin. The performance of activated carbons as electrodes in supercapacitors have shown superior results in comparison with electrodes made with commercial carbon tissues.

Wood-based activated carbons for supercapacitor electrodes with a sulfuric acid electrolyte

Abstract Wood-based activated carbons were synthesized in a two-stage thermochemical process using sodium hydroxide as an activator, and used as the electrode materials for supercapacitors with a sulfuric acid electrolyte. The dependence of pore structure parameters and the electrochemical properties of the activated carbons on the synthesis conditions was investigated. Results indicate that an electric double layer is formed within micropores while meso and macropores are responsible for ion transport. Excess activation under a high activation temperature and/or a high mass ratio of sodium hydroxide to carbonaceous material leads to high meso and macropore volumes, which increase electrolyte uptake and therefore decrease the specific capacitance based on cell mass. The optimum activated carbon is obtained at an activation temperature of 600 °C with a mass ratio of sodium hydroxide to carbonaceous material of 1.25.

Wood based activated carbons for supercapacitor electrodes with sulfuric acid electrolyte

Abstract Activated carbons (ACs) based on wood charcoal were synthesized via sodium hydroxide activation and studied as electrode material in supercapacitors (sulfuric acid electrolyte). In focus were the porous structure of the ACs and their electrochemical properties as a function of the synthesis conditions. The data of surface area and pore volume and pore size dimensions (determined by N2 adsorption and evaluated based on three theories) of the ACs activated at 700°C and with NaOH/carbonizate ratios of 2 and 3.7 are reported, such as the specific capacitance (F g−1), specific resistance (Ohm cm), electrolyte volume (mm3 g−1) and the specific power capacity of a cell (Wh kg−1) of the supercapacitors made of various ACs. It was established that the porosity is increasing with increasing activation temperature and activator rate while the specific capacitance of the device increased up to 390 F g−1 based on elementary cell mass.

Synthesis of graphene-like materials by pyrolysis of hydrocarbons in thermal plasma and their properties

A method to synthesize graphene-like materials using dc high current divergent anode-channel plasma torch has been developed. Carbon atoms are generated by decomposition of propane-butane and methane in a thermal plasma jet. Products of synthesis are characterized by electron microscopy, thermogravimetry, Raman spectroscopy and porosimetry. Effect of experimental conditions on the morphology, phase composition and porosity of the products of synthesis are investigated. The optimal conditions have been found.

Effect of porous structure of activated carbon electrodes on characteristics of double-layer supercapacitors

Porous structure of electrode materials was studied and the role played by macroporous in electrodes of model double-layer supercapacitors was experimentally analyzed. It was shown that the excess macropore volume in electrodes has an adverse effect and, on the whole, reduces in a complicated way the specific electrochemical characteristics of these devices. This makes necessary to develop the optimal electrode structure as regards not only nanoporous, but also macroporous structure.

Highly Porous Wood Based Carbon Materials for Supercapacitors

Wood based activated carbons synthesized by two-stage thermocatalytical synthesis with NaOH activator were studied and used as supercapacitor electrodes (sulphuric acid electrolyte). Porous structure and electrochemical properties of carbons vs synthesis conditions were assessed. It was found that there are correlations between carbons synthesis variables, their porosity and supercapacitors functional characteristics. At the temperature 600 o C and activator/precursor ratio 1.25 porosity decreased, however energy capacitance of supercapacitor increased calculating on elementary cell mass.