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Porous carbon materials (PСM) with different pore distributions in size and size of the specific surface area up to 250 m² /g were obtained by changing the carbonization temperature of plant biomass, namely walnut shells. The electrodes of electrochemical supercapacitors are formed based on the obtained carbon materials. The electrochemical behavior of PCM in 33% aqueous KOH solution has been studied by cyclic voltammetry and galvanostatic discharge-discharge methods and the value of their specific capacitance. The physicochemical processes occurring at the carbon electrode/electrolyte interface have been investigated by the method of impedance spectroscopy. [ABSTRACT FROM AUTHOR]

Fractal structure of porous carbon materials (PСMs) obtained by thermal modification under different regimes was investigated using the method of low-temperatureporometry. It was set that at modification temperatures of 300 and 600°C, materials with a developed microporous structure are formed, the surface fractal dimension of which is 2.64. When the modification temperatures are 400 and 500°C, the value of the fractal dimension of the surface decreases to a value of 2.22 with an increase in the duration of modification, which indicates the formation of an almost smooth surface as a result of the intensive removal of carbon atoms from the surface layers and a decrease in the number of micropores due to their transition into mesopores. [ABSTRACT FROM AUTHOR]

In this work, lanthanum (LaMnO3), strontium (SrMnO3) and Sr-doped lanthanum (La0.7Sr0.3MnO3) manganites with the perovskite structure were synthesized by the sol-gel autocombustion method. Moreover, the obtained material structure was investigated by the XRD method. Additionally, the electrochemical properties of nanoporous carbon materials (CMs), lanthanum (LaMnO3) and strontium (SrMnO3) manganites, as well as La0.7Sr0.3MnO3 were investigated by the methods of chronoamperometry and voltammetry, and the application of these materials as electrodes (anode and cathode) of hybrid electrochemical supercapacitors (HECs) was tested. The hybrid electrochemical system of the CM/KOH/La0.7Sr0.3MnO3 type was formed. The employment of this system made it possible to increase the operating voltage range of HEC based on aqueous electrolytes from 0-1 to 0-1.4 V and, consequently, increase the energy characteristics of a unit cell. It was determined that high specific capacitance values were recorded for HECs with an electrode based on La0.7Sr0.3MnO3 and amounted to about 235 F/g at 1 mV/s. At the same time, much lower specific capacitance values were obtained for HECs with electrodes based on LaMnO3 and SrMnO3, which were about 130 F/g and 40 F/g, respectively. [ABSTRACT FROM AUTHOR]

Potentiodynamic and galvanostatic investigations of hybrid electrochemical capacitor (HEC) models formed on the base of nanoporous carbon material (NCM) are performed. NCM is obtained from raw materials of plant origin (hemp fire) and modified lithium–manganese spinel Li1.2Mn1.8O4 . The influence of the surface morphology of carbon material on the electric capacity of the HEC is revealed. The total electric capacitance of the HEC models is determined, and its distribution is carried out on the capacitance, which is ensured by the formation of a double electric layer (DEL), and the redox capacitance due to the passage of Faraday reverse reactions. [ABSTRACT FROM AUTHOR]

In this work, the crystal structure of alpha-MnO2 has been obtained by the hydrothermal method. It was determined that the obtained material has a tunnel structure with average particle sizes of 12-15 nm. The electrochemical performances of α-MnO2 in an aqueous solution of 30 % KOH based electrolyte have been investigated by cyclic voltammetry and galvanostatic cycling methods. At the same time, it was determined that the specific capacity of the α-MnO2/electrolyte system decreased from 90 F/g to 55 F/g with an increase of the scan rate from 2 to 10 mV/s. Thus, the maximum values of specific capacitance about 104 F/g were obtained at 0.5 mV/s. The Coulomb efficiency of the electrochemical system is constant and independent of the cycle number under the charge/discharge process. Therefore, the total capacity of the material under investigation can be divided into the capacity of the double electric layer and the diffusioncontrolled redox capacity due to the Faraday reverse redox reactions. It was determined that the contribution of pseudocapacity is 90 % of the total specific capacity. In addition, it has been determined that the α-MnO2/KOH electrochemical system is stable under long-term cycling process. [ABSTRACT FROM AUTHOR]

The structural-adsorption characteristics of nanoporous carbon materials (NСMs), obtained by thermochemical activation of vegetable raw materials by orthophosphoric acid with different mass ratio, are investigated in the article using the method of low temperature nitrogen sorption and scanning electron microscopy. Calculations of the specific surface area and pore size distribution allowed to determine the optimal parameters of the mass ratio of the activator and the raw materials, in which the obtained material has the highest parameters of the porous structure. The optimum conditions for NCMs obtaining are established, which can be used as electrodes of electric energy storage devices. [ABSTRACT FROM AUTHOR]

Copyright of Nanosistemi, Nanomateriali, Nanotehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Nano- & Electronic Physics is the property of Sumy State University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The ZnSe quantum dots in a matrix of nanoporous carbon are synthesized in the work. For this purpose, nanoporous carbon was synthesized with the required pore size distribution. From the received photoluminescence spectra, it was found that the peak near the band edge in the excitation spectrum can be assigned to the highest transfer efficiency of photogenerated carriers at the correlated sub-band states (about 34 meV below the conduction band of ZnSe) to the deep center states. [ABSTRACT FROM AUTHOR]

Electrochemical study of hybrid super-capacitor based on porous carbon material and the LiMn1.5Fe0.5O4 anode has been performed. It is shown that the degree of crystallinity of spinel increases with synthesis temperature. It is established that hybrid super-capacitor with anode based on spinel synthesized at 1073 K has the best operating parameters that is explained by the lack of amorphous component and intensive intercalation of lithium ions in nanoscale anode particles. [ABSTRACT FROM AUTHOR]

The electrochemical system based on laser irradiated composite of nanoscale titanium dioxide/nanoporous carbon is formed, the charge accumulation processes in this system depending on the composition of the composite and the impact of the laser irradiation on these processes are studied. It is shown that the laser irradiation increases the specific capacity of the composite systems 50 times at the discharge current of 5 mA, which is a result of the emergence of new and modified guest positions in composite components. [ABSTRACT FROM AUTHOR]

The results of electrochemical studies of nanoporous carbon as an electrode material for electrochemical capacitors are presented in the work. Nanoporous carbon material (NCM) is obtained from raw materials of plant origin by its carbonization and subsequent activation in potassium hydroxide. It is established that there is an optimal ratio 1 : 1 between content of KOH and carbon material at chemical activation, while the maximum specific capacity of NCM is 180 F/g. An equivalent electrical circuit, which allows modeling the impedance spectra in the frequency range of 10 – 3-105 Hz, is proposed and a physical interpretation of each element of the electrical circuit is presented. [ABSTRACT FROM AUTHOR]

The adsorption activity of activated carbon was found to depend on conditions of chemical treatment of precursor with orthophosphoric acid. As a precursor, dried apricot seeds were milled to a fraction of 0.25-1 mm. The surface area and value of pore capacity of carbon material increase with H3PO4 concentration. As a result, a mesoporous carbon with 0.9-1.23 cm3/g pores value was prepared, giving adsorption activity for methylene blue 310-350 mg/g and methyl orange 365-370 mg/g. [ABSTRACT FROM AUTHOR]

Chemical activation of nanoporous carbon material with nitric acid, followed by activation in a stream of argon at different temperatures, initiates formation on the surface of the material of amide, pyrrole and pyridine nitrogen compounds that improves the hydrophilic properties and increases its electrical conductivity. Value of the specific capacity of N-enriched carbon material in KOH aqueous solution increases by 30 % and an additional heat treatment in the temperature range of 440-460°C increases it by 10 %. [ABSTRACT FROM AUTHOR]