Optical-luminescence properties of ZnO and TiO2 nanopowders obtained by pulsed laser reactive ablation

Journal of Materials Science: Materials in Electronics - The ZnO and TiO2 nanopowders have been prepared by means of the pulsed laser reactive ablation of metallic (Zn, Ti) targets. The Structural,...     

On the hierarchy of the influences of porous and electronic structures of carbonaceous materials on parameters of molecular storage devices

The relation between porous structure, electronic properties of carbonaceous material and the capacitance of its interface with an electrolyte is discussed. It is shown that, in an electric double-layer, the contribution of pseudocapacitive charge accumulation is determined, mainly, by the position of Fermi level in the carbonaceous material and depends on thermodynamic parameters of ions in the electolytic solution. The sizes of the pores in which the processes of capacitive and pseudocapacitive charge accumulation dominate are determined. Theoretical analysis of the processes taking place on the nanoporous carbon|electrolyte interface has made it possible to recognize the intercalative nature of pseudocapacity and to find the criterion of its manifestation in the form of the formation of a continuous series of stable valency phases.     

Improvement of supercapacitor parameters by nickel ion intercalation into activated carbon

The relation between the porous structure and the electron structure in carbon materials was investigated in order to optimize the efficiency of the physical-chemical processes in an electric double layer (EDL) formed at the boundary between the carbon material and the electrolyte (KOH 30 % aqueous solution). In particular, an Ni²⁺ intercalative modification of nanoporous carbon resulted in more than a triple increase in the specific capacitance and a significant improvement of the charge-discharge kinetics in the EDL.     

Influence of chemical modification of activated carbon surface on characteristics of supercapacitors

The influence of the change of Fermi level electrons position of activated carbon μ_C caused by chemical modification of its porous surface by Mn²⁺ ions on its capacitive characteristics in 7.6 m KOH, 4 m KI, 2 m ZnI₂ aqueous solutions is investigated in this work. The detection of adsorbed Mn²⁺ ions on the surface of activated carbon was carried out according to methods of secondary ionic mass spectrometry (SIMS). An increase in electronic density on the Fermi level of modified with Mn²⁺ activated carbon was determined with a help of X-ray photoelectron spectroscopy (XPS) data. Capacitive characteristics of the electrodes have been investigated by means of electrochemical impedance spectroscopy, computer modeling, and galvanic discharge. The correlation between electronic structure of modified activated carbon (MAC) and thermodynamic characteristics of ions of the used electrolytes is established. On the basic of the obtained experimental data, electrochemical system of the hybrid capacitor with a specific capacitance of 1740 F g⁻¹ and with a specific energy of 30 mWh g⁻¹ is developed.     

Fe2+- and Er2+-intercalative modification of porous and electron structure of activated carbon and its influence on supercapacitor parameters

An influence of both porous and electron structure on the processes in an electric double layer (EDL) determining the main working parameters of carbon-based supercapacitors has been studied in order to improve them. The investigations involved impedance spectroscopy, X-ray small angle scattering, confocal micro-Raman spectroscopy, infra-red and Mössbauer spectroscopy. Fe²⁺- and Er²⁺-intercallative modifications of nanoporous carbon were performed. It was found that the modification process characteristics correlated with the structure parameters of the EDL.