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This article presents the technology for the preparation of a nitrogen-containing nanoporous bio-carbon and investigates its properties. It has been shown that the synthesised bio-carbon is characterised by a high degree of homogeneity, which has been confirmed by energy dispersive spectroscopy. The obtained bio-carbon has a micromesoporous structure, which has been confirmed by the results of studies using the method of low-temperature nitrogen adsorption and desorption. It was found that the specific surface area of biochar is 1247 m2/g. The data on nitrogen adsorption and desorption were compared with the data on small-angle X-ray scattering, and it was found that the micropores in the synthesised bio-carbon are open pores, while mesopores remain closed. The energy dispersion analysis showed that the structure of the bio-carbon does not contain ferromagnetic atoms, but due to the addition of nitrogen, the synthesised bio-carbon in a magnetic field has the properties of a ferromagnet with a characteristic hysteresis of the specific magnetisation. It was found that this material has a saturation magnetisation σs of 1.4 A∙m2∙kg−1 and a coercive force Hc of 10 kA/m. Symmetric supercapacitors were fabricated from the synthesised bio-carbon material with 30% aqueous KOH and 1 M Na2SO4 as electrolytes. It was found that for bio-carbon synthesised at 800 °C, the specific capacitance in a 30% aqueous solution of KOH is 180 F/g, and in a 1 M aqueous solution of Na2SO4, it is 124 F/g. The cyclic voltammetry of the fabricated supercapacitors at different rates of potential expansion was investigated and analysed. Impedance studies on these supercapacitors were carried out. The equivalent electrical circuits describing the electrochemical processes in the studied supercapacitors were constructed and characterised. [ABSTRACT FROM AUTHOR]

In the work, nanostructured Fe3O4/C composites based on natural raw materials (beet pulp and corn stalks) are synthesised in various ways. Iron chloride FeCl3 is used as an activator. The synthesised composites are investigated using the following methods, scanning electron microscopy, X-ray diffractometry, nitrogen adsorption/desorption porometry, magnetometry, impedance and galvanostatic measurements. The presence of nanosized Fe3O4 magnetite in the synthesised carbon structures is disclosed. Based on the magnetic measurements, the particle size of Fe3O4 is on average 50 nm for the sample of the composite synthesised from beet pulp in one step, 30 nm for the sample of the composite synthesised from beet pulp in two steps, 33 nm for the composite synthesised from corn stalks in one step, and 29 nm for the composite synthesised from corn stalks in two steps. It is shown that the two-step synthesis using pre-carbonised raw materials gives the specific capacitance of the composite made with beet pulp at 96 F/g, and for the composite made with corn stalks at 95 F/g. The high coulombic efficiency (>95%) and the stability of the electrical capacitance during long-term cycling make it possible to use Fe3O4/C composites for the manufacture of supercapacitor electrodes with aqueous electrolytes. [ABSTRACT FROM AUTHOR]

The article investigates the adsorption of basic (Methylene blue) and acidic (Congo red) dyes by three types of industrial activated carbon synthesized from natural raw materials. Using the method of isothermal adsorption/desorption of nitrogen, the porous structure of all types of carbon was studied, and the effect of the size of the adsorbent particles on the adsorption capacity was shown. It was established that the adsorption isotherms of both dyes can be described using the Langmuir model. It is assumed that dye molecules are weakly bound to the surface of the carbon material due to van der Waals and hydrophobic interactions. It is shown that the adsorption of Methylene blue is significantly greater than the adsorption of Congo red. This is due to the peculiarities of the dissociation of the functional groups of dye molecules, as well as the almost twice the length of Congo red molecules compared to Methylene blue molecules. It is shown that the boundary amount of adsorbed Methylene blue allows us to estimate the specific surface area of microporous activated carbon with high accuracy if the hydrophilicity of the surface of this carbon is taken into account. [ABSTRACT FROM AUTHOR]

In this work, we present findings on the syntheses and study of properties of InSe nanohybrid. The introduction of guest component in GaSe matrix leads to an increase in inhomogeneities, which is clearly confirmed by the strengthening of the low-frequency horizontal branch of Nyquist diagrams. A constant magnetic field counteracts this effect and changes the behavior of the impedance hodograph at low frequencies to the opposite. Illumination leads to a colossal increase in quantum capacitance, which is clearly demonstrated in the Nyquist diagram. For the synthesized InSe nanohybrid the interesting behavior of the current-voltage characteristic is reported. As a result of studies of the synthesized InSe nanohybrid the effect of "negative capacity" is observed, the magnitude of which can be controlled by the electric field. Based on the constructed impedance model and proposed N-barrier model, the physical mechanisms of the investigated processes are suggested. [ABSTRACT FROM AUTHOR]

Synthesis of Ni/C nanostructured composites based on a natural raw material, i.e., wheat straw, is carried out in this work. The synthesis is performed by one- and two-stage methods using NiCl2 as the activating agent. The X-ray diffraction and EDS analyses reveal the presence of metallic nickel in the structure of the composites, whereas magnetic measurements showed that nickel was contained in the porous carbon matrix in the nanoparticle state. For nanocomposites synthesized by the one-stage method, the largest contribution to the formation of the porous structure might be attributed to pores with radii from 5 to 30 nm; for a nanocomposite synthesized in two stages, the pore distribution function exhibits a narrow isolated peak with a maximum of around 2.6 nm. Based on the obtained magnetic data, the coercive force, specific saturation magnetization and nickel content in nanocomposites are calculated. For the measured values of the coercive force, the average size of magnetic moment carriers is determined to be ~100 nm for the two-stage synthesis nanocomposite and ~100 ÷ 110 nm for the one-stage synthesis nanocomposites. The developed Ni/C nanocomposites might be used as a cheap material for energy storage applications or as magnetically controlled adsorbents. [ABSTRACT FROM AUTHOR]

Nickel/carbon composites were synthesized by the carbonization method with the use of the steam-gas activation technique. Beet pulp and corn stems were used as initial raw materials for composites synthesis. The obtained substances were analyzed by means of scanning electron microscopy, X-ray diffraction analysis, and magnetic properties investigation. The presence of nickel in synthesized composites was estimated during analysis, and the average particle size of nickel was determined as well. The specific surface area of the obtained samples was measured by the technique of Methylene blue sorption from the aqueous solution. The results of the performed investigation demonstrate clearly the promising application of synthesized composites as magneto-active sorbents, which could be easily separated from water solutions. [ABSTRACT FROM AUTHOR]

The article comprises synthesis of magnetically susceptible carbon sorbents based on bio raw materials – beet pulp. The synthesis was performed by one- and two-step methodology using FeCl3 as an activating agent. X-ray diffraction methods showed an increase in the distance between graphene layers to 3.7 Å in biocarbon synthesized by a two-step technique and a slight decrease in inter-graphene distance to 3.55 Å for biocarbon synthesized by an one-step technique. In both magnetically susceptible samples, the Fe3O4 magnetite phase was identified. Biocarbon synthesized by a two-step technique is characterized by a microporous structure in which a significant volume fraction (about 35%) is made by pores of 2.2 and 5 nm radius. In the sample after a one-step synthesis, a significant increase in the fraction of pores with radii from 5 to 30 nm and a decrease in the proportion of pores with radii greater than 30 nm can be detected. Based on the analysis of lowangle X-ray scattering data, it is established that carbon without magnetic activation has the smallest specific area of 212 m²∙сm–3, carbon after one-stage synthesis has a slightly larger area of 280 m²∙сm–3, and after two-stage synthesis has the largest specific surface area in 480 m²∙сm–3. The adsorption isotherms of blue methylene have been studied. Biocarbon obtained by two-step synthesis has been shown to have significantly better adsorption properties than other synthesized biocarbons. Isotherms have been analysed based on the Langmuir model. [ABSTRACT FROM AUTHOR]

This article analyzes the issue of developing ecologically safe technologies for obtaining the electrochemically activated water solutions for ensuring the rational use of water resources and reducing the volume of discharges of harmful substances into the environment. The necessity of controlling the depth of electrochemical activation for obtaining ecologically safe industrial water solutions and reducing the energy consumption of this process was substantiated. The ecological advantages of electrochemically activated solutions application were presented as compared to the chemical solutions in the technologies of activated carbon surfaces modification to increase the supercapacitors electrode specific capacitance, preparation of the gypsum plaster mixing water to improve the physicochemical properties of gypsum stone, as well as efficiency of use of disinfectant based on the electrochemically activated water solutions solutions, approbated in the sugar production industry. It was experimentally confirmed that the depth of electrochemical activation significantly affects the efficiency of practical use of activated water solutions. The proposed theoretical models allow prediction of the activation modes for solving specific problems. [ABSTRACT FROM AUTHOR]

We report on the complex GaSe-based hierarchical structures GaSe(CS(NH2)2), GaSe(SmCl3) and GaSe(CS(NH2)2(SmCl3)) synthesized by an intercalation method. The conductive properties of synthesized clathrates and their relation to hierarchical structural complexity were explored by an impedance spectroscopy technique. The impedance response, thermostimulated discharge spectra, and photo- and magnetoresistive effects are reported. Based on the obtained results, the impurity energy spectra were calculated. A strong low-frequency inductive response, observable in the GaSe(SmCl3) clathrate, makes this material promising for the development of gyrator-free nanodelay lines potentially applicable in nanoelectronics. Hierarchical GaSe(CS(NH2)2(SmCl3)) clathrate, on the other hand, reveals hysteresis of the current–voltage characteristics, apparently confirming an accumulation of electric energy at interphase boundaries. A relevant spin battery effect, observable experimentally in stationary magnetic fields, demonstrates a principal possibility of the electric energy accumulation at a quantum level. [ABSTRACT FROM AUTHOR]