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The work is devoted to the study of the influence of synthesis conditions on the properties of water-insoluble rubidium salts of phosphotungstic acid (PTA). Such heteropoly compounds have a wide range of applications, including in the field of electrocatalysts and solid electrolytes for various electrochemical devices. The acid salts of PTA with high activity of acid sites on the particle surface are of particular interest. It is known that the properties of water-insoluble PTA salts strongly depend on synthesis conditions, such as the ratio of reagents, temperature, concentrations, and other parameters. The work examines the influence of the ratio and concentration of reagents on the sizes of crystallites and agglomerates, specific surface area (SSA), porosity, water content, and ionic conductivity of the synthesized PTA salts. The SSA value of the obtained samples varied in the range of 84–123 m2 g−1, and the ionic conductivity was 13–90 mS cm−1 at room temperature and 75% RH. An increase in the acid concentration and the degree of proton substitution led to an increase in SSA, accompanied by an increase in particle sizes without changing the size of crystallites. The results of the work may be useful for the development of new materials based on the obtained salts in many fields, including hydrogen energy.

The first results of the deposition of coatings from accelerated ions of fluorinated fullerene C60(CF3)12 are presented. The coatings are formed at room temperature on Si substrates from a beam of singly charged ions with an energy of 5 keV, as well as from an ion beam that also contains doubly charged ions and a certain amount of ionized fragments of molecules. The properties and structure of coatings obtained from accelerated ions of fluorinated fullerene are compared with the properties and structure of coatings obtained from accelerated fullerene C60 ions under the same conditions. According to X-ray photoelectron spectroscopy (XPS), fluorinated fullerene coatings contain about 4% fluorine. Investigations of the coatings structure and chemical bonds by X-ray photoelectron spectroscopy and Raman scattering show that the presence of fluorine leads to a decrease in the content of sp3-bonds in the coatings and the formation of graphite-like sp2-structures. Coating hardness (H) and Young's modulus (E) compared to C60 ion coatings decrease from 36 to 18 GPa and from 245 to 133 GPa, respectively, while the H/E ratio remains the same (~0.14). Tribological tests have shown for all coatings the friction coefficient is close to 0.1. All coatings are also characterized by a very low wear, less than 10–7 mm3/(N m). For coatings obtained from C60(CF3)12 ions, the contact angle is ~76°–78°. In the absence of fluorine, for the coating obtained from C60 ions, it is ~90°. [ABSTRACT FROM AUTHOR]

From accelerated C60 ions at temperatures of 200 and 300°C hard wear-resistant carbon coatings were deposited. It has been established that the mechanical properties of the coatings are determined by the substrate temperature (Ts) and the energy composition of the beam. The hardness of coatings deposited from ions with an energy of 7 keV exceeds 50 GPa and is practically independent of Ts. The presence of and with an energy of ~14 and 21 keV, respectively, in the beam leads to a result that is not typical for carbon coatings—the hardness increases by more than 1.3 times with an increase in Ts from 200 to 300°C (from 31.6 to 41.6 GPa). In this case, according to Raman spectroscopy data, the size of graphite nanocrystals in the coating increases with temperature up to almost 2 nm. Coatings obtained under conditions of irradiation with and ions are characterized by minimal wear (1.5 × 10–8 mm3/(N m), Ts = 200°C) and minimal friction coefficient (μ = 0.05 for Ts = 300°C). We attribute the unusual dependence of hardness on Ts and the improvement in the tribological properties of coatings to the formation of a composite structure based on a diamond-like matrix and graphite nanocrystals in this Ts range. [ABSTRACT FROM AUTHOR]

The current study focuses on the production of biochars derived from aquatic plants, specifically red seaweed Ahnfeltia and seagrass Zostera and Ruppia, found in brackish lagoons in the Sea of Okhotsk, Sakhalin Island. These biochars were obtained through a stepwise pyrolysis process conducted at temperatures of 500 and 700 °C. The characteristics of the biochars, including their elemental composition, specific surface area, and particle size distribution, were found to be influenced by both the type of biomass used and the pyrolysis temperature. The primary objective of this research was to investigate the potential of these biochars to be used as negative electrodes for lithium ion batteries. Among the various samples we tested, the biochar derived from the macroalgae Ahnfeltia tobuchiensis, produced at 700 °C, exhibited the highest carbon content (70 at%) and nitrogen content (>5 at%). The reversible capacity of this particular biochar was measured to be 391 mAh g−1 during the initial cycles and remained relatively stable at around 300 mAh g−1 after 25 cycles. These findings suggest that biochars derived from aquatic plants have the potential to be utilized as effective electrode materials in lithium ion batteries. The specific properties of the biochar, such as its elemental composition and surface area, play a significant role in determining its electrochemical performance. Further research and optimization of the pyrolysis conditions may lead to the development of biochar-based electrodes with improved capacity and cycling stability, thereby contributing to the advancement of sustainable and environmentally friendly energy storage systems. [ABSTRACT FROM AUTHOR]

The work is devoted to the study of the influence of synthesis conditions on the properties of water-insoluble rubidium salts of phosphotungstic acid (PTA). Such heteropoly compounds have a wide range of applications, including in the field of electrocatalysts and solid electrolytes for various electrochemical devices. The acid salts of PTA with high activity of acid sites on the particle surface are of particular interest. It is known that the properties of water-insoluble PTA salts strongly depend on synthesis conditions, such as the ratio of reagents, temperature, concentrations, and other parameters. The work examines the influence of the ratio and concentration of reagents on the sizes of crystallites and agglomerates, specific surface area (SSA), porosity, water content, and ionic conductivity of the synthesized PTA salts. The SSA value of the obtained samples varied in the range of 84–123 m2 g−1, and the ionic conductivity was 13–90 mS cm−1 at room temperature and 75% RH. An increase in the acid concentration and the degree of proton substitution led to an increase in SSA, accompanied by an increase in particle sizes without changing the size of crystallites. The results of the work may be useful for the development of new materials based on the obtained salts in many fields, including hydrogen energy. [ABSTRACT FROM AUTHOR]

The carbon films formed by accelerated C60 ion deposition are investigated by transmission electron microscopy and X-ray photoelectron spectroscopy. It is demonstrated that amorphous carbon films are formed at an ion-beam energy of 7 keV and a temperature of the substrate of 100–200°C. Substrate temperature increase to 300°C results in the formation of nanocomposite films consisting of graphite nanocrystals embedded in an amorphous carbon matrix. The presence of double- and triple-charged C60 ions with an energy of 14 and 21 keV respectively in the beam results in a decrease in the temperature of formation of the nanocomposite to 200°C. As the result of analysis of the data collected from various sample depths by X-ray photoelectron spectroscopy and Auger-electron spectroscopy, it is found that the sp3/sp2 ratio in the surface layers is higher than in the sample bulk, both in the case of a monoenergetic 7 keV beam, and in the presence of multicharged high-energy ions in the beam. If high-energy ions are present in the beam, then the sp3/sp2 ratio is higher and depends, in a complex way, on the temperature of deposition. The maximum amount of sp3 bonds in the surface layers is found at a temperature of deposition of 350°C and is equal to 88%. The water drop contact angle for this film is 96°, which is similar to the contact angle of the diamond surface. [ABSTRACT FROM AUTHOR]

The electrocatalytic activity of materials in the 10% Pt/Ti1-xRuxO2-δ system, where x = 0-0.3 (0 ≤ Ru ≤ 30 mol %), in the reactions of hydrogen electrooxidation in the presence of CO is studied in the liquid three-electrode cell and a model of fuel cell. It is shown that the tolerance of the electrocatalysts towards CO is determined by the crystal structure of the support: the support with the rutile structure provides a higher rate of CO desorption than the support with the anatase structure. The potential of the onset of CO oxidation decreases with increasing concentration of dopant in the support from 650 mV for 10% Pt/TiO2 to 480 mV (NHE) for 10% Pt/Ti0.91Ru0.09O2-δ (rutile). The use of these materials as the anodic catalysts of fuel cell operating with hydrogen containing 30 ppm CO enabled us to obtain a current density by 7 times higher as compared with the 20% PtRu/C E-Tec catalysts. [ABSTRACT FROM AUTHOR]

The electrocatalytic activity of materials in the 10% Pt/Ti1-xRuxO2-δ system, where x = 0-0.3 (0 ≤ Ru ≤ 30 mol %), in the reactions of hydrogen electrooxidation in the presence of CO is studied in the liquid three-electrode cell and a model of fuel cell. It is shown that the tolerance of the electrocatalysts towards CO is determined by the crystal structure of the support: the support with the rutile structure provides a higher rate of CO desorption than the support with the anatase structure. The potential of the onset of CO oxidation decreases with increasing concentration of dopant in the support from 650 mV for 10% Pt/TiO2 to 480 mV (NHE) for 10% Pt/Ti0.91Ru0.09O2-δ (rutile). The use of these materials as the anodic catalysts of fuel cell operating with hydrogen containing 30 ppm CO enabled us to obtain a current density by 7 times higher as compared with the 20% PtRu/C E-Tec catalysts. [ABSTRACT FROM AUTHOR]