Krapivko A.L.

Master of Arts (M.A.), Moscow Technological University

Energy-efficient nanocomposite membrane-electrode blocks for chemical current sources

Abstract
Electrode materials based on platinum metal nanoparticles are widely used to create alternative energy sources with high specific characteristics. Industrial carbon-containing carriers and perfluorinated proton exchange membranes of the Nafion type are used as matrices for the fuel cell electrodes formation. In this work, new effective polymer-carbon catalysts modified with platinum nanoparticles have been synthesized. Physicochemical and functional characteristics of nanocomposites have been studied by electron microscopy, X-ray phase analysis, small-angle X-ray scattering and cyclic voltammetry. Increased catalytic activity and stability of the formed electrodes in hydrogen-oxygen fuel cells had been found. The test results of hydrogen-air fuel cells in model operating conditions had been obtained. The current density maximum parameters of the membrane-electrode assemblies had been found for nanocomposites formed on multi-walled carbon nanotubes with a solubilization coefficient of ω equal to 1.5 and a platinum content of 0.35 mg/cm2. The creation of new membrane-electrode assemblies helps to reduce the cost of chemical current sources, as well as increase their energy efficiency.
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FORMATION AND RESEARCH OF BIMETALLIC ELECTRODE MATERIALS ON POLYMER-CARBON CARRIER MATRICES FOR ENERGY POWER SOURCES

Abstract
Fuel cells are promising devices for direct conversion of chemical energy into electrical energy from the point of view of efficiency and low emission of pollutants. The main component of fuel cells is a solid polymer electrolyte. Membranes made of perfluorinated sulfonated copolymers of the Nafion type with different content of sulfogroups satisfy most of the application conditions, because they have a sufficiently high degree of proton conductivity, stability in electrolyte solutions and high mechanical strength. The principal disadvantage of such membranes is their relatively low ion selectivity and a decrease in mechanical strength at temperatures above 100oC. To improve the characteristics of the membrane, various modification methods are used, including various additives and metal nanoparticles. The main obstacle to the widespread large-scale use of fuel cells is their cost, in which the main part is the cost of electrocatalysts based on platinum metals. Therefore, the development of effective electrode materials with a reduced content of platinum metals is an urgent task. In this work, bimetallic platinum-ruthenium nanoparticles were synthesized on combined carrier matrices consisting of a Nafion polymer membrane and carbon nanotubes. The sizes of Pt-Ru nanoparticles were compared with varying the molar ratio of wa-ter:surfactant from 1.5 to 8. It was found that the minimum size is characteristic of nanoparticles obtained with a maximum platinum content in nanoparticles (7:1) and the degree of solubilization ω = 1.5. It was found that in the methanol oxidation reaction, electrode materials based on bimetallic Pt-Ru nanoparticles (7:1) demonstrate the greatest catalytic activity when the catalyst is loaded 0.2 mg/cm2 on polymer substrates with the addition of multi-walled carbon nanotubes at a temperature of 60oC.
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PALLADIUM NANOELECTROCATALYSTS ON COMBINED MATRIX-SUPPORTS FOR CHEMICAL POWER SOURCES

Abstract
Fuel cells with direct oxidation of formic acid are promising converters of chemical reaction energy into electricity due to the high open-circuit potential, safe (non-flammable and non-toxic) fuel and higher energy characteristics compared to chemical current sources with direct oxidation of alcohols. The crossover effect with a low formic acid content allows the thin membrane application, as well as a high concentration of fuel (up to 20 M), which helps to increase the structure specific power parameters as a whole. Catalysts based on Pt or Pd are widely used in the electrooxidation reaction of formic acid. It has been known that catalysts based Pd are more effective than that Pt due to their resistance to carbon monoxide as the main reaction product. In this paper, the volt-ampere and watt-ampere characteristics of formic acid-based fuel cells and air under model operating conditions were studied. The tests were carried out on a certified laboratory stand of a fuel cell, to which a working model of the investigated membrane-electrode unit was connected. The optimal characteristics of the catalyst loading are established to achieve optimal parameters of current density and specific power. The creation of new catalysts and the modification of existing ones will help to increase the electrodes operation time, reduce the production cost, in-crease their efficiency by increasing efficiency, and also use as fuel not only hydrogen, but also other fuels such as formic acid.
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DETERMINATION OF GLUCOSE IN AQUEOUS SOLUTIONS BY VOLTAMMETRY AT THE COPPER QUASIMICROELECTRODE

Abstract
Development of new sensors for detecting substances in different environments is now of great interest. Voltammetry methods, used in this article, allow one to carry out analysis in the field with almost no sample preparation. This study was carried out to investigate possibilities of quantitative glucose determination on copper quazimicroelectrode in aqueous solutions, including human blood. Process of preparation of copper indicator quazimicroelectrode with effective area consisting of ensemble of copper wires is described in this article. Glucose determination technique in aqueous solutions and the results of testing this electrode in quantitative determination of glycose in human blood are reported. The comparison of the results of investigated copper sensor with reference sensor is carried out. Statistically processed results of glucose determination are described. Copper advantages as electrode material are discussed. Designed electrode can find application in medical analysis laboratories and port-able devices for glucose determination in the field.
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