2022

Archives Journal Chemical Bulletin Vol. 5

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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THE JOINT INFLUENCE OF SUCCAROSE AND HIGHLY DISPERSED CALCIUM HYDROSILICATES ON THE STRENGTH DEVELOPMENT KINETICS OF CEMENT CONCRETE

Abstract
Сement hydration accelerator (highly dispersed calcium hydrosilicates) and hydration retarder (sucrose) are components of calcium silicate dispersion (CSD). Their joint influence on the processes of setting and hardening of cement composites is considered. The content of 10% CSD in the composition of the composite binder (CB) leads to a shift of the thermal maximum on the thermokinetic curve by a day. At the same time, at the late stages of hydration (>70 hours), the heat release rate remains consistently high, it is 2-3 times higher than the heat release rate of the control sample. The setting kinetics of CB pastes depends on the content of CSD in its composition and is of an extreme nature. The effectiveness of CSD in the composition of CB was evaluated on the example of ordinary heavy concrete (B25) with the replacement of cement with CSD. The results of assessing the change in the strength of concrete at CB are supplemented with calculated strength indicators in the future up to 1800 days hardening. The expected compressive strength of concrete samples on a composite binder is 1.8 times higher than the strength of the control sample.
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STUDY OF THE EFFECT OF ANIONS ON THE DISSOLUTION RATE OF CO2O3 AND CR(OH)3

Abstract
Сhromium compounds are widely used in industry, therefore, studies related to the study of the process of dissolution of oxides in various environments, including aggressive ones, are relevant. Currently, a huge amount of experimental material has been accumulated on the dissolution of metal oxides and hydroxides. Despite this, the effect of anions on the dissolution rate of these compounds has not yet been sufficiently studied, models have not been developed and generalized dissolution mechanisms have not been found. This article presents experimental studies on the effect of nitrate and sulfate ions on the dissolution rate of chromium (III) oxide and hydroxide. It was found that chromium (III) oxide and hydroxide dissolve better in sulfuric acid in the presence of nitrate ions than sulfate ions. Moreover, chromium (III) hydroxide dissolves better in acids with the addition of anions than chromium (III) oxide. Based on the data obtained, using the equation of the chain mechanism (the Barton-Stransky model), we found the functional dependence of the specific rate of dissolution on the concentration of anions in an acidic medium. With the help of the mathematical computer program MathCad, models of the dissolution of chromium oxide phases were selected. A scheme of the mechanism of the heterogeneous process of dissolution of chromium oxide and hydroxide in acidic media was proposed.
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