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Том 54, № 5 (2018)
- Год: 2018
- Статей: 7
- URL: https://journals.rcsi.science/1023-1935/issue/view/11859
Article
Effect of Perchloric Acid on Proton-Conducting Properties of Sulfonated Calix[4]Arene
Аннотация
Calix[4]arenesulfonic acid complexation with perchloric acid is studied. The stoichiometric composition of the complex is shown to be calix[4]arene/HClO4 = 1/1. The complex is most stable against humidity changes as far as its proton-conducting properties are concerned. Its specific proton conductivity varies from 3 × 10–3 to 5 × 10–2 S/cm; the conductivity activation energy is 0.16 ± 0.04 eV. The studying of the effect of HClO4 amount on the samples’ physico-chemical properties at low humidity showed the proton transfer in the material to be determined by the crystallites’ bulk, rather than surface, characteristics.
409-414
Pt(Cu)/C Electrocatalysts with Low Platinum Content
Аннотация
The structure characteristics and the electrochemical behavior of Pt(Cu)/C electrocatalysts synthesized by consecutive deposition of copper and platinum on carbon-support microparticles is studied. The stability and catalytic activity of Pt(Cu)/C materials in reactions of oxygen electroreduction and methanol electrooxidation are assessed and compared with analogous characteristics of a commercial Pt/C material. It is shown that combining the method of galvanic displacement of Cu by Pt with the additional chemical deposition of Pt favors optimization of the structure and functional characteristics of Pt(Cu)/C electrocatalysts. The effect of thermal treatment on the characteristics and properties of electrocatalysts is studied and the optimal conditions of such pretreatment are revealed.
415-425
The Effect of Electrochemical and Gas Phase Activation of High Surface Area Carbon Black Ketjen Black EC 600 DJ on Its Surface Composition, Electrochemical Capacitance, and Stability
Аннотация
The effect of electrochemical and gas-phase activation of high-surface-area carbon black Ketjen Black EC 600 DJ on its stability and electrochemical capacitance is studied. The electrochemical activation is carried out according to the “start–stop” protocol (1–1.5 V, 0.5 V/s). The stability of samples is assessed based on variation of their effective resistance (based on the results of cyclic voltammetry (CVA)) and electrochemical capacitance (based on CVA and galvanostatic data) with the cycle number. The changes in the texture and surface properties of activated samples are studied by the methods of nitrogen low-temperature adsorption and X-ray photoelectron spectroscopy. The gas-phase activation of high-surface-area carbon black Ketjen Black EС 600 DJ is shown to impair its stability, while the electrochemical oxidation of carbonblack samples leads to a considerable (two-fold) increase in their electrochemical capacitance.
426-432
Stability of Anionic Complexes in Halide Melts of Bivalent Metals
Аннотация
The effect of volume variation at the possible dissociation equilibria of (MX4)2– anionic complexes in halide melts of bivalent metals are analyzed in terms of the mean-sphere approximation (MSA) of the statistical theory. Within the framework of the simplified model of charged hard spheres of different diameters and valences, the complete system of equilibrium equations is obtained, i.e., equations of the law of mass action and equations of state. This system makes possible self-correlated calculations of both the equilibrium concentration of autocomplexes and the melt density. It is shown that the simplest approximation of the complex diameter as the treble diameter of simple ions overestimates the effects of volume variations when considering dissociation. Taking into account the superposition of spheres makes it possible to describe the smoother volume variations with the temperature.
433-441
The Effect of Particle Size on the Processes of Charging and Discharging of the LiFe0.97Ni0.03PO4/C/Ag Cathode Material
Аннотация
Olivine-structured LiFe0.97Ni0.03PO4/C/Ag nanomaterials of varying dispersibility are prepared by using sol–gel synthesis with subsequent milling. The materials are certified using X-ray diffraction analysis, scanning electron microscopy, low-temperature nitrogen adsorption, and electrochemical testing under the lithium-ion battery operating conditions. The LiFe0.97Ni0.03PO4/C/Ag cathode material primary particles’ size was shown to decrease, under the intensifying of ball-milling, from 42 to 31 nm, while the material’s specific surface area increased from 48 to 65 m2/g. The discharge capacity, under slow charging–discharging (C/8), approached a theoretical one for all materials under study. It was found that under fast charging–discharging (6 C and 30 C) the discharge capacity is inversely proportional to the particles’ mean size. The discharge capacity under the 6 С current came to 75, 94, 97, and 106 mA h/g for the initial material and that milled at a rotation velocity of 300, 500, and 700 rpm, respectively. An increase in the lithium diffusion coefficient upon the samples’ intense milling is noted.
442-450
Estimation of Corrosion Rate of Bulk and Powder Ni–Re Alloy
Аннотация
The corrosion current density of Ni–Re alloy (15.8 wt % Re) was estimated using recently developed method of compensating additives. The alloy was fabricated by the electrodeposition in the form of bulk specimen and the powder prepared of this specimen. The electrodeposition was performed in stirred 5 × 10–3 M HCl solution. The method enabled us to determine the corrosion rate with no external polarization of studied specimens and at virtually constant pH value. A specific electrochemical activity of powder surface was estimated by comparing the corrosion currents of bulk and powder specimens. The powder was intended for testing its catalytic activity in several electrochemical reactions.
451-455
Short Communications
Cathodic Component of Corrosion Process: Polarization Curve with Two Tafel Portions
Аннотация
A method for the analysis of corrosion process involving two cathodic reactions and one anodic reaction is proposed. By way of example, this method is used to calculate a particular cathodic polarization curve with two Tafel portions. The calculated polarization curve coincides with the experimental curve measured on stainless steel in 0.5 M HCl solution.
456-458