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1.
A method for preparing sulfate-oxalate chromium-plating solutions by reducing Cr(VI) from industrial chromium-plating electrolytes to Cr(III) with a Na2SO3 solution is proposed. 相似文献
2.
Danilov A. I. Molodkina E. B. Baitov A. A. Pobelov I. V. Polukarov Yu. M. 《Russian Journal of Electrochemistry》2002,38(7):743-753
Initial stages of copper electrocrystallization on glassy carbon from sulfuric acid electrolytes of pH 0.3 and 3.7 are studied by the method of potentiostatic current transients on rotating and stationary ring–disk electrode. The rate of copper deposition in a 0.5 M Na2SO4 + 0.01 CuSO4 (pH 3.7) solution is marginally higher than in a 0.5 M H2SO4 + 0.01 CuSO4 acid electrolyte (pH 0.3) at the expense of adsorption of sulfate and hydroxide ions on the substrate surface and the copper crystals. Regularities governing the multistage discharge of copper ions, the formation of the new phase nuclei, and the deposit dissolution are analyzed. The results of the study are compared with the data on the kinetics of copper electrocrystallization on a platinum electrode. The acceleration of the copper deposition on glassy carbon in the acid solution of pH 0.3, as compared with platinum, is due to accelerated discharge of copper ions and increased number of univalent copper ions in the near-electrode layer of solution. The oxygen-containing surface groups of glassy carbon (quinone–hydroquinone, carbonyl, etc.) are probably active centers for the discharge of copper ions and three-dimensional nucleation. 相似文献
3.
A. V. Rudnev E. B. Molodkina A. I. Danilov Yu. M. Polukarov J. M. Feliu 《Russian Journal of Electrochemistry》2006,42(4):381-392
The kinetics of underpotential deposition, three-dimensional nucleation, and growth of copper deposits at cathodic overpotentials on a Pt(111) electrode in solutions containing 0.5 M H2SO4, 10 mM CuSO4, and 0–200 mM acetonitrile (AcN) is studied by the cyclic voltammetry, potentiostatic current transients, and scanning probe microscopy methods. At low volume concentrations of acetonitrile ([AcN] ≤ 4 mM), adsorbed acetonitrile molecules accelerate the formation of a co-adsorption lattice of copper adatoms with anions due to local electrostatic effects at the charged interface. At higher concentrations, the underpotential deposition process is hampered, but the desorption of copper adatoms occurs at potentials more positive than those at low acetonitrile concentrations. This effect is attributed to a stabilizing action of acetonitrile molecules situated on the layer of copper adatoms and, in part, on platinum. At [AcN] = 0.4–40 mM, adsorbed acetonitrile molecules accelerate the growth of the bulk copper deposit, but the nucleation stage is hindered. The dependence of the copper amount on the deposition potential at [AcN] = 40 mM exhibits a maximum at 0.15–0.17 V. This effect was previously observed in weakly acid solutions (pH 1.7–3.0) containing no acetonitrile. The maximum rate of the deposit growth corresponds to an optimum number of crystallites (which is not too great) and an optimum distance between the growing centers in conditions of mixed kinetics “diffusion + electron transfer.” A substantial number of complexes Cu(I)-AcN forms at high acetonitrile concentrations. 相似文献
4.
Danilov A. I. Molodkina E. B. Polukarov Yu. M. 《Russian Journal of Electrochemistry》2004,40(6):597-603
The formation of a copper adatom layer on polycrystalline platinum in a copper sulfate solution is studied by cyclic voltammetry in different cycling ranges at 0.1 V s–1. The copper adatom deposition kinetics is controlled by the following factors. The substrate's top layer structure during the oxygen exit onto the surface may be unstable at anodic limits E
a = 0.90–1.35 V. The concentration of copper oxides (active centers) may be higher at E
a = 0.8–0.95 V. The balance between different adsorption sites differs in different cycling conditions. Of importance is the number of complexes Oss–Pt
n
–SO4 and Oss–Pt
n
–Oc, where Oss is subsurface oxygen and Oc is chemisorbed oxygen. 相似文献
5.
Danilov A. I. Molodkina E. B. Polukarov Yu. M. 《Russian Journal of Electrochemistry》2002,38(7):732-742
Initial stages of copper electrocrystallization on glassy carbon from sulfuric acid electrolytes of pH 0.3 and 3.7 are studied by the cyclic voltammetry method on rotating and stationary ring–disk electrode. The rate of nucleation and growth of a metallic phase of copper in a 0.5 M Na2SO4 + 0.01 CuSO4 (pH 3.7) solution is marginally higher than in a 0.5 M H2SO4 + 0.01 M CuSO4 acid electrolyte (pH 0.3). Regularities governing the multistage discharge of copper ions, the formation of the new phase nuclei, and the deposit dissolution are analyzed. No copper adlayers form on glassy carbon at potentials more positive than the equilibrium potential of a reversible copper electrode, the copper nucleation occurs via the Volmer–Weber mechanism. The oxygen-containing surface groups of glassy carbon (quinone–hydroquinone, carbonyl, etc.) are probably active centers for the discharge of copper ions and the nucleation of the new phase. The results of the study are compared with the data on the kinetics of copper electrocrystallization on a platinum electrode. 相似文献
6.
7.
Danilov A. I. Molodkina E. B. Polukarov Yu. M. 《Russian Journal of Electrochemistry》2004,40(6):585-596
The oxidation of polycrystalline platinum in 0.5 M H2SO4 is studied by cyclic voltammetry at potential scan rates of 5–500 mV s–1 while varying the potential cycling range. The scheme, which is proposed for explaining the observed acceleration and deceleration of oxygen sorption at 0.75–1.0 V, accounts for the presence of oxygen in the subsurface layers of platinum (Oss) and the formation of a barrier layer comprising complexes Oss–Pt
n
–SO4. Cycling platinum secures certain steady-state contents of Oss at 0.01–1.35 V. In an anodic scan, Oss accumulates at E > 0.85 V (slow post-electrochemical stage) due to exchange of platinum and oxygen atom sites. In a cathodic scan, the desorption of most oxygen gives way to the adsorption of anions, which prevent residual Oss from appearing on the surface. The residual Oss disappears at E < 0.1 V after a sufficiently complete desorption of anions and the destruction of stable complexes Oss–Pt
n
–SO4. Varying the potential cyclic limit leads, after a delay, to other steady-state Oss contents. 相似文献
8.
Savinova D. V. Molodkina E. B. Danilov A. I. Polukarov Yu. M. 《Russian Journal of Electrochemistry》2004,40(7):687-694
The formation of an adatom layer on polycrystalline platinum and the three-dimensional nucleation of copper in a copper perchlorate solution are studied by cyclic voltammetry at 0.1 V s–1 while varying potential ranges and by recording potentiostatic current transients. About 0.6 monolayers of copper adatoms are deposited when cycling with anodic limit E
a = 1.35 V, the process is slower than that in an acid sulfate solution. Decreasing E
a accelerates the process (nearly one monolayer forms for E
a = 0.80–0.95 V in a cathodic scan) due to an increased number of active centers (metastable copper oxides) and, probably, to a change in the platinum surface microstructure. Oxygen for copper oxides is presumably supplied by water molecules adsorbed on a monolayer of copper adsorbed atoms and by subsurface oxygen (Oss), which appears on the platinum surface after the destruction of complexes Oss–Pt
n
–ClO4. Both the copper nucleation and the deposit growth accelerate at higher concentrations of copper oxides, which form at low E
a. High cathodic overvoltages decrease the number of active crystallization centers due to reduction or removal of copper oxides. 相似文献
9.
A. B. Drovosekov M. V. Ivanov V. M. Krutskikh Yu. M. Polukarov 《Russian Journal of Electrochemistry》2010,46(2):136-143
Catalytic activity, chemical composition, and structure of Ni-Re-B, Ni-Mo-B, and Ni-W-B alloys obtained by chemical-catalytic
reduction of metal ions were studied. Introduction of a doping element into the nickel-boron alloy changes the catalytic activity
of the alloy surface as regards concurrent partial reactions of heterogeneous hydrolysis of dimethylamine borane, reduction
of nickel atoms, evolution of molecular hydrogen, boron, and carbon. The aim of the work was to elucidate the causes for nonlinear,
bell-shaped dependence of partial rates of dimethylamine borane hydrolysis and hydrogen evolution on the concentration of
the doping element in the alloy. The structure and uniformity of distribution of elements in the coatings were evaluated.
Estimation of the grain size in the deposits based on the broadening of reflex (111) evidences the nanocrystalline structure
of the obtained alloys. The minimum grain size (<20 nm) corresponds to the doping element concentration within the alloy with
the maximum catalytic activity. Boron content in the alloys decreases at an increase in the doping element concentration.
The observed acceleration of the heterogeneous reaction of dimethylamine borane hydrolysis is explained by a change in the
catalytic activity of the coating surface as a result of the subsystem restructuring during the formation of an alloy between
nickel and the doping element. 相似文献
10.
S. D. Antipov G. E. Gorjunov A. F. Djura Ju. M. Polukarov D. V. Sadkov P. N. Stetsenko E. N. Terentjev V. V. Shestakov 《Hyperfine Interactions》1993,78(1-4):391-396
A mathematical approach for the evaluation of hyperfine field distribution functions based on an analytical approximation of Mössbauer spectra was developed. The calculations were performed for different model spectra andfor the experimental spectra of crystalline andamorphous alloys. It was possible to obtain an adequate interpretation of complicated Mössbauer spectra of multicomponent heterophase amorpho-crystalline alloys of the Nd-Fe-B-type. 相似文献