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The oxygen reaction at the interface LaF3(CeF3)|electrode,O2(g) is studied in air on Pt and C electrodes and electrodes modified by supported oxides of Co, Sr, and/or La on C, Si, or Pt substrates. The experimental methods used are voltammetry with a linear potential change and stripping voltammetry and cyclic voltammetry. The voltammetric response is dependent on the nature of solid electrolyte and electrode, the balance between the substrate and active agent, and on the conditions of thermal treatment of electrodes. Mobile oxygen forms are discovered at interfaces CeF3|C (Co x O y ), 2 ([C] : [Co] = 1 : 10, 1 : 20); CeF3|C (Co x O y ), 2([C] : [Co] = 1 : 10); and CeF3|Pt (Co x O y ), O2([Pt] : [Co] = 1 : 40). The peak current I pa in the anodic curves increases with extending the limit of cathodic potential scan E rc. The peak current I pc in the cathodic curves increases with extending the limit of anodic potential scan E ra.  相似文献   
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The reduction of immobile cations La3+ and Ce3+ in fluoride-conducting solid electrolytes (FSE) LaF3 (Eu2+ 0.8 mol %), LaF3 (Sr2+ 5 mol %), and CeF3 (Sr2+ 5 mol %) in contact with Ag, Bi, Si, La, Ce, and Sm working electrodes is studied by chronoamperometry and voltammetry with linear potential scan. Discovered is linear dependence of initial segments of potentiostatic transients of cathodic current on t 1/2 at FSE interfaces with Ag, Bi, La, Ce, and Sm. The dependence is due to diffusion-controlled instantaneous nucleation of Ln and Ce. The La3+ and Ce3+ reduction at the FSE/Ag interface is reversible in a narrow region. The reduction and oxidation of La3+ and Ce3+ (cations of the FSE rigid lattice) at the FSE/Me (Me = La, Ce and Sm, Bi, Si) interface is irreversible and involves a chemical reaction.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 662–672.Original Russian Text Copyright © 2005 by Turaeva, Kot, Urchukova, Murin.  相似文献   
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The electrochemical behavior of the LaF3 : Eu2+| interface (Me = Sm, Ce, Gd, V, Ag) is studied using stripping voltammetry. Current–voltage curves for cells Ag, AgCl|KCl and KF|LaF3 : Eu2+|Sm (or Ce) may be viewed as background curves for analyzing solid-phase reactions with other metallic electrodes. The substrate material is found to affect properties of interfaces LaF3 : Eu2+/Gd (or V), which are characterized either by solid-phase reactions involving the fluoride ion of a solid electrolyte or by reactions involving oxygen. Regularities, obtained for silver in contact with LaF3 : Eu2+, link electrochemical signals of the reaction of the silver fluoride formation with the contact area.  相似文献   
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Electrochemical measurements are carried out on three-phase boundaries LaF3:Eu2+/Me, oxygen gas, where Me = Ti, Be, Ta, Au and also on the boundaries of CeF3:Sr2+ with Ag-supported Ag and Bi microelectrodes by the methods of linear scan voltammetry, chronoamperometry, and cyclic voltammetry. The conditions beneficial for reduction of oxygen gas, transformations of chemisorbed oxygen, and the appearance of its mobile forms are considered. Results on the interaction of gaseous oxygen with metals in contact with LaF3:Eu2+ single crystals are generalized. The correlation is found between the oxygen reduction potential and the difference of electronegativities Δχ Me-O. The relationship is revealed between the oxygen reduction potential and the Me-Me bond energy by taking into account the structural factor f/k n, where f is the number of binding electrons and k n is the coordination number.  相似文献   
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The kinetics of low-sized phase formation on polarization of the interface between LaF3:Eu2+ and Pb–Sn, Sn–Bi, and Sb–Bi alloys is studied by the potentiostatic and linear voltammetry methods. The analysis of anodic transients shows that the new phase formation involving fluoride ions from the solid electrolyte proceeds by the mechanism of instantaneous two-dimensional or three-dimensional nucleation. Comparison of calculated and experimental transients describing the instantaneous nucleation with either two-dimensional growth on the I/I m vs. t/t m coordinates or three-dimensional growth on the I 2/I m 2 vs. t/t m coordinates shows adequate agreement between the model and the initial regions of experimental curves. The properties of phases formed depend on the alloy composition and the polarization conditions as well as on the energy of interaction between components in the alloy and in the new phase.  相似文献   
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Kinetics of fluorideion exchange at the interface between a LaF3:Eu2+ single crystal and solution with different pF and pH is studied by the galvanostatic and potentiometric methods and also by impedance spectroscopy. Anodic galvanostatic transients are linearized in the coordinates ln (η–ηmax) vs. t, which suggests that the exchange rate in alkaline solutions is limited by surface diffusion of fluorine adions. The surface concentration of fluorine adions с 0 and the surface diffusion flow ν 0 are assessed. Impedance spectroscopy studies of the exchange processes indicate that the charge-transfer resistance R F and the heterogeneous reaction resistance R P increase with the increase in the рН of the fluoride-containing solution and also with the increase in the time of exposure of the fluoride-selective electrode membrane in a neutral solution with pH 6.4 and the high (pF 2) content of fluorides.  相似文献   
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The electrochemical properties of single crystals of cerium fluoride alloyed with bivalent cations Sr2+, Ca2+, Ba2+, Sr2+ + Ca2+, Sr2+ + Ba2+, Ba2+ + Ca2+ and also with La3+ and La3+ + Ba2+ cations are studied using the dynamic voltammetry and impedance spectroscopy. The conductivity of symmetrical cells with Ag electrodes is determined using the method of impedance spectroscopy in the frequency range from 450 to 5 kHz at the temperatures from 20 to 100°C: for CeF3: Sr2+ (0.5 mol %) + Ba2+ (0.5 mol %), σ = σ0 exp[(?0.284 ± 0.005/kT]; for CeF3:Ca2+ (0.5 mol %) + Sr2+ (0.5 mol %), σ = σ0 exp[(?0.292 ± 0.017/kT]. The steady-state and dynamic voltammogams of symmetrical electrochemical cells with nonpolarizable reference electrodes and CeF3 single crystals alloyed with Sr2+, Ca2+, and Ba2+ bivalent cations exhibited ohmic polarization. For cells with CeF3 containing La3+ as an admixture, a hysteresis was observed, which could not be eliminated by chemical and electrochemical treatment of crystals. In the dynamic voltammetric curves of asymmetric cells with nonpolarizable and silver electrode and CeF3 crystals alloyed with Sr2+, Ca2+, and Ba2+, a range of ideal polarizability (from 0 to ~?2.7 V), and also cerium redox processes and silver fluorination-boundary regeneration were observed. In the dynamic voltammetric curves of asymmetric cells with CeF3 containing La3+ admixture, no range of ideal polarizability was observed; however, the reactions of silver fluorination and reduction of solid-electrolyte cerium were well pronounced at the corresponding potentials.  相似文献   
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The voltammetry method with a linear potential scan is used for investigating the effect the electrode material (Ni, Co, electrodes on the basis of cobalt oxides modified with carbon) exerts on the reduction of gaseous oxygen at interfaces solid fluoride-conducting electrode LaF3:Eu2+/electrode, O2, and conjugated processes. Properties of the modified electrodes are characterized by the impedance spectroscopy, scanning electron microscopy, and x-ray photoelectron spectroscopy methods. The oxygen reaction is irreversible at the LaF3:Eu2+|Ni (or Co) interfaces. At the interface of LaF3:Eu2+ with modified electrodes Co (C n at %), where n = 5 and 9, mobile forms of oxygen are reversible and the reduction of gaseous and chemisorbed oxygen is controlled by diffusion with different effective kinetic parameters.  相似文献   
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