Rate‐determining steps of oxygen surface exchange kinetics on Sr2Fe1.5Mo0.5O6−δ

The oxygen surface kinetics of Sr2Fe1.5Mo0.5O6−δ was determined using the 16O2/18O2 isotope exchange method with gas phase analysis at 600-800 °C. The heterogeneous exchange rates (rH) and the oxygen diffusion coefficients (D) were calculated by processing the concentration dependences of the 18O fraction using Ezin's model. The rates of oxygen dissociative adsorption (ra) and incorporation (ri) were calculated based on a model using the three exchange type rates. It has been established that the rates ra and ri were comparable in this temperature range. Assumptions were made about the effect of the chemical composition of the surface on the rate of oxygen adsorption. It was found that the oxygen exchange coefficient (k) of Sr2Fe1.5Mo0.5O6−δ is comparable to that of La0.6Sr0.4MnO3±δ oxide. High values of the oxygen diffusion coefficient were found for Sr2Fe1.5Mo0.5O6−δ. The values were comparable to those of the double cobaltite praseodymium-barium and exceed by more than an order those of lanthanum‐strontium manganite. © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).Russian Foundation for Basic Research, RFBR: 00161Government Council on Grants, Russian FederationThe study was partly financially supported by the Russian Foundation for Basic Research (17-08-00161) and the Russian Federation Government, agreement 02.A03.21.0006 (no. 211)

Understanding the Oxygen Reduction Kinetics on Sr2-xFe1.5Mo0.5O6-δ: Influence of Strontium Deficiency and Correlation with the Oxygen Isotopic Exchange Data

This paper presents, for the first time, the results of studies of the electrochemical reaction of oxygen reduction on Sr2Fe1.5Mo0.5O6-δ and Sr-deficient Sr1.95Fe1.5Mo0.5O6-δ, as promising electrodes for solid state electrochemical devices, by the electrochemical impedance method with the subsequent interpretation of the data using the concepts outlined in the Adler et al. model. It was established that the oxygen reduction reaction for both electrodes is determined by two relaxation processes associated with oxygen diffusion, oxygen surface exchange, and Knudsen diffusion in the pores of the electrode. Strontium deficiency was found to have a positive effect on the electrochemical activity of the electrodes, enhancing the stage related to oxygen diffusion and surface exchange. Also, for the first time, for Sr2Fe1.5Mo0.5O6-δ, a quantitative correlation for the surface oxygen exchange and diffusion coefficients obtained from the impedance data and by the isotopic exchange method is demonstrated. © 2021 Elsevier B.V.The authors are grateful to A.S. Farlenkov for the SEM images and A.V. Khrustov for the calculation of the microstructure parameters. The facilities of shared access center "Composition of Compounds" of IHTE UB RAS were used

HIGHLY CONDUCTIVY SOLID-STATE ELECTROLYTE (La,Sr)(Ga,Fe,Mg)O3-δ: INFLUENCE OF IRON CATIONS ON STRUCTURAL AND TRANSPORT PROPERTIES

Samples of a highly conductive electrolyte based on (La,Sr)(Ga,Mg,Fe)O3-δ by conventional solid state method were synthesized. Resistivity decreases with an increase in content of iron cations in the sample in air and remains at same level in wet hydrogen (3% H2O)

H/D Isotopic Exchange and Electrochemical Kinetics of Hydrogen Oxidation on Ni-Cermets with Oxygen-Ionic and Protonic Electrolytes

Ni–Zr0.82Y0.18O1.91 (YSZ) and Ni–La0.90Sr0.10ScO2.95 (LSS) cermets for solid oxide and protonic ceramic electrochemical cells were studied by means of H/D isotope exchange with the gas phase equilibration method for the first time. The experiments were carried out at 2 mbar of dry hydrogen in the temperature range of 400–800 ᵒC. The three parallel channels of hydrogen surface exchange were found to exist in both Ni-YSZ and Ni-LSS cermets. The mechanism of hydrogen isotope exchange for Ni-YSZ was found to be temperature independent, while, in the case of Ni-LSS, the mechanism changed with temperature and was more complicated at lower temperatures (400–600 °C). It was revealed that hydrogen spillover was the rate-determining step for both cermets. The electrochemical kinetics of hydrogen oxidation were studied on symmetric cells with a YSZ supported electrolyte and Ni-YSZ electrodes and with an LSS supported electrolyte and Ni-LSS electrodes in a wet (3 vol % H 2O) hydrogen atmosphere at 1 atm. The mechanism of hydrogen oxidation on the Ni-LSS electrode differs from that of the Ni-YSZ electrode. It changes with temperature and is also more complicated at a lower temperature range. © 2021 Elsevier B.V.This work is supported by the State Assignment of Ministry of Science and Higher Education of the Russian Federation [No. AAAA-A19-119020190078-6 ], and the Act 211 of the Government of the Russian Federation, agreement [No. 02. A03.21.0006 ]. The facilities of the Shared Access Centre “Composition of Compounds” and Unique Scientific Setup “Isotopic Exchange” of IHTE UB RAS were used. The authors are grateful D.M. Solodyankina and A.Yu. Stroeva for support in the preparation of samples

Design of Materials for Solid Oxide Fuel Cells, Permselective Membranes, and Catalysts for Biofuel Transformation into Syngas and Hydrogen Based on Fundamental Studies of Their Real Structure, Transport Properties, and Surface Reactivity

Advances in design of materials for solid oxide fuel cells, oxygen and hydrogen separation membranes, and catalysts for biofuel conversion into syngas and hydrogen are reviewed. Application of new efficient techniques of material synthesis and characterization of their atomic-scale structure, transport properties, and reactivity allowed to develop new types of efficient cathodes and anodes for solid oxide fuel cells, asymmetric supported oxygen, and hydrogen separation membranes with high permeability and structured catalysts with nanocomposite-active components demonstrating high performance and stability to coking in steam/autothermal reforming of biofuels. © 2021 Elsevier B.V.This work was supported by the АААА-А21-121011390007-7 budget project of the Boreskov Institute of catalysis. A.A.Y. gratefully acknowledges financial support within the project CICECO — Aveiro Institute of Materials ( UIDB/50011/2020 and UIDP/50011/2020 ) financed by national funds through the FCT/MCTES and when appropriate cofinanced by FEDER under the PT2020 Partnership Agreement

Application of promising electrode materials in contact with a thin-layer ZrO2-based supporting electrolyte for solid oxide fuel cells

The paper presents the results of an investigation into thin single- and triple-layer ZrO2-Sc2O3-based electrolytes prepared using the tape-casting technique in combination with promising electrodes based on La2NiO4+δ and Ni-Ce0.8Sm0.2O2-δ materials. It is shown that pressing and joint sintering of single electrolyte layers allows multilayer structures to be obtained that are free of defects at the layer interface. Electrical conductivity measurements of a triple-layer electrolyte carried out in longitudinal and transverse directions with both direct and alternating current showed resistance of the interface between the layers on the total resistance of the electrolyte to be minimal. Long-term tests have shown that the greatest degradation in resistance over time occurs in the case of an electrolyte with a tetragonal structure. Symmetrical electrochemical cells with electrodes fabricated using a screen-printing method were examined by means of electrochemical impedance spectroscopy. The polarization resistance of the electrodes was 0.45 and 0.16 Ohm∙cm2 at 800 °C for the fuel and oxygen electrodes, respectively. The distribution of relaxation times method was applied for impedance data analysis. During tests of a single solid oxide fuel cell comprising a supporting triple-layer electrolyte having a thickness of 300 microns, a power density of about 160 mW/cm2 at 850 °C was obtained using wet hydrogen as fuel and air as an oxidizing gas. © 2020 by the authors.Russian Foundation for Basic Research, RFBR: 17‐08‐ 01227Government Council on Grants, Russian FederationFunding: The study was partly financially supported by the Russian Foundation for Basic Research (17‐08‐ 01227), Russian Federation Government, agreement 02.A03.21.0006 (No. 211) and “InEnergy” LTD agreement of 2018

The influence of meteorological factors on the seasonal development of stroke in Yekaterinburg

The article considers the influence of meteorological factors on the occurrence and development of cerebrovascular disorders. It is revealed that the stroke risk increases significantly when rapid and significant changes of atmospheric pressure and temperature of atmospheric air.В статье рассматривается влияние метеорологических факторов на возникновение и развитие нарушений мозгового кровообращения. Выявлено, что риск развития инсульта достоверно увеличивается при быстрых и значительных изменениях атмосферного давления и температуры атмосферного воздуха

Electrical and electrochemical properties of La2NiO4+δ-based cathodes in contact with Ce0.8Sm0.2O2-δ electrolyte

The current work focuses on the investigation of the structural and electrical properties of La2NiO4±δ, La1.7Sr0.3NiO4±δ and La1.7Ca0.3NiO4±δ layered perovskites and electrochemical performance of the cathodes on their base in contact with the Ce0.8Sm0.2O1.9 electrolyte with special attention given to the influence of the introduction of the sintering additives (CuO, Bi0.75Y0.25O1.5) into cathode layers on their in-plane and polarization resistances. Studies by the dc four-probe technique and impedance spectroscopy were performed on the samples with/without the collector layer on a base of LaNi0.6Fe0.4O3 with different sintering temperatures of the electrode layers. © 2014 The Authors. Published by Elsevier Ltd.This work has been partly done using facilities of the shared access center "Composition of compounds" IHTE, UB RAS, and supported by the Russian Foundation for Basic Research, the Government of Sverdlovsk region and Presidium of Ural Branch of RAS (projects №№13-03-96098, 14-03-00414, 14-08-31030, 12-S-3-1016)

Characterization of Ni-cermet degradation phenomena I. Long termresistivity monitoring, image processing and X-ray fluorescenceanalysis

The present paper is devoted to Ni-cermet degradation phenomena and places emphasis on experimental approaches and data handling. The resistivity of Ni-YSZ cermet (nickel and 8 mol.% yttria stabilized zirconia) anode substrates was monitored during 3000 h at 700 and 800 °C in a gas mixture of 80 vol.% water vapor and 20 vol.% hydrogen. The experimentally evaluated dependence of resistivity of the Ni-YSZ substrates can be well described by exponential decay functions. Post test analysis by image processing and XRF (X-ray fluorescence) analysis for characterization of the microstructure and elemental composition were carried out for virgin samples and after 300, 1000 and 3000 h of exposure time. The 3D-microstructure was reconstructed using an original spheres packing algorithm. Two processes leading to the Ni-YSZ degradation were observed: Ni-phase particle coarsening and volatilization. The effect of these processes on resistivity and such microstructure parameters as porosity, Ni-phase fraction, Ni and YSZ phases particle size distributions, triple phase boundary length, and tortuosity factor are considered in this paper