Comparative study of electrophoretic deposition of doped BaCeO3-based films on La2NiO4+δ and La1.7Ba0.3NiO4+δ cathode substrates

This paper presents the results of a comparative study of methods to prevent the loss of barium during the formation of thin-film proton-conducting electrolyte BaCe0.89Gd0.1Cu0.01O3-δ (BCGCuO) on La2NiO4+δ-based (LNO) cathode substrates by electrophoretic deposition (EPD). Three different methods of the BCGCuO film coating were considered: the formation of the BCGCuO electrolyte film without (1) and with a protective BaCeO3 (BCO) film (2) on the LNO electrode substrate and the formation of the BCGCuO electrolyte film on a modified La1.7Ba0.3NiO4+δ (LBNO) cathode substrate (3). After the cyclic EPD in six stages, the resulting BCGCuO film (6 μm) (1) on the LNO substrate was completely dense, but the scanning electron microscope (SEM) analysis revealed the absence of barium in the film caused by its intensive diffusion into the substrate and evaporation during the sintering. The BCO layer prevented the barium loss in the BCGCuO film (2); however, the protective film possessed a porous island structure, which resulted in the deterioration of the film's conductivity. The use of the modified LBNO cathode also effectively prevented the loss of barium in the BCGCuO film (3). A BCGCuO film whose conductivity behavior most closely resembled that of the compacts was obtained by using this method which has strong potential for practical applications in solid oxide fuel cell (SOFC) technology. © 2019 by the authors.Government Council on Grants, Russian FederationFunding: This research was funded by the Government of the Russian Federation (Agreement 02.A03.21.0006, Act 211)

A reversible protonic ceramic cell with symmetrically designed Pr2NiO4+δ-based electrodes: Fabrication and electrochemical features

Reversible protonic ceramic cells (rPCCs) combine two different operation regimes, fuel cell and electrolysis cell modes, which allow reversible chemical-to-electrical energy conversion at reduced temperatures with high efficiency and performance. Here we present novel technological and materials science approaches, enabling a rPCC with symmetrical functional electrodes to be prepared using a single sintering step. The response of the cell fabricated on the basis of P-N- BCZD|BCZD|PBN-BCZD (where BCZD = BaCe0.5Zr0.3Dy0.2O3-δ, PBN = Pr1.9Ba0.1NiO4+δ, P = Pr2O3, N = Ni) is studied at different temperatures and water vapor partial pressures (pH2O) by means of volt-ampere measurements, electrochemical impedance spectroscopy and distribution of relaxation times analyses. The obtained results demonstrate that symmetrical electrodes exhibit classical mixed-ionic/electronic conducting behavior with no hydration capability at 750 °C; therefore, increasing the pH2O values in both reducing and oxidizing atmospheres leads to some deterioration of their electrochemical activity. At the same time, the electrolytic properties of the BCZD membrane are improved, positively affecting the rPCC's efficiency. The electrolysis cell mode of the rPCC is found to be more appropriate than the fuel cell mode under highly humidified atmospheres, since its improved performance is determined by the ohmic resistance, which decreases with pH2O increasing. © 2018 by the authors.Российский Фонд Фундаментальных Исследований (РФФИ): 18-38-20063Funding: The majority of this work was carried out under the budgetary plans of Institute of High Temperature Electrochemistry. The design of new electrode materials and their characterization was also funded by the Russian Foundation for Basic Research, grant number 18-38-20063. Dr. Dmitry Medvedev is also grateful to the Council of the President of the Russian Federation (scholarship СП-161.2018.1) for supporting the studies devoted to search of new Co-free electrode materials

Моделирование микроструктуры и расчет фактора извилистости для катодных материалов LSM-YSZ

In this work changes in physico-chemical properties (oxygen interphase exchange rate and specific resistance) and microstructure parameters (TPB length and tortuosity factor) with time have been analyzed to find the quantitative relationships on the example of composite cathode material LSM-YSZ. 3D microstructure of LSM-YSZ materials has been reconstructed and tortuosity factor has been calculated on the basis of SEM image analysis using the original software.В работе на примере композиционного материала LSM-YSZ сравнивается изменение физико-химических свойств (скорости межфазного обмена кислорода и удельного сопротивления) и параметров микроструктуры (протяженности ТФГ и фактора извилистости) от времени с целью нахождения количественных взаимосвязей. Для электродных материалов LSM-YSZ проведена 3D-реконструкция микроструктуры и рассчитан фактор извилистости на основе результата анализа изображений РЭМ с использованием оригинального программного обеспечения.This work was done under financial support from RFBR grant № 12-03-31847 / 12 and the Federal Program № 2012-1.3.1-12-000-2006-004, number 8713.Работа выполнена при финансовой поддержке грантов РФФИ № 12-03-31847/12 и ФЦП № 2012-1.3.1-12-000-2006-004, соглашение № 8713

Water uptake and transport properties of La1-xCaxScO3-α proton-conducting oxides

In this study, oxide materials La1-xCaxScO3-α (x = 0.03, 0.05 and 0.10) were synthesized by the citric-nitrate combustion method. Single-phase solid solutions were obtained in the case of calcium content x=0.03 and 0.05,whereas a calcium-enriched impurity phasewas found at x=0.10. Water uptake and release were studied by means of thermogravimetric analysis, thermodesorption spectroscopy and dilatometry. It was shown that lower calcium content in the main phase leads to a decrease in the water uptake. Conductivity wasmeasured by four-probe direct current (DC) and two-probe ascension current (AC)methods at different temperatures, pO2 and pH2O. The effects of phase composition,microstructure and defect structure on electrical conductivity, as well as correlation between conductivity and water uptake experiments, were discussed. The contribution of ionic conductivity of La1-xCaxScO3-α rises with decreasing temperature and increasing humidity. The domination of proton conductivity at temperatures below 500 °C under oxidizing and reducing atmospheres is exhibited. Water uptake and release as well as transport properties of La1-xCaxScO3-α are compared with the properties of similar proton electrolytes, La1-xSrxScO3-α, and the possible reasons for their differences were discussed. © 2019 by the authors.Russian Science Foundation, RSF: 16-13-00053Government Council on Grants, Russian FederationMinistry of Education and Science of the Republic of KazakhstanFunding: The research was partially supported by the Russian Science Foundation (Grant №16-13-00053) and the Ministry of Education and Science of the Republic of Kazakhstan (Project No. AP05130148). The education activity of Ph.D. and students involved into this work is supported by Act 211 of Government of the Russian Federation, agreement No. 02.A03.21.0006

Features of electrophoretic deposition of a ba-containing thin-film proton-conducting electrolyte on a porous cathode substrate

This paper presents the study of electrophoretic deposition (EPD) of a proton-conducting electrolyte of BaCe0.89Gd0.1Cu0.01O3-Δ (BCGCuO) on porous cathode substrates of LaNi0.6Fe0.4O3-Δ (LNFO) and La1.7Ba0.3NiO4+Δ (LBNO). EPD kinetics was studied in the process of deposition of both a LBNO sublayer on the porous LNFO substrate and a BCGCuO electrolyte layer. Addition of iodine was shown to significantly increase the deposited film weight and decrease the number of EPD cycles. During the deposition on the LNFO cathode, Ba preservation in the electrolyte layer after sintering at 1450 °C was achieved only with a film thickness greater than 20 μm. The presence of a thin LBNO sublayer (10 μm) did not have a pronounced effect on the preservation of Ba in the electrolyte layer. When using the bulk LBNO cathode substrate as a Ba source, Ba was retained in a nominal amount in the BCGCuO film with a thickness of 10 μm. The film obtained on the bulk LBNO substrate, being in composition close to the nominal composition of the BCGCuO electrolyte, possessed the highest electrical conductivity among the films deposited on the various cathode substrates. The technology developed is a base step in the adaptation of the EPD method for fabrication of cathode-supported Solid Oxide Fuel Cells (SOFCs) with dense barium-containing electrolyte films while maintaining their nominal composition and functional characteristics. © 2020 by the authors.This research received no external funding. This work was performed in the framework of the IEP UB RAS state assignment (EPD technology development) and the IHTE UB RAS budget task (SOFC technology development). The XRD and microstructure study was carried out using the equipment of the Shared Access Center "Composition of compounds" (Institute of High Temperature Electrochemistry, Ural Branch of the Russian Academy of Sciences, Yekaterinburg, Russia). The authors acknowledge Zhuravlev, V.D., the head of the Laboratory of chemistry of compounds of rare-earth elements (Institute of Solid State Chemistry, UBRAS,Yekaterinburg, Russia), Bogdanovich, N.M., scientific researcher of the Laboratory of solid oxide fuel cells (IHTE UB RAS), and Lyagaeva, J.G., senior scientific researcher of the Laboratory of Electrochemical Devices Based on Solid Oxide Proton Electrolytes (IHTE UB RAS) for the development of the synthesis methods used in this study

Effect of Li2O–Al2O3–GeO2–P2O5 glass crystallization on stability versus molten lithium

Glass and glass-ceramic NASICON-type electrolytes of Li1.5Al0.5Ge1.5(PO4)3 composition were obtained by melt quenching and glass crystallization, respectively. The stability of the solid electrolytes to molten metallic Li was studied by immersing the samples and holding them at 230 °C for 72 h. Li|glass|Li and Li|glass-ceramics|Li electrochemical cells were assembled and their resistance was measured by impedance spectroscopy at 200 °C for 9 days. It was established that, unlike the glass, the glass-ceramics did not change in its phase composition and molecular structure after the tests. It is shown that Li1.5Al0.5Ge1.5(PO4)3 glass-ceramics is chemically stable in contact with metallic Li. © 2019 Elsevier B.V.Russian Science Foundation, RSF: 18-73-00099The reported study was funded by the Russian Science Foundation according to the research project No. 18-73-00099 . The authors are grateful to Antonov B.D. and Vovkotrub E.G. The research has been carried out with the equipment of the Shared Access Center “Composition of Compounds” of Institute of High Temperature Electrochemistry of the Ural Branch of the RAS, Ekaterinburg, Russian Federation

Formation of conductive oxide scale on 33NK and 47Nd interconnector alloys for solid oxide fuel cells

Two grades of chromium-free alloys were studied in order to apply them as interconnectors for solid oxide fuel cells. The surface modification methods were proposed for each alloy with the purpose of forming of oxide scales considering the required physicochemical properties. Investigations of the structure and properties of the obtained oxide scales were performed and the efficiency of the chosen surface modification methods was approved. The samples with the surface modification exhibited higher conductivity values in comparison with the nonmodified samples. A compatibility study of samples with surface modification and glass sealant of chosen composition was accomplished. The modified samples demonstrated good adhesion during testing and electrical resistance less than 40 mOhm/cm2 at 850 ◦C in air, which allowed us to recommend these alloys with respective modified oxide scales as interconnectors for SOFC. © 2019 by the authors.Russian Foundation for Basic Research, RFBR: 17-58-10006This research was funded by the Russian Foundation of Basic Research grant number 17-58-10006. The facilities of the shared access center "Composition of Compounds" of IHTE UB RAS were used in this work

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