Barium Cerate Research Articles

Electric Field-Assisted Pressureless Sintering of Ceramic Protonic Conductors

Gadolinium, yttrium and samarium-doped barium cerate (BCGd, BCY and BCSm, respectively) polycrystalline green pellets were submitted to electric field-assisted pressureless sintering experiments isothermally in the temperature range 800-1200oC under 100-200 V cm-1 electric fields, limiting to 1-5 A the electric current pulse amplitude. The sintering experiments were carried out in ambient atmosphere with the pellets positioned inside a vertical dilatometer furnace with Pt-Ir electrodes connected either to a power supply for applying the electric field or to an impedance analyzer for collecting [-Z''(ω) x Z'(ω)] data to evaluate the bulk and the grain boundary contributions to the electrical resistivity. Near full density was achieved in the sintered samples. The combined results of dilatometry and impedance spectroscopy measurements before and after flash sintering show substantial improvement of the electrical conductivity of flash sintered specimens. Joule heating is assumed to be the primary effect of the electric current pulse through the specimens. Improved grain-to-grain contact and the removal of depleted chemical species due to Joule heating at the space charge region are proposed, respectively, as the reasons for the almost total disappearance of the grain boundary component in the impedance diagrams and the improvement of the bulk electrical conductivity.

Electric Field-Assisted Pressureless Sintering of Ceramic Protonic Conductors

Gadolinium, yttrium and samarium-doped barium cerate pressed pellets were submitted to flash sintering experiments isothermally in the temperature range 800-1300oC under 200 V cm-1 electric field. The pellets were positioned inside a dilatometer furnace with Pt-Ir electrodes connected either to a power supply or to an impedance analyzer to evaluate the bulk and the grain boundary contributions to the electrical resistivity. Near full density was achieved in the sintered samples. The combined results of dilatometry and impedance measurements in conventionally and flash sintered specimens show substantial improvement of the electrical conductivity. Joule heating is assumed to be the primary effect for sintering. Improved grain-to-grain contact and the removal of depleted chemical species due to Joule heating at the space charge region are proposed, respectively, as the reasons for the decrease of the grain boundary component in the impedance diagrams and the improvement of the bulk electrical conductivity.

Structure and transport properties of the spark plasma sintered barium cerate based proton conductor

Abstract BaCe 0.7 Y 0.2 In 0.1 O 3–δ (BCYI) compositions were prepared by a modified Pechini method, following this the ceramic samples were consolidated using conventional sintering (CS) and spark plasma sintering (SPS) at 1250–1500 °C for 3–10 min. The structural and microstructural characteristics of the samples were determined using XRD, SEM and TEM. The total, bulk and grain boundary ionic conductivities were evaluated using the AC impedance method in dry air, wet air and dry Ar. It was shown that application of SPS in case of nanocrystalline BCYI allows to reduce the sintering time, and in case of microcrystalline BCYI application of SPS after CS allows to improve hardness and total conductivity through reduction of grain boundary resistance.

Fabrication and characterization of a double-layer electrolyte membrane for BaCeO3-based reversible solid oxide cells (RSOCs)

Barium cerate is viewed as one of the advanced high temperature proton conductors, while the chemical stability of such a material is vulnerable in air at high temperatures. In this work, a double-layer electrolyte membrane was prepared by dip-coating an additional layer of BaZr0.8Y0.2O3-δ (BZY2) on a BaCe0.8Y0.2O3-δ (BCY2) layer. The effects of the additional BZY2 layer on the phase composition, the electrolyte morphology and the electrical properties of whole electrolyte membrane have been systematically investigated. The results showed that the double-layer electrolyte membrane had a layered structure. The anode-supported single cell using this double-layer electrolyte exhibited a greatly improved chemical stability. These results demonstrated that this double-layer electrolyte had a great potential to be used as a stable proton conductor with an acceptable conductivity for reversible solid oxide cells (RSOCs).

Heat capacity on data of DSC calorimetry and thermodynamic functions of barium cerate doped by holmium and indium oxides in the temperature range of 200–700 K

For the first time the heat capacity of BaCe0.7Ho0.2In0.1O2.85 was measured in the temperature range of 200–700 K. Calorimetric experiments were performed using differential scanning calorimetry (DSC). We identified three areas where heat capacity was smoothly varying: 200–500, 500–573, and 573–700 K. The heat capacity in all these areas has been described by polynomials. Heat capacity of BaCe0.7In0.1Ho0.2O2.85 in the temperature range 200–500 K is well described by a polynomial: C p,m ° = 55.606 + 0.23556 T − 1.9546 × 10−4 T 2 − 1.2072 × 10−8 T 3. The heat capacity in the range of 500–573 K is well described by a polynomial of the form: C p,m ° = 429.55 − 0.66985 T + 4.0801 × 10−4 T 2 − 1.8387 × 107/T2. The heat capacity in the temperature range 573–700 K is well described by the equation: C p,m ° = 135.72 − 0.060195 T + 6.7994 × 10−5 T 2. The enthalpy increments (H m ° (T) − H m ° (298.15)) and entropy (S m ° (T)) were evaluated from heat capacity data (T = 200–700 K).

Regularities of oxygen and water thermal desorption from barium cerate doped by neodymium, samarium, and gadolinium

Processes of thermal desorption of oxygen molecules and water from BaCe1–x M x O3–δ, where M= Nd, Sm, and Gd, presintered in air at the temperature of 650°C are studied. It is found that oxygen is desorbed only from neodymium–doped barium cerate and is almost not evolved from barium cerate doped by samarium and gadolinium. The amount of desorbed oxygen features a square dependence on cationic doping by neodymium. At similar degrees of cationic doping, the amount of water desorbed from neodymium–doped barium cerate is always lower than that from the cerate doped by samarium and gadolinium. The obtained experimental data on thermal desorption and analysis of literature data served as a basis for the conclusion as to the mixed valency of neodymium Nd(III)–Nd(IV) in BaCe1–x Nd x O3–δ. In this case, at similar doping degrees x, the hydration degree of BaCe1–x Nd x O3–δ is lower and the oxygen index is higher than in BaCe1–x (Sm,Gd) x O3–δ. The differences become more pronounced at high degrees of cationic doping and must decrease at an increase in temperature.

Aggregatively stable suspensions of micrometer powders of doped barium cerate for electrophoretic deposition of thin-film coatings of solid-oxide fuel cells

Potentialities of the method of electrophoretic deposition of thin-film coatings based on micrometer powders of multidoped barium cerate BaCe0.8Sm0.19Cu0.01O3–δ (BCSCuO) and BaCe0.89Gd0.1Cu0.01O3–δ (BCGCuO) were considered. Micrometer powders of BCSCuO and BCGCuO were produced by the methods of solid-phase and citrate-nitrate syntheses, respectively. The dispersity, fraction composition, and electrokinetic potential of nonaqueous suspensions of these powders and the electrokinetic parameters of the electrophoretic deposition process were examined. An ultrasonic treatment and ultracentrifugation produced aggregatively stable suspensions of BCGCuO and BCSCuO micrometer particles in a mixed (70/30 vol %) isopropanol–acetyl acetone medium. These suspensions are characterized by high positive values of the zeta potential (+24 and +28 mV, respectively). Thin film coatings of the electrolyte materials BCSCuO and BCGCuO, which are of interest for the technology of medium-temperature solid-oxide fuel cells, were produced by the electrophoretic deposition onto a dense model cathode.

Effects of the Air Flow Rate and Electrolyte Thickness on the Durability of Yttria-doped Barium Cerate (BCY)-based Solid Oxide Fuel Cells

Effects of the Air Flow Rate and Electrolyte Thickness on the Durability of Yttria-doped Barium Cerate (BCY)-based Solid Oxide Fuel Cells

A study of the electrophoretic deposition of thin-film coatings based on barium cerate nanopowder produced by laser evaporation

The method of laser ablation of a target, followed by condensation, was used to obtain a weakly aggregated BCSO nanopowder from barium cerate. The dispersity, fraction composition of the nanopowder, electrokinetic potential of its nonaqueous dispersions, and electrokinetic parameters of the electrophoretic deposition process were determined. An ultrasonic treatment produced a stable suspension of the BCSO nanopowder in a mixed isopropanol–acetyl acetone medium (70/30 vol %). The suspension is characterized by a high and positive ζ-potential of +30 mV. The electrophoretic deposition onto a dense model cathode was used to obtain thin-film BCSO coatings that are of interest for the technology of solid-oxide fuel cells. The phase composition of the coating was examined. It was found that the successive annealings of the nanopowder at temperatures of 800–1400°C make it possible to reduce the content of unidentified crystalline phases in BCSO to trace levels (< 5 vol %).

Study of Synthesis and Crystal Structure of Barium Cerate at High Temperatures

Crystalline barium cerate was synthesized by oxalate coprecipitation from nitrates of barium and cerium [1]. The oxalate precursor prepared by chemical methods was calcined at different temperatures up to 950°C. The barium cerate was studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). X-ray diffraction investigation enables the determination of the phases that originate at different stages of synthesis and the crystal structure of final barium cerate, as well. From XRD patterns the average size of coherent regions was estimated by using Halder-Wagner method [2]. Both size and shape of crystallites were also studied by scanning electron microscopy. It was found that crystallites of barium cerate arise within the initial particles of the oxalate precursor.

Structural and morphological analysis of barium cerate electrolyte for SOFC application

AbstractGadolinium doped barium cerate (BCG) electrolytes Ce0.8Gd0.2O1.9+ xBaO (x = 0.1 and 0.4) were prepared by wet chemical method for the use in solid oxide fuel cells operating at intermediate temperatures (600 °C to 800 °C). The as-prepared powder sample was calcined at 900 °C. The calcination temperature was identified using differential scanning calorimetry (DSC) analysis. The orthorhombic perovskite phase formation was confirmed by XRD analysis. From TEM results, the particle size was found to be about 32 nm which is in a good agreement with XRD results. BCG nanoparticles were formed at lower sintering temperature due to using microwave furnace. By reducing the sintering temperature of solid electrolyte through microwave technique, the percentage of barium loss was successfully reduced and the prepared electrolyte can be a good choice for solid oxide fuel cells operating at intermediate temperatures.

Electrochemical Synthesis of Ammonia Using Proton Conducting Solid Electrolyte and Ru-doped BaCe0.9Y0.1O3-δ Electrode Catalyst

The effect of ruthenium (Ru) addition to yttrium doped barium cerate (BaCe0.9Y0.1O3-δ) used as a cathode catalyst for electrochemical synthesis of ammonia in a double chamber reactor cell has been studied. The BaCe0.9Y0.1O3- δ (BCY) and BaCe0.8Y0.1Ru0.1O3- δ (BCYR) powders were synthesized by a co-precipitation method. The Ni-BCY and Ni-BCYR cermet were employed as a cathode and the Ni-BCY cermet was also used as an anode. As an electrolyte, the BCY pellet was synthesized by the sintering at 1300 ºC with small amount of NiO as a sintering aid. Electrochemical synthesis of ammonia from dry nitrogen and wet hydrogen was conducted at 500 ºC using each fabricated cell. The maximum production rate of ammonia was 5.30 × 10-10 mol s-1 cm-2 at applied voltage of –0.6 V vs open circuit voltage using the Ni-BCYR|BCY(NiO)|Ni-BCY cell, indicating the positive effect of Ru addition to BCY.

Electrical properties and chemical stability of BaCe0.9Y0.1O3-BaWO4 composites synthesized by co-sintering and impregnation method

BaCeO3-based materials exhibit high electrical conductivity, however undergo degradation in CO2 and H2O containing atmospheres. In this work the BaCe0.9Y0.1O3-BaWO4 composites were prepared by co-sintering and via impregnation methods. The main motivation was to locate the barium tungstate on the grain boundary of Y-doped barium cerate and enhance the functional properties of final material comparing to single phase BaCe0.9Y0.1O3−δ. It was found that used synthesis procedures lead to two phase materials with doped barium cerate as the main phase and BaWO4 as the second one. The Electrochemical Impedance Spectroscopy (EIS) measurements performed at dry air, 100% HR air and 5% H2 in Ar atmospheres for temperature range 200–700°C allowed to determine the electrical conductivity of synthesized materials. Introduction of BaWO4 second phase into host BaCe0.9Y0.1O3−δ modified the electrical properties of bulk and grain boundary for materials synthesized by both co-sintering and for impregnation method. However, the effect of synthesis procedure was observed mainly for grain boundary contribution. Chemical resistance of composites toward CO2 and water vapour was estimated based on the CO2/H2O exposure test in which samples were exposed to CO2 and H2O rich atmosphere at 25°C for 700h. It was observed that chemical stability of composites in corrosive atmosphere was significantly higher comparing to single phase BaCe0.9Y0.1O3−δ regardless to the synthesis procedure.

Fabrication and characterization of a tubular ceramic fuel cell based on BaZr0.1Ce0.7Y0.1Yb0.1O3-δ proton conducting electrolyte

A proton conducting anode supported tubular fuel cell is fabricated in this research using the highly proton conductive BaZr0.1Ce0.7Y0.1Yb0.1O3-δ (BZCYYb) electrolyte. The cell is in a Ni-BZCYYb/BZCYYb/LSCF-BZCYYb configuration consisting of a support, electrolyte and cathode with thicknesses of 680 μm, 25 μm and 90 μm, respectively. The cell delivers maximum power densities of 331, 362 and 416 mW/cm2 at 600, 650 and 700 °C, respectively. AC impedance spectroscopy results show values of 0.94 Ω.cm2, 0.73 Ω.cm2, and 0.60 Ω.cm2 for total resistance at the corresponding temperatures while the major resistance contributor is the ohmic resistance. The Ni-BZCYYb anode microstructure shows detachment of Ni and the BZCYYb in most regions as well as pores inside the Ni grains. Despite the low anode porosity (25%), the cell gives a very low concentration polarization value (0.05 Ω.cm2) indicating that the fuel gas could readily diffuse into the microstructure. This might be attributed to water forming on the cathode side, which masks the necessity of having a high porosity anode. The cell fails when tested under CO:H2 of 1:1 at 700 °C due to significant carbon (graphite) formation indicating that proton conductors based on barium cerates are not appropriate choices for application under hydrocarbon fuels.

Mass spectrometric study of thermodynamic properties of BaO-CeO2. The formation enthalpy of BaCeO3 (solid)

Barium cerate with additions of rare-earth or 3-d metal oxides is widely used for production of solid electrolytes, ionic, and electron–ionic conductors. Knudsen effusion mass spectrometry was used to study vaporization processes and thermodynamic properties of solid solutions in the BaO – CeO2 system at the temperature 2000 K. Ba, BaO, CeO and CeO2 were found as the main vapor species over the samples studied. Activity values and Gibbs energy of BaO and CeO2 in the samples studied were calculated. The activities of barium and cerium oxides in the concentration range of the homogeneous melt (70–32 mol. % of BaO) and in the region from 32 to 5 mol % of BaO (solid solution of CeO2 + liquid) have low negative deviations from the ideal case. The determined value of the standard formation enthalpy of solid barium cerate is equal to −1692 ± 17 kJ/mol.

Synthesis, stability and conductivity of SrCe0.8-xZrxY0.2O3-δ as electrolyte for proton conducting SOFC

Strontium cerate (SrCeO3) exhibits proton conductivity in humidified atmosphere at elevated temperature. However this material is unstable in CO2 and H2O atmosphere. Thought its proton conductivity is lower than barium cerate (BaCeO3) there is scope to improve its stability, sinterability and ionic conductivity by substituting suitable cations at B-site. SrCe0.8-xZrxY0.2O3-δ (SCZY, with x=0.0, 0.2, 0.4, 0.6 and 0.8) powders were synthesized by sol gel route. Lattice parameters were generated from powder XRD data and it was found that with increase in Zr content the cell volume reduces. Chemical stability of sintered SCZY samples was evaluated in 100% CO2 using TG-DTA up to 1173K and also in boiling water. Zirconium doped samples exhibit enhanced chemical stability in presence of carbon dioxide and boiling water, with x≥0.4 compositions having no effect of both the reactive gases. Proton conductivity of SCZY samples were measured in moist N2 atmosphere. Activation energy for proton conduction was also evaluated.

Síntese do cerato de bário pelo método de complexação combinando EDTA-citrato e avaliação catalítica na oxidação do monóxido de carbono testada em reator de leito fixo

Resumo A perovskita de cerato de bário foi sintetizada com base no método de complexação combinando EDTA-citrato e suas propriedades catalíticas testadas na reação de oxidação do monóxido de carbono em um reator de leito fixo variando a vazão de alimentação (50 e 100 mL.min-1) e a temperatura (100 a 550 °C). A fase cristalina de interesse foi obtida com tamanho de cristalito de 133 nm, junto com uma pequena quantidade de BaCO3 (3%). Quando sintetizado pelo método de complexação combinando EDTA-citrato, o cerato de bário apresenta um formato esférico irregular com aglomerados de diferentes tamanhos e com a presença de poros de diferentes tamanhos distribuídos aleatoriamente, sendo sua área superficial específica igual a 2,61 m2.g-1. Na vazão de 50 mL.min-1 ocorreu maior conversão quando comparado com a de 100 mL.min-1, sendo mais evidente entre 300 e 400 °C. Além disso, na vazão de 50 mL.min-1 ocorreu conversão total de CO em CO2 a 400 °C, enquanto que em 100 mL.min-1 a conversão foi de aproximadamente 60%. Com o uso da perovskita como catalisador o processo de oxidação é completo a 400 °C, enquanto que na reação sem catalisador a conversão completa é alcançada somente a 550 °C. Apesar da sua pequena área superficial, o BaCeO3 é altamente reativo na oxidação do monóxido de carbono.

Electrochemical and Thermal Catalytic Syntheses of Ammonia over Yttrium-Doped Barium Zirconate and Cerate Perovskites Supported Ruthenium Catalysts

To resolve a global serious problem on energy consumption by human, the development of various new processes which a renewable energy and a surplus electric power generated from thermal and nuclear power plants are converted to the energy easy to handle is required. As one possible process, a technological process that electrical energy is convert to a chemical substance, so-called energy carrier, is raised. As a candidate of energy carrier, methylcyclohexane (MCH), ammonia (NH3), hydrogen peroxide (H2O2), formic acid (HCOOH) are considered in recent years. In the present work, we have paid attention to NH3. In other words, it is an electrolysis process to produce NH3 from the nitrogen contained in air and the hydrogen supplied by the electrolysis of water. For this electrochemical synthesis process, H2O or H2 is oxidized to proton at the anode, and proton is transported through the proton conducting electrolyte to the cathode. And then, N2 is reacted with proton and reduced to NH3 at the cathode. The lower the operation temperature, the more effective the electrolysis synthesis process of ammonia from N2 and H2O, compared with a conventional Harber-Bosch process. However, the development of solid electrolyte exhibiting high conductivity at lower temperature and the selection of electrode catalyst materials and electrode design to improve the reaction rate of ammonia synthesis for the cathode are required. Therefore, in this study, we have focused on the Ru based catalyst which is well known to be excellent catalysts for thermal catalytic synthesis of ammonia. Furthermore, Ba-Zr-Y and Ba-Ce-Y perovskite-type oxides exhibiting high proton conductivity have been used as a support material to improve the cell performance for electrochemical ammonia synthesis. Firstly, the Ru/Ba-Zr-Y and/or Ba-Ce-Y perovskites solid catalyst was prepared, and its thermal catalytic property for ammonia synthesis was evaluated using a fixed bed flow reactor. As results of comparison tests, Ru/Ba-Zr-Y catalyst showed higher activity than Ru/Ba-Ce-Y catalyst. Furthermore, it was found that an addition of 10wt% of Y component to BaZrO3 perovskite enhances the catalytic performance significantly. And noted that Ru/Ba-Zr-Y catalyst exhibited higher performance than a conventional Ru-Cs+/MgO catalyst. Based on various characterization, we consider that electron transfer from Ba-Zr-Y perovskite to Ru species enhances the dissociation of N-N bond, leading to the high activity for ammonia synthesis. Additionally, in the present work, we have studied the effect of current loading to the catalyst on the catalytic performance for ammonia synthesis to evaluate the applicability of Ru/Ba-Zr-Y catalyst to an electrode catalyst. Acknowledgments This work was supported by CREST, Japan Science and Technology Agency.

In Situ X-Ray Absorption Spectroscopic Studies on Proton Conduction Mechanism of Zr, Y Co-Doped Barium Cerate for Organic Hydride Fuel Cell Operating at Intermediate Temperature

Introduction A new type of fuel cell utilizing organic hydrides as a fuel, such as methylcyclohexane – toluene system attracts a lot of attention because they are good hydrogen career from the point of view of safety, easy handling, and high energy density. This type of fuel cell using proton using proton conductive oxide electrolyte is required to operate at intermediate temperature (400°C) from the perspective of reaction efficiency and thermal decomposition of organic hydride. In order to develop the fuel cell system, proton conductive electrolyte with higher conductivity and chemical stability is needed, and proton conducting perovskite oxides are anticipated to achieve above requirements. Among these perovskite oxides, BaCe0.9-xZrxO3-δ has been investigated widely due to its high proton conductivity and chemical stability. [1] However, further enhancement of proton conductivity is required to apply the material for fuel cell application, to investigate the proton conducting mechanism. In this study, we analyzed the fine structure of BaCe0.9-xZrxO3-δ by in situX-ray absorption spectroscopy (XAS), and reveal its proton conducting mechanism. Experimental BaCe0.9-xZrxO3-δ was prepared by the solid-state reaction method. Stoichiometric BaCO­­­­­­­3, CeO­2, ZrO2, and Y2O3 powders were mixed by ball milling with ethanol at 400 rpm for 10 hours. After drying, they were calcined at 1400°C for 10 hours in air, and then grounded by ball milling again with ethanol for 20 hours. Dried powder was pressed at 120 kg/cm2 into cylindrical pellets. These pellets were vacuum packed and hydrostatic pressed at 200 MPa for 5 min. They were embedded in the same composition powder and sintered at 1700°C for 10 hours in air. After sintering, the pellets were polished with a diamond slurry by a grinding machine. For conductivity measurements, Pt paste was applied to both phases of the pellets. The measurement was carried out under wet 3% H2/N2, wet 21%O2/N2 (pH2O = 1.7×103 Pa), and dry 21%O2/N2. The XAS measurement was carried out at BL01B1 of SPring-8. Two kinds of samples for X-ray absorption measurements were prepared as follows. For ex situ measurements, sintered pellets were grounded by an alumina mortar and mixed with BN powder. Obtained powder was molded into cylindrical pellets by uni-axial press. For in situ sample, these pellets were polished and their thickness became 100 mm. For in situ XAS measurements, the temperature range was room temperature to 600°C, and the atmosphere was wet 3% H2/N2 (pH2O = 1.7×103 Pa) and dry 21%O2/N2. Results and Discussion The metal cation – oxide distance were calculated by XRD and EXAFS analysis. Ce-O and Y-O distance were significantly longer than average M-O distance. It implies that in BaCe0.9-xZrxO3-δ­ structure, CeO6 and YO6 octahedral are tilting due to their larger ionic radii than Zr4+. These tilting sites contribute to reduction of symmetry in the crystal structure. At high temperature, Ce-O and Zr-O distance became drastically longer. Increase of the M-O length mitigates the repulsion between proton and metal cation, promoting the proton conductivity. Ce-O distance was shortened in wet 3% H2 atmosphere. It implies that protonic defect is stabilized around Ce4+because of its low electronegativity. This work revealed the relation between fine structure of proton conducting perovskites and their proton conductivity, and showed the guide of material design with higher proton conductivity. REFERENCES [1]K. Katahira, Y. Kohchi, T. Shimura and H. Iwahara, Solid State Ionics, 138, 91 (2000) [2] A. Longo, F. Giannici, A. Balerna, C. Ingrao, F. Deganello,and A. Martorana, Chem. Mater., 18, 5782 (2006).

Electrochemical Synthesis of Ammonia Using Proton Conducting Solid Electrolyte and Ru-Doped BaCe0.8Y0.1Ru0.1O3- d Electrode Catalyst

Introduction Recently, the demands for the renewable energy such as water power, wind power, and solar power have increased around the world. These energy production is affected by the climate, and thus, stable power supply is difficult. In addition, the development of technologies of energy storage and transportation is important for effective utilization of the surplus power. Ammonia is a chemical material produced massively and is used in fertilizer and industrial process such as organic synthesis and nitrate acid. In the recent years, ammonia has been paid attention as an energy carrier substance because its hydrogen content and energy density are significantly high. The current process of ammonia production is a Haber-Bosch process. This process, however, requires the high pressure and temperature condition. Thus, a new synthesis process need to be developed. The electrochemical synthesis of ammonia as shown in Fig. 1 is considered to be an effective process of ammonia synthesis from N2 and H2O and/or H2. However, the formation rate of ammonia for the electrochemical synthesis has not been achieved at the demanded level; thus, there are needed to improve ammonia synthesis performance of electrode catalyst and ion conductivity of electrolyte. Therefore, in the present work, to improve the electrochemical synthesis process of ammonia, we have studied the effect of Ru-doping into yttrium-doped barium cerate as an electrode catalyst. Experimental The proton conducting BaCe0.9Y0.1O3- d (BCY) solid electrolyte was synthesized by a co-precipitation method. The BCY powder was mixed with a small amount of NiO as a sintering aid. The resultant powder was uniaxially pressed at 2 MPa into a pellet, followed by cold isostatic pressing at 200 MPa. The pellet was calcined at 1300 ºC for 12 h to obtain BCY pellet. The BaCe0.8Y0.1Ru0.1O3- d (BCYR) was also prepared by the co-precipitation method. The BCY and BCYR powders were mixed with isometric NiO powders by a planetary ball milling, followed by the calcination at 1200 ºC for 5 h. The NiO-BCYR slurry mixed with polyethylene glycol was pasted on one side of the BCY pellet as the cathode, and then, the sample pellet calcined at 1300 ºC for 5 h. After that, The NiO-BCY slurry mixed with polyethylene glycol was pasted on the other side of the pellet as the anode, followed by the calcination at 1300 ºC for 5 h. The powders and pellet were analyzed using X-ray diffraction (XRD), X-ray fluorescence (XRF) and transmission electron microscopy (TEM). Electrochemical synthesis of ammonia was conducted using the single cell fabricated at 500ºC. A gaseous mixture of N2 and Ar was fed into the working and a gaseous mixture of H2 and Ar was fed into the counter. Before the measurement, the Ni-BCY and Ni-BCYR electrodes were well reduced at 600 ºC for 2 h to activate the electrode. Results and discussion According to XRD analysis, both BCY and BCYR samples were assigned to perovskite-type oxides. In addition, Ru component is considered to be doped into BCY, evidenced from XRF and XRD analyses. As a result of electrolysis experiment, ammonia was synthesized electrochemically on the Ni-BCYR electrode. The maximum rate of ammonia formation was ca. 2.0 × 10-10 mol s-1 cm-2 at -600 mV of applied voltage. TEM images indicate that Ru particles existed on the Ni-BCYR surface after the reduction. Therefore, the reason of improvement is probably that the Ru particles on the electrode catalyzes N-N bond breaking. Faradaic efficiency of the ammonia formation was achieved ca. 3.0%, which means that proton on the cathode is mainly converted to hydrogen molecule. Conclusion Electrochemical synthesis of ammonia was carried out using proton conducting solid electrolyte from N2 and H2. Ammonia formation rate was improved by using Ni/BCYR electrode, because doping of Ru component enhances ammonia formation reaction at the cathode. The maximum rate of ammonia formation was ca. 2.0 × 10-10 mol s-1 cm-2 at 500 ºC. Acknowledgments This work was supported by CREST, Japan Science and Technology Agency. Reference [1] S. Giddey, S.P.S Badwal, A Kulkarni, Int. J. Hydrogen Energy 38 (2013) 14576-14594. [2] A. Skodra, M. Stoukides, Solid State Ionics 180 (2009) 1332-1336. [3] H. Iwahara, Solid State Ionics 77 (1995) 289-298. Figure 1