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Yttrium-doped barium zirconate is a commonly used electrolyte material for Protonic Ceramic Fuel Cells (PCFC) due to its high protonic conductivity and high chemical stability. However, it is also known for its poor sinterability and poor grain boundary conductivity. In this work, in response to these issues, reactive magnetron sputtering was strategically chosen as the electrolyte deposition technique. This method allows the creation of a 4 µm tick electrolyte with a dense columnar microstructure. Notably, this technique is not widely utilized in PCFC fabrication. In this study, a complete cell is elaborated without exceeding a sintering temperature of 1350 °C. Tape casting is used for the anode, and spray coating is used for the cathode. The material of interest is yttrium-doped barium zirconate with the formula BaZr0.8Y0.2O3−δ (BZY). The anode consists of a NiO-BZY cermet, while the cathode is composed of BZY and Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSFC) in a 50:50 weight ratio. The electrochemical impedance spectroscopy analysis reveals a global polarization resistance of 0.3 Ω cm2, indicating highly efficient interfaces between electrolytes and electrodes. [ABSTRACT FROM AUTHOR]

The performances of Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC) anode-supported planar cells with a 10 cm2 active surface were studied versus the combination of cathode thickness and the presence of an Anode Functional Layer (AFL). The temperature range was 500 to 650 °C, and Gd0.1Ce0.9O2−x (GDC) was used as the electrolyte material, Ni-GDC as the anode material, and La0.6Sr0.4Co0.2Fe0.8O3−d (LSCF48) as the cathode material. The power density, conductivity, and activation energy of different samples were determined in order to investigate the influence of the cathode thickness and AFL on the performance. These results showed an improvement in the performances when the AFL was not present. The maximum power density reached 370 mW·cm−2 at 650 °C for a sample with a cathode thickness of 50 µm and an electrolyte layer that was 20 µm thick. Moreover, it was highlighted that a thinner cathode layer reduced the power density of the cell. [ABSTRACT FROM AUTHOR]

In the last decades, several works have been carried out on solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) technologies, as they are powerful and efficient devices for energy conversion and electrochemical storage. By increasing use of renewable sources, a discontinuous amount of electricity is indeed released, and reliable storage systems represent the key feature in such a future energy scenario. In this context, systems based on reversible solid oxide cells (rSOCs) are gaining increasing attention. An rSOC is an electrochemical device that can operate sequentially between discharging (SOFC mode) and charging (SOEC mode); then, it is essential the electrodes are able to guarantee high catalytic activity, both in oxidation and reduction conditions. Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) has been widely recognized as one of the most promising electrode catalysts for the oxygen reduction reaction (ORR) in SOFC technology because of its astonishing content of oxygen vacancies, even at room temperature. The purpose of this study is the development of BSCF to be used as anode material in electrolysis mode, maintaining enhanced energy and power density. Impregnation with a La0.8Sr0.2MnO3 (LSM) discrete nanolayer is applied to pursue structural stability, resulting in a long lifetime reliability. Impedance spectroscopy measurements under anodic overpotential conditions are run to test BSCF and LSM-BSCF activity as the electrode in oxidation mode. The observed results suggest that BSCF is a very promising candidate as an oxygen electrode in rSOC systems. [ABSTRACT FROM AUTHOR]

In this work, BaZr 0.85 Y 0.15 O 3-δ was elaborated by a continuous hydrothermal process in supercritical conditions (410 °C/30.0 MPa). X-Ray diffraction, Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy analysis allowed to propose a description of the formation mechanism for this oxide in supercritical water. This mechanism consists in the precipitation of core-shell nanoparticles in which, the core is a Ba-deficient perovskite and the shell an oxyhydroxide species of Y and Zr. Then, Ba2+, Zr4+ and Y3+ are incorporated in the perovskite from the solution and from the shell. After an annealing treatment at 1000 °C for 1 h to homogenize the composition, the powder was pressed into a pellet and sintered at 1550 °C for 5 h to analyze its electrochemical properties. The total conductivity of this oxide is 2.5 × 10-3 S cm-1 at 600 °C in wet H 2 (3% H 2 O). Furthermore, electrochemical impedance spectroscopy measurements showed that its conduction is mainly protonic at a temperature lower than 575 °C. [ABSTRACT FROM AUTHOR]

Abstract: The need of interconnect to separate fuel and oxidant gasses and connect individual cells into electrical series in a SOFC stack appears as one of the most important point in fuel cell technology. Due to their high electrical and thermal conductivities, thermal expansion compatibility with the other cell components and low cost, ferritic stainless steels (FSS) are now considered to be among the most promising candidate materials as interconnects in SOFC stacks. Despite the formation at 800°C of a protective chromia Cr2O3 scale, it can transform in volatile chromium species, leading to the lost of its protectiveness and then the degradation of the fuel cell. A previous study demonstrated that in air, the application by metal organic chemical vapour deposition (MOCVD) of a nanometric layer of reactive element oxides (La2O3, Y2O3, Nd2O3) on FSS improved both the electrical conductivity and the oxidation resistance. The beneficial effect of this type of coating on FSS on oxidation resistance in H2/H2O (anode side) is not yet completely understood. So, the goal of this study is to apply reactive element oxide coating (La2O3, Y2O3, Nd2O3) on two FSS (a commercial, Crofer22APU, and a model, Fe30Cr) and to perform oxidation tests in H2/10%H2O. Kinetics was registered for 100h at 800°C and the corrosion products were characterized by SEM, EDX, TEM, SIMS and XRD. [Copyright &y& Elsevier]

The present work describes a novel process for the elaboration of a ceramic material. Y-doped barium zirconate, an electrolyte material for Protonic Ceramic Fuel cell, was synthesized by a continuous hydrothermal process in supercritical conditions (410 °C/30.0 MPa) using nitrate precursors and NaOH reactants. The use of supercritical water allowed the formation of particles of about 50 nm in diameter with a narrow size distribution. X-Ray Diffraction examination revealed that a major perovskite phase with few BaCO 3 and YO(OH) impurities was obtained. BaCO 3 is assumed to form due to faster kinetics than Y-doped BaZrO 3 resulting in a Ba-deficient perovskite phase. The Ba-deficiency limits the incorporation of yttrium into the perovskite structure. However, a thermal treatment at 1000 °C for 1 h allows to homogenize the composition and thus to obtain the compound Ba 1.01 Zr 0.85 Y 0.15 O 3-δ. [ABSTRACT FROM AUTHOR]

Abstract: The main drawback of Ni/YSZ anode supports for solid oxide fuel cell application is their low tolerance to reducing and oxidizing (RedOx) atmosphere changes, owing to the Ni/NiO volume variation. This work describes a structured approach based on design of experiments for optimizing the microstructure for RedOx stability enhancement. A full factorial hypercube design and the response surface methodology are applied with the variables and their variation range defined as: (1) NiO proportion (40–60wt% of the ceramic powders), (2) pore-former proportion (0–30wt% corresponding to 0–64vol.%), (3) NiO particle size (0.5–8μm) and (4) 8YSZ particle size (0.6–9μm). To obtain quadratic response models, 25 different compositions were prepared forming a central composite design. The measured responses are (i) shrinkage during firing, (ii) surface quality, (iii) as-sintered porosity, (iv) electrical conductivity after reduction and (v) expansion after re-oxidation. This approach quantifies the effect of all factors and their interactions. From the quadratic models, optimal compositions for high surface quality, electrical conductivity (>500Scm−1 at room temperature) and RedOx expansion (<0.2% upon re-oxidation) are defined. Results show that expansion after re-oxidation is directly influenced by the sample porosity whereas, surprisingly, the NiO content, varied between 40 and 60wt%, does not show any impact on this response. [Copyright &y& Elsevier]

Abstract: Ceria-based catalysts have been assessed for internal methane reforming at low temperature (400–600°C) in Solid Oxide Fuel Cell (SOFC). A combinatorial library of 15 metal (Cu, Pt, Ni) supported ceria was prepared using wet impregnation method. The ceria-based oxides are undoped or doped with metal transition (Zr) or by rare earth (Gd or Pr). The effect of the metal, the dopant and the surface area on the catalytic performances was investigated in high-throughput manner using a 16-parallel reactor. The catalysts were assessed in two different conditions, (i) in CH4 rich condition and (ii) in model reformate condition. Catalytic performances are very metal depending. In dry conditions, Cu-based catalysts do not produce H2 whereas Ni-catalysts are very active despite low carbon balance. However, when water and CO2 are added in the feed, the nature of the ceria plays an important role in the catalytic performances. At low temperature (T <550°C), most of Ni/ceria catalysts are not active under reformate conditions at low temperature while Pt catalysts appear more robust with respect to the conditions. From unsteady state parallel studies, we suggest that surface hydroxyl on ceria are the active species. [ABSTRACT FROM AUTHOR]

Abstract: (La0.8Sr0.2)(Mn1− y Fe y )O3±δ films with y =0, 0.2, 0.5, 0.8 and 1, a few hundred nanometers thick, were deposited onto polycrystalline yttria-stabilized zirconia YSZ by a magnetron co-sputtering technique using individual targets of La0.8Sr0.2MnO3 and La0.8Sr0.2FeO3. The deposition parameters, substrate temperature and gas pressure, were studied by scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray diffraction and interferential microscopy for their effects on the morphological, chemical, topographic and crystallographic properties of films and YSZ-film interfaces. (La0.8Sr0.2)(Mn1− y Fe y )O3± δ thin films were found to be homogeneous, dense and crystallized in the perovskite structure after deposition at 600 °C. Profilometry by secondary ion mass spectrometry and observations by Auger electron spectrometry after selective dissolution of the films were also used to investigate both morphology and quality of the YSZ-film interface after deposition. [Copyright &y& Elsevier]