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This paper deals with the fabrication and electrochemical study of a high temperature solid electrolyte supporting cell operating as SOFC (Solid Oxide Fuel Cell) and SOEC (Solid Oxide Electrolysis Cell). The cell is based on a dual membrane (DM) electrolyte design, advantageously separating the cell into three different chambers: hydrogen side, oxygen side, and dual membrane (DM), where HO production or splitting takes place in SOFC or SOEC mode respectively. The supporting electrolyte consists of a dense/porous/dense tri-layer, exclusively made of BaCeYO (monolithic design), which is a mixed anionic-protonic conductor. The assembly was fabricated by tape casting, adding pore formers to control porosity. The cell was then electrochemically studied under different operating conditions of temperature, overpotentials and gas feeding, either in SOFC and SOEC mode. From the results presented here, it can be observed that, in spite of dense and thick electrolyte layers and platinum electrodes, the electrochemical study of the cell showed: (i) promising power density, (ii) interesting SOFC/SOEC operating mode reversibility, (iii) proved HO production in the porous dual membrane when the cell operates as a fuel cell, and proved splitting of the HO molecules contained in the porous dual membrane when the cell operates as an electrolyser. Investigations of cell performance degradation were also conducted. [ABSTRACT FROM AUTHOR]

Abstract: The dual cell concept is a novel design for solid oxide fuel cells operating at intermediate temperature. The cell comprises a series of five layers with different compositions, alternating two dense electrolytes and three porous layers, i.e. the outer electrodes and a central membrane. The dual cell concept makes it possible to separate the compartment for water formation from both fuel and oxidant chambers. Such a three-chamber configuration gives many advantages related to fuel dilution, materials corrosion, and reversibility between fuel cell and electrolyser operational modes (SOFC/SOEC) at high temperature. Dual conductivity (protonic/anionic) can be achieved by joining two dense BaCe0.85Y0.15O3–δ (BCY) and Ce0.85Y0.15O2–δ (YDC) electrolytes through a porous ceramic central membrane made up of both materials. Complete anode-supported dual cells have been fabricated by a combination of pressing, casting, printing, wet spraying, and plasma spraying techniques. Electrochemical tests carried out by impedance spectroscopy showed the feasibility of the concept and successful reversible operation of the dual cell. The fabrication route, the microstructural and electrochemical testing results are reported in this work, and partially compared to simulated results from an electrochemical model developed describing the dual cell concept. [Copyright &y& Elsevier]

Aim of this work is to present, for the first time, the use of Dynamic Mechanical Analysis as a tool to characterize the thermo-mechanical behavior of green tapes defining the process conditions for the subsequent lamination step. This method was applied on tapes of protonic conductors, key-materials for different applications in the energy sector, from gas separation membranes to solid oxide fuel cells and electrolyzers. The pore former (rice starch) content was found to considerably affect the thermomechanical behavior (elastic and storage moduli, elongation to break, viscosity) of the tape and therefore the lamination process. The temperature required for a proper lamination increases from 50 up to 75 °C passing from the system without rice starch to the one with the highest pore former amount. This work identifies for the first time an optimal lamination viscosity (1010 Pa s), regardless the tapes formulation, required for a suitable adhesion among the layers. [ABSTRACT FROM AUTHOR]

Lanthanum doped strontium titanate–gadolinium doped cerium oxide (LST-GDC) anodic layers are sintered in air and further reduced in-situ at low temperature (750 °C) avoiding usually performed pre-reduction treatment at high temperature. The influence of various milling techniques and of powders with different specific surface area, on the microstructures of screen-printed anodes, is investigated. The combination of milling and sonication processes is efficient in reducing aggregation of the anode powders. The anode performance is improved when a planetary milling step is involved in the preparation of the screen printing inks. The use of gadolinium doped cerium oxide with high specific surface area decreases the polarization resistance. The rate of hydrogen oxidation is also enhanced by increasing porosity. [ABSTRACT FROM AUTHOR]

In the present contribution, we combine modeling and experimental study of electrochemical hydrogen oxidation at an alternative perovskite based mixed-conducting SOFC anode. Composite electrodes were produced by conventional wet ceramic processing (screen printing – spraying) and sintering on YSZ electrolytes (La 0.1 Sr 0.9 TiO 3-α -Ce 1-x Gd x O 2-α |YSZ) with different compositions and microstructure, and were electrochemically characterized using symmetrical button-cells configuration. An elementary kinetic model was developed and applied to explore the performance of LST based SOFC anode. A detailed multi-step heterogeneous chemical and electrochemical reaction mechanism was established taking into account transport of ions in all ionic phases, and gas transport in channel and porous media. It was found that heterogeneous chemistry at LST surface has capacitive behavior that alters the impedance spectra. In addition, surface charge-transfer reaction, which describes partial oxygen ionization, caused impedance feature and is rate-limiting at high temperature. The gas transport in the supply chamber (gas conversion) is significant only at moderate temperatures. [ABSTRACT FROM AUTHOR]