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We report on the systematic examination of the redox behavior of a novel metal-supported SOFC cell type based on a porous Cr/Fe support and a thin YSZ-electrolyte layer applied by PVD methods. The oxidation of the Ni catalyst at the anode and the subsequent damage to the fuel cell microstructure is one of the main contributions to degradation of an SOFC. Our cell concept was tested for tolerance to cyclic oxidation and reduction of the anode, employing gravimetric and electron microscopy methods. The effects of redox cycling on the microstructure are examined and compared to corresponding results from state-of-the-art anode-supported SOFCs.

Benefiting from a strong cooperation with Forschungszentrum Jülich, Karlsruhe Institute of Technology (KIT), and AVL List GmbH respectively, Plansee has been focusing on the development and industrialization of metal-supported SOFC and components for mobile applications. In the scope of some challenging development projects a novel MSC configuration and a first pilot fabrication route could be demonstrated successfully. Currently, the work is ongoing towards a continuous and reliable manufacturing of standard cells as well as the demonstration of system-relevant stack tests. This paper gives an overview about the latest results in cell and stack development as well as about the manufacturing route for cost-effective metal-supported cells.

Most sex differences in phenotype are controlled by gonadal hormones, but recent work on laboratory strain mice that present discordant chromosomal and gonadal sex showed that sex chromosome complement can have a direct influence on the establishment of sex-specific behaviours, independently from gonads. In this study, we analyse the behaviour of a rodent with naturally occurring sex reversal: the African pygmy mouse Mus minutoides, in which all males are XY, while females are of three types: XX, XX* or X*Y (the asterisk represents an unknown X-linked mutation preventing masculinisation of X*Y embryos). X*Y females show typical female anatomy and, interestingly, have greater breeding performances. We investigate the link between sex chromosome complement, behaviour and reproductive success in females by analysing several behavioural features that could potentially influence their fitness: female attractiveness, aggressiveness and anxiety. Despite sex chromosome complement was not found to impact male mate preferences, it does influence some aspects of both aggressiveness and anxiety: X*Y females are more aggressive than the XX and XX*, and show lower anxiogenic response to novelty, like males. We discuss how these behavioural differences might impact the breeding performances of females, and how the sex chromosome complement could shape the differences observed.

Scientific Reports 6: Article number: 22881; published online: 11 March 2016; updated: 22 April 2016 The original version of this Article contained an error in the title of the paper, where the word “Occurring” was incorrectly given as “Occuring”. In addition, the Acknowledgements section was incomplete.

The current paper reports the details of challenges and progress in the joint project on development of metal supported solid oxide fuel cells and stacks by the teams of German Aerospace Center (DLR), ElringKlinger, Sulzer Metco and Plansee. An account of the materials is given followed by the advances in the processing techniques which include alternative plasma spraying and colloidal spraying. Improvement in the cell and stack design is then discussed followed by challenges faced during stack building and operations and solution implemented.

The demand for clean and green energy has raised the consumption of hydrogen continuously during the last years. Hydrogen is most economically produced in large scale systems by methane steam reforming followed by pressure swing adsorption (PSA). However, with a rising demand for small-scale production of hydrogen, and as down-scaling to smaller PSA-systems (

The elaboration of the last generation of metal supported IT-SOFCs by physical surface deposition processes is really challenging. Atmospheric Plasma Spraying (APS) process appears to be well adapted to build the porous anode layer [1] whereas Reactive Magnetron Sputtering (RMS) technique is suitable to deposit thin and dense layer. In the present work, we have deposited a Ni-YSZ anode by APS on porous metallic supports (ITM) produced by PLANSEE SE. Then, a thin YSZ electrolyte film was applied by RMS. Details about the elaboration of the half cell could be found in a previous work [2]. Various strategies have been followed to deposit the cathode layer on top of the previously deposited anode and electrolyte coatings. The Mixed Ionic and Electronic Conductor K2NiF4 structured material presents interesting electrocatalytic properties [3] allowing its utilization as cathode layer. Recent studies deal with the use of thin layers as cathodes in IT-SOFCs [4]. Therefore, RMS process was also evaluated to deposit a thin La2NiO4 layer (LNO) according to already optimized operating conditions [5]. In order to compare the efficiency of this dense layer as an individual cathode or a bonding cathode layer, the complete IT-SOFC building was elaborated by replacing and/or adding a screen-printed La2NiO4 coating (SP LNO). This layer was developed and optimized in ICMCB laboratory and has shown interesting performances in LNO/GDC/LNO half cells [6]. GDC diffusion barrier layers were deposited by RMS in order to limit the deleterious interaction between active layers in use. Different cells with RMS LNO, SP LNO, and RMS LNO + SP LNO were produced and tested in a complete cell bench at 973 K. Impedance Spectroscopy and Voltametry measurements were performed on these samples to assess their electrochemical characteristics and performances. The electrochemical resistances of these cells are too high and their performances are still lower than the literature ones. Analyses of the samples after the electrochemical tests permit to identify the density of the RMS LNO layer as the limiting factor lowering the cathodic electrochemical reaction. The sintering step performed on complete cells with SP LNO deteriorates the layers deposited by RMS as well as the metallic support explaining these performances. Nevertheless, using LNO bonding layer manufactured by RMS seems to be an interesting way to improve the polarization resistance of the cell. References [1] D. Stöver, D. Hatiramani, R. Vaβen, R. Damani, Surface and Coatings Technology 201 (2006) 2002-2005. [2] J. Fondard, P. Bertrand, A. Billard, S. Skrabs, Th. Franco, G. Bertrand, P. Briois, Electrochemical Society Transactions 57 (2013) 673-682. [3] E. Boehm, J.-M.Bassat, P.Dordor, F. Mauvy, J-C.Grenier, Ph. Stevens, Solid State Ionics 176 (2005) 2717 – 2725. [4] I. Garbayo, V; Esposito, S. Sanna, A. Morata, D. Pla, L. Fonseca, N. Sabaté, A. Taracon, Journal of Power Sources 248 (2014) 1042-1049. [5] J. Fondard, A. Billard, G. Bertrand, P. Briois, Solid State Ionics 265 (2014) 73-79. [6] B. Philippeau, F. Mauvy, C. Mazataud, S. Fourcade, J-C. Grenier, Solid State Ionics 249-250 (2013) 17-25.

At the German Aerospace Center (DLR) in Stuttgart, a lightweight stack design for mobile applications was developed in cooperation with the automotive industry (BMW, Munich; Elring-Klinger, Dettingen; Rhodius, Weissenburg). This concept is based on the application of stamped metal sheet bipolar plates into which porous metallic substrate-supported cells (MSCs) are integrated. The paper concentrates on the one hand on the investigation of plasma sprayed button cells with a diameter of 48mm on porous metallic substrates during reduction/oxidation and thermal cycling. On the other hand, another focus lies in the electrochemical testing of short stacks in the cassette arrangement. The microstructure of the cells was characterized by optical microscopy, scanning electron microscopy (SEM), X-ray diffraction, and energy dispersive microanalysis (EDX) before and after operation. The cells and short stacks were electrochemically characterized mainly by long-term measurements (life cycle), by current-voltage measurements, and by impedance spectroscopy. In order to understand the nature of degradation mechanisms, the open-circuit voltages (OCV), the ohmic resistances, and the polarization resistances, during dynamic operation are compared and discussed. In order to distinguish between degradation effects due to the dynamic operation and usual stationary effects, these values are compared to values of noncycled cells. All of the cells investigated were able to withstand ten redox and ten thermal cycles without severe failure. Their redox- and thermal-cycling behavior are strongly dependent on their OCVs, which decrease during cycling. This proves that thermomechanical stresses in the electrolyte layer play a major role for the electrochemical performance of the cells during cycling. The improvement of the electrodes during the first 200h of operation and the ohmic resistance of the cells are not significantly influenced by the cycling. The first four-cell short stack with the cassette arrangement shows promising results with an OCV of ∼4V and an overall power of 92W at 800°C. The performances of the single cells are in the range of 180–220mW∕cm2. The differences in cell performance can be attributed to different polarization resistances of the cells in the cassettes, which might be caused by a nonuniform gas supply in the short stack.

In the thin-film solid oxide fuel cell (SOFC) concept of the German Aerospace Center (DLR) in Stuttgart, the entire membrane electrode assembly (MEA) is deposited onto a porous metallic substrate by an integrated multistep vacuum plasma spray (VPS) process. This concept enables the production of very thin and stable electrodes and electrolyte layers with a total cell thickness of only 100-120 μm. In this concept, the porous ferrite substrate material predominantly acts as mechanical cell support and as fuel gas distributor. In general, ferrite substrate alloys with high chromium and low manganese content show both excellent corrosion stability and adequate thermal expansion behavior. Nevertheless, at the high process temperature in the SOFC of∼800°C, atomic transport processes can show a detrimental effect on cell performance, at least at the required long-term operation. Problems arise, in particular, through diffusion processes of Fe-, Cr-, and Ni-species between the Ni/8YSZ anode and the ferrite steel-based substrate material. This can induce significant structure changes both in the anode and the substrate. As a reliable solution of this key problem, a plasma sprayed thin diffusion barrier layer is seen at the interface between anode and substrate, which consists of an electrically conductive and chemically stable ceramic component. For this purpose, some doped perovskite-type LaCrO 3 , such as La 1-x Sr x CrO 3-δ La 1-x Ca x CrO 3-δ or La 1-x Sr x Cr 1-y CO y O 3-δ were investigated and tested carefully at DLR. These types of perovskites show a high potential to fulfill all the required properties that are needed for the applicability as an anode-side diffusion barrier layer. The paper focuses on basic investigations of differently doped LaCrΟ 3 compounds under SOFC-relevant conditions concerning thermal expansion, electrical conductivity, chemical stability, etc. Furthermore, first results of electrically and electrochemically characterized half cells carried out with some qualified doped LaCrΟ 3 are shown. Finally, the diffusion barrier layer is demonstrated as a new SOFC component that is effective at cell operating conditions.

In recent years, SOFC technology has attained high interest for electrical power supply in vehicles as an Auxiliary Power Unit (APU) that operates independently from the main engine. In this paper, recent results are reported that have been achieved at DLR in adapting the DLR spray concept to the needs of an APU design based on plasma sprayed cells. Some major issues such as the porous metallic substrate, the characterization of the plasma sprayed cathode, the behavior of plasma sprayed cells during cycling experiments, and the development and application of an analytical tool for spatially-resolved electrochemical characterization are addressed.

In a novel auxiliary power unit (APU) stack concept for on-board electricity generation in vehicles and aircraft, a porous metallic substrate for cell support is used. In the plasma sprayed DLR SOFC concept, the substrate has to fulfil a variety of required properties. A combination of all these requirements in an integral substrate structure has turned out to be a key problem in this novel design. Therefore, together with some partners a substrate development process has been established. This paper focuses on different substrates developed at DLR and on the investigation methods that are used for it. Furthermore, it shows some results of gas permeability and leakage tests and of electrical and electrochemical characterisations under SOFC-relevant conditions that were carried out by means of the four-point measurement technique.

At the German Aerospace Center (DLR) in Stuttgart, a concept for planar SOFC using a metallic substrate support and thin-film layers, which are deposited by plasma spray processes (spray concept), has been developed. This concept enables the fabrication of the entire membrane-electrode assembly in a single consecutive spray process without any sintering steps or other thermal post-treatment after spraying, thus promising fast and cost-effective cell fabrication. Based on this concept adequate stack designs and stack technologies for the assembly of stacks have been developed for both stationary and mobile applications. The nature of the cell supporting substrate has a significant influence on the electrochemical performance of plasma sprayed cells; hence substrate development is a key issue. This paper describes the current status of development of the DLR spray concept including the stack designs, scale-up aspects of the fabrication technology, recent developments with substrates and the electrochemical characterization of single cells and short-stacks for both stationary and mobile application.

Metallic substrate supported thin-film SOFCs have been in development at DLR Stuttgart for nearly ten years. In the DLR SOFC concept, the entire cell is fabricated using an integrated multi-step vacuum plasma spray (VPS) process. The material and structure of the porous metallic substrates play an important role for the electrochemical performance of the sprayed cells. Therefore the paper concentrates on the investigation of different porous substrates, e.g. felts, foams and knitted wire structures, and on the electrochemical behaviour of the cells. The plasma sprayed cells with a size of 10 cm x 10 cm were characterised electrochemically by current-voltage measurements, impedance spectroscopy and by investigating their long term stability. In order to analyse possible degradation mechanisms, the cells were examined metallographically after operation. The different phases and elements were detected with the energy dispersive X-ray microanalysis (EDX) associated with the scanning electron microscope and the X-ray diffraction (XRD).

This paper focuses on the electrochemical characterization, such as current–voltage measurements, impedance spectroscopy and long-term operation of completely plasma-sprayed SOFC assemblies for a planar metallic substrate-supported thin film concept. The influence of the variation in operating conditions is presented. To determine the different resistances in the cells, the measured impedance spectra were fitted to an equivalent circuit. This enables further improvement of the electrochemical performance of the cells and allows the assembling of high performance SOFC stacks.

A key to the development of metal-supported solid oxide fuel cells (MSCs) is the manufacturing of gas-tight thin-film electrolytes, which separate the cathode from the anode. This paper focuses the electrolyte manufacturing on the basis of 8YSZ (8 mol.-% Y2O3 stabilized ZrO2). The electrolyte layers are applied by a physical vapor deposition (PVD) gas flow sputtering (GFS) process. The gas-tightness of the electrolyte is significantly improved when sequential oxidic and metallic thin-film multi-layers are deposited, which interrupt the columnar grain structure of single-layer electrolytes. Such electrolytes with two or eight oxide/metal layers and a total thickness of about 4 μm obtain leakage rates of less than 3 × 10−4 hPa dm3 s−1 cm−2 (Δp: 100 hPa) at room temperature and therefore fulfill the gas tightness requirements. They are also highly tolerant with respect to surface flaws and particulate impurities which can be present on the graded anode underground. MSC cell tests with double-layer and multilayer electrolytes feature high power densities more than 1.4 W cm−2 at 850 °C and underline the high potential of MSC cells.

International audience; A new cell design with metallic porous support was selected in order to face with the reduction of IT-SOFC's operation temperature. Nevertheless, the excessive roughness of the porous metallic interconnect induce additional problems when a thin electrolyte layer is required. In this work, an anode material (NiO-TSZ) by Atmospheric Plasma Spraying was deposited on metallic supports (ITM) produced by PLANSEE able to cover the roughness of the support. Then, a second thin and dense electrolyte layer (YSZ) by reactive magnetron sputtering was produced on the anode material. In this study, for both processing routes, the optimal process parameters regarding the structural, morphological and electrical characterizations were investigated.

The requirements for the usage of SOFCs for mobile applications are different compared to those for stationary applications. During the practical operation of a vehicle, the SOFC stack in an Auxiliary Power Unit (APU) will be thermally cycled frequently with several interruptions of the fuel gas supply. Therefore, the cells have to withstand several thousand rapid thermal as well as reduction-oxidation cycles. In contrary to the investigation of SOFCs for stationary application, few investigations have been performed concerning the behaviour of cells and stacks in dynamic operation. This paper concentrates on the investigation of Vacuum Plasma Sprayed (VPS) cell layers with a diameter of 48 mm under operating conditions. The cell layers were deposited on different porous metallic substrates. The microstructure of the cells was characterised before and after operation by optical light microscopy, Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and Energy Dispersive X-ray microanalysis (EDX). The cells were electrochemically characterized by time dependent measurements (life cycle), current-voltage-measurements and impedance spectroscopy. In order to understand the nature of degradation mechanisms, a thorough comparison and discussion is made among the open circuit voltages (OCV), ohmic resistances and the polarisation resistances before and after dynamic operation, respectively.

High-temperature fuel cells of the solid oxide fuel cell (SOFC) type as direct converter of chemical into electrical energy show a high potential for reducing considerably the specific energy consumption in different application fields. Of particular interest are advanced lightweight planar cells for electricity supply units in cars and other mobile systems. Such cells, in one new design, consist mainly of metallic parts, for example, of ferrite steels. These cells shall operate in the temperature range of 700 to 800 °C where oxidation and diffusion processes can be of detrimental effect on cell performance for long-term operation. Problems arise in particular by diffusion of chromium species from the interconnect or the cell containment into the electrolyte/cathode interface forming insulating phases and by the mutual diffusion of substrate and anode material, for example, iron and chromium from the ferrite into the anode and nickel from the anode into the ferrite, which in both cases reduces performance and system lifetime. Additional intermediate layers of perovskite-type material, (e.g., doped LaCrO3) applied with high-velocity direct-current vacuum plasma spraying (DC-VPS) can reduce such effects considerably if they are stable and of high electronic conductivity.

The thin-film SOFC concept of the DLR-Stuttgart allows for the usage of various ferritic steel materials for the fabrication of interconnector plates and the porous metallic substrate materials, which are primarily used for mechanical cell support. The advantages of ferritic steel alloys include a high temperature resistance, an adequate thermal expansion coefficient and a low cost availability. At DLR various ferritic steel materials were investigated and tested under SOFC relevant conditions. For the porous metallic substrate a separate development process is needed and because of the high demands during SOFC operation the substrate structure has to fulfil a variety of properties. Hence, the substrate development has turned out to be a key problem in the plasma sprayed SOFC concept. The paper provides an overview of material investigations and the substrate development process at DLR. Further, I-V characteristics of substrate-supported cells with different types of stack integration are presented.

A novel generation of a thin-film, metal supported solid oxide fuel cell (MSC) has been developed and demonstrated in the scope of the NextGen MSC project (funded by the German Federal Ministry of Economics and Technology) by Plansee, Forschungszentrum Jülich (FZ-J), and the Karlsruhe Institute of Technology (KIT), respectively. In the scope of this work, due to consequent electrolyte and electrode development, a novel cell configuration, based on Plansee's well-known porous FeCr alloy as mechanical cell support, could be established. Thus, first cell measurements at KIT indicate the feasibility and the reliability of the established cell manufacturing process. The tested cell has shown a current density of 1.52 A/cm² at 0.7 V and 820 °C. This corresponds with an area specific cell performance of 1,064 mW/cm2. Furthermore, during a cell operation time of approx. 300 hrs., the cell degradation was relatively low.

Metal-supported fuel cells (MSC) are one of the most focused SOFC technologies world-wide for so-called APUs (auxiliary power units) in heavy duty vehicles. In the scope of the present work MSC cells were developed on the basis of a porous support made from a ferritic oxide dispersion strengthened Fe-Cr alloy (ITM). A sintered anode of nickel and 8 mol% yttria stabilized zirconia (8YSZ) and an adaptation layer (8YSZ) were applied to provide a smooth surface with a defined residual porosity which allowed the deposition a very thin, gas-tight electrolyte layer (approx. 1.5 µm) of gadolinium doped ceria (GDC) by reactive sputtering. First cell and stack-tests with a lanthanum strontium cobalt ferrite (LSCF) cathode are presented. In the stack a current density of 1.2 A/cm² was reached at 800 °C and 0.7 V. This was the same power output as conventional anode-supported cells (ASC) under the same testing conditions. Therefore, it is shown that metal-supported cells can deliver the same electrochemical performance as anode-supported cells in a stack.

DLR is one of the pioneer groups to introduce metal supported solid oxide fuel cells (MS-SOFC) in mid 90s and it is continuing the development of the concept towards a reliable light weight 1 kW stack for APU in a funded consortium with ElringKlinger, Plansee and Sulzer Metco. The joint work is an integrated approach incorporating improved materials for functional layers, advanced industrial scale manufacturing and an evolved stack design to define a pilot production set-up for large volume manufacturing. At laboratory scale, the latest generation button cells (12 to 15 cm² effective area) exhibited more than 750 and 520 mW/cm² respectively with hydrogen and simulated reformate gas as fuel at 800{degree sign}C. 2000 hours tests were performed with degradation rate of less than 1.5%/kh. Redox stability of these cells was demonstrated for 20 cycles during which the anodes were fully oxidized. Up-scaling to 85 cm² and 100 cm² effective area cells was accomplished and the cells showed 400 mW/cm² power density using simulated reformate gas at a fuel utilisation of 32%. Further improvements consisting of developing large scale industrial processes for the fabrication of functional layers including low pressure plasma spraying (LPPS) and atmospheric plasma spraying (APS) with TriplexPro are in progress. The aim is to get higher productivity and reproducibility. In addition, a new alloy for interconnects and substrates will be incorporated to further enhance the durability of cells.

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