Development of contact coatings for SOFC

256 p.+anexosLa investigación en materiales de contacto cátodo-interconector que mejoren el flujo de electrones, es necesaria en la generación de energía sostenible mediante celdas de combustible de óxido sólido (SOFC). El uso de aleaciones metálicas como material interconector, permite reducir la temperatura de funcionamiento de las celdas SOFC, aumentando así su durabilidad y aplicabilidad; sin embargo, el mismo presenta como nuevo reto el desarrollo de materiales de contacto con propiedades óptimas. En este trabajo se recoge el desarrollo de estructuras multicomponente interconector-capa de contacto-cátodo. El uso de diferentes materiales de contacto, para la fabricación de estos sistemas, ha permitido la identificación y adaptación de las propiedades clave para obtener un material de contacto. Los primeros ensayos se han realizado empleando soportes metálico planos Crofer22APU y cátodos cerámicos La0.6Sr0.4FeO3, utilizando como capas de contacto tres óxidos mixtos: LaNi0.6Fe0.4O3-¿ (LNF), LaNi0.6Co0.4O3-¿ y (La0.8Sr0.2)0.95Fe0.6Mn0.3Co0.1O3. El uso de interconectores acanalados, que permitan el flujo del gas oxidante en un sistema real, ha dado lugar a la preparación de una nueva configuración para optimizar el contacto interconector-cátodo. Así, se ha desarrollado un composite, formado por una malla Fe-22Cr recubierta por inmersión en una suspensión cerámica, formulada a partir de los óxidos seleccionados previamente. Con objeto de simular la parte oxidante de un sistema operativo, garantizando el paso del gas oxidante a través del material de contacto, tras optimizar el sistema interconector-composite, y utilizando un láser de femtosegundos, se ha micromecanizado el composite para, posteriormente, depositar el cátodo sobre el mismo, desarrollando así una nueva estructura interconector-capa de contacto-cátodo

Effect of synthesis conditions on electrical and catalytical properties of perovskites with high value of A-site cation size mismatch

et al.The perovskite La0.15Sm0.35Sr0.08Ba0.42FeO3-δ has been prepared by the glycine nitrate route, varying the calcination temperature, fuel/oxidizer ratio and cooling rate, in order to study the sample preparation influence on the properties in the context of their application as a electrode material for SOFCs. The obtained materials have been characterized by X-ray diffraction, scanning electron microscopy, electrical and BET surface area measurements, and also the reaction between oxygen and CO, which can occur in SOFCs during the conversion of chemical energy into electrical energy. As overall results, all the samples present a phase segregation showing two perovskites with rhombohedral structure. SEM images show a well-necked morphology of the powders which are composed of nanosized particles and agglomerations of grains. The BET specific surface area of the samples decreases as calcination temperature increases, as well as for the quenched sample. The measured electronic conductivity values (<50 S/cm) are characteristic for samples with these high values of σ(r) (A cation size disorder). The catalytic activity tests for the CO oxidation reaction showed a T50% (“light-off temperature”, defined as the temperature at which 50% conversion of CO is achieved) value about 440°C–450 °C, CO conversion reaching 100% at approximately 600 °C for all the prepared perovskites. Then, for the La0.15Sm0.35Sr0.08Ba0.42FeO3-δ perovskite, CO conversion temperature is lower than usual SOFCs operating temperature. This points out to the technological interest of these materials in the framework of reducing the operating temperature of SOFCs.This research has been funded by the Ministerio de Ciencia e Innovación (CONSOLIDER-INGENIO 2010 CSD2009-00013), Ministerio de Economía y Competitividad (MAT2013-42092-R and MAT2012-30763), the Feder program of the Europen Union and Dpto. Educación, Política Lingüística y Cultura of the Basque Goverment (IT-630-13). The authors thank for technical and human support provided by SGIker of UPV/EHU. K. Vidal thanks UPV/EHU for funding.Peer Reviewe

Effect of the A cation size disorder and synthesis conditions on the properties of an iron perovskite series

Póster presentado en The Energy and Materials Research Conference - EMR2015 celebrado en Madrid (España) entre el 25-27 de febrero de 2015Solid state chemistry thrives on a rich variety of solids that can be synthesized using a wide range of techniques. It is well known that the preparative route plays a critical role on the physical and chemical properties of the reaction products, controlling the structure, morphology, grain size and surface area of the obtained materials. This is particularly important in the area of ABO3 perovskite compounds given that they have for long been at the heart of important applications [1]. Particularly, perovskite systems such as La1-xSrxFeO3 (LSF) are now receiving researchers attention for their interesting applications [2-4] such as ceramic membranes (CMs) for oxygen separation, solid oxide fuel cells (SOFCs) electrodes for efficient power generation, catalysts for complete oxidation of CO in vehicle engines, etc. In order to develop these advanced materials, combustion methods (glycine-nitrate, urea based, and other modifications) have been proposed as one of the most promising methods for their synthesis [5,6]. This method consists of a highly exothermic self-combustion reaction between the fuel (usually glycine, urea or alanine) and the oxidant (metal nitrates), that produces enough heat to obtain the ceramic powders. The characteristics (including purity, structure and size) of the combustion synthesis oxide powders are typically determined by several synthetic parameters, such as the species of fuel and oxidizer reactants, the fuel/oxidizer ratio, and the subsequent sintering treatment after combustion process [7]. In the other hand, physical properties of these perovskite materials are very sensitive to changes in the doping level (x), the average size of the A cations (), and the effects of A cation size disorder (σ2(rA)) quantified as σ2(rA) = – 2 [8]. Our searching approach to find the optimum synthetic conditions for new materials within the LSF system has been based on the study of only one of the indicated parameters isolated from the rest. In this sense, this study is focused on the effect of the variation of the cation size disorder, calcination temperature and the fuel/oxidizer ratio of glycine/nitrate on the structural, morphological, electrical and catalytic properties of a series of Ln0.5M0.5FeO3-δ perovskites (Ln = La, Sm; M = Ba, Sr)

Optimization of the large scale synthesis of the LSF-20 cathode material for SOFCs

Póster presentado en: 21st World Hydrogen Energy Conference 2016. Zaragoza, Spain. 13-16th June, 2016Solid oxide fuel cells (SOFCs) have the potential to be one of the cleanest and most efficient energy technologies for direct conversion of chemical fuels to electricity. Economically competitive SOFC systems appear poised for commercialization, but widespread market penetration will require continuous innovation of materials and fabrication processes to enhance system lifetime and reduce cost. Additional requirements arise for the technologies for synthesis of SOFC materials. These requirements originate from the demands for large scale SOFC industrial production. In this sense, solution combustion synthesis (SCS) is a simple and reproducible method used to obtain several types of ceramic oxides for a variety of applications. A typical SCS procedure utilizes a self-sustained exothermic reaction among well-mixed reactants to achieve the rapid and economical synthesis of particulate products. Up to 2008, SCS method has been adopted to fabricate more than 1000 kinds of oxide powders over more than 65 countries [1]. The properties of the resulting powders (crystalline structure, amorphous structure, crystallite size, purity, specific surface area and particle agglomeration) depend heavily on the adopted processing parameters [2,3]. The objective of this work is to obtain, on a large scale, the perovskite-type oxide La0.8Sr0.2FeO3 that shows promising properties as cathode for SOFC applications. In this study, the optimization of the large scale synthesis has been realized by the glycine-nitrate combustion method (Figure 1). In this sense, first of all, the effect of some parameters such as temperature, glycine/nitrate ratio and times and cooling rates used in the temperature treatments, that play a key role in the final properties of the obtained materials, has been analyzed. The characterization has been realized by ICP (inductively coupled plasma atomic emission spectroscopy) XRD (X Ray diffraction), SEM (scanning electron microscopy) and dilatometry.This research has been funded by the Ministerio de Economía y Competitividad (MAT2013-42092-R) with co-financing FEDER-EU) and Dpto. Educación, Política Lingüística y Cultura of the Basque Goverment (IT-630-13). The authors thank SGIker (UPV/EHU) technical support

Scalable synthetic method for SOFC compounds

Although economically competitive SOFC systems seems to be ready for commercialization, a broad inventory of key starting materials and fabrication processes are needed to enhance systems and reduce costs. These necessities are raised by the demands for large scale SOFC industrial production. Taking into account these reasons, we have synthesized the mean components of a fuel cell, on a large scale, by the glycine nitrate combustion method. The synthesized different components of SOFC have been the interconnector protective coating (MnCo1.9Fe0.1O4), contact layer (LaNi0.6Fe0.4O3), cathode (La0.6Sr0.4FeO3), interlayer (Sm0.2Ce0.8O1.9), electrolyte (ZrO2)0.92(Y2O3)0.08 and anode (Ni0.3O-(ZrO2)0.92(Y2O3)0.08) material, obtaining reproducible pure samples and amounts up to 12 g for each batch, being able to increase easily this amount to lots of hundred of grams. The obtained materials have been characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and X-ray fluorescence (XRF), X-ray diffraction (XRD), dilatometry, scanning electron microscopy (SEM), particle size distribution and conductivity measurements.Ministerio de Economía, Industria y Competitividad (MAT2016-76739-R) (AEI/FEDER, UE) and (MAT2015-2015-86078-R) Dpto. Educación del Gobierno Vasco (IT-630-13) European Regional Development Fund (ERDF). Ministerio de Economía y Competitividad (BES-2014-068433

Scalable synthetic method for SOFC compounds

Although economically competitive SOFC systems seems to be ready for commercialization, a broad inventory of key starting materials and fabrication processes are needed to enhance systems and reduce costs. These necessities are raised by the demands for large scale SOFC industrial production. Taking into account these reasons, we have synthesized the mean components of a fuel cell, on a large scale, by the glycine nitrate combustion method. The synthesized different components of SOFC have been the interconnector protective coating (MnCo1.9Fe0.1O4), contact layer (LaNi0.6Fe0.4O3), cathode (La0.6Sr0.4FeO3), interlayer (Sm0.2Ce0.8O1.9), electrolyte (ZrO2)0.92(Y2O3)0.08 and anode (Ni0.3O-(ZrO2)0.92(Y2O3)0.08) material, obtaining reproducible pure samples and amounts up to 12 g for each batch, being able to increase easily this amount to lots of hundred of grams. The obtained materials have been characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and X-ray fluorescence (XRF), X-ray diffraction (XRD), dilatometry, scanning electron microscopy (SEM), particle size distribution and conductivity measurements.Ministerio de Economía, Industria y Competitividad (MAT2016-76739-R) (AEI/FEDER, UE) and (MAT2015-2015-86078-R) Dpto. Educación del Gobierno Vasco (IT-630-13) European Regional Development Fund (ERDF). Ministerio de Economía y Competitividad (BES-2014-068433

Materiales para su aplicación en celdas SOFCs

Poster presentado en la conferencia: XXXV Bienal de la Real Sociedad Española de Química (A Coruña, 19-23 de Julio de 2015)Se han sintetizado cinco compuestos (La0.4Sr0.6FeO3, LaNi0.6Fe0.4O3, Zr0.8Y0.2O1.9 , Sm0.2Ce0.8O1.9 y MnCo1.9Fe0.1O4) mediante la técnica de combustión glicina - nitrato (G/N = 1) [1], para su utilización como cátodo, electrolito, barrera, capas de contacto y protectoras, en celdas de combustible de óxido sólido de temperatura intermedia (IT-SOFC). Las muestras se han caracterizado mediante difracción de rayos X (DRX) y microscopía electrónica de barrido (MEB), técnicas que han permitido analizar las estructuras y la morfología de los diferentes compuestos. La difracción de rayos X sobre muestra policristalina ha permitido identificar tanto el sistema cristalino de los compuestos como su grupo espacial. Microestructuralmente todos los materiales presentan un tamaño de grano pequeño y superficies homogéneas y porosas.Ministerio de Economía y Competitividad (MAT2013-42092-R), Dpto. de Educación, Política Lingüística y Cultura del Gobierno Vasco (IT-630-13),Fondo Europeo de Desarrollo Regional (FEDER) y Ministerio de Economía y Competitividad (BES-2014-068433)

Negative correlation of doping and conductivity in Ln1-xMxCr0.9Ni0.1O3 (Ln = La and/or Nd; M = Sr and/or Ca; x≤0.25) perovskites prepared by combustion synthesis as anode materials for SOFCs

A series of chromite perovskites with the general formula Ln1−xMxCr0.9Ni0.1O3 (Ln = La and/or Nd; M = Sr and/or Ca; x ≤ 0.25) has been prepared by three combustion synthesis routes using a different combustible substance each time: glycine, urea and sucrose. In order to isolate the effect of divalent dopant concentration from the A cation steric effects, the whole group has a fixed mean A cation radius, ≈ 1.22 Å, and cation size disorder, σ2(rA) ≈ 0.0001 Å2, but variable doping x. Their crystal structure, microstructure, electrical properties and expansion coefficients have been investigated on the basis of their possible use as anode materials for intermediate temperature solid oxide fuel cells (SOFC). Cell parameters, grain sizes, expansion coefficients and conductivities all are found to be dependent on x and the combustible substance used. The most interesting relationship is the negative dependence of the conductivity with x under H2 atmosphere: conductivity decreases with doping which is the opposite to the expected behavior for a p-type doped perovskites and has not been reported before.Ministerio de Economía y Competitividad, MAT2016-76739-R // Dpto. Educación, Política Lingüística y Cultura of the Basque Government, IT-630-1

Electrochemical and degradation behaviour study of different SOFC compounds

Presentación en: The Energy and Materials Research Conference - EMR2017. Lisbon (Portugal), 5-7 April 2017The present work is focused on manufacturing processes of the solid oxide fuel cell (SOFC) components with previously self-synthesized materials by combustion method [1-2]. The configuration used consists of planar electrolyte-supported symmetric cells, with dense yttria-stabilized zirconia (YSZ) membranes about 20mm diameter and a thickness near 300μm. Ni-yttria-stabilized zirconia cermet (Ni-YSZ) [3] and La0.6Sr0.4FeO3 (LSF40) [4] layers were deposited on the surfaces of the electrolyte as anode and cathode, respectively. In order to decrease the interlayer reactivity and improve the contact between them, Ce0.8Sm0.2O1.9 (SDC), LaNi0.6Fe0.4O3 (LNF60) and MnCo1.9Fe0.1O4 (MCF10) were added in different combinations as protection barrier [5], contact layer [6] and protective layer [7] material, respectively. The deposition of the different compounds has been carried out by manual colloidal spraying, using an organic base solution, or by screen printing. Cross section SEM images have been done to study morphologically the different starting layers. In order to study the degradation of the samples after 500h of exposure time at a temperature of 800 ºC, the energy-dispersive X-ray spectroscopy analysis of the cross sectional micrographs has been evaluated. Electrochemical impedance spectroscopy was used to characterize the electrochemical properties of the different components and multilayer structures.Economía, Industria y Competitividad (MAT2016-76739-R) (AEI/FEDER, UE) and (MAT2015-2015-86078-R) Dpto. Educación of the Basque Goverment (IT-630-13). European Regional Development Fund (ERDF). A. Wain-Martin thanks Ministerio de Economía y Competitividad for funding his work (BES-2014-068433)