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Infiltrated cathode materials for microtubular solid oxide fuel cells

AuthorsLaguna-Bercero, M. A. ; Orera, V. M.; Monzón, Hernán; Hanifi, Amir R.; Cunningham, Joshua; Etsell, Thomas H.; Sarkar, Partha
Issue Date2014
CitationEHEC 2014
AbstractMicrotubular Solid Oxide Fuel Cells (MT-SOFC) have recently attracted much interest as they are more resistant to thermal cycling, and they present shorter start-up/shut-down times and higher volumetric power densities in comparison with the traditional planar geometry. Standard NiO-YSZ (yttria stabilized zirconia) tubes used in our laboratory are fabricated by either extrusion or cold isostatic pressing (CIP) of NiO, YSZ and pore former powders, followed by spray coating or dipcoating of the YSZ electrolyte. Both components are then co-sintered at 1400 ºC. Typical oxygen electrodes such as LSCF (lanthanum strontium cobalt ferrite) or LSM (lanthanum strontium manganite) are deposited by dip-coating and sintered at 1150 ºC. Thermo-mechanical matching of cell components, catalyser coarsening and quality of interfaces are important issues in cell fabrication. Fabrication of electrodes by infiltration may contribute to reduce some of these problems as the cathode sintering stage is no longer needed. In this case we fabricate the oxygen electrode by infiltration of different cathode materials into a porous YSZ structure. One of the advantages of this fabrication method is an increased of TPB (triple-phase boundary) length compared with the standard cathode due to the smallest size of the dispersed catalyser particles having a higher surface area. In addition, since no sintering process of the cathode is needed the formation of nonconducting secondary phases such as non-conducting zirconates, and also the coarsening of the catalyser during sintering is eliminated. In the present work, results about infiltrated LSM cathodes using different LSM concentrations will be shown. The j-V (current density-voltage) measurements showed an increase of near 20% in terms of power density: 700 mW cm-2 at 0.7V and 850 ºC for a standard cell and 720 and 825 mW cm-2 at 0.7V and 850 ºC for similar tubular cells but with non-optimised and optimised LSM infiltrated cathodes, respectively. In addition, we will also present results on Nd2NiO4+δ cathodes infiltrated into porous yttria stabilized zirconia (YSZ). In order to obtain nickelate single phase, calcination times and temperatures of the salt precursors will be discussed. Anode supported microtubular cells using this cathode showed power densities of about 760 mW cm-2 at 800 ºC and a voltage as high as 0.8 V. No degradation was detected after 24 hours under current load, assuring reasonable stability of the cell. Preliminary solid oxide electrolysis cell (SOEC) results showed slightly better performances in comparison with SOFC operation. It is believed that infiltration of nickelate salt precursors followed by calcination proposed in this work avoids high temperature sintering of the nickelate phase with the electrolyte and as a consequence, prevents their reaction. For this reason, infiltrated nickelates are very attractive for their use as intermediate temperature (IT) SOFC cathodes.
DescriptionTrabajo presentado a la: "European Hydrogen Energy Conference" celebrada en Sevilla (España) del 12 al 14 de marzo de 2014.
Appears in Collections:(ICMA) Comunicaciones congresos
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