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Fabrication and characterization of microtubular SOEC in coelectrolysis mode

AutorMonzón, Hernán; Laguna-Bercero, M. A.; Orera, V. M.
Fecha de publicación2014
Citación11th European SOFC & SOE Forum (2014)
ResumenSimultaneous H2O and CO2 electrolysis, namely coelectrolysis, has been attracting attention lately as it offers the possibility of producing syngas from CO2 waste and steam. High temperature electrolysis offers lower electricity consumption compared to conventional low temperature electrolysis. This technology is particularly advantageous when coupled with another process able to provide waste heat, as the higher the electrolysis temperature the higher the heat-to-electric energy ratio required for the process. Solid oxide electrolyser cells (SOEC) are basically solid oxide fuel cells (SOFC) operating in regenerative mode. We have fabricated a series of electrode supported microtubular cells based on optimized design from previous studies and characterized them in coelectrolysis mode. Cathode support tubes based on nickel-yttria stabilized zirconia (Ni-YSZ) were shaped by plastic extrusion molding. YSZ electrolyte and LSM-YSZ (lanthanum-strontium doped manganite) cathode were added by successive dip coating and sintering steps at 1500⁰C and 1150⁰C, respectively. Cells were electrically contacted using platinum wire and paste and sealed to alumina tubes for gas input and output. Coelectrolysis was tested on a small tubular furnace at 850⁰C, feeding the cell with different gas flows containing steam, carbon dioxide, nitrogen and hydrogen in different compositions. Current density – voltage and electrochemical impedance spectra measurements were recorded using a VSP Potentiostat/Galvanostat (Princeton Applied Research, Oak Ridge, US). Output gas was analyzed using a gas chromatograph (Agilent Technologies MicroGC 900). Area specific resistance was calculated from recorded data as a function of inlet gas composition, yielding values ranging from 0.58 Ωcm2 when steam and CO2 rich flows are used to 2 Ωcm2 when a diluted composition is used. Gas chromatography was used to examine the hydrogen and carbon monoxide content in the output gas, finding a good agreement with the gas shift reaction equilibrium. Faraday efficiency was close to 100% on the studied conditions, meaning that little or no conduction takes place through the electrolyte. Additionally the electrolyte conduction threshold was found close to 1.8V in the diluted feeding conditions. Mild cell degradation was witnessed after several hours of operation at 600 mAcm-2. The possible causes of this degradation will be discussed in the present work.
DescripciónTrabajo presentado al: "11th European SOFC & SOE Forum" celebrado en Lucerne (Suiza) del 1 al 4 de julio de 2014.
URIhttp://hdl.handle.net/10261/122631
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