23,000 h steam electrolysis with an electrolyte supported solid oxide cell

An electrolyte supported solid oxide cell of 45 cm(2) area was operated in the steam electrolysis mode during more than 23,000 h before scheduled shutdown, of which 20,000 h with a current density of j = -0.9 A cm(-2). The cell consisted of a scandia/ceria doped zirconia electrolyte (6Sc1CeSZ), CGO diffusion-barrier/adhesion layers between electrolyte and electrodes, a lanthanum strontium cobaltite ferrite (LSCF) oxygen electrode, and a nickel/gadolinia-doped ceria (Ni/GDC) steam/hydrogen electrode. Voltage degradation in the operation period with j = -0.9 A cm(-2) was 7.4 mV/1000 h (0.57%/1000 h) and the increase in the area specific resistance 8 m Omega cm(2)/1000 h. The final cell voltage was 1.33 V (at 851 degrees C cell temperature). After dismantling, the cell showed no mechanical damage at electrolyte and H-2/H2O electrode; a small fraction of the oxygen electrode was delaminated. Impedance spectroscopy applied at the steady state DC current density confirmed a degradation dominated by an increasing ohmic term, mainly due to ionic conductivity decay in the electrolyte. In addition, a small non-ohmic and at least partly reversible 02 electrode contribution to degradation was identified, affected by a pollution from the (compressor) purge air. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.