Cell performance of strontium ruthenium oxide cathode/ Gd-doped ceria (GDC) electrolyte/ nickel-GDC anode system

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Cell performance was measured at 773-1073 K for Ni-GDC(Gd-doped ceria) anode-supported GDC film (60 μm thickness) with SrRuO₃ cathode using a 3 vol% H₂O-containing H₂ fuel. Reduction of particle size (< 1 μm) of SrRuO₃ cathode was effective to decrease the voltage drop at the cathode because of the increased length of triple phase boundary (GDC electrolyte-SrRuO₃ cathode-O₂ gas). Open circuit voltage (OCV) of GDC electrolyte in an anode atmosphere without H₂ fuel was close to the value calculated by Nernst equation for no electronic conduction. However, the OCV in a H₂-containing atmosphere decreased from the values by Nernst equation owing to the increased electronic conduction in a GDC film. This tendency of decrease in OCV became significant for thinner GDC film. This result was interpreted by the dissolution and dissociation of H₂ fuel in a GDC film to form protons and electrons (H₂ → 2H⁺ + 2e^-).