Synthesis and characterisation of Ni–SrCe0.9Yb0.1O3−δ cermet anodes for protonic ceramic fuel cells

Cermet anode material with a proton-conducting ceramic phase, Ni–SrCe0.9Yb0.1O3−δ, was synthesised by combustion from mixtures of molten nitrates and urea followed by sintering and reduction. Co-pressing the anode combustion powder on “green” SrCe0.9Yb0.1O3−δ electrolyte and co-firing produced symmetrical anode/electrolyte/anode assemblies with planar electrodes of thickness ca. 100 μm. The addition of Co(NO3)2·6H2O to the electrolyte as sintering aid lowered the sintering temperature to 1250 °C, thereby allowing high anode porosity while retaining good anode/electrolyte adherence. The anode microstructure is composed of a uniform distribution of submicron Ni and perovskite particles. Analysis of the symmetrical assemblies by a.c. impedance spectroscopy indicates that the electrode polarisation resistances are composed of at least two contributions. Stability issues concerning the Ni–SrCe0.9Yb0.1O3−δanodes in reducing atmospheres are discussed.