Optimization of Redox Stable Ni-YSZ Anodes for SOFCs by Two-Step Infiltration

Abstract

Infiltration of a polymeric nickel oxide precursor into a sintered porous ytrria –stabilized zirconia (YSZ) skeleton is a promising approach to achieve redox stable solid oxide fuel cells. In order to ensure that the porous YSZ skeleton was mechanically strong enough to withstand the stresses caused by the volumetric expansion of the Ni phase upon oxidation even at relatively high loadings, a polymeric YSZ precursor was infiltrated into to the porous YSZ skeleton, prior to NiO infiltration. It was shown that infiltration of YSZ precursor strengthened the porous YSZ skeleton without compromising from the porosity or initial YSZ particle size significantly. The amount of infiltrated YSZ and the subsequent heat-treatment temperature were determined to be important processing parameters in achieving redox stable Ni-YSZ anodes. Electrolyte supported SOFC (electrolyte thickness ∼ 180 μm) with redox stable anode prepared by YSZ and NiO infiltrations showed a power density of ∼0.41 Watt/cm2 at 800°C which did not change significantly after 20 redox cycles in 10%H2 – 90% Ar fuel. Impedance spectroscopy measurements at 800°C showed significantly low electrode polarization resistances (anode + cathode ∼ 0.07 Ohm.cm2 at 800°C) which remained stable upon redox cycling.