Impact of Reduction Parameters on the Initial Performance and Stability of Ni/(Sc)YSZ Cermet Anodes for SOFCs

In-situ reduction of Ni cermet anodes produces the porosity and influences the microstructure, performance and stability of the anodes. The impact on initial performance, stability and microstructure of two different reduction procedures currently in use at DTU Energy Conversion with reduction temperatures of 850 degrees C and 1000 degrees C was evaluated for tape-cast, thin electrolyte, Nickel/8 mol% Yttria-Stabilized Zirconia (Ni/8YSZ) or (Ni/10Sc1YSZ) symmetric cells. High temperature activation produced the lower Ohmic and polarization resistances related to Triple Phase Boundary (TPB) charge transfer processes for Ni/10Sc1YSZ cells. The Ni/8YSZ cells behaved oppositely with respect to reduction temperature. A hypothesis is proposed relating performance to variations in Ni microstructure, Ni/ceramic contacting and extent of TPB resulting from differences in reduction parameters. Further, the performance stability under high steam conditions was evaluated, and very stable performances and microstructures of the anode layers were observed.