Investigation of the Structural and Catalytic Requirements for High-Performance SOFC Anodes Formed by Infiltration of LSCM

Composites formed by infiltration of 45 wt % La0.8Sr0.2Cr0.5Mn0.5O3 (LSCM) into a 65% porous yttria-stabilized zirconia (YSZ) scaffold were investigated in order to understand the reasons this material is able to provide excellent anode performance in solid oxide fuel cells (SOFCs). Scanning electron microscopy showed that the LSCM forms a film over the YSZ after calcination at 1473 K but that this film undergoes cracking to expose a long three-phase boundary after reduction at 1073 K. Coulometric titration demonstrated that the reduction of LSCM and La0.8Sr0.2MnO3 occurred over a similar range of P(O-2) and that reduction is the likely cause for film cracking. To achieve low anode impedances in humidified H-2 at 973 K, it was necessary to add a catalyst. The addition of 0.5-1 wt % Pd, Rh, or Ni was sufficient to increase the maximum power density of SOFCs with 60 mu m thick YSZ electrolytes to >500 mW/cm(2) in humidified H-2 at 973 K. The addition of either 1 wt % Fe or 5 wt % ceria also improved power densities but to a lesser extent. Finally, the use of Pt paste as the current collector increased performance to a similar extent as intentionally adding catalyst, showing the importance of using inert materials in electrode testing.