Gael Corre

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

Composites formed by infiltration of 45 wt % La 0.8 Sr 0.2 Cr 0 .5 Ma 0.05 O 3 (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 La 0.8 Sr 0.2 MnO 3 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 μm 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.

Studies on Direct Ethanol use in SOFCs

We report here on the investigation of the direct use of ethanol in solid oxide fuel cells. While the operation on Ni-YSZ anodes leads to detrimental catalytic carbon deposition even at high steam to carbon ratio, diluted ethanol can be directly used on LSCM anodes. Steady operation seems achievable only at high temperatures (900°C) due to gas-phase reaction carbon deposits. However, it is demonstrated that the initial performance is fully recovered after removal of these deposits. The addition of CGO to the LSCM anode is shown to considerably improve the anode performance, by limiting the gas-phase carbon deposition to a small layer beneficial to the performance. Recorded performance was higher on diluted ethanol than on humidified hydrogen. No degradation was observed on short term tests, and a polarization resistance of 0.3 Ω.cm 2 was achieved on ethanol diluted (15 mol. %) in steam.