Effect of Sr-Doped LaCoO3 and LaZrO3 Infiltration on the Performance of SDC-LSCF Cathode

Abstract

The effects on performance of commercially produced solid oxide fuel cell (SOFC) were evaluated for two types of cathode infiltration: a mixed ionic-electronic conductor and an electronic insulator. The bi-layered cathode backbone consists of a thin, dual-phased functional layer containing Sm2O3-doped CeO2 (SDC) and La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) and a thick current collecting layer of LSCF. The backbone was infiltrated with either La0.6Sr0.4CoO3 (LSCo) or La1.97Sr0.03Zr2O7 (LSZ) using nitrate solution precursors, followed by calcination at 850 or 950°C, respectively. LSCo infiltration decreased the measured full cell overpotential by 28–40% after 6 wt % loading, and no further effect was observed with higher loading. The LSCo-infiltrated cells demonstrated stable performance for over 200 h of operation at 0.25 A/cm2 and 750°C. Conversely, cathode infiltration with electrically insulating LSZ pyrochlore had a negative influence on the cathode performance that became substantial with increased infiltrate loading. Characteristic wetting behavior of the two infiltrates on the composite backbone affects the dependency of infiltrate amounts on cathode performance. The results imply that the composite cathode reaction is primarily under the control of the surface exchange reaction rate. This comparative study demonstrates that the cathode performance of a commercially produced SOFC can be influenced by applying infiltrates in a simple process, and indicates that the infiltrate’s electrocatalytic activity and conductivity must be carefully considered when infiltrating a standard SDC-LSCF cathode.