Optimization of Sm0.5Sr0.5CoO3−δ-infiltrated YSZ electrodes for solid oxide fuel cell/electrolysis cell

Abstract

The Sm_0.5Sr_0.5CoO_3−δ (SSC) oxygen electrode has attracted much interest due to its high electrical conductivity and electrochemical activity. In this work, a SSC–YSZ (yttria stabilized zirconia) composite electrode was prepared by an infiltration process. First, cells with different SSC contents in the oxygen electrode and different sintering temperatures were prepared and tested in solid oxide fuel cell (SOFC) mode. An optimal cell with an SSC content of 45 wt% and sintering temperature of 850 °C shows favorable microstructure and relatively lower polarization resistance. The peak power densities of 0.96 W cm⁻² and polarization resistances as low as 0.39 Ω cm⁻² were obtained at 750 °C. Then, in solid oxide electrolysis cell (SOEC) mode, the effects of CO₂/H₂O ratio were investigated. Results indicated that the CO₂/H₂O ratio has little influence on the electrolysis performance in the range of 1 : 2–2 : 1. Finally, the electrochemical stability of the cell in both modes was tested at 750 °C for about 100 h. After a slight degradation in the initial 25 h, the cell showed good stability in SOFC mode, and no visible degradation was detected in SOEC mode in 100 h operation.