Electrocatalytic and operando characterization of state-of-the-art SOFC cathodes for applications at high CO2 concentration in novel clean power production cycles

Novel hybrid SOFC power production cycles with integrated CCS require perovskite cathodes able to tolerate up to 79 % v/v CO2/O2 oxidant mixtures at high temperature. Accordingly, we investigate at 700 °C the electrocatalytic effect of a 21 % O2 79 % CO2 mixture on two state-of-the-art SOFCs with different cathodes, LSCF-GDC/LSC (La0.6Sr0.4Co0.2Fe0.8O3-δ-Gd0.1Ce0.9O2+δ/La0.6Sr0.4CoO3+δ) and LSM-YSZ/LSM (La0.8Sr0.2MnO3-δ/Y0.16Zr0.92O2+δ). On LSCF-GDC/LSC, CO2 causes a reversible loss of power density compared to the conduction in air (from 500 to 420 mW/cm2 at 0.7 V), due to a kinetic inhibition by CO2. CO2 has no effect on LSM-YSZ/LSM, as 420 mW/cm2 is obtained in O2/CO2 and air. Stable performance is observed on both SOFCs over 350 h in O2/CO2 at 0.85 V. The interaction of CO2 with each perovskite is characterized with operando NAP-XPS and XRD (up to 20 bar) synchrotron experiments, and with thermogravimetry and SEM. SrCO3 forms at 700 °C on LSCF and LSC, but not on LSM.