Durability and kinetic effects of CO2-rich oxidizing streams on LSCF-based solid oxide fuel cells

In the SOS–CO 2 cycle, a novel hybrid cycle for blue power production, the solid oxide fuel cell's (SOFC) cathode is supplied with a CO 2 -rich oxidizing stream (e.g., 21 % O 2 79 % CO 2 vol.). The durability of state-of-the-art anode-supported SOFCs (25 cm 2 , SolydEra) with LSCF-GDC/LSC (La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ -Gd 0.1 Ce 0.9 O 3+δ /La 0.6 Sr 0.4 CoO 3+δ ) cathodes was tested at atmospheric pressure for 1090 h with 7 % humidified H 2 and reformate, at 700 °C and 0.85 V. The SOFC performance was investigated with periodic I/V curves and electrochemical impedance spectroscopy (EIS) measurements. The results highlighted a 24 % power density loss when air was replaced with the O 2 /CO 2 mixture (672 mW/cm 2 in air vs. 508 mW/cm 2 in O 2 /CO 2 with humidified H 2 ). A stable power output was observed, and complete reversibility was found when the air supply was restored. A distribution of relaxation times (DRT) analysis of the EIS spectra allowed to extract an anodic rate equation for the hydrogen oxidation reaction (HOR) and evaluate the frequency region affected by cathodic CO 2 . The kinetic effect of CO 2 was also studied via EIS on symmetric button cells at varying O 2 and CO 2 amounts, and a power-law rate equation was derived. The results verify the feasibility of the SOS–CO 2 cycle feed conditions at 700 °C and atmospheric pressure. • An industrial SolydEra SOFC (25 cm 2 ) tested for 1090 h with anodic H 2 and reformate. • The effect of a 21 % O 2 79 % CO 2 feed mixture is explored on the LSCF-GDC/LSC cathode. • 24 % power reduction at 0.7 V and 700 °C passing from air to 21 % O 2 79 % CO 2 . • No degradation is found supplying the 21/79 O 2 /CO 2 mixture at 700 °C for over 350 h. • Kinetic rate equation of the CO 2 effect on the oxygen reduction reaction is derived.