CO/CO 2 Study of High Performance La 0.3 Sr 0.7 Fe 0.7 Cr 0.3 O 3– δ Reversible SOFC Electrodes

In this study, we demonstrate that the La 0.3 Sr 0.7 Fe 0.7 Cr 0.3 O 3– δ (LSFCr) perovskite, examined here as a CO/CO 2 fuel electrode material intended for symmetrical, reversible solid oxide fuel cell (RSOFC) applications, is both high performing and stable towards CO 2 electrolysis (SOEC mode) and the oxidation of CO (SOFC mode). To demonstrate this, symmetrical LSFCr/GDC/YSZ/GDC/LSFCr cells were evaluated electrochemically by using both DC (cyclic voltammetry (CV) and galvanostatic) and AC (impedance) techniques. The cells were tested at 800 °C using either 90% CO 2 :10% CO or 70% CO 2 :30% CO at the fuel electrode and air flowing to the O 2 electrode. From the open circuit impedance data, the polarization resistance, measured at 800 °C in a 90% CO 2 :10% CO and 70% CO 2 :30% CO gas composition, was 1.3 Ω cm 2 and 0.9 Ω cm 2 , respectively. Both the CV and polarized impedance data showed that the cell performance is higher during the electrolysis of CO 2 than for the oxidation of CO. Furthermore, the cell showed a very stable activity during CO 2 electrolysis, with a degradation rate of only 0.057 mV h −1 after ca. 135 h of galvanostatic testing at –100 mA cm −2 in 90% CO 2 :10% CO at 800 °C.