Performance of La0.1Sr0.9Co0.8Fe0.2O3−δ and La0.1Sr0.9Co0.8Fe0.2O3−δ–Ce0.9Gd0.1O2 oxygen electrodes with Ce0.9Gd0.1O2 barrier layer in reversible solid oxide fuel cells

Abstract

La0.1Sr0.9Co0.8Fe0.2O3−δ (LSCF1982) and La0.1Sr0.9Co0.8Fe0.2O3−δ–Ce0.9Gd0.1O2 (LSCF1982–GDC) composite oxygen electrodes with a GDC barrier layer are tested in yttria stabilized zirconia (YSZ) electrolyte-based reversible solid oxide cells (RSOCs). Three button cell assemblies (1: NiO–YSZ|YSZ/GDC|LSCF1982; 2: NiO–YSZ/NiO–YSZ|YSZ/GDC|LSCF1982; and 3: NiO–YSZ/NiO–YSZ|YSZ/GDC|LSCF1982–GDC) are fabricated and their performance in solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) modes are studied at different temperatures (600 ≤ T/°C ≤ 800). The use of porous NiO–YSZ functional layer between hydrogen electrode and electrolyte leads to improvements in SOFC and SOEC (SOFC/SOEC) performance by improving the diffusion of reacting species inside the electrode. The effect of nature of oxygen electrode on SOFC/SOEC performance is studied, which indicates LSCF1982 oxygen electrode gives better performance than LSCF1982–GDC composite oxygen electrode, but LSCF1982–GDC composite oxygen electrode is more durable during reversible SOFC/SOEC operations. Stability of the button cells is studied in galvanostatic SOEC operation for 72 h and in reversible SOFC/SOEC operations. Current–voltage (I–V) tests and Electrochemical Impedance Spectroscopy (EIS) measurements indicate that the button cells show stable operation in SOEC mode. But successive SOFC → SOEC → SOFC operations indicate that the cells are not completely reversible. The possible reason for poor reversibility is found to be related with the grain growth in LSCF1982-based oxygen electrodes.