A comprehensive study of phase evolution and electrochemical performance of the Sr0.98Ti0.5Fe0.5O3-δ perovskite as fuel electrode for steam electrolysis

Perovskite-based electrodes have gained interest as alternatives to Ni-cermet fuel electrodes in solid oxide electrolysis cells (SOECs). This study investigates strontium-iron-titanate (STF) as a potential all-ceramic fuel electrode for SOECs. The chemical stability of pure STF during SOEC operating conditions at open circuit voltage (OCV) and the chemical reactivity between STF and yttria-stabilized zirconia (YSZ) under manufacturing and operation conditions are analyzed. The pure STF appears to be quite stable during SOEC operation. However, the STF and YSZ electrolyte powder mixture shows chemical interaction during manufacturing and operation conditions, confirming the need for a barrier layer between those two materials. Furthermore, the electrochemical performance of electrolyte-supported symmetrical and full cells is tested at different temperatures (650–800 °C) and steam concentrations (3–90 % H2O). A mid-term degradation test in steam electrolysis operation for ca. 1700 h is carried out under thermoneutral conditions (i = −0.43 A cm−2) at 800 °C in 50 % H2O + 50 % H2. A low Rp degradation rate (0.162 Ω cm2 kh−1) for the investigated cell containing STF fuel electrode is obtained. However, the increasing ohmic resistance during the operational period caused an overpotential increase with a rate of 195 mV kh−1. Finally, post-test analyses showed sufficient chemical stability, representing STF as a potential candidate as fuel electrode in SOECs.