Influence Of Binary‑Oxide Deposits on the Performance of Perovskite‑Based Fuel Electrodes in Steam and co‑Electrolysis

Kurzfassung

The mixed ionic-electronic conducting Ni-lean perovskite La0.20Sr0.25Ca0.45Ti0.95Ni0.05O3 (LSCTN) has been successfully investigated as an alternative fuel electrode material. Its structural stability, phase purity, and chemical compatibility have been verified using X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) [1]. In addition, our 16 cm2 single cell tests with the LSCTN fuel electrode have yielded the comparatively low polarization resistance of 72 mOhm·cm2 at 860 °C in steam electrolysis at open circuit voltage. However, contaminants observed during SOC stack operation have yet to be examined for their effect on the stability and performance of LSCTN cells. This aspect is crucial, as trace impurities of binary oxides are shown to significantly impact the exchange reactions in perovskite materials [2]. Therefore, in this work, we have investigated the effect of impurities that are recognized to originate from Balance of Plant (BoP) components and the feed water supply. Manganese (Mn) and chromium (Cr) traces may be released by steel components, while silicon (Si) is typically introduced by the water source. The impurities were infiltrated as cations Mn2+ and Cr3+ in the electrode microstructure using nitrate solutions. The silicon was introduced as the oxide SiO2. Then the samples were put under vacuum and finally fired at 450 °C for 1 h. The successful infiltration was corroborated using SEM. In addition to the investigated long-term stability, the electrochemical performance was assessed in steam and co-electrolysis by electrochemical impedance spectroscopy (EIS) and iV curves. The presented results will focus on the impact of binary oxides impurity infiltration on the electrochemical performance, and the long-term stability of LSCTN that could mimic real phenomena that occur in stacks over long operation time. A special focus of this study is the comparative analysis of impedance spectra between non infiltrated and infiltrated LSCTN using the Distribution of Relaxation Times (DRT) method.