Experimental investigation of segmented SOECs: Locally-resolved impedance and degradation characteristics

Abstract

High temperature solid oxide electrolysis cells (SOEC) provide an innovative solution for direct conversion of steam and electricity to hydrogen with the additional capability of adding CO2 to produce syngas. However, specific operating conditions can have a negative impact on the performance and lifetime of SOECs. In this context, the distributions of operational parameters such as gas species, temperature and current density within the cell structure influence local transport processes and reaction kinetics and can lead to locally different electrochemical potentials and thus degradation phenomena. This study focuses on experimental investigations of steam-electrode supported SOECs with segmented air electrodes with the main objective to measure EIS and thus identify locally-resolved impedance and degradation characteristics caused by different operating conditions in steam and co-electrolysis mode. Thereby, significant correlations between operating conditions, local effects, electrode processes and degradation mechanisms were observed and analyzed in detail using EIS, DRT and SEM.