Electrochemical Activity and Stability of Pure Gadolinium Doped Ceria as Fuel Electrode in Solid Oxide Electrolysis Cells

The state-of-the-art fuel electrode materials for solid oxide electrolysis cells (SOECs) are Ni-cermets due to their high electro-catalytic activity, high electrical conductivity and the low price. However, one major concern that must be solved for a widespread commercialisation is their poor degradation behaviour during electrolysis operation caused by for example Ni migration, depletion and agglomeration in the fuel electrode. One strategy to improve the durability of SOECs is the usage of alternative fuel electrode materials. For instance, completely Ni-free fuel electrodes may solve the problems of morphological degradation during operation and further could enhance redox cycling stability. Within possible candidates, gadolinium doped ceria (GDC) is an interesting material due to good stability towards carbon deposition and the possibility to host electro catalysis in electrolysis reactions [1, 2]. Furthermore, GDC (Ce 0.8 Gd 0.2 O 2-δ ) shows electronic conducting (700 °C, 0.028 S·cm -1 ) and ionic conducting (700 °C, 0.47 S·cm -1 ) properties at low partial pressures of oxygen and high temperatures [3]. Hence, in this work we have prepared electrolyte supported single cells with GDC (Ce 0.8 Gd 0.2 O 2- δ ) as single phase fuel electrode for their use as SOEC. The single cells (GDC//8YSZ//GDC//LSCF) were characterized by electrochemical impedance spectroscopy (EIS) and current-voltage characteristics in steam electrolysis, co-electrolysis and CO 2 electrolysis conditions exhibiting 70 % of the performance compared to similar produced Ni-GDC fuel electrode single cells at 900 °C [4]. Furthermore, the results include process analysis by EIS, long term stability experiments for steam electrolysis and CO 2 electrolysis conditions of at least 1000 hours and post characterization of the degraded cells by EIS, SEM and EDX analysis. [1] Nakmura et al. Journal of the Electrochemical Society 155 (2008) B563. [2] Chueh et al. Nature Materials 11 (2012) 155-161. [3] Maricle et al. Solid State Ionics 52 (1992) 173-182. [4] Unachukwu et al. Journal of Power Sources 556 (2023) 232436. Figure 1