Formulations of LSFN and LSCN as fuel electrode materials for high temperature co-electrolysis cells

Kurzfassung

The efficient utilization of CO2 and its conversion into CO has received great interest since it is considered a suitable path for decarbonisation of human activity and a promising climate protection measure. Solid Oxide Electrolysis Cells (SOECs) offer a single step conversion by electrolysing simultaneously H2O and CO2 to obtain syngas (H2 + CO). This can subsequently be used as feedstock in the Fischer – Tropsch process to yield liquid synthetic fuels. In contrast to the syngas obtained by steam reforming of methane, high temperature co-electrolysis is advantageous since it enables fuel production without consuming non-renewable fossil fuels. In addition, SOEC operation at high temperatures, favours electrode reaction kinetics and decreases the electrolyte resistance, thereby decreasing the required electrical energy for co-electrolysis. State-of-the-art Ni-based cermets have been widely studied as fuel electrode materials due to their high catalytic properties towards H2O/CO2 splitting, as well as for their high electrical conductivity. However, they are susceptible to impurities and irreversible degradation in operation, e.g. by nickel depletion in the functional fuel electrode at high over-potential, as one of several effects. Therefore, further investigations are needed in order to propose mitigation strategies based on detailed understanding of degradation mechanisms. As an alternative, Perovskite-based oxides are promising electrode materials for SOECs due to their catalytic activity and stability in dual atmospheres, besides of being potentially resistant towards migration phenomena. With the aim to implement perovskite-based materials for the fuel electrode of a SOEC, lanthanum-transition-metal perovskites were investigated: (La0.6-x Sr0.4) Fe0.8Ni0.2O3 and (La0.7-x Sr0.3)Cr0.85Ni0.15O3. These precursors were produced by soft chemistry methods by varying their A-site deficiency stoichiometry. Particle morphologies were characterized by SEM and formation of crystalline phases were corroborated by XRD and TGA. Results are presented and discussed with the perspective of SOEC application.