The Effect of B-Site Composition in Perovskites for Electrochemical CO2 Reduction in Solid Oxide Electrolysis Cells

Solid oxide electrolysis cells (SOECs) are promising systems for electrochemically converting CO2 to CO, which can then be converted into synthetic fuel or other chemicals using existing technologies. Ni-based SOEC electrodes have promising electrochemical activities, but they have limited longer-term performance due to poor redox stability and carbon deposition. Mixed ionic-electronic conducting (MIEC) oxides have been explored as alternatives to minimize these adverse effects due to their favorable redox properties. However, the electrochemical activities of MIECs are inferior to those of Ni-based cathodes. Therefore, improving electrochemical performance of MIEC-based SOEC cathodes requires an understanding of the factors that govern their activity.

This study investigates the effect of B-site cation composition on the electrochemical performance of CO2 reduction in SOECs. To accomplish this, SOECs were synthesized with consistent LSGM electrolyte and LSGM-LSCF anode electrocatalysts, while various 3d transition metal cations of La-based perovskites (LaBO3; B=Fe, Co, Ni, and Cr) were used as cathode electrocatalysts. Linear sweep voltammetry profiles (I-V curves) were used to compare the electrochemical performance of SOECs as a function of perovskite composition at the cathode. We find a significant dependence on the nature of the B-site cation. These studies can be used as a guidance toward improving the performance of MIEC-based SOECs.