Cobalt-free double-perovskite oxide Sr₂Ti_0.9FeNi_0.1O₆ as a promising electrode for symmetric solid oxide electrolysis cells

Symmetric solid oxide electrolysis cells (SSOECs) have attracted considerable interest because of their low fabrication cost and few compatibility issues. However, the development of SSOECs is restricted by the lack of electrode materials with desirable catalytic activity and stability. Herein, novel double-perovskite Sr₂Ti_1−xFeNi_xO₆ (STFNx) oxides are prepared and evaluated as electrodes for CO₂ electrolysis in SSOECs. The Sr₂Ti_0.9FeNi_0.1O₆ (STFNi01) electrode shows the best performance with the minimum polarization resistance. The physicochemical characterization reveals that Ni substitution increases the concentrations of surface-adsorbed oxygen species and electrical conductivity and enhances CO₂ chemical adsorption, improving the electrode surface reaction kinetics, as evidenced by the distribution of relaxation time analysis. The STFNi01 symmetric cell presents a current density of 0.91 A cm⁻² at 1.6 V and 800 °C and shows no performance degradation in the durability test due to the excellent carbon deposition resistance, indicating that STFNi01 is a promising electrode material for SSOECs.