Revealing the detrimental CO2 reduction effect of La0.6Sr0.4FeO3-δ-derived heterostructure in solid oxide electrolysis cells

Solid oxide electrolysis cells hold unique Faraday efficiency and favored thermodynamic/kinetics for CO 2 reduction to CO. Perovskite oxide–based composite materials are promising alternatives to Ni-based cermet electrodes in SOECs. However, contrary results of the electrocatalytic activity over single-phase perovskite oxide exist and the rationale of the negative effect is not well revealed. In this work, two-phase perovskite materials with various complementary properties and unique interfaces are self-assembled, which was realized by “subtractive” defect-driven phase separation. The obtained heterostructure electrodes showed reduced performance over that of single-phase materials although the cyclic stability was improved. The main reasons for the performance degradation are the decrease of electrical conductivity, oxygen vacancy concentration while increasing the average valence state of B-site Fe cations, and electrode surface Sr aggregation. This work highlights the self-assembly method and insight into the rational design and synthesis of active electrodes/catalysts for CO 2 conversion in solid oxide cells.