Carbon dioxide (CO₂) emissions have increased continuously and rapidly since the industrial revolution, contributing to the serious greenhouse effect and leading to global warming. To minimize this effect, more attentions have been devoted to convert CO₂ into useful chemicals such as carbon monoxide (CO), methane, methanol and dimethyl ether through sustainable, renewable, and alternative energy sources while lowering the dependence on fossil fuels. Although various technologies for CO₂ conversion have been employed, such as thermocatalytic, electrochemical, and photochemical reductions, the conversion of CO₂ to valuable products is relatively difficult due to its remarkably stable C=O bonds. Among them, the electrochemical reaction has a better possibility than the others because the electrochemical reaction is controllable and can utilize alternative energy sources for CO₂ conversion, potentially achieving a carbon-neutral energy cycle.

As an efficient energy storage method, several types of electrolysis cells have been studied to reduce CO₂ electrochemically. Due to the advantages of high energy efficiency, good stability, and high faradaic efficiency, solid oxide electrolysis cells (SOECs) are more promising for practical applications in the future than the other electrolysis cells. One challenge is to develop high-performance CO₂ conversion electrode, which should possess high catalytic activity, electronic and ionic conductivity, chemical stability in the CO₂ atmosphere, and good resistivity against carbon deposition. Cermets (e.g., Ni-YSZ) have been utilized as a traditional CO₂ conversion electrode for SOECs because Ni metal serves as not only the electrocatalyst but also the electronic conductor. However, the cermets have issues for CO₂ electrolysis due to the oxidation of Ni metal and carbon coking when exposed to a pure or concentrated CO₂ atmosphere. Therefore, mixed ionic-electronic conducting (MIEC) perovskites have been investigated as the potential cathode materials for CO₂ electrolysis, which should have high enough electrical conductivity and chemical stability in the CO₂ atmosphere.

Perovskites have been considered attractive catalytic materials in the fields of solid oxide fuel cells due to their acceptable electrical conductivity and coking resistance. However, these perovskites have shown relatively low catalytic activity compared to Ni-YSZ cermet. In this work, a novel perovskite has been developed by introducing active nanoparticles via an in situ exsolution process, which showed high performance for the conversion of CO₂ to CO. Its electrical conductivity and chemical stability in operating conditions for CO2 electrolysis have been systematically evaluated.

Acknowledgements

Financial support from the U.S. Department of Energy (DE-EE0009427) is greatly appreciated.