Ceramic composite cathodes for CO2 conversion to CO in solid oxide electrolysis cells

Abstract

The conversion of CO2 into commodity chemicals and liquid fuels through the integration of renewable energy with electrochemical processes is one of the fast-emerging areas of research in energy space. High temperature electrolysis of CO2 in solid oxide electrolysis (SOE) cells is one of the most efficient processes for CO2 to chemical conversion as these reactors can utilize both heat as well as electrical energy. One of the key components that requires further development is the cathode (CO2 reduction electrode). The traditional Ni based cathodes are prone to rapid degradation under cyclic loading conditions and also require the additional supply of a reducing gas such as hydrogen for maintaining Ni in the metallic state at operating temperatures. In this work, we have proposed and investigated a ceramic composite of nominally A-site deficient (La0.80Sr0.20)0.95MnO3-x (LSM) and Gd0.20Ce0.80O1.95 (GDC) as SOE cathode using scalable electrolyte supported tube cells. The cells were continuously operated for about 200 h with about 95% Faradaic efficiency. It was observed that LSM–GDC composite cathode was better not only in terms of electrochemical performance, but was also significantly more stable than LSM alone during the CO2 electrolysis process. The slight degradation (0.18 mA cm−2 per h) in the current density was attributed to the electrode coarsening, and the formation of SrCO3 phase possibly reducing electrocatalytically active sites. Based upon the electrochemical performance and stability data, LSM-GDC composite appears to be promising material for application as SOE cathode.