Enhancing Electrochemical CO2 Reduction on Perovskite Oxide for Solid Oxide Electrolysis Cells through In Situ A-Site Deficiencies and Surface Carbonate Deposition Induced by Lithium Cation Doping and Exsolution

Abstract

Solid oxide electrolysis cells (SOECs) hold enormous potential for efficient conversion of CO₂ to CO at low cost and high reaction kinetics. The identification of active cathodes is highly desirable to promote the SOEC's performance. This study explores a lithium-doped perovskite La_{0.6- x} Li_x Sr_0.4 Co_0.7 Mn_0.3 O_3-δ (x = 0, 0.025 0.05, and 0.10) material with in situ generated A-site deficiency and surface carbonate as SOEC cathodes for CO₂ reduction. The experimental results indicate that the SOEC with the La_0.55 Li_0.05 Sr_0.4 Co_0.7 Mn_0.3 O_3-δ cathode exhibits a current density of 0.991 A cm^-2 at 1.5 V/800 °C, which is an improvement of ≈30% over the pristine sample. Furthermore, SOECs based on the proposed cathode demonstrate excellent stability over 300 h for pure CO₂ electrolysis. The addition of lithium with high basicity, low valance, and small radius, coupled with A-site deficiency, promotes the formation of oxygen vacancy and modifies the electronic structure of active sites, thus enhancing CO₂ adsorption, dissociation process, and CO desorption steps as corroborated by the experimental analysis and the density functional theory calculation. It is further confirmed that Li-ion migration to the cathode surface forms carbonate and consequently provides the perovskite cathode with an impressive anti-carbon deposition capability, as well as electrolysis activity.

Keywords: CO2 electrolysis; alkaline metal doping; carbonate; perovskite oxide; solid oxide electrolysis cells.