Fe-decorated on Sm-doped CeO2 as cathodes for high-temperature CO2 electrolysis in solid oxide electrolysis cells

Abstract

Electrocatalytic CO2 reduction in solid oxide electrolysis cells (SOECs) can simultaneously convert CO2 to valuable chemicals or fuels by integrating with renewable energy so as to alleviate the greenhouse effects and energy crisis. Cerium oxide (CeO2) with high redox stability and catalytic activity toward CO2 reduction is considered a promising SOEC cathode. However, CeO2 is rarely directly employed as cathodes due to its unsatisfactory electrical properties. Suitable modification of CeO2 becomes essential to improve its electrocatalytic activity. Herein, Fe-decorated on Sm-doped CeO2 via a simple mechanical milling process was employed as cathodes for high-temperature CO2 electrolysis in SOEC. The addition of Fe species on Sm-doped CeO2 can greatly enhance the CO2 electrolysis efficiency, mainly attributing to the increased catalytic active sites, electronic pairs, and oxygen vacancy concentrations, which facilitated the CO2 adsorption and dissociation as well as the electron-ion transportation. The 1.0 wt.% Fe-decoreated on Sm-doped CeO2 showed the highest current density of 0.57 A cm−2 at 1.9 V under 800 °C. Moreover, the co-existence of doped and surface coated Fe species on Sm-doped CeO2 with moderate oxygen vacancies and adequate electronic transportation paths facilitate the high-temperature CO2 electrolysis.