DFT plus U study of CO2 reduction and CO oxidation on a reconstructed CeO2-x(110) facet

Catalytic oxidation of CO can remove toxic pollutants from gas emissions, whereas the reduction of CO2 can provide feedstock for fossil free products. Using density functional theory with a Hubbard U correction (DFT + U), the reduction of CO2 into CO is investigated on a reconstructed CeO2-x(110) facet at operatingsolid oxide electrolysis conditions. A reaction pathway is identified with nudged elastic band (NEB) through adsorption of CO2 as a monodentate carbonate, an intermediate CO2- and the transition state to the final adsorbed CO. The reaction barrier for CO2 reduction does not depend on the temperature, whereas the back reaction for CO oxidation decrease with temperatures. Different 4d and 5d transition metals and other suitable metals are screened as dopants to increase the activity for CO2 reduction. After the screening iridium is the most promising candidate. The same temperature dependencies are present for the Ir-doped surface as the undoped, whereas the back reaction barrier is decreased to half the undoped value. There is no evidence of destructive carbon deposition on the reconstructed CeO2-x(110) facet. (C) 2020 The Author(s). Published by Elsevier Ltd.