DFT+U study of CO₂ reduction and CO oxidation on a reconstructed CeO_2−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 CeO_2−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 CeO_2−x(110) facet.