First-principles study of the initial oxygen reduction reaction on stoichiometric and reduced CeO2 (111) surfaces as a cathode catalyst for lithium–oxygen batteries

Abstract

CeO₂ has been explored as an electro-catalyst for the cathode of lithium–oxygen batteries due to its good performance, especially in the initial discharging stage. In order to fully understand its initial oxygen reduction reaction (ORR), in this work, oxygen and lithium adsorptions and the initial ORR on stoichiometric and reduced CeO₂ surfaces were systematically investigated using density functional theory (DFT) calculations. Changes of free energy values and structural parameters of the intermediates and precursors of the initial ORR were also studied to identify the possible reaction paths. It was found that the oxygen atoms are preferably adsorbed on the reduced CeO₂ surface, whereas the lithium atoms are preferably adsorbed on both the stoichiometric and reduced CeO₂ surfaces; therefore, there exists a strong adsorption at the site with high oxygen coordination. The reduced CeO₂ with the surface oxygen vacancies was identified as the most critical surface for the initial oxygen reduction reaction. The path with the lithium adsorption as the first step was identified as the most probable one. A Li₃O₂ precursor was identified as the most possible initial structure of the catalyst to start the discharging process.