The Electronic Structure and Chemical Properties of a Ni/CeO2 Anode in a Solid Oxide Fuel Cell: A DFT + U Study

Using a model for the Ni/ceria anode of a solid oxide fuel cell (SOFC), we have performed a DFT + U study of H2 and CH4 activation on the ceria surface and elucidated the mechanisms of charge transfer as a result of ceria reduction. Bader’s Atoms in Molecules (AIM) analysis scheme establishes that deposition of nickel on stoichiometric ceria to form the Ni/ceria anode results in the transfer of electron density from Ni to CeO2. The subsequent removal of an oxygen atom from the ceria surface of the Ni/ceria anode in the process of fuel oxidation results in a minor transfer of electron density from ceria to Ni. The modest amount of transferred electron charge following vacancy formation can be explained by the fact that the rather shallow vacancy-induced occupied band in ceria has a lower energy than the top of the Ni valence band. We also show that the removal of an oxygen atom not bonded to Ni is more favorable (by 28 kcal/mol) than extraction of an oxygen, originally bonded to both Ni and Ce at the Ni/Ce...