A model to understand the oxygen vacancy formation in Zr-doped CeO 2: Electrostatic interaction and structural relaxation

Abstract

Using density functional theory with the inclusion of on-site Coulomb correction, the O vacancy formation energies of CexZr 1-xO2 solid solutions with a series of Ce/Zr ratios are calculated, and a model to understand the results is proposed. It consists of electrostatic and structural relaxation terms, and the latter is found to play a vital role in affecting the O vacancy formation energies. Using this model, several long-standing questions in the field, such as why ceria with 50% ZrO2 usually exhibit the best oxygen storage capacity, can be explained. Some implications of the new interpretation are also discussed. © 2009 American Chemical Society.