The influence of oxygen vacancy and Ce3+ ion positions on the properties of small gold clusters supported on CeO2−x(111)†
We studied the influence of oxygen vacancies on small Au clusters supported on CeO2 using dispersion-corrected density functional theory (DFT-D). Our results show that the effect of oxygen vacancies on Au clusters is highly dependent on the cluster size and the relative position of the cluster to the vacancy. We found that the Au particles are only affected by the vacancies if they are located directly within the cluster perimeter. Using Crystal Orbital Hamilton Population (COHP) analysis, we show that the oxygen vacancy can lead to the formation of Au–Ce bonds under destabilisation of the bonds to the Au atom at the vacancy site and subsequent distortion of the cluster structure. However, we found that such Au–Ce bond formation only occurs when the interactions between the Au atom at the vacancy site and the surrounding Au atoms are not critical for the overall cluster stability as, for example, in the case of the central atom in a planar Au7 cluster. The formation of an oxygen vacancy can change the charge of the supported gold cluster from positive (on stoichiometric CeO2) to neutral or negative on defective CeO2−x. Interestingly, the additional electron density is located only at the Au atom at the vacancy site and is not redistributed throughout the cluster. Investigation of the electrostatic potential of the cluster surface did not show any significant changes compared to the stoichiometric surface, other than those caused by structural changes of the Au cluster.