Unraveling the Nature of the Oxide-Metal Interaction in Ceria-Based Noble Metal Inverse Catalysts

Recently, it has been shown that model catalysts consisting of cerium oxide nanoparticles supported on noble metal surfaces are very convenient to clarify the reaction mechanism of important industrial reactions such as watergas shift, CO oxidation, and methanol synthesis from CO2. Moreover, these special inverse catalysts are highly active, even more than the regular metal/oxide catalyst in some cases. However, there is a lack of fundamental knowledge about the electronic nature of the supported CeOx nanoparticles (NPs) and their interaction with the noble metal support. In this work we have carried out DFT calculations on CeOx/Cu(111), CeOx/Ag(111), and CeOx/Au(111) interfaces for both supported particles and periodic 2D film. The most stable and most reduced CeOx NPs are found when supported on Cu(111), followed by Ag(111) and Au(111). A similar behavior is observed for periodic 2D CeO2(111) films supported on the M(111) surfaces, although the reducibility is lower and the stability higher in extended films than in small particles. The charge transfer contribution from the support dominates the strength of the oxide(film)metal interaction following the sequence Cu > Ag > Au. The high stability and reducibility of CeOx on Cu(111) and Ag(111) and the lower stability and reducibility on Au(111) are rationalized on the grounds of the metaloxide/metal charge transfer, the electronic structure of the system, work function of the metal surfaces, structural mismatch, and the nature of the interface bonding.