Density Functional Modeling of the Interactions of Platinum Clusters with CeO2 Nanoparticles of Different Size

We studied computationally the interaction of a representative metal duster Pt-8 with two groups of model ceria nanoparticles exhibiting crystalline-like atomic arrangement. Different adsorption positions of the cluster on nanoparticles Ce21O42 and Ce40O80 as well as on their analogues with an oxygen vacancy were considered. In the most stable composites of both stoichiometric nanoparticles, the platinum cluster partially reduces the oxide via electron transfer to the cerium ions. The effect of the platinum cluster on the calculated energy required for formation of an oxygen vacancy on ceria depends on the size of the nanoparticle and location of Pt-8 with respect to the vacancy. The interaction with platinum decreases the vacancy formation energy for the smaller nanoparticle from 1.67 to 1.23 eV, while for the larger nanoparticle the energy increases from 0.80 to 1.08 eV. Despite these different trends, the oxygen transfer from the ceria nanoparticles of both sizes to platinum is favorable: the calculated energy gain for the most preferable location of the oxygen atom on Pt-8 is-0.41 eV for Ce21O42 and -0.51 eV for Ce40O80. This formation of oxygen species on the noble metal cluster explains the experimentally identified much stronger activity of metal catalysts supported on ceria nanoparticles compared to those on the bulk-like ceria support.