Density Functional Calculation of Dioxygen Adsorption at Complexes of Ceria Nanoparticle with Atoms, Trimers and Tetramers of Silver
Molecular adsorption (MA) and dissociative adsorption (DA) of O2 on complexes of a model nanoparticle Ce21O42 (NP) with an atom and small clusters of silver have been addressed. According to results of density functional calculations formation energies of such systems (with respect to the non-interacting NP, Agn and O2) are calculated to be 2.0-4.4 eV. O2 adsorption energy (Ead(O2)) in the lowest-energy atomic complex with О2 in a bridging position between Ce ion and Ag bound on the {111} nanofacet (AgOO{Ce}-complex) is as high as ~1.3 eV. AgnOO{Ce}- and OAgnO{Ce}- bridging structures are formed in MA and DA lowest-energy complexes of Ag3 on {100} and {111} as well as Ag4 on {100} nanofacets. Bonding characteristics of the AgnOO{Ce}-structures match those for stable superoxo groups О2 <sup> - </sup>. Ead(О2) of the lowest-energy МА and DA complexes of O2 with Ag clusters are in the range of 0.5-1.1 and 1.4-2.0 eV, respectively. Activation energies for O2 dissociation in AgnOO{Ce}complexes (n=3, 4) calculated to be 1.5-2.1 eV indicate low rates of these oxidation rearrangements.