Theoretical study of O2 adsorption and CO2 formation in bimetallic dimer clusters Au-M

Cation, anion, and neutral states in Au-M dimer clusters have been calculated as a way to study in a small model, the Au-sites, and M-sites in a supported nanoparticle (NP). These charged states can be formed during a charge transfer process between certain atoms of the NP with the atoms of the support or simply with cationic or anionic defects. These results can be important to evaluate in a preliminary way, the relation between the activity of the Au-sites and M-sites because of its charge and the effectiveness of the adsorption of O-2, and the subsequent interaction between adsorbed O-2 and CO through a Langmuir-Rideal unimolecular mechanism. For the O-2 adsorption over Au active site, the Au-Ir, Au-Au, Au-Ag, Au-Pd, and Au-Cu dimers yielded negative binding energies in all the charge states considered (anion, cation, and neutral); when M active site was considered, Au-Cu and Au-Ag dimers also gave negative values of binding energies in all the charged states. Furthermore, there was observed that electron rich Au-sites are essential in the O-2 adsorption. (c) 2008 Wiley Periodicals, Inc.