Comparative density functional theory based study of the reactivity of Cu, Ag, and Au nanoparticles and of (111) surfaces toward CO oxidation and NO2 reduction.

The reactivity of Cu, Ag, and Au nanoparticles and of the corresponding (111) surfaces of these elements toward CO oxidation and NO(2) reduction has been investigated by means of DFT and DFT-D calculations. The co-adsorption energies of CO and O on Ag and Au surfaces are smaller than that corresponding to Cu surface but the oxidation reaction is energetically more favored for the heavier metals. The adsorption energy of NO(2), E(ads), is about 50 % larger on nanoparticles than on the metal perfect surfaces, following the almost general rule stating that the lower coordinated sites are those where the interaction is the largest. Interestingly for the co-adsorption and oxidation of CO an increase of reactivity is found for the Au nanoparticles, which is attributed to the large number of low coordinated sites due to the specific shape of this nanoparticle induced by the adsorbates.