Interaction of NO with Au nanoparticles supported on (100) terraces and topological defects of MgO

The adsorption of nitric oxide (NO) on Au_n (n = 1–3) particles deposited on anionic (O^2?) sites of MgO has been studied using the DFT (Density Functional Theory) approach. The regular O^2? sites of MgO(100) and the sites in edge and corner topological defects with high symmetry of MgO were considered. The adhesion energy of Au_n to MgO is larger for Au₂ and Au₃ due to higher polarization effects. On the other hand, the interaction strength of NO with supported Au_n particles depends mainly on the electronic configuration (open or closed shell) of the particle; the Au particles with odd number of atoms show larger NO binding energies. A comparison was performed with the reactivity of free Au_n particles. From this, it is possible to conclude that the support enhances the NO–Au_n bonding strength for the monomer, weakens this interaction in the case of the dimer, and does not have an effect in the trimers. Besides, the NO–Au_n bonding is essentially insensitive to the coordination of the anionic site where the Au_n particle is linked. A large red-shift of the N–O stretching frequency was obtained, particularly for the Au particles with odd number of atoms, due to a negative charge transfer from Au to NO.