Density Functional Studies of Small Au Clusters adsorbed on α-FeOOH: structural and electronic properties

LEANDRO F. FORTUNATO; CAROLINA ZUBIETA; FUENTE SILVIA A; PATRICIA G. BELELLI; RICARDO FERULLO

APPLIED SURFACE SCIENCE

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2016 vol. 387 p. 894 - 901

0169-4332

We report a density functional theory (DFT) investigation of the interaction of tiny Aun (n = 1-5) clusters on the bare and hydroxylated (110) surfaces of goethite (α-FeOOH). Both adsorption and nucleation processes were modeled. The adsorption is predicted to be strong on the bare surface and takes place through the interaction of Au atoms with unsaturated surface oxygen anions, accompanied with a charge transfer from the metal to the support. Au3, Au4 and Au5 planar structures resulted to be particularly stable due to polarization effects; indeed, Coulombic repulsion between basal Au atoms and surface oxygen anions promotes the displacement of the electronic density toward terminal Au atoms producing a Au+(basal)/Au-(terminal) polarization. On the hydroxylated surface, Au clusters adsorbs more weakly with respect to the bare surface, mainly through monocoordinated surface hydroxyl groups and tricoordinated oxygen ions. Concerning the atom-by-atom nucleation mechanism, while on the hydroxylated surface the nucleation energy is govern by the spin of the interacting systems, on the bare surface polarization effects seems to play a fundamental role.