Adsorption of Aun (n = 1–4) clusters on Fe3O4(001) B-termination

To understand the catalytic properties of Au nanoparticles supported on iron oxide, the adsorption structures and energies of Aun (n = 1–4) clusters on the stoichiometric, reduced and hydrated Fe3O4(001) B-terminations were systematically studied by using the GGA density functional theory method including the Hubbard parameter (U) to describe the on-site Coulomb interaction. It was found that the formation of a reduced surface with oxygen vacancies is much easier than that of an oxidized surface with iron vacancies. The most stable hydrated surface has dissociative H2O adsorption with the formation of surface hydroxyls, in agreement with the recent computational and experimental studies. Different adsorption configurations of Aun clusters have been found on the three surfaces. Au clusters prefer to bind with surface iron atoms, compared to surface oxygen atoms. The most stable adsorption configuration of single Au adatoms on the long bridge site to two surface O atoms is supported by a recent experimental study. The adsorbed Au atoms on surface iron atoms are reduced and negatively charged; and the Au atoms interacting either with surface oxygen atoms or the surface hydroxyls have less negative or positive charge. The surface hydroxyls can stabilize the adsorption of Aun clusters.