Interaction between transition metals (Co, Ni, and Cu) systems and amorphous silica surfaces: A DFT investigation

Abstract

Transition metals (Co, Ni, or Cu) systems supported on amorphous silica are promising materials for their unique surface chemical reactivity. Despite many investigations, the transition metal-support interactions for this type of materials are not yet well understood at the molecular level. In this work, periodic density functional theory calculations, were performed to investigate systematically the interaction between Co, Ni, or Cu species (monomers and clusters) and amorphous silica surfaces with densities of 3.3 and 4.6 OH/nm2. It is shown that the geometry, energetic stability, and magnetic properties of transition metal species deposited on amorphous silica surfaces depend strongly of the number of M-O-Si groups and, in few cases, of the number of M-OH-Si groups, with sometimes a strong effect on the silica surface that induces a reorganization of the silanol groups. Among monomers, cobalt is found to be the most stable on the silica surface while among clusters, the Ni cluster is the most strongly adsorbed. The magnetic moments of the adsorbed transition metal clusters on silica surface are found to be reduced with respect to their corresponding free clusters for Co and Ni.