Interaction of Co(CO)x with surface sites of SiO2: theoretical study

The interaction of Co(CO)4 and Co(CO)3 species with silica surface was modeled by a non-local density functional method. The geometries of the cobalt carbonyl complexes interacting with the silica surface via SiCo, SiOCCo and SiOCo bonds were optimised, and the interaction energies were calculated. The results of the adsorbate models and the surface complexes bonded via SiCo bonds were found to be in agreement with previously published theoretical data and with available experimental findings. According to our results, cobalt carbonyl species form strong bonds with silica sites and are plausible surface complexes. Bonding via carbonyl ligand was the weakest type of interaction, while bonding via surface oxygen was the strongest. The interaction energies of charged species were higher than those of the radical species. The bond distances between cobalt and its nearest neighbours decreased when there were fewer carbonyl ligands in the complex. The interaction energies and the bond distances between cobalt and its nearest neighbours correlated with the charge of the central cobalt atom.