Adsorption of Co2B2 and Ni2B2 Clusters on the TiO2 (110) Surface: a Density Functional Study

Based on density functional theory and generalized gradient approximation calculations, the adsorption of Co2B2 and Ni2B2 clusters on the rutile TiO2 (110) surface has been investigated utilizing periodic supercell models. Unambiguously, the results demonstrate that the hollow site turns out to be preferable for Co2B2 cluster while Ti2 site is for Ni2B2 cluster to adsorb. Orbital population analysis indicates a strong interaction between Co2B2 and O atom of TiO2 surface, which can be attributed to the overlap of Co 3d and surface O 2p orbital. Similarly, for Ni2B2 , the bonding interaction occurs mostly through the interaction of Ni 3d/4s and O 2p orbitals. Note that, there is also an interaction within the Co2B2 clusters (Ni2B2) through B 2s/2p and Co 3d orbitals (Ni 3d/4s). Moreover, orbital analysis results shows that the strong bonding between Ni2B2 and Ti2 site is due to the overlap of HOMO of Ni2B2 and d-orbital of five-coordinated titanium atoms.