Relationships between the surface electronic and chemical properties of doped 4d and 5d late transition metal dioxides.

Density functional theory calculations were performed to elucidate the underlying physics describing the adsorption energies on doped late transition metal dioxide rutiles. Adsorption energies of atomic oxygen on doped rutiles M(D)-M(H)O2, where transition metal M(D) is doped into M(H)O2, were expressed in terms of a contribution from adsorption on the pure oxide of the dopant M(D) and perturbations to this adsorption energy caused by changing its neighboring metal cations and lattice parameters to that of the host oxide M(H)O2, which we call the ligand and strain effects, respectively. Our analysis of atom projected density of states revealed that the t2g-band center had the strongest correlation with adsorption energies. We show that charge transfer mediated shifts to the t2g-band center describe the ligand effect, and the radii of the atomic orbitals of metal cations can predict the magnitude and direction of this charge transfer. Strain produces systematic shifts to all features of the atom projected density of states, but correlations between the strain effect and the electronic structure were dependent on the chemical identity of the metal cation. The slope of these correlations can be related to the idealized d-band filling. This work elucidates the underlying physics describing adsorption on doped late transition metal oxides and establishes a foundation for models that use known chemical properties for the prediction of reactivity.