Electronic Origin of the Surface Reactivity of Transition-Metal-Doped TiO2(110)

We investigate the surface reactivity of doped rutile M-TiO2(110) (M = V, Cr, Mo, W, Mn, Fe, Ru, Co, Ir, and Ni) using density functional theory (DFT) and Hubbard-U corrected DFT calculations (DFT+U method). The oxygen adsorption bond, used as the surface reactivity measure, is stronger on the doped TiO2 surfaces as compared with that on the undoped TiO2 surface. We relate this increase in reactivity of the doped TiO2 surfaces to the presence of localized surface resonances and surface states in the vicinity of the Fermi level. We find that the center of these localized states on doped TiO2 is a good descriptor for the oxygen adsorption energy. The inclusion of the Hubbard-U correction to DFT barely modifies the oxygen adsorption energy on undoped TiO2, whereas it destabilizes the oxygen adsorption energies on doped TiO2 when compared with results from standard DFT. Nevertheless, we find that the oxygen adsorption energy trends predicted by a standard GGA-DFT functional are reproduced when the Hubbard-U correction is applied.