Trends in C–O and N–O bond scission on rutile oxides described using oxygen vacancy formation energies

Reactivity trends on transition metals can generally be understood through the d-band model, but no analogous theory exists for transition metal oxides. This limits the generality of analyses in oxide-based catalysis and surface chemistry and has motivated the appearance of numerous descriptors. Here we show that oxygen vacancy formation energy (ΔE(Vac)) is an inexpensive yet accurate and general descriptor for trends in transition-state energies, which are usually difficult to assess. For rutile-type oxides (MO(2) with M = 3d metals from Ti to Ni), we show that ΔE(Vac) captures the trends in C–O and N–O bond scission of CO(2), CH(3)OH, N(2)O, and NH(2)OH at oxygen vacancies. The proportionality between ΔE(Vac) and transition-state energies is rationalized by analyzing the oxygen–metal bonds, which change from ionic to covalent from TiO(2) to NiO(2). ΔE(Vac) may be used to design oxide catalysts, in particular those where lattice oxygen and/or oxygen vacancies participate in the catalytic cycles.