Untangling product selectivity on clean low index rutile TiO surfaces using first-principles calculations

Computational modeling of metal oxide surfaces provides an important tool to help untangle complex spectroscopy and measured catalytic reactivity. There are many material properties that make rational catalytic design challenging, and computational methods provide a way to evaluate possible structural factors, like surface structure, individually. The mechanism of water oxidation or oxygen evolution is well studied on some anatase surfaces and the rutile TiO 2 (110) surface but has not yet been mapped on other low-index Miller rutile surfaces that are present in most experimental nano-titania catalysts. Here first principles calculations provide new insights into water oxidation mechanisms and reactivity of the most common low-index Miller facets of rutile TiO 2 . The reactivity of three surfaces, (101), (010), and (001), are explored for the first time and the product selectivity of multistep electron transfer on each surface is compared to the well-studied (110) surface. Density functional theory shows that a peroxo, O (p) , intermediate is more favorable for water oxidation on all facets. The &z.rad;OH radical formation is favored on the (001) facet resulting in a high overpotential for oxygen evolution reaction (OER). The (101) and (110) facets have low overpotentials, ∼0.3 V, and favor two-electron proton-coupled electron transfer to produce H 2 O 2 . The only facet that prefers direct OER is (001), leading to O 2 evolution in a four-electron process with an overpotential of 0.53 V. A volcano plot predicts the selectivity and activity of low-index Miller facets of rutile TiO 2 , revealing the high activity of the peroxo OER mechanism on the (010) facet. Reactivity and selectivity of stoichiometric low-index Miller surfaces of rutile TiO 2 are mapped, and the proton-coupled electron transfer mechanism of oxygen evolution is evaluated for product selectivity on each surface.