Steps on Rutile TiO2(110): Active Sites for Water and Methanol Dissociation

We present a detailed investigation of the structure and activity of extended defects namely monoatomic steps on (1x1)-TiO2(110). Specifically, the two most stable <001> and <1-11> step edges are considered. Employing an automated genetic algorithm that samples a large number of candidates for each step edge, more stable, reconstructed structures were found for the <1-11> step edge, while the bulk truncated structures were recovered for the <001> step edge. We demonstrate how oxygen vacancies along these defects have lower formation energies than on flat terraces and how water and methanol molecules adsorb dissociatively on reduced <1-11> step edges. Our findings are in agreement with earlier experimental results and indicate an important contribution from step edges to the reactivity of the TiO2(110) surface.