Molecular chemisorption as the theoretically preferred pathway for water adsorption on ideal rutile TiO2(110)

By taking careful account of slab thickness and adsorbate orientation effects we present, for the first time, periodic density functional calculations predicting the preference of water to adsorb in a molecular state on the ideal rutile TiO2(110) surface at all coverages < or =1 monolayer (ML). Moreover, while this has been predicted previously for 1/4 ML coverage [Phys. Rev. Lett. 87, 266104 (2001)]], we show that the assertion made in that work, that dissociation is energetically unfeasible on the ideal surface, is incorrect. Our results thus resolve a long-standing discrepancy between theory and experiment and significantly improve the understanding of water chemistry on TiO2 surfaces.