Location of Trapped Hole on Rutile-TiO2(110) Surface and Its Role in Water Oxidation

The trapped hole and its nature on rutile TiO 2 (110) surface has been fully examined by first-principles GGA+U method with U(p) ranged from 3.0 to 7.0 eV. The bridge oxygen is found to be the most stable hole trapping site, and it is of a p-type orbital perpendicular to the bridge oxygen row. How the hole reacts with a H 2 O molecule above the surface is investigated with constrained minimization method. The highest occupied molecular orbital of approaching H 2 O is found to hybridize with the hole orbital and to form bonding and antibonding orbitals. An electron is seen to be transferred from H 2 O to the bridge oxygen mediated by the formed bonding state. The electron transfer is accompanied by H 2 O dissociation concertedly, which results in a hydroxyl radical adsorbed on the surface sharing the hole orbital with an in-plane oxygen atom. The reaction pathway is also estimated.