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

The trapped hole and its nature on rutile TiO2(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 H2O molecule above the surface is investigated with constrained minimization method. The highest occupied molecular orbital of approaching H2O is found to hybridize with the hole orbital and to form bonding and antibonding orbitals. An electron is seen to be transferred from H2O to the bridge oxygen mediated by the formed bonding state. The electron transfer is accompanied by H2O 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.