Photoinduced Charge Transfer from Titania to Surface Doping Site

We evaluate a theoretical model in which Ru is substituting for Ti at the (100) surface of anatase TiO2. Charge transfer from the photoexcited TiO2 substrate to the catalytic site triggers the photocatalytic event (such as water oxidation or reduction half-reaction). We perform ab initio computational modeling of the charge transfer dynamics on the interface of the TiO2 nanorod and catalytic site. A slab of TiO2 represents a fragment of the TiO2 nanorod in the anatase phase. Titanium to ruthenium replacement is performed in a way to match the symmetry of the TiO2 substrate. One molecular layer of adsorbed water is taken into consideration to mimic the experimental conditions. It is found that these adsorbed water molecules saturate dangling surface bonds and affect the electronic properties of systems investigated. The modeling is performed by the reduced density matrix method in the basis of Kohn-Sham orbitals. A nanocatalyst modeled through replacement defect contributes energy levels near the bottom of the conduction band of the TiO2 nanostructure. An exciton in the nanorod is dissipating due to interaction with lattice vibrations, treated through nonadiabatic coupling. The electron relaxes to the conduction band edge and then to the Ru site with a faster rate than the hole relaxes to the Ru site. These results are of importance for an optimal design of nanomaterials for photocatalytic water splitting and solar energy harvesting.