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 photo-excited TiO₂ substrate to the catalytic site triggers the photo-catalytic event (such as water oxidation or reduction half-reaction). We perform ab-initio computational modeling of the charge transfer dynamics on the interface of TiO₂ nanorod and catalytic site. A slab of TiO₂ represents a fragment of TiO₂ nanorod in the anatase phase. Titanium to ruthenium replacement is performed in a way to match the symmetry of 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 drastically affect the electronic properties of systems investigated. The modeling is performed by reduced density matrix method in the basis of Kohn-Sham orbitals. A nano-catalyst modeled through replacement defect contributes energy levels near the bottom of the conduction band of TiO₂ nano-structure. An exciton in the nano-rod is dissipating due to interaction with lattice vibrations, treated through non-adiabatic coupling. The electron relaxes to conduction band edge and then to the Ru cite with faster rate than hole relaxes to the Ru cite. These results are of the importance for an optimal design of nano-materials for photo-catalytic water splitting and solar energy harvesting.