Photoinduced Charge Transfer from Titania to Surface Doping Site

Abstract

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.

Enhanced multiple exciton generation in amorphous silicon nanowires and films

“…So, additionally one needs to compute exciton relaxation times due to phonon emission, and, then, contributions to R 1 , R 2 from decays of a photon into low-energy excitons. At the atomistic level, this task can be achieved by employing the finite temperature/real time technique of perturbative many-body quantum mechanics [102][103][104], or the reduced density matrix method [76,[105][106][107].…”

Charge Transfer Mechanism in Titanium-Doped Microporous Silica for Photocatalytic Water-Splitting Applications

“…were used to compose the density matrix for each instant of time in such a way that it matches the initial conditions Equation (14) [6][7][8]22]. The electron in the conduction band and the hole in the valence band are indicated by e and h, respectively.…”

“…In addition, index e was used with the appreciation that equations for holes are the same as for electrons. Utilizing the above information, the charge density distribution, rate of energy dissipation, and rate of charge transfer were calculated as follows [6][7][8]22,33].…”

“…The addition of titanium atoms to the inner surface of the silica pore walls provides a photoactive material [5] and introduces numerous charge transfer states, which can be analyzed by atomistic computational modeling [6][7][8]. It has been known since the 1970s that titanium dioxide (TiO 2 ) can be used in water-splitting applications [9].…”

“…This information helps to identify orbital transitions due to excitations, which are of interest. Molecular dynamics [19] are simulated, which leads to couplings [20] and eventually to electron dynamics of photoexcitation [21] that then provides excitation lifetimes [22] and details of the charge transfer meachanism [6][7][8]. These lifetimes are an integral part of making conclusions about a material and its photocatalytic properties.…”