First-principles Study Of Novel Materials For Energy Storage And Photovoltaic Conversion

TiO2 nanotube is a highly promising anode material for rechargeable Li-ion batteries. Computational studies based on density functional theory (DFT) have been performed for TiO2 nanotubes aiming at key issues related to lithium insertion sites and lithium diffusion properties. As a possible vacancy, oxygen vacancy cannot be fully eliminated with current fabrication procedures in TiO2 nanotubes and it can affect the electronic structures and properties of TiO2 nanotubes. Our electronic structure calculations show lithium is favorable on both inner and outer surface of perfect and oxygen-vacancy doped TiO2 nanotubes at low lithium concentration. A systematic investigation of the effect of oxygen vacancy on Li-ion diffusion suggests that the bridging oxygen plays a very positive role in the Li-ion diffusion, the barrier energies of the stable diffusion pathway decrease from 0.8 eV to 0.55 eV. One-dimensional anatase nanotubes have an advantage in lithium ion diffusion compared with bulk anatase (0.623 eV) and other nanotube materials (>1.8 eV).Using the Ab initio non-adiabatic molecular dynamics method, we studied the electron transfer and energy relaxation processes between Au25 clusters and pyrene dye molecules. Adiabatic and non-adiabatic mechanism commonly affects the process of electron transfer. The adiabatic mechanism dominate the electron transfer, which is indicated from the evolution of the occupation and localization for adiabatic states, The time constant of electron transfer is 140 fs. Its energy relaxation time is 17.5 ps, which is much larger than the electron transfer time scale It can be concluded that the fluorescence quenching is caused by the fast electron transfer from Au cluster to the pyrene, the HOMO of pyrene will be filled quickly by electrons from energy levels of gold cluster, preventing the generation of fluorescence. The experimental results can be well undertood based on our simulation.The artical used a method of the first principle calculation to systematically study anatase nanotubes and gold nanoclusters. These two kinds of nanomaterials were considered as a new energy storage material and photoelectric conversion material respectively and provide new ideas of corresponding mechanism and rational design.