Zhou Bao-xue

TiO2 nanotube arrays and TiO2-nanotube-array based dye-sensitized solar cell

To substitute the non-regular nano-crystalline semiconductor for a novel kind of ordered microstructure is a very important aspect in the domain of dye-sensitized solar cell. One of the researching hotspots is the highly-ordered TiO2 nanotube architecture. As a new type of titania nano-material, titania nanotube arrays have drawn extraordinary attention due to its distinctive morphology, notable photoelectrical and hydro-sensitive performance. At 100% sun the new kind of TiO2 nanotube arrays solar cell exhibits an overall conversion efficiency of 5.44%. This paper introduces the preparation methods of titania nanotube arrays, the existing problems and recent progress in titania nanotube arrays solar cell.

Light scattering of nanocrystalline TiO2 film used in dye-sensitized solar cells

This paper studies the light scattering and adsorption of nanocrystalline TiO2 porous films used in dye-sensitized solar cells composed of anatase and/or rutile particles by using an optical four-flux radiative transfer model. These light properties are difficult to measure directly on the functioning solar cells and they can not be calculated easily from the first-principle computational or quantitative theoretical evaluations. These simulation results indicate that the light scattering of 1–25 nm TiO2 particles is negligible, but it is effective in the range of 80 and 180 nm. A suitable mixture of small particles (10 nm radius), which are resulted in a large effective surface, and of larger particles (150 nm radius), which are effective light scatterers, have the potential to enhance solar absorption significantly. The rutile crystals have a larger refractive index and thus the light harvest of the mixtures of such larger rutile and relatively small anatase particles is improved in comparison with that of pure anatase films. The light absorption of the 10 μm double-layered films is also examined. A maximal light absorption of double-layered film is gotten when the thickness of the first layer of 10 nm-sized anatase particles is comparable to that of the second larger rutile layer.

Preparation of nanocrystalline anatase TiO2 using basic sol-gel method

Nanocrystalline titanium dioxide particles with anatase structure and high thermal stability have been synthesized using the basic sol-gel method. The particle size and morphology were refined under hydrothermal conditions in the presence of different concentrations of tetramethylammonium hydroxide (TMAH) at 210°C and 230°C. XRD and TEM analysis showed that the TiO2 particles obtained were homogeneous and monodispersive at low contents of TMAH. All intense peaks, clearly observed in the XRD patterns, were assigned to the anatase phase and no rutile phase was observed. At high contents of TMAH, nanoscale small (10–30 nm) and larger (>100 nm) TiO2 particles were one-pot synthesized. The nanocrystalline TiO2 particles synthesized by this method have good thermal stability. With the sintering temperature of up to 650°C, all the XRD peaks maintained good agreement with the anatase reference data.

Preparation, Characterization and Visible Light Photocatalytic Activity of Nitrogen-doped TiO2

The N-doped TiO2 polycrystalline powder was synthesized through calcining the hydrolysis product of tetra-butyl titanate with ammonia. The photocatalytic activity of N-doped TiO2 powder with anatase phase calcined at 400 °C was 2.7 times higher than that of Degussa P25 for phenol decomposition under visible light. All samples had mesoporous structures. X-ray photoelectron spectroscopy confirmed that a trace amount of N atoms remained in the anatase polycrystalline TiO2 powder when calcined at 400 °C as substitutional atoms at the oxygen sites. UV-Vis and EPR analyses indicated that oxygen vacancy states were created during the course of N-doped TiO2 powder formation. It is considered that substitutional N atoms, oxygen vacancy states, large BET surface areas and mesoporous structure are important factors for the N-doped photocatalyst to present a high vis-activity.