No abstract

Understanding the mechanism for growing TiO(2) nanotubes is important for controlling the nanostructures. The hydroxide nano-islands on the Ti surface play a significant role at the initial stage of anodization by forming the very first nano-pores at the interface between hydroxide islands and substrate and eliminating the H(2)O electrolysis. A quantitative time dependent SEM study has revealed a nanotube growth process with an initial linear increase of pore diameter, film thickness and number of pores. During the anodization of titanium, different current transient curves are observed for Ti samples with or without hydroxide on the surface. The transient current profile has been quantitatively analyzed by fitting several distinctive stages based on a growth mechanism supported by SEM observations. It is found that a saturated cubic dependent equation is appropriate to fit a short current upturn due to the increase of the surface area.

A high-temperature, high-pressure, pulsed-gas sampling and detection system has been developed for testing new catalytic and photocatalytic materials for the production of solar fuels. The reactor is fitted with a sapphire window to allow the irradiation of photocatalytic samples from a lamp or solar simulator light source. The reactor has a volume of only 3.80 ml allowing for the investigation of very small quantities of a catalytic material, down to 1 mg. The stainless steel construction allows the cell to be heated to 350 °C and can withstand pressures up to 27 bar, limited only by the sapphire window. High-pressure sampling is made possible by a computer controlled pulsed valve that delivers precise gas flow, enabling catalytic reactions to be monitored across a wide range of pressures. A residual gas analyser mass spectrometer forms a part of the detection system, which is able to provide a rapid, real-time analysis of the gas composition within the photocatalytic reaction chamber. This apparatus is ideal for investigating a number of industrially relevant reactions including photocatalytic water splitting and CO reduction. Initial catalytic results using Pt-doped and Ru nanoparticle-doped TiO as benchmark experiments are presented.

The production rate and saturation point of Ti3+ defect sites on titanium dioxide P-25 and anatase nanoparticles doped with Au101(PPh3)21Cl5 (Au101) metal nanoclusters were investigated under synchrotron X-ray irradiation alone, as well as combined X-ray and UV radiation. The saturation point in the growth of the normalized relative populations of Ti3+ centers on anatase and P-25 titania nanoparticles with and without Au101 nanoclusters present at the surface was found to vary with the type of support. It was influenced by the presence of gold nanoclusters: a higher concentration of Ti3+ centers was generated where gold nanoclusters were deposited onto anatase nanoparticles and irradiated by both X-ray and UV photons, compared with X-ray irradiation alone. Conversely, all samples based on the TiO2 P-25 support displayed reduced levels of Ti3+ center populations at the saturation points under combined X-ray and UV combined radiation, compared to the samples exposed exclusively to X-ray radiation. The initial rate of production of Ti3+ defect sites was found to decrease for combined UV and X-ray irradiation in the case when Au101 was deposited onto anatase. However, the opposite trend in the initial production rate of Ti3+ centers was observed in the case of Au101 deposited onto the TiO2 P-25 surface.