Preparation and characterization of nanosized Pt/Au particles on TiO2-nanotubes

TiO2-nanotubes were prepared by hydrothermal treatment of TiO2 powders in concentrated NaOH solution at 110 °C for 90 h. The immobilization of Pt and Au was carried out by photochemical deposition method with TiO2-nanotubes suspending in an aqueous solution containing H2PtCl6·6H2O or HAuCl4·3H2O. Transmission electron micrographs revealed that the diameter of the as-made TiO2-nanotube is about 10 nm with an inner diameter around 6 nm. The nanotube shows layered structures similar to the carbon nanotubes. The layer spacing is about 0.88 nm. Nanosized Pt (∼2 nm) and Au (∼10 nm) particles were dispersed uniformly on the surface of the nanotubes. The BET surface area of the nanotube is ∼200 m2/g as estimated by N2 adsorption isotherm, that was not significantly affected after the immobilization of Pt or Au. In-situ IR spectroscopic studies revealed that the Pt/TiO2-nanotube is highly active for CO2 hydrogenation, while Au/TiO2-nanotube exhibits pronounced activity for CO oxidation at room temperature. In general, Pt/TiO2-nanotubes presents a relatively higher activity than Au/TiO2-nanotubes, and the catalytic activities of TiO2 supported Pt and Au catalysts are significantly enhanced by the high surface area of TiO2-nanotube.