Preparation of Pt-loaded TiO2 Nanotubes/Nanocrystals Composite Photocatalysts and Their Photocatalytic Properties

The composite photocatalysts combining high adsorptive capacity with enhanced photocatalytic efficiency are expected to be more efficient catalysts for the pollutant removal in the wastewater. TiO2 nanotubes (TNTs) were synthesized via hydrothermal method using Degussa P25 titania as raw material. The Pt-loaded TiO2 nanotubes/nanocrystals composite photocatalysts (Pt/TNNs) were prepared via one-step synthesis method involved the vapor phase hydrolysis setup, where TNTs were added into the ethanol solution containing chloroplatinic acid and citric acid (as the reductant). During the water vapor treatment, some of the nanotubes were transformed into anatase TiO2 nanocrystals and a small amount of TNTs were kept as the tubular morphologies, thus the composite had a higher adsorptive capacity. The as-prepared samples were characterized by X-ray diffraction, transmission electron microscope and N-2 isothermal adsorption-desorption. Results showed that the Pt nanoparticles with crystallite size of 4 nm were uniformly dispersed onto the surface of remaining TNTs and anatase TiO2 nanocrystals with crystallite size of 8 nm derived from the transformation of TNTs, and the composite photocatalysts kept a specific surface area of more than 216 m(2)/g. The photocatalytic activity of Pt/TNNs was evaluated by the degradation rate of acid red G (ARG) and methylene blue (MB) under UV irradiation. The results showed that the pristine TNTs had good adsorptive ability but very poor photocatalytic activity. After loading with Pt nanocrystals, Pt/TNNs obtained via water vapor treatment at 120 degrees C exhibited much higher photocatalytic efficiency compared with the pristine TNTs.