Doping bismuth ions into photocatalytic materials is one of the most effective methods for preparing highly visible-light-active photocatalysts. In order to develop high-performance photocatalytic materials that are easy to produce, even in industrial quantities, we developed a facile method to prepare bismuthdoped titanium dioxide (Bi-doped TiO 2 ) by hydrothermal synthesis followed by thermal annealing treatment. Bi-doped TiO 2 can be applied in the field of photodecolorization of organic dye and photocatalytic hydrogen generation. High concentration doping (>5.00 mol%) resulted in the morphological change of Bi-doped TiO 2 from nanofibre to nanorod observed by transmission electron microscopy. The crystal structure evolution and elemental composition were analysed by combining Raman spectroscopy, X-ray crystallography and X-ray photoelectron spectroscopy. For the photodegradation of organic dye methyl orange, all Bi-doped TiO 2 showed less activity than pristine TiO 2 nanofibres under UV irradiation. 5.00 mol% and 10.00 mol% Bi-doped TiO 2 showed higher activities than pristine TiO 2 nanofibres under visible light irradiation. For the photocatalytic hydrogen generation measurement, none of the Bi-doped TiO 2 showed a detectable value under visible light irradiation. However, under UV irradiation, various Bi-doped TiO 2 catalysts exhibited a detectable photocatalytic hydrogen production rate. 0.50 mol% Bi-doped TiO 2 exhibited the highest performance. The result could be due to the relatively lower overpotential for hydrogen production. Our study developed a series of visible-light-active Bi-doped TiO 2 catalysts, and it could replace the traditional TiO 2 catalysts decorated with a high-cost noble metal.
TiO 2 nanotubes promoted with Pt metal were prepared and tested to be the photocatalytic dehydrogenation catalyst in neat ethanol for producing H 2 gas ðC 2 H 5 OH ! C 3 CHO þ H 2 Þ. It was found that the ability to produce H 2 , the liquid phase product distribution and the catalyst stability of these promoted nano catalysts all depended on the Pt loading and catalyst preparation procedure. These Pt/TiO 2 catalysts with TiO 2 nanotubes washed with diluted H 2 SO 4 solution produced 1, 2-diethoxy ethane (acetal) as the major liquid phase product, while over those washed with diluted HCl solution or H 2 O, acetaldehyde was the major liquid phase product.
Hydrogenated titanium dioxide has attracted intensive research interests in pollutant removal applications due to its high photocatalytic activity. Herein, we demonstrate hydrogenated TiO2 nanofibers (H:TiO2 NFs) with a core-shell structure prepared by the hydrothermal synthesis and subsequent heat treatment in hydrogen flow. H:TiO2 NFs has excellent solar light absorption and photogenerated charge formation behavior as confirmed by optical absorbance, photo-Kelvin force probe microscopy and photoinduced charge carrier dynamics analyses. Photodegradation of various organic dyes such as methyl orange, rhodamine 6G and brilliant green is shown to take place with significantly higher rates on our novel catalyst than on pristine TiO2 nanofibers and commercial nanoparticle based photocatalytic materials, which is attributed to surface defects (oxygen vacancy and Ti3+ interstitial defect) on the hydrogen treated surface. We propose three properties/mechanisms responsible for the enhanced photocatalytic activity, which are: (1) improved absorbance allowing for increased exciton generation, (2) highly crystalline anatase TiO2 that promotes fast charge transport rate, and (3) decreased charge recombination caused by the nanoscopic Schottky junctions at the interface of pristine core and hydrogenated shell thus promoting long-life surface charges. The developed H:TiO2 NFs can be helpful for future high performance photocatalysts in environmental applications.
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