Photoinduced reactivity of titanium dioxide

3.1.1. Covalent Interactions 1355 3.1.2. Noncovalent Interactions 1356 3.1.3. π-π Stacking 1356 3.1.4. Electrostatic Interactions 1357 3.2. In Situ Synthesis Directly on the CNT Surface 1358 3.2.1. Electrochemical Techniques 1358 3.2.2. Sol-Gel Process 1361 3.2.3. Hydrothermal and Aerosol Techniques 1363 3.2.4. Gas-Phase Deposition 1364 3.3. Comparison of Synthesis Techniques 1368 4. Properties and Potential Applications of CNT-Inorganic Hybrids 1368

Carbon Nanotube−Inorganic Hybrids

Yellow-colored N-doped TiO2 (NTO) powders were synthesized by spray pyrolysis from a mixed aqueous solution containing TiCl4 and an N-precursor (urea, guanidine, or ammonium fluoride). All resulting powders possessed spherical particles with an average particle diameter of 0.45 μm, however, the surface morphologies of particles significantly depended on the N-precursors. A porous surface was observed for the particles prepared by using NH4F as N-precursor. Acetaldehyde and trichloroethylene decompositions were used as probe reactions to evaluate the photocatalytic activity of these NTO powders under visible-light (vis) irradiation. The NTO powder prepared from a mixed solution of TiCl4 and NH4F demonstrated the highest photocatalytic activity among three N-precursors, and it was much higher than that of commercial P 25. This high photocatalytic activity was ascribed to a synergetic effect of several factors: its porous and acidic surface, doped N atoms, and simultaneously codoped F atoms during nitrogen introduction. However, no correlation between N-concentration and photocatalytic activity was observed.

Visible-light-driven nitrogen-doped TiO2 photocatalysts: effect of nitrogen precursors on their photocatalysis for decomposition of gas-phase organic pollutants

Novel Pb3Nb4O13/fumed SiO2 composite photocatalysts were prepared by a deposition−precipitation method for rhodamine B (RhB) photodegradation under visible light irradiation. Techniques such as XRD, UV−vis reflectance spectroscopy, and SEM were adopted to explore the characteristics of samples. Compared to the unsupported Pb3Nb4O13 sample, the composite photocatalysts showed notably improved photocatalytic activities for RhB degradation as the result of significantly strengthened interaction between the dye molecules and the Pb3Nb4O13 active component. The kinetic analysis demonstrated that rhodamine (the completely de-ethylated product of RhB) can be more easily degraded than RhB, and thus, the N-de-ethylation process is the rate-limited step of RhB photodegradation over Pb3Nb4O13/fumed SiO2 composites. It was proposed that there could be three different reaction routes for RhB photodegradation over the Pb3Nb4O13/fumed SiO2 composite materials, including the direct degradative oxidation of RhB in solutio...

Photocatalytic Degradation of Rhodamine B over Pb3Nb4O13/Fumed SiO2 Composite under Visible Light Irradiation

Enhanced visible light-induced photoelectrocatalytic degradation of phenol by carbon nanotube-doped TiO2 electrodes

Transition metal salts were added to aerogels of TiO2–SiO2 mixtures. The resulting M–TiO2–SiO2 (M = transition metal, in general present in the form of oxides) materials had very high surface areas (600–1000 m2/g) and pore volumes (1–4 cm3/g), and contained highly dispersed transition metal oxides. Several samples were active photocatalysts for acetaldehyde oxidation to carbon dioxide using visible light; in particular chromium, cobalt, and nickel. These intimate aerogel mixtures were only active when SiO2 was present (i.e. M–TiO2 aerogels were not). High oxidation states of the transition metal ions (e.g. Cr6+, Co3+) appear to be important in bringing about visible light photocatalyst activity.

S Uma

Papers

Visible light photocatalysis in transition metal incorporated titania-silica aerogels