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The article explores the synthesis of titanium dioxide composite nanomaterials and its applications. Topics discussed include metal and metal oxide, nonoxide semiconductor, and carbon titanium oxide composites. Also mentioned are template composites such as anodized aluminum oxide, ordered mesoporous silica and zeolites, and yolk-shell and core-shell.

Photocatalytic reduction of CO2 holds great promises for addressing both the environmental and energy issues that are facing the modern society. The major challenge of CO2 photoreduction into fuels such as methane or methanol is the low yield and poor selectivity. Here, we report an effective strategy to enhance the reduction potential of photoexcited electrons by fluorination of mesoporous single crystals of reduced TiO2-x. Density functional theory calculations and photoelectricity tests indicate that the Ti3+ impurity level is upswept by fluorination, owing to the built-in electric field constructed by the substitutional F that replaces surface oxygen vacancies, which leads to the enhanced reduction potential of photoexcited electrons. As a result, the fluorination of the reduced TiO2-x dramatically increases the CH4 production yield by 13 times from 0.125 to 1.63 µmol/g·h under solar light illumination with the CH4 selectivity being improved from 25.7% to 85.8%. Our finding provides a metal-free strategy for the selective CH4 generation from CO2 photoreduction. [ABSTRACT FROM AUTHOR]

We demonstrate that anatase TiO2 nanocrystals composed of a nanocrystal core and nanorod antennas can be produced via a nonaqueous colloidal seed-mediated growth method. Anatase TiO2 nanocrystals with defined morphologies were first prepared as seeds, and then secondary anatase TiO2 nanorods were grown on the defined facets of the seeds under appropriate conditions. Systematic studies on the growth mechanism reveal that the formation of core--antenna nanocrystals involves an epitaxial growth process with specific orientational preference governed by both thermodynamic and kinetic factors. By manipulating the reaction conditions including the precursor amount and introduction rate, the epitaxial growth behavior can be well controlled. By further varying the morphology of seed nanocrystals, we have also been able to produce core-antenna anatase TiO2 nanocrystals with complex spatial configurations in a highly predictable manner. The high structural configurability and predictability offered by this seed-mediated growth method may provide great opportunities in enhancing the performance of TiO2-based nanostructures in many energy-related applications. As a demonstration, we show by simply manipulating the core--antenna structures that the photocatalytic activity of the anatase nanocrystals can be improved from the relatively less active seed nanocrystals or pure nanorods to the extent that exceeds the activity of the commercial P2S titania. [ABSTRACT FROM AUTHOR]