2.3. Evaluation of Photocatalytic Water Splitting 6507 2.3.1. Photocatalytic Activity 6507 2.3.2. Photocatalytic Stability 6507 3. UV-Active Photocatalysts for Water Splitting 6507 3.1. d0 Metal Oxide Photocatalyts 6507 3.1.1. Ti-, Zr-Based Oxides 6507 3.1.2. Nb-, Ta-Based Oxides 6514 3.1.3. W-, Mo-Based Oxides 6517 3.1.4. Other d0 Metal Oxides 6518 3.2. d10 Metal Oxide Photocatalyts 6518 3.3. f0 Metal Oxide Photocatalysts 6518 3.4. Nonoxide Photocatalysts 6518 4. Approaches to Modifying the Electronic Band Structure for Visible-Light Harvesting 6519

Semiconductor-based Photocatalytic Hydrogen Generation

Carbonaceous nanomaterials for the enhancement of TiO2 photocatalysis

Novel carbon self-doped TiO2 sheets (CTS) with exposed {001} facets were synthesized by hydrothermal treatment of titanium carbide (TiC) in a HNO3-HF mixed aqueous solution. In this synthesis TiC was used as a precursor of TiO2 and a source of C, which was self-doped into the lattice of anatase sheets. The resulting CTS materials were examined as photocatalysts for degradation of methylene blue (MB) in aqueous solutions under visible light irradiation (λ > 420 nm). These materials exhibited an enhanced absorption in the whole visible-light region and an obvious red shift at the absorption edges. The first-principle density functional theory (DFT) calculations provided a further confirmation for the aforementioned red shift and for noticeable reduction of the band gap of C-doped TiO2 sheets with exposed {001} facets. The photocatalytic studies of CTS showed that these sheets exhibited much higher photocatalytic activity than that of the C-doped TiO2 nanoparticles due to the presence of exposed {001} facets. In addition, separation of CTS after photocatalytic reaction from slurry by filtration or sedimentation and their reuse is easier in comparison to conventional nanosized powder photocatalysts.

Fabrication and enhanced visible-light photocatalytic activity of carbon self-doped TiO2 sheets with exposed {001} facets

Carbon-doped TiO 2 (C-TiO 2 ) was successfully prepared from a conventional sol–gel synthesis without using external carbon precursors whereas all the previous reports on the synthesis of C-TiO 2 utilized them. The carbons contained in titanium alkoxide precursor could be incorporated into the lattice of TiO 2 with creating mid-bandgap electronic states through the controlled calcination. The level of carbon doping was changed sensitively depending on the calcination temperature, which was verified by UV–visible diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. The charge pair generation/recombination in C-TiO 2 was compared under visible and UV light through a time-resolved diffuse reflectance spectroscopy study, which suggested the presence of midgap energy levels induced by the incorporation of carbon dopants. The carbon doping was maximal when the calcination temperature was around 200–250 °C and hindered at higher temperatures. The visible light activities of the prepared TiO 2 samples for the conversion of 4-chlorophenol and iodide were also strongly dependent on the calcination temperature and maximized at around 250 °C. This study implies that the carbon doping in TiO 2 can be obtained even unintentionally in the conventional sol–gel synthesis.

Carbon-doped TiO2 photocatalyst synthesized without using an external carbon precursor and the visible light activity

A critical overview is presented on the role that first row p-block elements boron, carbon, nitrogen and fluorine, employed as dopants of TiO2, have in improving the capability of this photocatalyst in harvesting solar light for photocatalytic applications. The peculiar physicochemical properties of doped TiO2 materials are described in terms of the results of both theoretical calculations and photocatalytic efficiency tests, in relation to their bulk and surface features. The limitations of doping titania with non metal elements are outlined and a few recent examples of very promising co-doping effects are discussed.

Doping TiO2 with p-block elements: Effects on photocatalytic activity

Facile preparation of micro-mesoporous carbon-doped TiO2 photocatalysts with anatase crystalline walls under template-free condition.

The effects of an inner constraint layer and alumina particles on the microstructure, strength, and shrinkage of the laminated low-temperature cofired ceramic (LTCC) green sheet were investigated. A crystalline glass mixed with alumina particles was used as inner constraint layer. Sintering shrinkage in the x-y direction of the LTCC is related to the bending strength of the alumina particle and glass-ceramic layer used for an inner-constraint layer. The crystallization temperature about crystalline glass is important. In the self-constrained sintering LTCC, the soft point of crystalline glass should be above 870°C. Smaller alumina particles in the inner-constraint layer produced a substrate with a high bending strength.

Yun Lu

Papers

Facile preparation of micro-mesoporous carbon-doped TiO2 photocatalysts with anatase crystalline walls under template-free condition.

Research on self-constrained sintering low-temperature cofired ceramic