Jian-Wei Chen

TiO2/activated carbon fibers photocatalyst: Effects of coating procedures on the microstructure, adhesion property, and photocatalytic ability

In order to more easily separate TiO(2) photocatalyst from the treated wastewater, TiO(2) film was immobilized on the surface of activated carbon fibers (ACFs) by employing two kinds of coating procedures, dip-coating, and hydrothermal treatment. The effects of coating procedures on microstructure of TiO(2)-coated ACFs (TiO(2)/ACFs), such as morphology, porous property, crystal structure, and light absorption characteristics were investigated in detail. The adhesion property between TiO(2) film and ACFs was evaluated by ultrasonic vibration, and the photocatalytic activity of TiO(2)/ACFs was tested by the photocatalytic decoloration of methylene blue solution. The results show that hydrothermal treatment presented many advantages to obtain high-performance TiO(2)/ACFs photocatalyst in comparison with dip-coating. Hydrothermal treatment could improve the binding property between TiO(2) films and ACFs, which endowed the as-obtained TiO(2)/ACFs photocatalyst with improved reusable performance, and TiO(2)/ACFs synthesized by hydrothermal treatment presented higher photocatalytic activity.

Recent progress in the preparation and application of semiconductor/graphene composite photocatalysts

Graphene is a new material with a single-layer laminar structure of carbon atoms that possesses favorable physical and chemical properties such as high electrical conductivity, high chemical stability, and large specific surface area. Combining graphene with semiconductors to form composite photocatalysts can extend its light absorption edge, improve the migration rate of charge carriers, and enhance the adsorption capacity of contaminants. The unique two-dimensional planar structure of graphene endows composite photocatalysts with many excellent properties. Herein, the properties of graphene, semiconductor, and composite photocatalysts are first introduced. The various preparation methods of semiconductor/graphene composite photocatalysts are then presented, and the mechanisms behind enhanced photocatalysis are summarized. Four typical applications of composite photocatalysts: elimination of organic pollutants, hydrogen production, organic fuel production via CO2 reduction, and photocatalytic sterilization, are described in detail. Finally, the direction of future research on semiconductor/graphene composite photocatalysts is explored.

Carbon-doped titania nanoplates with exposed {001} facets: facile synthesis, characterization and visible-light photocatalytic performance

C-doped TiO2 nanoplates (CTNP) with exposed {001} facets were successfully synthesized by hydrothermal treatment of TiC powder in a HF–HNO3 mixed aqueous solution for the first time. The effects of hydrothermal temperature (140, 160, 180 and 200 °C) on the crystal phase, morphology, specific surface area and porous properties, surface element composition, optical response properties of the resultant samples were investigated in detail, and the photocatalytic activities of these obtained CTNP samples for the degradation of methylene blue (MB) were evaluated under visible light irradiation. The results showed that precursor cubic TiC was transformed into anatase TiO2 with the morphology of well-defined nanoplate completely after hydrothermal treatment for 30 h. The specific surface area of CTNP was significantly improved in comparison with that of micrometer sized C-doped TiO2 plates (CTP) due to smaller particle size. Due to C-doping, CTNP presented red-shift absorption edge, which supported it with strong visible-light response. All these factors led to as-prepared CTNP having more excellent visible-light photocatalytic activity in comparison with micrometer sized CTP. The CTNP synthesized at 180 °C presented the optimal visible-light photocatalytic activity with a high reaction rate constant (0.03692 min−1) among the four CTNP samples. Based on the results of the present study, a reasonable mechanism of photocatalysis on CTNP under visible light was proposed.

The composite of nitrogen-doped anatase titania plates with exposed {001} facets/graphene nanosheets for enhanced visible-light photocatalytic activity.

Composite photocatalysts composed of nitrogen-doped anatase TiO2 plates with exposed {001} facets (NTS) and graphene nanosheets (G) were firstly synthesized by a facile one-pot hydrothermal process. The morphologies, structural properties, and photocatalytic activities of the resultant NTS/G composites were investigated in detail. Graphene nanosheets were demonstrated play three important roles in the NTS/G composites, as transporter of photo-excited electrons, extender of light absorption range and enhancer of adsorptive capacity, respectively. Due to the effective charge anti-recombination, the efficient utilization of the visible light and the high adsorptive capacity to target pollutants, the composites exhibited significant improvement in photocatalytic degradation of methylene blue under visible light irradiation. Based on the results, the mechanism of enhanced visible-light photocatalytic activity on NTS/G composites was proposed.

Sol-Gel to Prepare Nitrogen Doped TiO2 Nanocrystals with Exposed {001} Facets and High Visible-Light Photocatalytic Performance

A series of N-doped TiO2 nanocrystals with exposed facets was prepared successfully by sol-gel method for the first time. The physicochemical properties of these resultant photocatalysts were characterized by XRD, TEM, XPS, and DRS, and their photocatalytic performances were evaluated by photocatalytic decoloration of methylene blue solution under visible light ( nm) irradiation. The results showed that the N-doped TiO2 nanocrystals with exposed facets showed higher photocatalytic activity than P25. The enhanced photocatalytic performance can be attributed to synergistic effects of several factors, such as good crystallinity, better light response characteristic, and high reactivity of facets.