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Author

Jeffrey C.S. Wu

Other affiliations: Delft University of Technology
Bio: Jeffrey C.S. Wu is an academic researcher from National Taiwan University. The author has contributed to research in topics: Photocatalysis & Catalysis. The author has an hindex of 52, co-authored 139 publications receiving 8298 citations. Previous affiliations of Jeffrey C.S. Wu include Delft University of Technology.


Papers
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TL;DR: This work provides a general bottom-up route for designing and preparing novel monolayer materials with ultrafast charge separation and active surface and leads to the outstanding performances of the monolayers material in solar energy conversion.
Abstract: Two-dimensional-layered heterojunctions have attracted extensive interest recently due to their exciting behaviours in electronic/optoelectronic devices as well as solar energy conversion systems. However, layered heterojunction materials, especially those made by stacking different monolayers together by strong chemical bonds rather than by weak van der Waal interactions, are still challenging to fabricate. Here the monolayer Bi2WO6 with a sandwich substructure of [BiO](+)-[WO4](2-)-[BiO](+) is reported. This material may be characterized as a layered heterojunction with different monolayer oxides held together by chemical bonds. Coordinatively unsaturated Bi atoms are present as active sites on the surface. On irradiation, holes are generated directly on the active surface layer and electrons in the middle layer, which leads to the outstanding performances of the monolayer material in solar energy conversion. Our work provides a general bottom-up route for designing and preparing novel monolayer materials with ultrafast charge separation and active surface.

534 citations

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TL;DR: In this paper, an improved sol-gel method using a homogeneous hydrolysis technique was used to synthesize Titania and Cu-loaded titania, which reached a steady state 250μmol/g after 20h of irradiation.
Abstract: Carbon dioxide was photocatalytically reduced to produce methanol in an aqueous solution using 254 nm UV irradiation. Titania and Cu-loaded titania were synthesized by an improved sol–gel method using a homogeneous hydrolysis technique. The grain size of TiO 2 and Cu/TiO 2 were uniform and average diameters were approximately 20 nm. Photocatalytic reduction was conducted in a quartz reactor with a UV lamp irradiating at the center. XPS analysis reveals that Cu 2p 3/2 is 933.4 eV indicating primary Cu 2 O species on the TiO 2 supports. EDX and XPS revealed that most copper clusters were on the TiO 2 surface. The optimum amount of copper loading was 2.0 wt.% for the highest dispersion among catalysts. The methanol yield of 2.0 wt.% Cu/TiO 2 was 118 μmol/g following 6 h of UV illumination. The yield was much higher than those of sol–gel TiO 2 and Degussa P25, whose yields were 4.7 and 38.2 μmol/g, respectively. The methanol yield reached a steady-state 250 μmol/g after 20 h of irradiation. Experimental results indicated that the methanol yield was significantly increased by adding NaOH. The caustic solution dissolved more CO 2 than did pure water. In addition, the OH − in aqueous solution also served as a strong hole scavenger. The redistribution of the electric charge and the Schottky barrier of Cu and TiO 2 facilitates electron trapping via supported Cu. The photocatalytic efficiency of Cu/TiO 2 was markedly increased because of the lowering the re-combination probability for hole–electron pairs. The highest quantum and energy efficiencies achieved were 10 and 2.5%, respectively.

532 citations

Journal ArticleDOI
TL;DR: In this article, a series of vanadium-doped TiO 2 catalysts were synthesized by two modified sol-gel methods, and the TEM micrographs showed the sizes of primary particles were in the range of 6-20nm.
Abstract: A series of vanadium-doped TiO 2 catalysts were synthesized by two modified sol–gel methods. V-doped TiO 2 was found to be mainly preserved its anatase phase after calcination at 400 °C. The TEM micrographs showed the sizes of primary particles were in the range of 6–20 nm. The increase of vanadium doping promoted the particle growth, and enhanced “red-shift” in the UV-Vis absorption spectra. The XPS (X-ray photoelectron spectroscopy) could not detect vanadium indicating negligible vanadium on the surface of catalysts, furthermore, there were also no peak of vanadium oxide in the XRD patterns. XAS (X-ray absorption spectroscopy) analysis indicating V 4+ instead of V 5+ implied that vanadium either substituted Ti 4+ site or embedded in the vacancy of TiO 2 structure. Therefore, vanadium was concluded to be highly dispersed inside the TiO 2 structure. The photocatalytic activity was evaluated by the degradation of crystal violet (CV) and methylene blue (MB) under visible light irradiation. The degradation rate of CV and MB on V-doped TiO 2 were higher than those of pure TiO 2 . As the results, V-doped TiO 2 possessed better absorption ability of visible light.

427 citations

Journal ArticleDOI
TL;DR: In this article, a modified sol-gel process was used to synthesize copper-loaded titania (Cu/TiO2) catalysts for CO 2 photocatalytic reduction and the yield of methanol was evaluated.

399 citations

Journal ArticleDOI
TL;DR: In this article, a comprehensive review of the development of photocatalytic water splitting for generating hydrogen, particularly under visible-light irradiation, is given, which includes an introduction of hydrogen production technologies.
Abstract: Hydrogen is the ideal fuel for the future because it is clean, energy efficient, and abundant in nature. While various technologies can be used to generate hydrogen, only some of them can be considered environmentally friendly. Recently, solar hydrogen generated via photocatalytic water splitting has attracted tremendous attention and has been extensively studied because of its great potential for low-cost and clean hydrogen production. This paper gives a comprehensive review of the development of photocatalytic water splitting for generating hydrogen, particularly under visible-light irradiation. The topics covered include an introduction of hydrogen production technologies, a review of photocatalytic water splitting over titania and non-titania based photocatalysts, a discussion of the types of photocatalytic water-splitting approaches, and a conclusion for the current challenges and future prospects of photocatalytic water splitting. Based on the literatures reported here, the development of highly stable visible–light-active photocatalytic materials, and the design of efficient, low-cost photoreactor systems are the key for the advancement of solar-hydrogen production via photocatalytic water splitting in the future.

377 citations


Cited by
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Journal ArticleDOI
TL;DR: Approaches to Modifying the Electronic Band Structure for Visible-Light Harvesting and its Applications d0 Metal Oxide Photocatalysts 6518 4.4.1.
Abstract: 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

6,332 citations

Journal ArticleDOI
TL;DR: In this paper, photo-induced superhydrophilicity was used on the surface of a wide-band gap semiconductor like titanium dioxide (TiO 2 ) for photocatalytic activity towards environmentally hazardous compounds.

4,241 citations

Journal ArticleDOI
TL;DR: Plasmon-enhanced water splitting on composite photocatalysts containing semiconductor and plasmonic-metal building blocks is focused on, and recently reported plasMon-mediated photocatallytic reactions on plAsmonic nanostructures of noble metals are discussed.
Abstract: Recent years have seen a renewed interest in the harvesting and conversion of solar energy. Among various technologies, the direct conversion of solar to chemical energy using photocatalysts has received significant attention. Although heterogeneous photocatalysts are almost exclusively semiconductors, it has been demonstrated recently that plasmonic nanostructures of noble metals (mainly silver and gold) also show significant promise. Here we review recent progress in using plasmonic metallic nanostructures in the field of photocatalysis. We focus on plasmon-enhanced water splitting on composite photocatalysts containing semiconductor and plasmonic-metal building blocks, and recently reported plasmon-mediated photocatalytic reactions on plasmonic nanostructures of noble metals. We also discuss the areas where major advancements are needed to move the field of plasmon-mediated photocatalysis forward.

4,074 citations

Journal ArticleDOI
TL;DR: In this article, the up-to-date development of the above-mentioned technologies applied to TiO 2 photocatalytic hydrogen production is reviewed, based on the studies reported in the literature, metal ion-implantation and dye sensitization are very effective methods to extend the activating spectrum to the visible range.
Abstract: Nano-sized TiO 2 photocatalytic water-splitting technology has great potential for low-cost, environmentally friendly solar-hydrogen production to support the future hydrogen economy. Presently, the solar-to-hydrogen energy conversion efficiency is too low for the technology to be economically sound. The main barriers are the rapid recombination of photo-generated electron/hole pairs as well as backward reaction and the poor activation of TiO 2 by visible light. In response to these deficiencies, many investigators have been conducting research with an emphasis on effective remediation methods. Some investigators studied the effects of addition of sacrificial reagents and carbonate salts to prohibit rapid recombination of electron/hole pairs and backward reactions. Other research focused on the enhancement of photocatalysis by modification of TiO 2 by means of metal loading, metal ion doping, dye sensitization, composite semiconductor, anion doping and metal ion-implantation. This paper aims to review the up-to-date development of the above-mentioned technologies applied to TiO 2 photocatalytic hydrogen production. Based on the studies reported in the literature, metal ion-implantation and dye sensitization are very effective methods to extend the activating spectrum to the visible range. Therefore, they play an important role in the development of efficient photocatalytic hydrogen production.

3,714 citations

Journal ArticleDOI
TL;DR: In this paper, the development of different strategies to modify TiO2 for the utilization of visible light, including non metal and/or metal doping, dye sensitization and coupling semiconductors are discussed.
Abstract: Fujishima and Honda (1972) demonstrated the potential of titanium dioxide (TiO2) semiconductor materials to split water into hydrogen and oxygen in a photo-electrochemical cell. Their work triggered the development of semiconductor photocatalysis for a wide range of environmental and energy applications. One of the most significant scientific and commercial advances to date has been the development of visible light active (VLA) TiO2 photocatalytic materials. In this review, a background on TiO2 structure, properties and electronic properties in photocatalysis is presented. The development of different strategies to modify TiO2 for the utilization of visible light, including non metal and/or metal doping, dye sensitization and coupling semiconductors are discussed. Emphasis is given to the origin of visible light absorption and the reactive oxygen species generated, deduced by physicochemical and photoelectrochemical methods. Various applications of VLA TiO2, in terms of environmental remediation and in particular water treatment, disinfection and air purification, are illustrated. Comprehensive studies on the photocatalytic degradation of contaminants of emerging concern, including endocrine disrupting compounds, pharmaceuticals, pesticides, cyanotoxins and volatile organic compounds, with VLA TiO2 are discussed and compared to conventional UV-activated TiO2 nanomaterials. Recent advances in bacterial disinfection using VLA TiO2 are also reviewed. Issues concerning test protocols for real visible light activity and photocatalytic efficiencies with different light sources have been highlighted.

3,305 citations