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

비만아 부모의 돌봄 경험: q 방법론

Semiconductor photocatalysts have important applications in renewable energy and environment fields. To overcome the serious drawbacks of low efficiency and narrow light-response range in most stable semiconductor photocatalysts, many strategies have been developed in the past decades. This review attempts to provide a comprehensive update and examination of some fundamental issues in titania (TiO2)-based semiconductor photocatalysts, such as crystal growth, doping and heterostructuring. We focus especially on recent progress in exploring new strategies to design TiO2-based photocatalysts with unique structures and properties, elucidating the chemical states and distribution of dopants in doped TiO2, designing and fabricating integrated heterostructure photocatalysts with different charge-carrier transfer pathways, and finally identifying the key factors in determining the photocatalytic efficiency of titania-based photocatalysts.

Titania-based photocatalysts—crystal growth, doping and heterostructuring

We report on a novel heterojunction WO3/BiVO4 photoanode for photoelectrochemical water splitting. The heterojunction films are prepared by solvothermal deposition of a WO3 nanorod-array film onto fluorine-doped tin oxide (FTO) coated glass, with subsequent deposition of a low bandgap, 2.4 eV, visible light responding BiVO4 layer by spin-coating. The heterojunction structure offers enhanced photoconversion efficiency and increased photocorrosion stability. Compared to planar WO3/BiVO4 heterojunction films, the nanorod-array films show significantly improved photoelectrochemical properties due, we believe, to the high surface area and improved separation of the photogenerated charge at the WO3/BiVO4 interface. Synthesis details are discussed, with film morphologies and structures characterized by field emission scanning electron microscopy and X-ray diffraction.

Nanostructured WO3/BiVO4 Heterojunction Films for Efficient Photoelectrochemical Water Splitting

Enhanced photocatalytic activity of ZnO/CuO nanocomposite for the degradation of textile dye on visible light illumination.

Co3O4/BiVO4 composite photocatalyst with a p−n heterojunction semiconductor structure has been synthesized by the impregnation method. The physical and photophysical properties of the composite photocatalyst have been characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transimission electron microscopy (TEM), BET surface area, and UV−visible diffuse reflectance spectra. Co is present as p-type Co3O4 and disperses on the surface of n-type BiVO4 to constitute a heterojunction composite. The photocatalyst exhibits enhanced photocatalytic activity for phenol degradation under visible light irradiation. The highest efficiency is observed when calcined at 300 °C with 0.8 wt % cobalt content. On the basis of the calculated energy band positions and PL spectra, the mechanism of enhanced photocatalytic activity has been discussed.

Efficient photocatalytic degradation of phenol over Co3O4/BiVO4 composite under visible light irradiation.

A visible-light responsive photocatalyst consisting of Ag–AgCl composite dispersed over BiVO 4 (Ag–AgCl/BiVO 4 ) was synthesized via a photolysis and calcination method. The effects of synthetic conditions such as Ag contents, molar ratios of chlorine to silver and calcination temperatures have been discussed. The coupling Ag–AgCl composite structure, which is necessary for the high photoactivity, comes into being by partially converting Ag nanoclusters into AgCl during heat treatment. The discoloration efficiency of methyl orange over the as-prepared Ag–AgCl/BiVO 4 was more than 90% after 120 min under visible light irradiation. In the Ag–AgCl/BiVO 4 system, the coupled processes of excitation from valence band of AgCl to the sensitizer Ag nanoparticles and the surface plasmonic resonance of Ag nanoparticles mainly contributed to its high activity. In addition, the presence of BiVO 4 changed the hole transfer process, and O 2 − became to be the solely main active specie in the degradation reaction. The photocatalytic activity can be further improved by the addition of hole scavengers.

Synthesis and photocatalytic performance of the efficient visible light photocatalyst Ag–AgCl/BiVO4

Bismuth oxide based (BOB) materials display strong potentials in visible light photocatalytic applications, but are greatly restricted by the poor stability for organic degradation in aqueous solutions. Herein, a unique heterostructural photocatalyst, nonstoichiometric bismuth oxyiodide Bi 2 O 3− x I 2 x ( x  = 0.243) covered with iodine intercalated Bi 2 O 2 CO 3 , were developed through a treatment of Bi 7 O 9 I 3 in urea solution and subsequent calcinations. The interesting formation chemistry of this heterostructure were revealed and their dramatically enhanced photoresponse properties were studied. The lower amount of iodine in Bi 2 O 3− x I 2 x contributes a higher oxidation potential of photogenerated holes, while the presence of outlayer of iodine intercalated Bi 2 O 2 CO 3 retards the transformation of inner bismuth oxyiodide. We anticipate this strategy can be generalized to tune iodine contents and to fabricate delicate BOB photocatalytic heterostructures with desirable performance for environmental applications.

Jun Cai

Papers

Efficient photocatalytic degradation of phenol over Co3O4/BiVO4 composite under visible light irradiation.

Synthesis and photocatalytic performance of the efficient visible light photocatalyst Ag–AgCl/BiVO4

Efficient visible light photocatalytic heterostructure of nonstoichiometric bismuth oxyiodide and iodine intercalated Bi2O2CO3

Efficient Photocatalytic Degradation of Phenol over Co3O4/BiVO4 Composite under Visible Light Irradiation.

Facilitated photoinduced electron storage and two-electron reduction of oxygen by reduced graphene oxide in rGO/TiO2/WO3 composites