Zeyan Wang

Highly Efficient Visible‐Light Plasmonic Photocatalyst Ag@AgBr

Visible improvements: Owing to the plasmon resonance of silver nanoparticles deposited on the surface of AgBr, the newly-prepared plasmonic photocatalyst Ag section signAgBr has a strong absorption in the visible region (see picture) and shows high efficiency in the photodegradation of organic pollutants under visible light.

Oxygen Vacancy Induced Band-Gap Narrowing and Enhanced Visible Light Photocatalytic Activity of ZnO

Oxygen vacancies in crystal have important impacts on the electronic properties of ZnO. With ZnO(2) as precursors, we introduce a high concentration of oxygen vacancies into ZnO successfully. The obtained ZnO exhibits a yellow color, and the absorption edge shifts to longer wavelength. Raman and XPS spectra reveal that the concentration of oxygen vacancies in the ZnO decreased when the samples are annealed at higher temperature in air. It is consistent with the theory calculation. The increasing of oxygen vacancies results in a narrowing bandgap and increases the visible light absorption of the ZnO. The narrowing bandgap can be confirmed by the enhancement of the photocurrent response when the ZnO was irradiated with visible light. The ZnO with oxygen vacancies are found to be efficient for photodecomposition of 2,4-dichlorophenol under visible light irradiation.

In situ ion exchange synthesis of the novel Ag/AgBr/BiOBr hybrid with highly efficient decontamination of pollutants

A novel Ag/AgBr/BiOBr hybrid was prepared by a rational in situ ion exchange reaction between BiOBr hierarchical microspheres and AgNO(3) in ethylene glycol followed by light reduction, which displayed superior visible light driven photocatalytic activities in sterilization of pathogenic organism and degradation of organic dye compared to N-doped P25.

An anion exchange approach to Bi2WO6 hollow microspheres with efficient visible light photocatalytic reduction of CO2 to methanol

An anion exchange strategy is explored to synthesize Bi(2)WO(6) hollow microspheres based on the microscale Kirkendall effect. The as-prepared Bi(2)WO(6) hollow microspheres display high CO(2) adsorption capacity and visible light photocatalytic conversion efficiency of CO(2) into methanol without the aid of any co-catalyst.

In-Situ-Reduced Synthesis of Ti3+ Self-Doped TiO2/g-C3N4 Heterojunctions with High Photocatalytic Performance under LED Light Irradiation

A simple one-step calcination route was used to prepare Ti(3+) self-doped TiO2/g-C3N4 heterojunctions by mixture of H2Ti3O7 and melamine. X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR) spectroscopy, and UV-Vis diffuse reflectance spectroscopy (UV-vis DRS) technologies were used to characterize the structure, crystallinity, morphology, and chemical state of the as-prepared samples. The absorption of the prepared Ti(3+) self-doped TiO2/g-C3N4 heterojunctions shifted to a longer wavelength region in comparison with pristine TiO2 and g-C3N4. The photocatalytic activities of the heterojunctions were studied by degrading methylene blue under a 30 W visible-light-emitting diode irradiation source. The visible-light photocatalytic activities enhanced by the prepared Ti(3+) self-doped TiO2/g-C3N4 heterojunctions were observed and proved to be better than that of pure TiO2 and g-C3N4. The photocatalysis mechanism was investigated and discussed. The intensive separation efficiency of photogenerated electron-hole in the prepared heterojunction was confirmed by photoluminescence (PL) spectra. The removal rate constant reached 0.038 min(-1) for the 22.3 wt % Ti(3+) self-doped TiO2/g-C3N4 heterojunction, which was 26.76 and 7.6 times higher than that of pure TiO2 and g-C3N4, respectively. The established heterojunction between the interfaces of TiO2 nanoparticles and g-C3N4 nanosheets as well as introduced Ti(3+) led to the rapid electron transfer rate and improved photoinduced electron-hole pairs separation efficiency, resulting in the improved photocatalytic performance of the Ti(3+) self-doped TiO2/g-C3N4 heterojunctions.

Facile Template-Free Synthesis of Bi2O2CO3 Hierarchical Microflowers and Their Associated Photocatalytic Activity

Hierarchical Bi(2)O(2)CO(3) flowerlike microstructures have been synthesized for the first time using a facile, template-free, and low-temperature solution method. With an average diameter of about 3 microm, the as-prepared Bi(2)O(2)CO(3) microflowers are composed of numerous two-dimensional nanosheets with oriented terminal engagement. On the basis of electron microscopy observations, a plausible growth mechanism is proposed as a spatial self-assembly process accompanied by Ostwald ripening. The molar ratio of the initial reagents plays an important role in determining the morphologies of the Bi(2)O(2)CO(3) microstructures. UV/Vis spectroscopy is employed to analyze the band gaps of the products. Both mesopores and macropores are revealed in the Bi(2)O(2)CO(3) microflowers by means of nitrogen sorption and pore-size distribution. Moreover, evaluated by the degradation of methyl orange under UV illumination, the photocatalytic performance of the Bi(2)O(2)CO(3) hierarchical microflowers is almost six times higher than that of commercial Bi(2)O(2)CO(3). The higher specific surface area, the meso/macropores, and the intra-electric field formed between the (Bi(2)O(2))(2+) layer and the slabs comprising CO(3) (2-) in the Bi(2)O(2)CO(3) crystal structure, are believed to facilitate the separation of the photoinduced electrons and holes and thus improve the corresponding photocatalytic activity.

Highly Efficient Visible Light Plasmonic Photocatalysts Ag@Ag(Cl,Br) and Ag@AgCl‐AgI

New plasmonic photocatalysts Ag@Ag(Cl,Br) and Ag@AgCl‐AgI were synthesized by the ion‐exchange process between AgCl and a potassium halide (KBr, KI), then by reducing some Ag+ ions in the surface region of Ag(Cl,Br) and AgCl‐AgI particles to Ag0 species. The Ag nanoparticles were formed from Ag(Cl,Br) and AgCl‐AgI by a light‐induced chemical reduction. The Ag@Ag(Cl,Br) and Ag@AgCl‐AgI particles have irregular shapes and their sizes vary between 100 nm and 1.3 μm. The as‐grown plasmonic photocatalysts show strong absorption in the visible‐light region, owing to the plasmon resonance of Ag nanoparticles. The ability of this compound to oxidize methylic orange and reduce CrVI under visible light was compared with those of other reference photocatalysts. These plasmonic photocatalysts have been shown to be highly efficient under visible‐light irradiation.

Efficient Separation of Photogenerated Electron‐Hole Pairs by the Combination of a Heterolayered Structure and Internal Polar Field in Pyroelectric BiOIO3 Nanoplates

Semiconductor photocatalysts are important for new energy exploitation and decontamination of hazardous organic pollutants because they can photoconvert solar energy into chemical energy, photodecompose organic materials, and photoreduce carbon dioxide. However, their practical applications still remain beyond our grasp due to their poor quantum yield, which arises from the rapid recombination of photogenerated electron-hole (e-h) pairs. In principle, heterostructures can separate photogenerated electrons and holes efficiently because the different components possess different valence band (VB) and conduction band (CB) edges. However, the electron-hole separation becomes inefficient if there is no good contact between the different components. It is challenging to find a simple method that efficiently separates photogenerated electrons and holes. Bismuth-based layered semiconductors have long been an important subject for photocatalysis. Nanostructures of Bi2WO6, [4] Bi2MoO6, [5] BiOX (X=Cl, Br, I), Bi2S3, [7] Bi2O2CO3 [8] have been prepared by various methods and used as the photocatalysts for decomposing organic pollutants. However, bismuth-based layered materials with high photocatalytic activity have not been found yet. The heterolayered bismuth oxide iodate, BiOIO3, [9] is pyroelectric, and its stereoactive lone-pairs on both Bi and I cations are located at the BiO6 hexagonal and IO3 trigonal pyramidal sites, respectively. The BiO6 pyramids edge-share to form the Bi2O4 layers (Figure 1a), the two surfaces of which are corner-shared with IO3 pyramids to form BiOIO3 slabs (Figure 1b). The pyroelectricity of BiOIO3 does not arise from the BiO6 pyramids, but from the IO3 pyramids. The local dipole moments of the BiO6 pyramids are practically canceled out, but those of the IO3 pyramids are not, thereby leading to a pyroelectric polarization along the c-axis direction (Figure 1b). Under an electric field, electrons and holes move in opposite directions. Bastard et al. reported that the CB and VB electrons in GaAs quantum wells can be spatially separated by applying an external electric field. Thus, it is reasonable to suppose that photogenerated e-h pairs of a pyroelectric compound can be effectively separated by the internal polar field and hence exhibit a good photocatalytic activity. In this Communication we verify this hypothesis by studying the heterolayered pyroelectric compound BiOIO3 to find that it is an efficient photocatalyst under ultraviolet (UV) light irradiation, far superior to that of TiO2 (P25). We synthesize BiOIO3 nanoplates by using a simple hydrothermal method. Bi ACHTUNGTRENNUNG(NO3)3·5 H2O and KIO3 were used as the sources of Bi and IO3, which are environmentally friendly and inexpensive. Figure 2 shows the typical XRD pattern of the as-prepared BiOIO3 product. All the XRD peaks are indexed to orthorhombic BiOIO3 (space group: Pca21; a= 5.6584(4), b=11.0386(8), c=5.7476(4) ), which indicates a high purity of the obtained product. The intense and sharp diffraction peaks demonstrate that the product is well crys[a] W. Wang, Prof. Dr. B. Huang, Z. Wang, X. Qin, X. Zhang State Key Laboratory of Crystal Materials Shandong University, Jinan 250100 (P. R. China) Fax: (+86)0531-88365969 E-mail : bbhuang@sdu.edu.cn [b] X. Ma, Prof. Dr. Y. Dai School of Physics Shandong University, Jinan 250100 (P. R. China) [c] Prof. Dr. M.-H. Whangbo Department of Chemistry North Carolina State University Raleigh, North Carolina, 27695-8204 (USA) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201302884. Figure 1. a) A perspective view of the Bi2O4 layer in BiOIO3, in which the large cyan and small white circles represent the Bi and O atoms, respectively. b) A perspective view of the BiOIO3 slab, in which a Bi2O4 layer shares O corners with IO3 units. The arrows along the c-direction indicate the direction of the pyroelectric polarization, which results from the dipoles of the individual IO3 units.

Chemical Adsorption Enhanced CO2 Capture and Photoreduction over a Copper Porphyrin Based Metal Organic Framework

Effective CO2 capture and activation is a prerequisite step for highly efficient CO2 reduction. In this study, we reported a case of Cu(2+) in a porphyrin based MOF promoted enhanced photocatalytic CO2 conversion to methanol. Compared with the sample without Cu(2+), the methanol evolution rate was improved as high as 7 times. In situ FT-IR results suggested that CO2 chemical adsorption and activation over Cu(2+) played an important role in improving the conversion efficiency.

Crystal facets controlled synthesis of graphene@TiO2 nanocomposites by a one-pot hydrothermal process

We report a facile and simple way to synthesize graphene@TiO2 nanocomposites with controlled crystal facets by a one-pot hydrothermal process. By controlling the concentrations of the starting materials and reaction times, graphene@TiO2 nanocomposites with various exposed crystal facets can be obtained. The surface states and the growth process of graphene@TiO2 nanocomposites have been studied. Owing to the exposed high-reactive crystal facets and high dispersities of TiO2 nanocrystals on graphene surfaces, the as-prepared sample exhibited enhanced photocatalytic activities over graphene@P25 nanocomposites.