Showing papers by "Jiaguo Yu published in 2012"
TL;DR: This critical review summarizes the recent progress in the design and fabrication of graphene-based semiconductor photocatalysts via various strategies including in situ growth, solution mixing, hydrothermal and/or solvothermal methods.
Abstract: Graphene, a single layer of graphite, possesses a unique two-dimensional structure, high conductivity, superior electron mobility and extremely high specific surface area, and can be produced on a large scale at low cost. Thus, it has been regarded as an important component for making various functional composite materials. Especially, graphene-based semiconductor photocatalysts have attracted extensive attention because of their usefulness in environmental and energy applications. This critical review summarizes the recent progress in the design and fabrication of graphene-based semiconductor photocatalysts via various strategies including in situ growth, solution mixing, hydrothermal and/or solvothermal methods. Furthermore, the photocatalytic properties of the resulting graphene-based composite systems are also discussed in relation to the environmental and energy applications such as photocatalytic degradation of pollutants, photocatalytic hydrogen generation and photocatalytic disinfection. This critical review ends with a summary and some perspectives on the challenges and new directions in this emerging area of research (158 references).
2,451 citations
TL;DR: A new composite material consisting of TiO(2) nanocrystals grown in the presence of a layered MoS(2)/graphene hybrid as a high-performance photocatalyst for H( 2) evolution without noble metals is reported.
Abstract: The production of H2 by photocatalytic water splitting has attracted a lot attention as a clean and renewable solar H2 generation system. Despite tremendous efforts, the present great challenge in materials science is to develop highly active photocatalysts for splitting of water at low cost. Here we report a new composite material consisting of TiO2 nanocrystals grown in the presence of a layered MoS2/graphene hybrid as a high-performance photocatalyst for H2 evolution. This composite material was prepared by a two-step simple hydrothermal process using sodium molybdate, thiourea, and graphene oxide as precursors of the MoS2/graphene hybrid and tetrabutylorthotitanate as the titanium precursor. Even without a noble-metal cocatalyst, the TiO2/MoS2/graphene composite reaches a high H2 production rate of 165.3 μmol h–1 when the content of the MoS2/graphene cocatalyst is 0.5 wt % and the content of graphene in this cocatalyst is 5.0 wt %, and the apparent quantum efficiency reaches 9.7% at 365 nm. This unusu...
2,201 citations
TL;DR: This work creates a green and simple way for using RGO as a support to enhance the photocatalytic H(2)-production activity of Zn(x)Cd(1-x)S, and demonstrates that RGO is a promising substitute for noble metals in photocatalyst H( 2)-production.
Abstract: Design and preparation of efficient artificial photosynthetic systems for harvesting solar energy by production of hydrogen from water splitting is of great importance from both theoretical and practical viewpoints. ZnS-based solid solutions have been fully proved to be an efficient visible-light driven photocatalysts, however, the H2-production rate observed for these solid solutions is far from exciting and sometimes an expensive Pt cocatalyst is still needed in order to achieve higher quantum efficiency. Here, for the first time we report the high solar photocatalytic H2-production activity over the noble metal-free reduced graphene oxide (RGO)-ZnxCd1–xS nanocomposite prepared by a facile coprecipitation-hydrothermal reduction strategy. The optimized RGO-Zn0.8Cd0.2S photocatalyst has a high H2-production rate of 1824 μmol h–1 g–1 at the RGO content of 0.25 wt % and the apparent quantum efficiency of 23.4% at 420 nm (the energy conversion efficiency is ca. 0.36% at simulated one-sun (AM 1.5G) illuminati...
815 citations
TL;DR: A review of surface plasmon resonance-mediated photocatalysis can be found in this article, where the authors highlight diverse applications of plasmoric photocatalysts in mineralization of organic pollutants, organic synthesis and water splitting.
Abstract: Harvesting abundant and renewable sunlight in energy production and environmental remediation is an emerging research topic. Indeed, research on solar-driven heterogeneous photocatalysis based on surface plasmon resonance has seen rapid growth and potentially opens a technologically promising avenue that can benefit the sustainable development of global energy and the environment. This review briefly summarizes recent advances in the synthesis and photocatalytic properties of plasmonic composites (e.g., hybrid structures) formed by noble metal (e.g., gold, silver) nanoparticles dispersed on a variety of substrates that are composed of metal oxides, silver halides, graphene oxide, among others. Brief introduction of surface plasmon resonance and the synthesis of noble metal-based composites are given, followed by highlighting diverse applications of plasmonic photocatalysts in mineralization of organic pollutants, organic synthesis and water splitting. Insights into surface plasmon resonance-mediated photocatalysis not only impact the basic science of heterogeneous photocatalysis, but generate new concepts guiding practical technologies such as wastewater treatment, air purification, selective oxidation reactions, selective reduction reactions, and solar-to-hydrogen energy conversion in an energy efficient and environmentally benign approach. This review ends with a summary and perspectives.
464 citations
TL;DR: In this paper, hierarchical macro/mesoporpous TiO2-graphene composites with low loadings were first produced by a simple one-step hydrothermal method using tetrabutyl titanate as the titanium precursor.
Abstract: Graphene, a single layer of graphite, possesses a unique two-dimensional structure, high conductivity, superior electron mobility and extremely high specific surface area, and can be obtained on a large scale at low cost. Thus, it has been regarded as an excellent catalyst support. Recently, graphene-based semiconductor photocatalysts have attracted more attention due to their enhanced photocatalytic activity. In this work, hierarchical macro/mesoporpous TiO2–graphene composites with low loadings (0–0.2 wt.%) of graphene were first produced by a simple one-step hydrothermal method using tetrabutyl titanate as the titanium precursor. The prepared composite samples presented enhanced photocatalytic activity in photodegradation of acetone in air. Graphene content exhibited an obvious influence on photocatalytic activity and the optimal graphene addition content was determined. At the optimal graphene concentration (0.05 wt.%), the prepared composites showed the highest photocatalytic activity, exceeding that of pure TiO2 and Degussa P-25 by a factor of 1.7 and 1.6, respectively. The enhanced photocatalytic activity is due to graphene as an excellent electron acceptor and transporter, thus reducing the recombination of charge carriers and enhancing the photocatalytic activity. The transient photocurrent response experiment further confirmed the transfer of photogenerated electrons from TiO2 to graphene and the suggested mechanism.
352 citations
TL;DR: This is the first study to investigate heterogeneous photo-Fenton catalysis by nanocatalysts with well-defined architectures by investigating visible-light-induced photodegradation of model dye rhodamine B in the presence of hydrogen peroxide over hematite architectures.
Abstract: Structure–reactivity correlations are a central theme in heterogeneous catalysis. In general, the crystallographic surface structure of a catalyst is determined by its exposed facets, and the enclosed facets of a particle-like catalyst in turn determine its geometric shape as well as catalytic properties. Tuning the shape of catalysts, therefore, is essential in developing new catalysts and modifying existing ones with desirable reactivity, selectivity, and stability. Indeed, great advances have been achieved on model catalysts, and insights into the structure–reactivity correlations are crucial not only for our understanding of catalytic processes, but also for generating new concepts to guide the rational design of practical catalysts. In recent years, significant attention has been directed towards using solar-driven photocatalysts to degrade aqueous organic pollutants (for example, azo dyes). In view of being naturally abundant and environmentally benign, iron oxides show great promise. Among iron oxides, hematite (aFe2O3) is the most thermodynamically stable semiconductor (Eg = 2.1–2.2 eV) that can absorb visible light, that is, a substantial fraction of the solar spectrum. a-Fe2O3 has a wide range of applications, such as light-induced water splitting, solar cells, lithium ion batteries, and biotechnology. Most studies to date have been carried out on powder substrates in which particle shapes are inherently not welldefined, making it difficult to explore the structure–reactivity correlations. While the vast majority of studies on the impact of particle shape on photocatalytic reactivity are limited to titanium dioxide (TiO2), [18–27] far less information is available regarding the shape effects on other photocatalysts, including iron oxides. In this regard, systematic studies on heterogeneous photo-Fenton catalysis, a technologically promising process in wastewater treatment, by iron-bearing nanocatalysts with particular shapes are still lacking. 29] Over the past decade, size, shape, and architecture control of low-dimensional nanomaterials (for example, nanodots, nanorods, and nanosheets) with unusual properties has seen rapid growth. For example, in one-dimensional (1D) anisotropic nanostructures, it is possible to enhance the photoreactivity by tuning the direction and path of photogenerated charge carriers through quantum confinement while minimizing the e –h recombination. Herein, we investigate visible-light-induced photodegradation of model dye rhodamine B (RhB) in the presence of hydrogen peroxide (H2O2) over hematite architectures, namely 1D nanorods, 2D nanoplates, and 3D nanocubes. Herein we use “architectures” to describe hematite nanostructures that can be assembled by nano-building units by oriented attachment. 36, 39] To the best of our knowledge, this is the first study to investigate heterogeneous photo-Fenton catalysis by nanocatalysts with well-defined architectures. The detailed synthesis of a-Fe2O3 architectures [39–42] is described in the Experimental Section and the Supporting Information. The structure, stoichiometry, and oxidation state of the as-prepared a-Fe2O3 architectures were characterized using X-ray diffraction (XRD; Supporting Information, Figure S1a), micro-Raman (Supporting Information, Figure S1b), and high-resolution X-ray photoelectron spectroscopy (XPS; Supporting Information, Figure S1c,d), and results demonstrate that all samples are pure a-Fe2O3 with a rhombohedral hexagonal phase (space group R3̄c). The morphology and crystallinity of as-prepared a-Fe2O3 architectures were analyzed using transmission electron microscopy (TEM), high-resolution TEM (HRTEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). A TEM image for 2D nanoplates is shown in Figure 1a. All of the nanoplates display a well-defined hexagonal shape. Based on a SEM (Supporting Information, Figure S2a) and TEM analysis (Figure 1 a; Supporting Information, Figure S2b), the width and thickness of the plates is determined to be (208.5 27.3) and (14.6 2.6) nm, respectively. A representative HRTEM image (Figure 1 b) and fast Fourier transforms (FFT; inset in Figure 1b) show the lattice fringe to be 0.25 nm, which is consistent with (110), ( 120), and ( 210) planes, respectively. Thus, the resulting basal plane is (001). Vertically aligned plates that are frequently observed (Supporting Information, Figure S2b,c) are wedgeshaped and the lateral facets are ascribed to {102}. A TEM [*] X. M. Zhou, J. Y. Lan, Prof. G. Liu, Prof. K. Deng, Prof. Y. L. Yang, Prof. G. J. Nie, Prof. L. J. Zhi National Center for Nanoscience and Technology Beijing, 100190 (China) E-mail: liug@nanoctr.cn zhilj@nanoctr.cn
278 citations
TL;DR: In this paper, an Ag 2 O cocatalyst was applied on the surface of Bi 2 WO 6 nanoparticles by an impregnation method followed by a low-temperature treatment (100-350°C) and their performance was evaluated by the photocatalytic decolorization of methyl orange solution under visible light irradiation.
Abstract: Cocatalyst modification is an efficient strategy to improve the photocatalytic efficiency of photocatalysts by promoting the effective separation of photogenerated electrons and holes. However, most of the cocatalysts are restricted to noble metals (e.g., Ag, Au, Pt) and seldom investigation has been focused on their oxides. In this study, Ag 2 O cocatalyst was coated on the surface of Bi 2 WO 6 nanoparticles by an impregnation method followed by a low-temperature treatment (100–350 °C) and their photocatalytic performance was evaluated by the photocatalytic decolorization of methyl orange solution under visible-light irradiation. It was found that after the surface coating of Ag 2 O, the obtained Ag 2 O/Bi 2 WO 6 composites exhibited an obvious higher photocatalytic activity than the unmodified Bi 2 WO 6 nanoparticles and N-doped TiO 2 . Owing to the photosensitive property of pure Ag 2 O phase, the Ag–Ag 2 O composite easily formed during the decomposition process of organic substances under visible-light irradiation. On the bases of experimental result and band structure analysis, an Ag–Ag 2 O cocatalyst-enhanced photocatalytic mechanism is proposed; namely, the Ag–Ag 2 O cocatalyst possibly reduces oxygen via a multi-electron transfer mechanism. The present results suggest that Ag–Ag 2 O can act as a new and effective cocatalyst for the enhanced photocatalytic performance of photocatalysts, which provides a new approach for the design and development of high-performance visible-light photocatalysts.
259 citations
TL;DR: In this paper, a visible-light-responsive photocatalyst Ag2CO3 was prepared by a facile precipitation reaction between NaHCO3 and AgNO3, which showed relatively high photocatalytic activity toward rhodamine B (RhB) degradation in aqueous solution.
Abstract: A novel visible-light-responsive photocatalyst Ag2CO3 was prepared by a facile precipitation reaction between NaHCO3 and AgNO3. The as-prepared samples showed relatively high photocatalytic activity toward rhodamine B (RhB) degradation in aqueous solution. The observed photoreactivity on Ag2CO3 was attributed to the synergetic effects of small band gap, great oxidation potential of photogenerated holes, and high separation efficiency of photogenerated electrons and holes. Nevertheless, Ag2CO3 was unstable under visible light due to the photocorrosion resulting from metallic silver formation. The photocorrosion of Ag2CO3 can be efficiently inhibited by adding AgNO3 in the photocatalytic reaction system owing to the lower electrode potential of Ag/AgNO3 than that of Ag/Ag2CO3. Our results shed new light on the photocatalytic activity as well as photocorrosion mechanism of silver-containing compounds and inhibit the method of photocorrosion.
254 citations
TL;DR: In this paper, an Ag/Ag(I)-TiO2 photocatalyst was prepared by a facile impregnated method in combination with a calcination process and the photocatalytic activity was evaluated by the decomposition of methyl orange and phenol solutions under both UV- and visible-light irradiation, respectively.
Abstract: Ag modification has been demonstrated to be an efficient strategy to improve the photocatalytic performance of TiO2 photocatalysts. However, the previous studies about the Ag modification are only restricted to the surface loading of metallic Ag or Ag(I) doping, investigations have seldom been focused on the simultaneously deposited and doped Ag/Ag(I)-TiO2 photocatalyst. In this study, Ag/Ag(I)-TiO2 photocatalyst was prepared by a facile impregnated method in combination with a calcination process (450 °C) and the photocatalytic activity was evaluated by the photocatalytic decomposition of methyl orange and phenol solutions under both UV- and visible-light irradiation, respectively. It was found that Ag(I) doping resulted in the formation of an isolated energy level of Ag 4d in the band gap of TiO2. On the basis of band-structure analysis of Ag/Ag(I)-TiO2 photocatalyst, a possible photocatalytic mechanism was proposed to account for the different UV- and visible-light photocatalytic activities. Under visi...
233 citations
TL;DR: In this article, the effects of graphene loading on the microstructures and photoelectric conversion performance of dye-sensitized solar cells were investigated, and a moderate amount of graphene (0.75 wt%) largely lowered the DSSC performance, which not only impaired the crystallinity of the TiO2-NSs but also shielded the light adsorption of the dyes and reduced the number of photogenerated electrons.
Abstract: Dye-sensitized solar cells (DSSCs) based on TiO2 nanosheets (TiO2-NSs)/graphene nanocomposite films were fabricated, and the effects of graphene on the microstructures and photoelectric conversion performance of the as-fabricated DSSC were investigated. The graphene loading clearly influences the textural properties (including specific surface areas, porosity and pore volume) and the optical absorption properties. Moreover, the charge transfer and transport versus the charge trapping and recombination is also affected by the graphene loading. As a consequence, the photoelectric conversion efficiency of the TiO2-NSs/graphene nanocomposite film electrodes can be improved to a great extent upon graphene loading, dependent on the loading amount of graphene. A moderate amount of graphene ( 0.75 wt%) largely lowered the DSSC performance. Higher graphene loading not only impaired the crystallinity of the TiO2-NSs, but also shielded the light adsorption of the dyes and reduced the number of photogenerated electrons.
205 citations
TL;DR: This review briefly summarizes recent advances in fluorine ions-mediated morphology control of anatase TiO(2) in the forms of nanotube arrays, nanosheets with high-energy facets, and hollow spheres.
Abstract: This review briefly summarizes recent advances in fluorine ions-mediated morphology control of anatase TiO2 in the forms of nanotube arrays, nanosheets with high-energy facets, and hollow spheres. The correlations between the enhanced photocatalytic activity and structural and morphological modifications of anatase TiO2 by fluorine ions are addressed.
TL;DR: The results presented herein shed new light on the photostability of Ag(3) PO(4) spherical particles and are potentially applicable to other photocatalytically active composites.
Abstract: Ag(3)PO(4) spherical particles were synthesized by a facile precipitation method using silver nitrate and Na(2) HPO(4) as precursors. The as-prepared samples had a high photocatalytic activity toward Rhodamine B (RhB) degradation under visible-light illumination. With increasing recycling times the photocatalytic activity first increased and then decreased. Based on systematic characterization of particles by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV/Vis absorption spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM), a possible mechanism responsible for the improvement and subsequent decline of the photocatalytic performance of Ag(3)PO(4) is proposed. Ag(3)PO(4) spherical particles recycled for four times showed the highest photocatalytic activity because, according to our mechanism, Ag nanoparticles deposited on Ag(3)PO(4) acted as electron trapping centers to prevent photogenerated electron-hole pairs from recombination. A further increase in the recycle times decreases the photocatalytic activity owing to the shielding effect by Ag layers on the surface of Ag(3)PO(4). The results presented herein shed new light on the photostability of Ag(3) PO(4) spherical particles and are potentially applicable to other photocatalytically active composites.
TL;DR: Significantly, the incorporated graphene exerts combined effects on the adsorption and charge transfer dynamics in TiO(2)-graphene nanocomposites, which together endow them with good photocatalytic reactivity and tunable photoc atalytic selectivity in decomposing MO and MB in aqueous solution.
Abstract: Mesoporous TiO2–graphene nanocomposites are fabricated in high yield via two successive steps: (1) hydrothermal hydrolysis of Ti(SO4)2 in an acidic suspension of graphene oxide to gain TiO2–graphene oxide nanocomposites; (2) UV-assisted photocatalytic reduction of graphene oxide to get the TiO2–graphene nanocomposites. The anatase TiO2 nanocrystals with a crystallite size of 10–20 nm are densely packed and supported on meshy graphene sheets with close interfacial contacts, which is confirmed by transmission electron microscopy (TEM) together with Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Although a low graphene loading (0–2 wt%) slightly influences the textural properties (including the crystallite size, specific surface areas, and pore volume etc.), the incorporation of graphene in TiO2–graphene nanocomposites greatly increases the adsorption capacity towards azo dyes such as MO and MB, which is possibly associated with their unique surface properties. Significantly, the incorporated graphene exerts combined effects on the adsorption and charge transfer dynamics in TiO2–graphene nanocomposites, which together endow them with good photocatalytic reactivity and tunable photocatalytic selectivity in decomposing MO and MB in aqueous solution.
TL;DR: Results from this study illustrate an entirely new approach to fabricate semiconductor composites containing graphene-bismuth with high visible-responsive photocatalytic performance.
Abstract: A facile template-free hydrothermal approach is developed to synthesize hierarchical flower-like graphene–Bi2O2CO3 microcomposites. The as-prepared samples were systematically characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, N2 adsorption–desorption and UV-visible diffuse reflectance spectroscopy. The photocatalytic activity of the as-prepared samples was evaluated towards degradation of Rhodamine B (RhB) under visible light. Compared to hierarchical Bi2O2CO3, hierarchical flower-like graphene–Bi2O2CO3 microcomposites show enhanced photocatalytic activity. In addition, our results indicate that both the physico-chemical properties and associated photocatalytic activity of graphene–Bi2O2CO3 composites are shown to be dependent on graphene loadings. The highest photocatalytic performance can be achieved for the graphene–Bi2O2CO3 microcomposites with 1.0 wt% graphene. The underlying mechanism responsible for the formation of graphene–Bi2O2CO3 composites and enhanced photoreactivity was discussed. Results from this study illustrate an entirely new approach to fabricate semiconductor composites containing graphene–bismuth with high visible-responsive photocatalytic performance.
TL;DR: This review presents a comprehensive description of the F-mediated synthesis and unique properties of fluorinated semiconductor photocatalysts, in particular titanium dioxide (TiO(2).
TL;DR: This work shows a possibility for the utilization of low cost CNT as a substitute for noble metals in the photocatalytic H(2)-production but for the first time shows a significant enhancement in the H( 2)-production activity by using metal-free carbon materials as effective co-catalysts.
Abstract: Visible light photocatalytic H(2) production from water splitting using solar light is of great importance from the viewpoint of solar energy conversion and storage. In this study, a novel visible-light-driven photocatalyst multiwalled carbon nanotube modified Cd(0.1)Zn(0.9)S solid solution (CNT/Cd(0.1)Zn(0.9)S) was prepared by a simple hydrothermal method. The prepared samples exhibited enhanced photocatalytic H(2)-production activity under visible light. CNT content had a great influence on photocatalytic activity and an optimum amount of CNT was determined to be ca. 0.25 wt%, at which the CNT/Cd(0.1)Zn(0.9)S displayed the highest photocatalytic activity under visible light, giving an H(2)-production rate of 78.2 μmol h(-1) with an apparent quantum efficiency (QE) of 7.9% at 420 nm, even without any noble metal cocatalysts, exceeding that of pure Cd(0.1)Zn(0.9)S by more than 3.3 times. The enhanced photocatalytic activity was due to CNT as an excellent electron acceptor and transporter, thus reducing the recombination of charge carriers and enhancing the photocatalytic activity. Furthermore, the prepared sample was photostable and no photocorrosion was observed after photocatalytic recycling. Our findings demonstrated that CNT/Cd(0.1)Zn(0.9)S composites were a promising candidate for the development of high-performance photocatalysts in photocatalytic H(2) production. This work not only shows a possibility for the utilization of low cost CNT as a substitute for noble metals (such as Pt) in the photocatalytic H(2)-production but also for the first time shows a significant enhancement in the H(2)-production activity by using metal-free carbon materials as effective co-catalysts.
TL;DR: In this paper, bimodal meso-/macroporous SiO2 hollow sphere (BMSHS) samples with high specific surface areas were prepared by a hydrothermal method.
Abstract: Carbon dioxide capture and storage (CCS) solutions have received enormous attention because CO2 is a primary greenhouse gas and plays a key role in global warming and climate change. In this work, bimodal meso-/macroporous SiO2 hollow sphere (BMSHS) samples with high specific surface areas were prepared by a hydrothermal method. Cetyltrimethylammonium bromide (CTAB) and perfluorododecanoic acid (PFDOA) were used as cotemplates and the CTAB/PFDOA weight ratio (R) was varied. The prepared samples were further modified with tetraethylenepentamine (TEPA), and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), differential thermal analysis (DTA), thermal gravimetric analysis (TGA), and N2 physisorption techniques. This was followed by CO2 capture tests using a pure CO2 stream in the temperature range of 35–130 °C. The results showed that all of the prepared samples contained small mesopores with a peak pore size of ca. 3–4 nm and larger mesopores or macropores with a peak pore diameter of ca. 103 to 117 nm. The mesopores and macropores are from the shell and the cavity of hollow spheres, respectively. The R exhibited a significant influence on the specific surface area, as the specific surface areas increased with increasing R. All of the TEPA-modified samples exhibited good CO2 adsorption abilities, which were related to the amount of loaded TEPA, adsorption temperature, and the specific surface areas of the samples. A optimal amount of TEPA loading (about 50 wt%) and adsorption temperature (about 110 °C) were determined. The CO2 adsorption amount increased proportionally with the specific surface area. The maximum CO2 adsorption amount (4.41 mmol g−1 adsorbent) was achieved on the BMSHS sample prepared at R = 40 and TEPA loading of 50 wt%. The present study provides new insight into the design and synthesis of novel porous materials for CO2 capture.
TL;DR: Novel rattle-type carbon-alumina core-shell spheres prepared by using glucose and metal salt as precursors via a simple one-pot hydrothermal synthesis followed by calcination indicate that the resulting carbon- alumina particles are powerful adsorbents for the removal of Orange-II dye from water with maximum adsorption capacity.
Abstract: Porous micro- and nanostructured materials with desired morphologies and tunable pore sizes are of great interests because of their potential applications in environmental remediation. In this study, novel rattle-type carbon–alumina core–shell spheres were prepared by using glucose and metal salt as precursors via a simple one-pot hydrothermal synthesis followed by calcination. The microstructure, morphology, and chemical composition of the resulting materials were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N2 adsorption–desorption techniques. These rattle-type spheres are composed of a porous Al2O3 shell (thickness ≈ 80 nm) and a solid carbon core (diameter ≈ 200 nm) with variable space between the core and shell. Furthermore, adsorption experiments indicate that the resulting carbon–alumina particles are powerful adsorbents for the removal of Orange-II dye from water with maximum ad...
TL;DR: In this article, surface fluorine coverage is required to balance the aforementioned conflicting effects and achieve the higher mineralization rate, and the surface fluorination favored the RhB adsorption and hole transfer between RhB molecules and BiVO4 photocatalyst.
Abstract: BiVO4 crystals with monoclinic-phase and controllable morphologies were synthesized by NaF-mediated hydrothermal processes using Bi(NO3)3 and V2O5 as precursors. The NaF added as a structural controller not only affected the crystal evolution processes of BiVO4 crystals, but also enabled the in situ surface fluorination of the as-synthesized BiVO4 crystals. Interestingly, the photocatalytic oxidation reactions of RhB occurred in a stepwise manner over fluorinated BiVO4 photocatalyst, that is, a faster de-ethylation process (conversion of RhB into rhodamine) followed by a relatively slower mineralization process, involving the destruction of the conjugated structure in rhodamine. Surface fluorination favored the RhB adsorption and hole transfer between RhB molecules and BiVO4 photocatalyst, thus progressively enhancing the initial direct hole transfer mediated de-ethylation process. In contrast, surface fluorination exerts compromised effects on the ·O2− mediated mineralization process, enhancing surface RhB adsorption versus retarding electron transfer from BiVO4 photocatalyst to O2 giving rise to ·O2−, and consequently, moderate surface fluorine coverage is required to balance the aforementioned conflicting effects and achieve the higher mineralization rate. The present study not only demonstrates that the photocatalytic efficiency can be modified by tuning photogenerated active species and photocatalytic reaction processes, but also provides new insights into the fluorination effects on the semiconductor photocatalysis.
TL;DR: In this article, a multi-armed CdS nanorod was synthesized using a solvothermal method with dodecylamine as solvent, and the prepared Cds showed especially high and stable photocatalytic H2-production activity with aqueous lactic acid solution as sacrificial reagent.
Abstract: Visible light photocatalytic H2 production from aqueous solutions using solar light is of great importance from the viewpoint of solar energy conversion and storage and environment protection. In this study, a novel visible-light-driven photocatalyst, multi-armed CdS nanorods, was synthesized using a solvothermal method with dodecylamine as solvent. The prepared CdS nanorod samples showed especially high and stable photocatalytic H2-production activity with aqueous lactic acid solution as sacrificial reagent and Pt as co-catalyst under visible light irradiation. The CdS nanorod sample prepared at 140 °C for 12 h exhibited a high H2-production rate of 1.21 mmol h−1 (about 3.2 times higher than that of CdS nanoparticles (NPs) formed in water) with a very small amount of Pt (0.23 wt%) and a quantum efficiency (QE) of 51% at a wavelength of 420 nm. This high photocatalytic H2-production activity can be attributed to the synergistic effects of several factors such as the hexagonal phase structure, high surface area, great pore volume and good crystallization. Furthermore, the prepared CdS nanorod sample was photostable and no photocorrosion was observed after photocatalytic recycling. Our work demonstrated that multi-armed CdS nanorods were a promising candidate for the development of high-performance visible-light photocatalysts in photocatalytic H2 production and that the morphology of the CdS nanocrystals had a great effect on the photocatalytic H2-production activity.
TL;DR: In this study, the AgI nanoparticles were immobilized on the surface of Ag(8)W(4)O(16) nanorods by an anion-exchange route and their photocatalytic activities were evaluated by photoc atalytic decomposition of methyl orange and phenol solutions under visible-light irradiation.
Abstract: AgI is instable under light irradiation owing to its photosensitive properties, while a supported Ag–AgI composite has been demonstrated to be a stable photocatalyst. However, seldom investigations have been focused on the photocatalytic activity (including deactivation) and photoinduced stability of the photosensitive AgI materials. In this study, the AgI nanoparticles were immobilized on the surface of Ag8W4O16 nanorods by an anion-exchange route and their photocatalytic activities were evaluated by photocatalytic decomposition of methyl orange and phenol solutions under visible-light irradiation. A photoinduced self-stabilizing mechanism of the AgI nanoparticles was proposed to account for the formation of a stable Ag–AgI photocatalyst, namely, instable AgI can transform into a stable Ag–AgI photocatalyst after in situ formation of partial Ag on the surface of AgI nanoparticles. The photocatalytic performance of the immobilized AgI photocatalyst was greatly influenced by the formation of metallic Ag. With increasing repetitions of photocatalytic experiments, the initial deactivation was accompanied by the rapid increase of metallic Ag owing to the reduction of lattice Ag+, while the subsequently stable activity corresponds to the formation of a stable Ag–AgI composite photocatalyst. Compared with the un-immobilized AgI photocatalyst, the immobilized AgI nanoparticles exhibited a higher and more stable photocatalytic performance.
TL;DR: A novel TiO(2) double-layer (DL) film designed as the photoanode of dye-sensitized solar cells (DSSCs) could significantly improve the efficiency of DSSCs owing to its synergic effects.
TL;DR: Ambient S annealing was adopted to regulate the crystallinity of a ZnS microsphere, which resulted in a significant improvement in the photocatalytic hydrogen production activity (PHPA), possibly because the inter-polar electric field of the wurtzite phase could promote the separation of photo-excited electron-hole pairs.
Abstract: Ambient S annealing was adopted to regulate the crystallinity of a ZnS microsphere, which resulted in a significant improvement in the photocatalytic hydrogen production activity (PHPA). Moreover, with S ambient treatment, wurtzite ZnS showed better PHPA than sphalerite ZnS, possibly because the inter-polar electric field of the wurtzite phase could promote the separation of photo-excited electron–hole pairs.
TL;DR: The sample calcined at 600 °C exhibited the highest photocatalytic activity, corresponding to the maximal formation rate of ˙OH on the photocatalyst, which is attributed to the improvement of anatase TiO(2) crystallization, the formation of multi-phase structures including anatase, cubic Zn( 2)TiO(4), hexagonal ZnTiO
Abstract: TiO2-based composite nanotubes, based on an in situ template dissolution method, were one-step fabricated in a mixed aqueous solution of ammonium hexafluorotitanate and boric acid using ZnO nanorods as templates, and then the samples were calcined at different temperatures. The photocatalytic activity of the samples was evaluated by photocatalytic decoloration of Methyl Orange (MO) aqueous solution at ambient temperature under UV light. The results showed that the prepared sample possessed nanoscale tubular morphology with a wall thickness of ca. 30–50 nm, inner diameters of ca. 50–150 nm and lengths of ca. 400–2000 nm. The calcined samples exhibited excellent stabilization of the anatase phase in a wide temperature range of 300–800 °C. The un-calcined and calcined samples possessed hierarchically macro-mesoporous structures. The sample calcined at 600 °C exhibited the highest photocatalytic activity, corresponding to the maximal formation rate of ˙OH on the photocatalyst. This is attributed to the improvement of anatase TiO2 crystallization, the formation of multi-phase structures including anatase, cubic Zn2TiO4, hexagonal ZnTiO3 and cubic ZnTiO3, and the presence of hierarchically macro-mesoporous structures.
TL;DR: In this paper, the State Key Laboratory of Advanced Technology for Material Synthesis and Processing, Wuhan University of Technology, Luoshi Road 122 (Wuhan 430070).
Abstract: 1 State Key Laboratory of Advanced Technology for Material Synthesis and Processing, Wuhan University of Technology, Luoshi Road 122, Wuhan 430070, China 2Department of Chemistry and Biochemistry, Kent State University, Kent, OH 44242, USA 3Department of Chemistry, School of Science, Wuhan University of Technology, Wuhan 430070, China 4 School of Chemistry and Environment, Beijing University of Aeronautics and Astronautics, Beijing 100191, China
TL;DR: The fluoride free TiO2 anatase nanoplates exhibited the best photocatalytic activity in oxidizing the NO gas to NO2 and NO3− and exhibited a higher photonic efficiency than Degussa P25, which was used as a reference.
Abstract: TiO2 anatase nanoplates and hollow microspheres were fabricated by a solvothermal–hydrothermal method using titanium isopropoxide as a titanium precursor and hydrofluoric acid as a capping agent in order to enhance the formation of the {001} crystal facets of the anatase nanocrystals. These different morphological structures of TiO2 anatase can be achieved by only changing the solvent, keeping the amount of the precursor and of the capping agent identical during the solvothermal–hydrothermal process. After calcination of the samples, the adsorbed fluoride atoms on the {001} crystal facets of the TiO2 anatase nanocrystals were completely removed from their surface according to XPS analysis. The calcined TiO2 anatase structures were higher crystallized and the specific surface area of the catalysts increased, enhancing their photocatalytic activity in comparison to the non-calcined TiO2 anatase structures. All TiO2 anatase samples with adsorbed as well as non-adsorbed fluoride atoms on their {001} crystal facets, exhibited a higher photonic efficiency than Degussa P25, which was used as a reference. The fluoride free TiO2 anatase nanoplates exhibited the best photocatalytic activity in oxidizing the NO gas to NO2 and NO3
−.
TL;DR: In this article, α-Fe 2 O 3 nanomaterials were prepared using glycine as structure-directing agent via a simple hydrothermal synthesis followed by calcination.
TL;DR: In this article, a theoretical model on actively Q-switched Nd3+-doped quasi-three-level laser including the energy transfer upconversion and ground state reabsorption is developed.
Abstract: A theoretical model on actively Q-switched Nd3+-doped quasi-three-level laser including the energy transfer upconversion and the ground state reabsorption is developed. The analytical expressions of the fractional thermal loading and the average output power are obtained, and the influence of ETU effects on laser performance for different repetition rate is analyzed. The average output power and the thermal focal length of the Q-switched 946 nm laser are acquired in experiment. The good agreement between the experimental data and theoretical results demonstrates the reliability of the theoretical model.