Particles of sub-micron size possess significant capacity to adsorb organic molecules from aqueous media. Semiconductor photocatalysts in particle form could potentially be utilized for dye removal through either physical adsorption or photo-induced chemical process. The photocatalytic and adsorption capabilities of Cu2O particles with various exposed crystal facets have been studied through separate adsorption capacity test and photocatalytic degradation test. These crystals display unique cubic, octahedral, rhombic dodecahedral, and truncated polyhedral shapes due to specifically exposed crystal facet(s). For comparison, Cu2O particles with no clear exposed facets were also prepared. The current work confirms that the surface charge critically affects the adsorption performance of the synthesized Cu2O particles. The octahedral shaped Cu2O particles, with exposed {111} facets, possess the best adsorption capability of methyl orange (MO) dye due to the strongest positive surface charge among the different types of particles. In addition, we also found that the adsorption of MO follows the Langmuir monolayer mechanism. The octahedral particles also performed the best in photocatalytic dye degradation of MO under visible light irradiation because of the assistance from dye absorption. On top of the photocatalytic study, the stability of these Cu2O particles during the photocatalytic processes was also investigated. Cu(OH) 2 and CuO are the likely corrosion products found on the particle surface after the photocorrosion in MO solution. By adding hole scavengers in the solution, the photocorrosion of Cu2O was greatly reduced. This observation confirms that the photocatalytically generated holes were responsible for the photocorrosion of Cu2O.

A series of spinel solid solutions Li4x/3Co2−2xTi1+2x/3O4 (LCT, 0.2 ≤ x ≤ 0.8) were synthesized and their structures and microwave dielectric properties were characterized in detail. The distribution of cations at A and B sites in the lattice has been analyzed by using Rietveld refinement. The microstructure and dielectric properties were studied by scanning electron microscope and microwave network analyzer. The solid solutions undergo a discontinuous B-site, Li/Ti order–disorder phase transition from a disordered cubic phase to an ordered cubic phase with increasing x values from 0.4 to 0.6. With increasing the A-site lithium content, the LCT ceramics exhibit improved dielectric permittivity er (20.3–26.5), high Q × f value (≥29 400 GHz) and a tailored temperature coefficient of resonant frequency τf from −40 to 10 ppm per °C. Optimized microwave dielectric properties were achieved for the composition with x = 0.8: er = 26.5, Q × f ≈ 29 400 GHz and τf ≈ 10 ppm per °C. A correlation between the cation distribution and microwave dielectric loss is discussed in detail.

Polymeric g-C3N4 is a promising candidate for solar hydrogen production. However, its hydrogen production rate is low when used alone due to fast recombination of photogenerated electron-hole pairs. In this paper, we report much improved hydrogen production by coupling g-C3N4 with two-phase anatase/brookite TiO2 nanoparticles to form multiple heterojunctions. Results have shown that under visible light illumination, photogenerated electrons transfer from g-C3N4 to TiO. In addition, systematic comparison was carried out among different type of heterojunctions, viz., g-C3N4 coupled with a single phase of TiO2 (anatase or brookite), dual-phase TiO2 (anatase/brookite or anatase/rutile), or a three-phase TiO2 (anatase/brookite/rutile) mixture. g-C3N4 with two-phase anatase/brookite TiO2 produces the largest amount of hydrogen under visible light illumination. The comparison reveals two important factors behind photo catalytic hydrogen generation: effective charge transfer and the conduction band potential position. The band edge positions of all the constituent phases of the heterojunction have to be more cathodic than the hydrogen reduction potential in order to realize the full benefit of effective charge separation. (C) 2016 Elsevier Inc. All rights reserved.

In this paper, we synthesized composites consisting of reduced graphene oxide (rGO) and two-phase anatase/brookite TiO2 particles. Results showed that with the addition of rGO to anatase/brookite TiO2, the photocatalytic H2 production from aqueous methanol solution over Pt loaded catalyst is greatly enhanced. This is attributed to effective charge separation leading to the inhibition of photogenerated electron–hole recombination as evidenced from photoluminescence (PL) spectroscopic measurement. Moreover, with the rGO – anatase/brookite TiO2 composite, the H2 production is 2.3 times the amount of H2 produced by rGO – P25 TiO2 (which consists of anatase and rutile particles) composite. The comparison illustrates the importance of the conduction band potential position. As the conduction band potential of brookite TiO2 is more cathodic than anatase and rutile TiO2, it is energetically more favorable for reductive hydrogen production. Through the concept of compositing rGO with two-phase semiconductor photocatalyst, our work has elucidated the importance of effective charge transfer as well as conduction band potential position in photocatalytic hydrogen generation.

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTDefect Engineered g-C3N4 for Efficient Visible Light Photocatalytic Hydrogen ProductionQiuling Tay†, Pushkar Kanhere†, Chin Fan Ng‡, Shi Chen‡, Sudip Chakraborty§, Alfred Cheng Hon Huan‡∥, Tze Chien Sum‡, Rajeev Ahuja§, and Zhong Chen*†View Author Information† School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore‡ Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore§ Department of Physics and Astronomy, Uppsala University, Box 516, Uppsala 75120, Sweden∥ Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, #16-16 Connexis North, Singapore 138632, Singapore*(Z.C.) E-mail: [email protected]Cite this: Chem. Mater. 2015, 27, 14, 4930–4933Publication Date (Web):July 13, 2015Publication History Received20 June 2015Revised3 July 2015Published online14 July 2015Published inissue 28 July 2015https://doi.org/10.1021/acs.chemmater.5b02344Copyright © 2015 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views8560Altmetric-Citations362LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (927 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Atmospheric chemistry,Defects,Defects in solids,Electrical conductivity,Hydrogen Get e-Alerts

A systematic investigation into the influence of the degree of fluorination on the static and dynamic wetting behavior of TiO2‐based nanobelt (TNB) particles with various liquids is described. The effect of the degree of fluorination and the surface tension of the liquid on the occurrence and stability of liquid marbles, foams or dispersions are studied and the wetting behavior and arrangement of particles at the air–liquid surface are observed. Using contact angle (θ) measurements, the relation between the type of particle‐stabilized material and θ is established. For liquids of relatively high tension like water or formamide which do not wet the fluorinated particles, a powder‐like material (marble) is formed. For polar oils of intermediate tension (35–50 mN m−1), which partially wet the fluorinated particles, stable air‐in‐oil foams can be prepared in which particles form a close‐packed layer enveloping air bubbles. Liquids of relatively low tension, e.g., ethanol or polydimethylsiloxane, wet the particles forming a uniform dispersion and partial sedimentation. By contrast, the as‐prepared hydrophilic TNB particles are rapidly wetted by all the liquids as expected due to their high surface energy. The stable cross‐stacked TNB particles with fluoroalkylsilane (FAS) modification could be a versatile platform in a wide range of applications, especially for fluidic devices (e.g., biofluids, gas sensing, and lab‐on‐a‐chip devices). In a proof‐of‐concept study, the oil–water separation performance of fabrics with chemically stable TNB/FAS coating and the liquid isolation by a TNB/FAS shell for highly sensitive gas sensing or reagent assays are investigated.

A new two-dimensional (2D) oxosulfide, (N2H4)2Mn3Sb4S8(μ3-OH)2 (1), has been successfully synthesized under surfactant-thermal conditions with hexadecyltributylphosphonium bromide as the surfactant. Compound 1 has a layered structure and contains a novel [Mn3(μ3-OH)2]n chain along the b-axis. The photocatalytic activity for compound 1 has been demonstrated under visible-light irradiation and continuous H2 evolution was observed. Our results indicate that surfactant-thermal synthesis could be a promising method for growing novel crystalline oxochalcogenides with interesting structures and properties.

Photocatalysis has become increasingly popular for applications in the energy and environmental fields. However, in its conventional form as a pristine (white) semiconductor oxide, e.g., titania (TiO2), the photocatalyst has a wide band gap and does not respond to a large fraction of the solar power available across the visible region. Recently, some success has,been reported in the in situ synthesis and deposition of melon [poly (tri-s-triazine) with an empirical formulation of H3C6N9] onto TiO2 to act as a visible sensitizer. In the present contribution, we report the interesting finding that composites based on hydrogen titanate cores bearing shells of melon and the related graphitic carbon nitride (g-C3N4) as sensitizers are far superior in simulated solar (visible) light-driven photodegradation of methyl orange (MO) dye and ethanol photo-oxidation as compared to the individual components. These layered titanate nanotubes/nanobelts also offer a practical advantage by promoting the build-up of melon from urea as compared to anatase Ti02. This is believed to be linked to the higher density coverage of titanates by surface OH groups and their Bronsted acidic properties, which promote polymerization. Development of the melon structure was verified by diffuse reflectance infrared spectroscopy (DRIFTS) and solid-state nuclear magnetic resonance (C-13 NMR). The melon layer was found to be fully developed after thermal activation at similar to 400 degrees C and photostable under open beam irradiation. More severe heat treatment led to melon degradation, as confirmed by TGA, and loss of visible-responsive photocatalytic activity.

Photocatalytic H2 production from water splitting using semiconductor photocatalysts has attracted much attention due to the increasing global energy crisis. In the past few decades, numerous photocatalysts have been proposed, however, it is still a challenge to develop highly active photocatalysts for water splitting under visible light. Here we report a new composite material consisting of Cu0.02In0.3ZnS1.47 (CIZS) nanospheres and reduced graphene oxide (rGO) nanosheets as a highly active photocatalyst for hydrogen evolution under visible light. These composites were prepared through a solvothermal method in which rGO nanosheets served as a supporting material to load CIZS nanospheres. The nanocomposites demonstrated a high H2 production rate of 3.8 mmol h−1 g−1, which is about 1.84 times that of pure CIZS nanospheres under visible-light irradiation. The high H2 production rate arose from the presence of graphene, which served as an electron collector and transporter to efficiently lengthen the lifetime of photogenerated charge carriers from CIZS nanospheres. This study presents an effective approach to synthesize graphene-based nanocomposites in the field of energy conversion.

Highly crystalline pure brookite and two-phase anatase/brookite TiO2 nanostructures were synthesized via a simple hydrothermal method with titanium sulfide as the precursors in sodium hydroxide solutions. The control of the phase composition has been demonstrated via solution concentration and reaction time, and the phase transformation mechanism has been elucidated. Photocatalytic activities of the as-synthesized two-phase anatase/brookite TiO2, pure anatase nanoparticles, and pure brookite nanoplates were appraised via photocatalytic hydrogen evolution in aqueous methanol solution. Results have shown that the photocatalytic activity is higher for the two-phase anatase/brookite TiO2 and brookite nanoplates as compared to pure anatase nanoparticles despite the lower surface areas of the two-phase anatase/brookite TiO2 and brookite nanoplates. From the Mott-Schottky analysis, brookite phase is shown to have a more cathodic conduction band edge potential than anatase phase, which leads to more energetically favorable hydrogen reduction. Moreover, femtosecond transient absorption spectroscopy measurements suggests that the photoexcited electrons transfer from brookite to anatase phase-leading to further enhancement of the photocatalytic activity. In comparison with the highly active two-phase commercial benchmark P25, our synthesized two-phase anatase/brookite TiO2 is 220% more active when measured by the H-2 yield per unit area of the photocatalyst surface.

The coexistence of low-index facets with a highly photoactive {001} facet in anatase TiO2 nanocrystals has been recently found beneficial to enhance the photocatalytic performance of TiO2 via a synergistic effect. In this paper, this synergistic effect has been further extended from a single crystal to interconnected nanocrystals with dominating {001} or {010} facet in intact hierarchical TiO2 nanostrucutre. The particles synthesized at the optimal condition showed outstanding photocatalytic hydrogen production of 364.2 mu mol.g(-1).h(-1), which is about four times as much as that of commercial P25 (96.5 mu mol-g(-1).h(-1)). Femtosecond transient spectroscopy and density functional theory (DFT) study indicates that effective electron-hole separation takes place within these nanostructures. This new prototype of synergy, which we denote as quasi-heterojunctions, shows that enhanced photocatalytic performance could be derived in the same anatase phase by synthesizing appropriate faceted nanostructures. This work provides a new dimension to facet engineering of TiO2 and other semiconductor photocatalysts.

The coexistence of low-index facets with a highly photoactive {001} facet in anatase TiO2 nanocrystals has been recently found beneficial to enhance the photocatalytic performance of TiO2 via a synergistic effect. In this paper, this synergistic effect has been further extended from a single crystal to interconnected nanocrystals with dominating {001} or {010} facet in intact hierarchical TiO2 nanostrucutre. The particles synthesized at the optimal condition showed outstanding photocatalytic hydrogen production of 364.2 μmol·g–1·h–1, which is about four times as much as that of commercial P25 (96.5 μmol·g–1·h–1). Femtosecond transient spectroscopy and density functional theory (DFT) study indicates that effective electron–hole separation takes place within these nanostructures. This new prototype of synergy, which we denote as quasi-heterojunctions, shows that enhanced photocatalytic performance could be derived in the same anatase phase by synthesizing appropriate faceted nanostructures. This work provid...

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

From atomic level to understand the cluster-size-dependant behavior of dye-sensitized photocatalysts is very important and helpful to design new photocatalytic materials. Although the relationship between the photocatalytic behaviors and particles' size/shape has been widely investigated by theoretical scientists, the experimental evidences are much less. In this manuscript, we successfully synthesized three new ruthenium dye-sensitized polyoxometalates (POM-n, n relate to different size clusters) with different-sized POM clusters. Under visible-light illumination, all three complexes show the stable O2 evolution with the efficient order POM-3 > POM-2 > POM-1. This cluster-size-dependent catalytic behavior could be explained by the different numbers of M = Ot (terminal oxygen) bonds in each individual cluster because it is well-known that Mo = Ot groups are the catalytically active sites for photooxidation reaction. The proposed mechanism of water oxidation for the dye-sensitized POMs is radical reaction process. This research could open up new perspectives for developing new POM-based WOCs.

Cu-In-Zn-S (CIZS) nanoporous spheres were prepared by using a facile room temperature method. The band gaps of the CIZS spheres could be tuned by changing the amount of Cu doped. The obtained CIZS nanoporous spheres exhibited excellent photocatalytic activity for hydrogen production from water under visible light irradiation without any co-catalysts.

For the purpose of efficiently utilizing the renewable solar energy, it is of vital importance to understand the key factors that contribute to the performance merits for photocatalysis applications. In this work, we find that anatase titania nanostructures with high efficiency in photoelectrochemical cell (PEC) do not necessarily retain the same good performance when used in direct heterogeneous reaction (DHR). Investigation is carried out to elucidate how the electronic properties of the different nanostructures are correlated with the PEC and DHR efficiencies. Good PEC cell performance is identified to be related to topotactically formed samples with intimately connected particles that facilitate easy charge transfer. Additional benefit for PEC cell is found to be achieved from the vectorial conduction pathway in the pseudo one dimensional structure. On the other hand, high activity of DHR photocatalysis is attributed mainly to the exposed high reactivity crystal facets. The presence of anatase TiO2 {010} facets is identified to enhance electron-hole separation and create specific surface states that facilitate interactions across the semiconductor/electrolyte interfaces.

A nanohybrid plasmonic photocatalyst, comprising Ag-AgX (X = Cl, Br, I) nanoparticles anchored on titanate nanotubes, was fabricated via a silver ion incorporation process followed by hydrogen halide injection and light-irradiation. The Ag-AgX-titanate nanotubes (Ag-AgX-TNT) hybrid with a high surface area could synergistically adsorb and degrade methylene blue (MB) under visible light, viz., the titanate nanotubes adsorb MB onto their surfaces, which aids the degradation of MB by Ag-AgX nanoparticles. The excellent degradation performance of Ag-AgX under visible light originated from its localized surface plasmonic resonance effect. Therefore, this integrated silver halides/titanate hybrid can efficiently degrade MB dye, and shows good potential for waste water treatment utilizing solar irradiation.

Photocatalysis has attracted significant interest to solve both the energy crisis and effectively combat environmental contamination. However, as the most widely used photocatalyst, titania (TiO2) suffers from inefficient utilization of solar energy due to its wide band gap. In the present paper, we describe a method to extend the absorption edge of photocatalyst to visible region by the surface plasmon effect of silver. Silver ions are photo-reduced onto the surface of titanate nanotubes, which are synthesized by a conventional hydrothermal method. The as-synthesized Ag/titanate composite is transformed into Ag/titania nanoparticles by annealing at different temperatures. It is found that the interaction of Ag nanoparticles with the supports (titanate/titania) plays a key role for the visible light activity. The samples annealed at low temperature (<350°C) do not show significant activity under our conditions, while the one annealed at 450°C shows fast-degradation of methyl orange (MO) under visible light irradiation. The detailed mechanisms are also discussed.