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1

Heterogeneous photocatalysis: From water photolysis to applications in environmental cleanup  

Microsoft Academic Search

Water splitting and environmental cleanup are two active fields in heterogeneous photocatalysis, which are both closely related to the research in semiconductor photoelectrochemistry since the 1960s. The present review paper will attempt to describe some of the progress and resulting achievements in these two fields, and to briefly discuss the future prospects. We will cover the major developments worldwide but

Akira Fujishima; Xintong Zhang; Donald. A. Tryk

2007-01-01

2

Photochemical cleavage of water by photocatalysis  

Microsoft Academic Search

A bifunctional redox catalyst, composed of Pt and RuO2 co-deposited on a colloidal TiO2 carrier, is a highly potent mediator for water decomposition by visible light1. The system contains apart from the sensitizer (Ru(bipy)2+3) an electron relay-methylviologen. The latter is reduced on light excitation, and the photoreaction is coupled with catalytic steps2 generating H2 and O2 from water. To rationalize

Enrico Borgarello; John Kiwi; Ezio Pelizzetti; Mario Visca; Michael Grätzel

1981-01-01

3

Heterogeneous photocatalysis for water purification: Contaminant mineralization kinetics and elementary reactor analysis  

Microsoft Academic Search

Heterogeneous photocatalysis is the third and newest of an emerging series of photolytic technologies for water treatment and purification. The earlier examples of ultraviolet ozonation and ultraviolet peroxidation involved direct photoactivation of the contaminant and\\/or dissolved oxidant and are dominated by solution phase chemistry. Photocatalysis, in contrast, involves photoactivation of the heterogeneous catalyst (an example of indirect photochemical processes) and

David F. Ollis; Craig Turchi

1990-01-01

4

Nanostructured Titanium Oxide Film- And Membrane-Based Photocatalysis For Water Treatment  

EPA Science Inventory

Titanium Oxide (TiO2) photocatalysis, one of the ultraviolet (UV)-based advanced oxidation technologies (AOTs) and nanotechnologies (AONs), has attracted great attention for the development of efficient water treatment and purification systems due to the effectiveness ...

5

Light-harvesting photocatalysis for water oxidation using mesoporous organosilica.  

PubMed

An organic-based photocatalysis system for water oxidation, with visible-light harvesting antennae, was constructed using periodic mesoporous organosilica (PMO). PMO containing acridone groups in the framework (Acd-PMO), a visible-light harvesting antenna, was supported with [Ru(II) (bpy)3 (2+) ] complex (bpy=2,2'-bipyridyl) coupled with iridium oxide (IrOx ) particles in the mesochannels as photosensitizer and catalyst, respectively. Acd-PMO absorbed visible light and funneled the light energy into the Ru complex in the mesochannels through excitation energy transfer. The excited state of Ru complex is oxidatively quenched by a sacrificial oxidant (Na2 S2 O8 ) to form Ru(3+) species. The Ru(3+) species extracts an electron from IrOx to oxidize water for oxygen production. The reaction quantum yield was 0.34?%, which was improved to 0.68 or 1.2?% by the modifications of PMO. A unique sequence of reactions mimicking natural photosystem?II, 1)?light-harvesting, 2)?charge separation, and 3)?oxygen generation, were realized for the first time by using the light-harvesting PMO. PMID:24890840

Takeda, Hiroyuki; Ohashi, Masataka; Goto, Yasutomo; Ohsuna, Tetsu; Tani, Takao; Inagaki, Shinji

2014-07-14

6

Electrocatalysis in water electrolysis with solid polymer electrolyte  

Microsoft Academic Search

Powders of IrO2 were used as anode catalysts in water electrolysis cells with solid polymer electrolyte (SPE). The catalyst was prepared by a pyrolysis process in a nitrate melt at 340°C and then annealed at different temperatures from 440 to 540°C. The catalyst materials were applied to an electrode membrane assembly (MEA) and studied in situ in an electrolysis cell

Egil Rasten; Georg Hagen; Reidar Tunold

2003-01-01

7

High concentrated phenol and 1,2-propylene glycol water solutions treatment by photocatalysis  

Microsoft Academic Search

The degradation of high phenol and 1,2-propylene glycol concentrations (1g\\/l) in water solutions by TiO2-photocatalysis has been studied. Important differences between the degradation mechanism of both molecules have been observed. From the obtained data it may be suggested that degradation of phenol takes place onto the catalyst surface by means of formation of peroxo-compounds. At low phenol concentrations another mechanism,

J. Araña; E. Tello Rendón; J. M. Doña Rodr??guez; J. A. Herrera Melián; O. González D??az; J. Pérez Peña

2001-01-01

8

New Photocatalysis for Effective Degradation of Organic Pollutants in Water  

Microsoft Academic Search

The presence of harmful compounds in water supplies and in the discharge of wastewater from chemical industries, power plants, and agricultural sources is a topic of global concern. The processes and technologies available at the present time for the treatment of polluted water are varied that include traditional water treatment processes such as biological, thermal and chemical treatment. All these

M. Zarei Chaleshtori; G. B. Saupe; S. Masoud

2009-01-01

9

Solar photocatalysis: a clean process for water detoxification  

Microsoft Academic Search

The photocatalytic degradation of various toxic organic compounds has been proposed as a viable process to detoxify drinking water. Irradiating pulverulent semi-conductors like TiO2 in suspension or fixed to various supports in aqueous solutions containing organic pollutants, creates a redox environment able to destroy these pollutants. Solar photocatalytic mineralization of organic water pollutants has a strong potential in the industrial

Didier Robert; Sixto Malato

2002-01-01

10

Degradation of Chlorobenzene by the Hybrid Process of Supercritical Water Oxidation and TiO2 Photocatalysis  

Microsoft Academic Search

A novel hybrid process of hydrothermal or supercritical water oxidation and TiO2 photocatalysis was developed to examine the degradation of chlorobenzene as a model of the oxidative decomposition of organic pollutants. Aqueous solutions of chlorobenzene containing H2O2 as the oxidizing agent and\\/or colloidal TiO2 nanoparticles as catalyst, were fed into the reactor with the temperature and the pressure controlled to

Ai Shimokawa; Noritsugu Kometani; Yoshiro Yonezawa

2010-01-01

11

A Current Perspective on Photocatalysis  

SciTech Connect

The efficient conversion of solar photons into solar electricity and solar fuels is one of the most important scientific challenges of this century owing to dwindling fossil fuel reserves and the need for clean energy. While research in the direct conversion of solar energy to electricity in the areas of low-cost photovoltaic (PV) systems based on all-inorganic semiconductors, dye-sensitized solar cells, organic, and molecular PV is more technically advanced than its direct conversion to fuels, electricity may not be the ultimate primary solar energy conversion choice owing to the intermittence of solar radiation, the considerable energy loss during transmission, the availability of cost-effective storage media for electricity, and the continuing need for liquid transportation fuels. On the other hand, the direct conversion of solar photons to fuels such as H{sub 2}, CO, alcohols, and hydrocarbons using H{sub 2}O and CO{sub 2} as feedstocks offers a solution for the storage and distribution of solar energy in the form of stable chemical bonds that can be activated to provide energy at arbitrary times and locations. The latter approach to photocatalysis is generally called artificial photosynthesis, and has received renewed interest over the past five or so years. While 'photocatalysis' has not traditionally been restricted to the generation of 'solar fuels,' and has included the production of other useful chemicals, polymerization, and environmental remediation applications, the recent upsurge of interest has been driven mostly by renewable energy issues. It was the pioneering work on photo-electrochemical splitting of water to H{sub 2} and O{sub 2} by n-type TiO{sub 2} using ultraviolet light, by Fujishima and Honda in 1972, that ushered in the area of research that has come to be known as 'solar fuels,' and that has led to the terms 'photocatalysis' and 'solar fuels' becoming almost synonymous. This special issue of ChemSusChem is devoted to providing a current perspective on the field of photocatalysis. It contains invited papers from leading researchers in a wide range of important aspects of the field that address materials, photophysical, photochemical, and electrocatalysis issues. The area remains primarily the domain of basic research studies because progress toward the promise offered by the early work has (at least until recently) been slow, despite its significance having become increasingly recognized. The present collection of papers deals with new semiconductor photocatalysts, molecular catalysts for hydrogen production and water oxidation, dye-sensitized photoelectrochemical cells, and electrochemical CO{sub 2} reduction. Overall photochemical water splitting without any applied bias potential is achieved in several systems, especially under UV irradiation. Further advances are also achieved in a few semiconductor systems, such as GaZn oxynitrides or two-step (so-called 'Z-scheme') systems to produce H{sub 2} and O{sub 2} without any sacrificial reagent under visible irradiation. When band gaps of semiconductors are narrowed to absorb more visible light for greater efficiency, or when band positions are not suitable for carrying out one-electron redox processes, multielectron catalysts are required to promote proton-coupled electron transfer reactions in producing solar fuels. In homogeneous photocatalysis systems, sacrificial reagents are typically used to investigate the catalytic activity, detailed kinetics, and mechanisms of a half reaction. Photoelectrolysis systems with immobilized catalysts (metals, metal oxides, or molecular catalysts) on electrodes can separate oxidized products, such as O{sub 2}, and reduced products, such as H{sub 2}, CO, CH{sub 3}OH, and others, by means of proton- or hydroxide-conducting membranes. The following paragraphs briefly summarize these contributions. In the area of UV-driven water splitting, Townsend et al. prepared Pt-and/or IrO{sub x}-coated niobate (Nb{sub 6}O{sub 17}{sup 4-}) nanoscrolls and tested photochemical water reduction with methanol as a sacrificial rea

Fujita, E.; Muckerman, J.T.; Domen, K.

2011-02-18

12

Decontamination and disinfection of water by solar photocatalysis: Recent overview and trends  

Microsoft Academic Search

In recent years, there has been a tremendous amount of research and development in the area of photocatalysis (heterogeneous and homogeneous), a process included in a special class of oxidation techniques defined as Advanced Oxidation Processes (AOPs), all characterized by the same chemical feature, production of OH radicals. This paper reviews the use of sunlight to produce the OH radicals

S. Malato; P. Fernández-Ibáñez; M. I. Maldonado; J. Blanco; W. Gernjak

2009-01-01

13

Studies on various reactor configurations for coupling photocatalysis and membrane processes in water purification  

Microsoft Academic Search

General aspects and perspectives of heterogeneous photocatalysis for the treatment of polluted aqueous effluents are presented. Some experimental results obtained by using various configurations of photocatalytic membrane reactors (PMRs) are reported. The configurations studied were: (i) irradiation of the cell containing the membrane, with three sub-cases: (i1) catalyst deposited on the membrane; (i2) catalyst in suspension, confined by means of

Raffaele Molinari; Leonardo Palmisano; Enrico Drioli; Mario Schiavello

2002-01-01

14

A Taylor vortex reactor for heterogeneous photocatalysis  

Microsoft Academic Search

Heterogeneous photocatalysis is a promising advanced oxidation process for water purification. One of the limitations in photocatalysis has been inherently low photoefficiencies. Recent studies show that the photoefficiency of formate decomposition can be increased through the use of controlled periodic illumination. In this study, a Taylor vortex reactor was designed, constructed and tested as a novel photocatalytic reactor that incorporated

Richard D. Noble; C KOVAL

1995-01-01

15

Photoelectrochemistry, photocatalysis and photoreactors, fundamentals and developments  

SciTech Connect

Represented here is an investigation of the fundamentals, developments and case studies related to the fields of photoelectrochemical and photocataclytic methods, which are both means of water photosplitting. This volume examines a wide variety of reactions to the goal of more efficiently using solar energy. A section is also devoted to the area of photoreactors. Topics include: photoelectrochemistry, homogeneous photocatalysis, heterogeneous photocatalysis, and photoreactors.

Schiavello, M.

1985-01-01

16

TiO2\\/AC Composites for Synergistic Adsorption-Photocatalysis Processes: Present Challenges and Further Developments for Water Treatment and Reclamation  

Microsoft Academic Search

Titanium dioxide supported on activated carbon, or TiO2\\/AC composite, exhibits bifunctionality of adsorption and photocatalysis in synergism. The authors review the TiO2\\/AC synthesis techniques, characteristics, and performances in removing organic pollutants in water. Practical issues pertinent to applications of the TiO2\\/AC composite in water treatment and reclamation are discussed. These include dispersing the particles and recovering from the product water,

Teik-Thye Lim; Pow-Seng Yap; Madhavi Srinivasan; Anthony G. Fane

2011-01-01

17

Electrocatalysis for Oxygen Electrodes in Fuel Cells and Water Electrolyzers for Space Applications.  

National Technical Information Service (NTIS)

In most instances separate electrocatalysts are needed to promote the reduction of O2 in the fuel cell mode and to generate O2 in the energy storage-water electrolysis mode in aqueous electrochemical systems operating at low and moderate temperatures (T g...

J. Prakash D. Tryk E. Yeager

1989-01-01

18

Electrocatalysis for oxygen electrodes in fuel cells and water electrolyzers for space applications  

NASA Technical Reports Server (NTRS)

In most instances separate electrocatalysts are needed to promote the reduction of O2 in the fuel cell mode and to generate O2 in the energy storage-water electrolysis mode in aqueous electrochemical systems operating at low and moderate temperatures (T greater than or equal to 200 C). Interesting exceptions are the lead and bismuth ruthenate pyrochlores in alkaline electrolytes. These catalysts on high area carbon supports have high catalytic activity for both O2 reduction and generation. Rotating ring-disk electrode measurements provide evidence that the O2 reduction proceeds by a parallel four-electron pathway. The ruthenates can also be used as self-supported catalysts to avoid the problems associated with carbon oxidation, but the electrode performance so far achieved in the research at Case Western Reserve University (CWRU) is considerably less. At the potentials involved in the anodic mode the ruthenate pyrochlores have substantial equilibrium solubility in concentrated alkaline electrolyte. This results in the loss of catalyst into the bulk solution and a decline in catalytic activity. Furthermore, the hydrogen generation counter electrode may become contaminated with reduction products from the pyrochlores (lead, ruthenium).

Prakash, Jai; Tryk, Donald; Yeager, Ernest

1989-01-01

19

Electrocatalysis for oxygen electrodes in fuel cells and water electrolyzers for space applications  

NASA Astrophysics Data System (ADS)

In most instances separate electrocatalysts are needed to promote the reduction of O2 in the fuel cell mode and to generate O2 in the energy storage-water electrolysis mode in aqueous electrochemical systems operating at low and moderate temperatures (T greater than or equal to 200 C). Interesting exceptions are the lead and bismuth ruthenate pyrochlores in alkaline electrolytes. These catalysts on high area carbon supports have high catalytic activity for both O2 reduction and generation. Rotating ring-disk electrode measurements provide evidence that the O2 reduction proceeds by a parallel four-electron pathway. The ruthenates can also be used as self-supported catalysts to avoid the problems associated with carbon oxidation, but the electrode performance so far achieved in the research at Case Western Reserve University (CWRU) is considerably less. At the potentials involved in the anodic mode the ruthenate pyrochlores have substantial equilibrium solubility in concentrated alkaline electrolyte. This results in the loss of catalyst into the bulk solution and a decline in catalytic activity. Furthermore, the hydrogen generation counter electrode may become contaminated with reduction products from the pyrochlores (lead, ruthenium).

Prakash, Jai; Tryk, Donald; Yeager, Ernest

1989-12-01

20

Photocatalysis Using Semiconductor Nanoclusters  

SciTech Connect

We report on experiments using nanosize MoS{sub 2} to photo-oxidize organic pollutants in water using visible light as the energy source. We have demonstrated that we can vary the redox potentials and absorbance characteristics of these small semiconductors by adjusting their size, and our studies of the photooxidation of organic molecules have revealed that the rate of oxidation increases with increasing bandgap (i.e. more positive valence band and more negative conduction band potentials). Because these photocatalysis reactions can be performed with the nanoclusters fully dispersed and stable in solution, liquid chromatography can be used to determine both the intermediate reaction products and the state of the nanoclusters during the reaction. We have demonstrated that the MoS{sub 2} nanoclusters remain unchanged during the photooxidation process by this technique. We also report on studies of MoS{sub 2} nanoclusters deposited on TiO{sub 2} powder.

Thurston, T.R.; Wilcoxon,J.P.

1999-01-21

21

Integration of separation and photocatalysis using an inorganic membrane modified with Si-doped TiO 2 for water purification  

Microsoft Academic Search

An unsymmetrical inorganic membrane with Si-doped TiO2 layers was fabricated for the purpose of realizing filtration and photocatalysis in a single device in water purification process. Tetra-n-butyl titanate [Ti(OC4H9)4, TBOT] and tetraethyl orthosilicate [Si(OC2H5)4, TEOS] were used as precursors of TiO2 and Si element source, and Si-doped TiO2 photocatalytic layer was coated on a commercial Al2O3 membrane by sol–gel technique.

Ning Ma; Xie Quan; Yaobin Zhang; Shuo Chen; Huimin Zhao

2009-01-01

22

Silver and gold icosahedra: one-pot water-based synthesis and their superior performance in the electrocatalysis for oxygen reduction reactions in alkaline media.  

PubMed

Much effort has gone into generating polyhedral noble metal nanostructures because of their superior electrocatalytic activities for fuel cells. Herein, we report uniform, high-yield icosahedral silver and gold nanoparticles by using a facile one-pot, seedless, water-based approach that incorporates polyvinyl pyrrolidone and ammonia. Electrocatalysis of the oxygen-reduction reaction was carried out in alkaline media to evaluate the performance of the icosahedral nanoparticles. They showed excellent stability and much higher electrocatalytic activity than the spherelike nanoparticles; they display a positive shift in reduction peak potential for O(2) of 0.14 and 0.05 V, while the reduction peak currents of the silver and gold icosahedra are 1.5- and 1.6-fold, respectively, better than the spherelike nanoparticles. More importantly, the icosahedral nanoparticles display electrocatalytic activities comparable with commercial Pt/C electrocatalysts. The facile preparation of icosahedral silver and gold nanoparticles and their superior performance in the oxygen reduction reaction render them attractive replacements for Pt as cathode electrocatalysts in alkaline fuel cells. PMID:21344521

Kuai, Long; Geng, Baoyou; Wang, Shaozhen; Zhao, Yanyan; Luo, Yinchan; Jiang, Han

2011-03-14

23

Electrocatalysis on gold.  

PubMed

This perspective article reviews recent advances in the study of important catalytic reactions on gold electrodes. The paper discusses both oxidation and reduction reactions: the oxidation of carbon monoxide and alcohols as well as the oxygen reduction reaction on gold electrodes and also a brief discussion of other interesting reactions on gold electrodes such as the amine borane oxidation and the CO2 reduction. A common theme in electrocatalysis on gold is the sensitive dependence of various reaction rates on pH and gold surface structure. The electrocatalysis of redox reactions on gold is highly pH dependent, often preferring alkaline media, due to the prominent role of negatively charged reaction intermediates related to the fact that gold does not bind the neutral intermediates strongly enough. Gold also tends to be a selective catalyst, again due to its weak adsorption properties, as on gold the reaction often stops when a difficult bond breaking or making event will be the necessary next step. PMID:24728379

Rodriguez, Paramaconi; Koper, Marc T M

2014-07-21

24

Solar photocatalysis for detoxification and disinfection of contaminated water: pilot plant studies  

Microsoft Academic Search

Photocatalytic processes in the presence of titanium dioxide provide an interesting route to destroy hazardous organic contaminants, being operational in the UV-A domain with a potential use of solar radiation. A preliminary evaluation of a photocatalytic process for water purification has been made to assess its effectiveness in reducing contaminant concentrations of drinking water standards. Studies reported in this paper

A. Vidal; A. I. D??az; A. El Hraiki; M. Romero; I. Muguruza; F. Senhaji; J. González

1999-01-01

25

Arsenic removal from water employing heterogeneous photocatalysis with TiO 2 immobilized in PET bottles  

Microsoft Academic Search

Arsenic oxidation (As(III) to As(V)) and As(V) removal from water were assessed by using TiO2 immobilized in PET (polyethylene terephthalate) bottles in the presence of natural sunlight and iron salts. The effect of many parameters was sequentially studied: TiO2 concentration of the coating solution, Fe(II) concentration, pH, solar irradiation time; dissolved organic carbon concentration. The final conditions (TiO2 concentration of

Anne Hélène Fostier; Maria do Socorro Silva Pereira; Susanne Rath; José Roberto Guimarães

2008-01-01

26

Titanium dioxide photocatalysis  

Microsoft Academic Search

Scientific studies on photocatalysis started about two and a half decades ago. Titanium dioxide (TiO2), which is one of the most basic materials in our daily life, has emerged as an excellent photocatalyst material for environmental purification. In this review, current progress in the area of TiO2 photocatalysis, mainly photocatalytic air purification, sterilization and cancer therapy are discussed together with

Akira Fujishima; Tata N. Rao; Donald A. Tryk

2000-01-01

27

The Degradtion of Humic Substance using Continuous Photocatalysis Systems  

Microsoft Academic Search

Photocatalytic oxidation is an emerging technology in water and wastewater treatment. Photocatalysis often leads to complete degradation of organic pollutants without the need for chemicals. This study investigated the degradation of humic substances in water using photocatalysis systems coupled with physio?chemical processes such as adsorption and\\/or flocculation. Dissolved Organic Carbon (DOC) removal of PAC?TiO2 was improved by a factor of

N. Areerachakul; S. Vigneswaran; J. Kandasamy; C. Duangduen

2008-01-01

28

Electrocatalysis at metal nanomaterials  

NASA Astrophysics Data System (ADS)

Direct liquid fuel cells, such as direct methanol fuel cells and direct formic acid fuel cells, have attracted much attention in the past decades due to the need of clean and efficient power sources. One of the most critical issues in the development of highly efficient fuel cells is to increase the rates of fuel-cell reactions as a commercial product. As a result, the topic of electrocatalysis plays a significant role in the investigations of fuel cell reactions. For methanol oxidation, platinum based nanomaterials are the most important catalysts. For formic acid oxidation, both platinum and palladium based nanomaterials are widely employed as the catalysts. Recently, shape-control of the nanoparticles has become an imperative task due to the fact that most of the reactions in fuel cells are sensitive to the surface structure of the catalysts. Though numerous studies have been conducted in past to elucidate the catalytic activity on the nanomaterials with different shapes, the results are inconclusive. Herein, systematic comparison of catalytic activity toward methanol and formic acid oxidation on shape-controlled cubic platinum-based alloy nanoparticles with different alloy element are reported in this dissertation. Methanol and formic acid oxidation reactions on spherical and cubic Pt-Cu nanoparticles are also studied. Cu-Pd nanoparticles are synthesized through galvanic redox reactions to provide significantly higher and much more stable formic acid oxidation activities. Interparticle distance effect is investigated on two dimensional nanoparticle array electrodes with controlled particle size, which is ideal model system for exploring the interparticle distance effects on the voltammetric behavior and reaction mechanisms.

Dai, Lin

29

Performing a microfiltration integrated with photocatalysis using an Ag-TiO 2\\/HAP\\/Al 2O 3 composite membrane for water treatment: Evaluating effectiveness for humic acid removal and anti-fouling properties  

Microsoft Academic Search

Membrane filtration has been increasingly used for water treatment and wastewater reclamation in recent years. To further improve the effectiveness of membrane process and reduce membrane fouling, a highly reactive photocatalytic membrane, Ag-TiO2\\/hydroxiapiate (HAP, Ca10(PO4)6(OH)2)\\/Al2O3, was employed to realize microfiltration (MF) coupling photocatalysis for surface water treatment. The effectiveness on the potential of membrane was investigated by removing humic acid

Ning Ma; Yaobin Zhang; Xie Quan; Xinfei Fan; Huimin Zhao

2010-01-01

30

Water oxidation on pure and doped hematite (0001) surfaces: prediction of Co and Ni as effective dopants for electrocatalysis.  

PubMed

In photoelectrochemical cells, sunlight may be converted into chemical energy by splitting water into hydrogen and oxygen molecules. Hematite (?-Fe(2)O(3)) is a promising photoanode material for the water oxidation component of this process. Numerous research groups have attempted to improve hematite's photocatalytic efficiency despite a lack of foundational knowledge regarding its surface reaction kinetics. To elucidate detailed reaction mechanisms and energetics, we performed periodic density functional theory + U calculations for the water oxidation reaction on the fully hydroxylated hematite (0001) surface. We investigate two different concentrations of surface reactive sites. Our best model involves calculating water oxidation mechanisms on a pure (1×1) hydroxylated hematite slab (corresponding to 1/3 ML of reactive sites) with an additional overlayer of water molecules to model solvation effects. This yields an overpotential of 0.77 V, a value only slightly above the 0.5-0.6 V experimental range. To explore whether doped hematite can exhibit an even lower overpotential, we consider cation doping by substitution of Fe by Ti, Mn, Co, Ni, or Si and F anion doping by replacing O on the fully hydroxylated surface. The reaction energetics on pure or doped hematite surfaces are described using a volcano plot. The relative stabilities of holes on the active O anions are identified as the underlying cause for trends in energetics predicted for different dopants. We show that moderately charged O anions give rise to smaller overpotentials. Co- or Ni-doped hematite surfaces give the most thermodynamically favored reaction pathway (lowest minimum overpotential) among all dopants considered. Very recent measurements (Electrochim. Acta 2012, 59, 121-127) reported improved reactivity with Ni doping, further validating our predictions. PMID:22788792

Liao, Peilin; Keith, John A; Carter, Emily A

2012-08-15

31

Electrocatalysis with vitamin B sub 12 in water-in-oil microemulsions at carbon-fiber microelectrodes  

SciTech Connect

Microemulsions are clear, thermodynamically stable dispersions containing oil, surfactant and water. They are crude models of biological membranes and can be used to investigate some of the organizational influence of membranes in lipid and protein synthesis, energy transduction, ion and group transport, etc. This thesis concerns the investigation of microemulsion properties as media in which catalytic reduction of vicinal dibromides can take place with the electrochemically generated Co(I) form of Vitamin B{sub 12}. Methods to study fundamental properties of resistive w/o AOT/H{sub 2}O/isoctane were developed. Microelectrodes of approximate radius of 6 {mu}m were prepared and characterized. Nonlinear regression was applied to the analysis of steady state voltammograms obtained at carbon-fiber microelectrodes. Reversible regression models were used to analyze data for oxidation of ferrocene in acetonitrile with and without added electrolyte. An estimate of cell resistance in highly resistive media was obtained by including ohmic drop in the model for reversible electron transfer. The electrocatalytic reduction of 1,2-dibromoethane (EDB), 1,2-dibromobutane (DBB), and trans-1,2-dibromocyclohexane (DBCH) with Vitamin B{sub 12} in pH {le} 3 water MeCN and w/o microemulsions of AOT/H{sub 2}O/isoctane at carbon fiber microelectrode was investigated. The microviscosity of w/o microemulsions were estimated from the Stokes-Einstein equation using ferrocene as a probe. Results show that the diffusion of molecules in the microemulsions are similar to their diffusion in organic phase (isoctane). Nonlinear regression analysis of the data for AOT w/o microemulsions describing the dependence of D{prime} on C{sub x} enables an estimate of micelle diffusion coefficients.

Owlia, A.

1989-01-01

32

Aniline degradation by combined photocatalysis and ozonation  

Microsoft Academic Search

The combination of TiO2-assisted photocatalysis and ozonation in the degradation of aniline in aqueous solution is investigated. From the experimental results obtained it is observed that the ozonation pretreatment followed by photocatalysis strongly increases the yield of TOC removal in comparison to either ozonation or photocatalysis carried out separately. The opposite sequence (photocatalysis pretreatment followed by ozonation) does not enhance

Laura Sánchez; José Peral; Xavier Domènech

1998-01-01

33

Photocatalysis-assisted water filtration: using TiO2-coated vertically aligned multi-walled carbon nanotube array for removal of Escherichia coli O157:H7.  

PubMed

A porous ceramic was coated with vertically aligned multi-walled carbon nanotubes (MWCNTs) by spray pyrolysis. Titanium dioxide (TiO2) nanoparticles were then coated onto this densely aligned MWCNT. The presence of TiO2/MWCNT interfacial arrays was confirmed by X-ray diffraction (XRD), scanning electron microscope-energy dispersive analysis of X-ray (SEM-EDAX) and transmission electron microscope (TEM). This is a novel report in which water loaded with a most dreadful enterohemorrhagic pathogenic strain of Escherichia coli O157:H7 was filtered through TiO2/MWCNT coated porous ceramic filter and then analysed. Bacterial removal performance was found to be significantly lower in control i.e. plain porous ceramic (P<0.05) as compared to TiO2/MWCNT coated ceramic. The photocatalytic killing rate constant for TiO2-ceramic and MWCNT/TiO2-ceramic under fluorescent light was found be 1.45×10(-2) min(-1) and 2.23×10(-2) min(-1) respectively. Further, when I-V characteristics were performed for TiO2/MWCNT composite, it was corroborated that the current under light irradiation is comparatively higher than that in dark, thus proving it to be photocatalytically efficient system. The enhanced photocatalysis may be a contribution of increased surface area and charge transfer rate as a consequence of aligned MWCNT network. PMID:23910358

Oza, Goldie; Pandey, Sunil; Gupta, Arvind; Shinde, Sachin; Mewada, Ashmi; Jagadale, Pravin; Sharon, Maheshwar; Sharon, Madhuri

2013-10-01

34

Semiconductor photocatalysis--mechanistic and synthetic aspects.  

PubMed

Preceding work on photoelectrochemistry at semiconductor single-crystal electrodes has formed the basis for the tremendous growth in the three last decades in the field of photocatalysis at semiconductor powders. The reason for this is the unique ability of inorganic semiconductor surfaces to photocatalyze concerted reduction and oxidation reactions of a large variety of electron-donor and -acceptor substrates. Whereas great attention was paid to water splitting and the exhaustive aerobic degradation of pollutants, only a small amount of research also explored synthetic aspects. After introducing the basic mechanistic principles, standard experiments for the preparation and characterization of visible light active photocatalysts as well as the investigation of reaction mechanisms are discussed. Novel atom-economic C-C and C-N coupling reactions illustrate the relevance of semiconductor photocatalysis for organic synthesis, and demonstrate that the multidisciplinary field combines classical photochemistry with electrochemistry, solid-state chemistry, and heterogeneous catalysis. PMID:23212748

Kisch, Horst

2013-01-14

35

DNA sensing by electrocatalysis with hemoglobin  

PubMed Central

Electrocatalysis offers a means of electrochemical signal amplification, yet in DNA-based sensors, electrocatalysis has required high-density DNA films and strict assembly and passivation conditions. Here, we describe the use of hemoglobin as a robust and effective electron sink for electrocatalysis in DNA sensing on low-density DNA films. Protein shielding of the heme redox center minimizes direct reduction at the electrode surface and permits assays on low-density DNA films. Electrocatalysis with methylene blue that is covalently tethered to the DNA by a flexible alkyl chain linkage allows for efficient interactions with both the base stack and hemoglobin. Consistent suppression of the redox signal upon incorporation of a single cytosine-adenine (CA) mismatch in the DNA oligomer demonstrates that both the unamplified and the electrocatalytically amplified redox signals are generated through DNA-mediated charge transport. Electrocatalysis with hemoglobin is robust: It is stable to pH and temperature variations. The utility and applicability of electrocatalysis with hemoglobin is demonstrated through restriction enzyme detection, and an enhancement in sensitivity permits femtomole DNA sampling.

Pheeney, Catrina G.; Guerra, Luis F.; Barton, Jacqueline K.

2012-01-01

36

DNA sensing by electrocatalysis with hemoglobin.  

PubMed

Electrocatalysis offers a means of electrochemical signal amplification, yet in DNA-based sensors, electrocatalysis has required high-density DNA films and strict assembly and passivation conditions. Here, we describe the use of hemoglobin as a robust and effective electron sink for electrocatalysis in DNA sensing on low-density DNA films. Protein shielding of the heme redox center minimizes direct reduction at the electrode surface and permits assays on low-density DNA films. Electrocatalysis with methylene blue that is covalently tethered to the DNA by a flexible alkyl chain linkage allows for efficient interactions with both the base stack and hemoglobin. Consistent suppression of the redox signal upon incorporation of a single cytosine-adenine (CA) mismatch in the DNA oligomer demonstrates that both the unamplified and the electrocatalytically amplified redox signals are generated through DNA-mediated charge transport. Electrocatalysis with hemoglobin is robust: It is stable to pH and temperature variations. The utility and applicability of electrocatalysis with hemoglobin is demonstrated through restriction enzyme detection, and an enhancement in sensitivity permits femtomole DNA sampling. PMID:22733728

Pheeney, Catrina G; Guerra, Luis F; Barton, Jacqueline K

2012-07-17

37

Open-framework gallium borate with boric and metaboric acid molecules inside structural channels showing photocatalysis to water splitting.  

PubMed

An open-framework gallium borate with intrinsic photocatalytic activities to water splitting has been discovered. Small inorganic molecules, H3BO3 and H3B3O6, are confined inside structural channels by multiple hydrogen bonds. It is the first example to experimentally show the structural template effect of boric acid in flux synthesis. PMID:24512540

Gao, Wenliang; Jing, Yan; Yang, Jia; Zhou, Zhengyang; Yang, Dingfeng; Sun, Junliang; Lin, Jianhua; Cong, Rihong; Yang, Tao

2014-03-01

38

Environmental green chemistry as defined by photocatalysis.  

PubMed

Photocatalysis is efficient in several fields. Firstly, in selective mild oxidation: oxidation of gas and liquid hydrocarbons (alkanes, alkenes, cyclo-alkanes, aromatics) into aldehydes and ketons. Primary and secondary alcohols are also oxidized into their corresponding aldehydes or ketones. The high selectivity was ascribed to a photoactive neutral, atomic oxygen species. Once platinized (only 0.5wt.% Pt) titania may catalyze reactions involving hydrogen (deuterium-alkane isotopic exchange and alcohol dehydrogenation). For fine chemicals, high initial selectivities enable titania to address most of the twelve principles of "green chemistry", such as the synthesis of 4-tert-butyl-benzaldehyde, an important intermediate in perfume industry by direct selective oxidation of 4-tert-butyl-toluene with air. A new field recently appeared: thio-photocatalysis. Oxygen was replaced by sulfur, using H(2)S as a convenient and reactive source. For instance, the conversion of propene in 1-propanthiol was successfully obtained. The reaction was performed using either CdS or TiO(2). The latter was much more active than CdS. In environmental photocatalysis, titania becomes a total oxidation catalyst once in presence of water because of the photogeneration of OH radicals by neutralization of OH(-) surface groups by positive holes. Many toxic inorganic ions are oxidized in their harmless upper oxidized state. The total degradation of organic pollutants (pesticides, herbicides, insecticides, fungicides, dyes, etc. ...) is the main field of water photocatalytic decontamination. The UVA solar spectrum can de advantageously used as demonstrated by many campaigns performed in the solar pilot plant at the "Plataforma Solar de Almeria" (Spain). PMID:17532130

Herrmann, J-M; Duchamp, C; Karkmaz, M; Hoai, Bui Thu; Lachheb, H; Puzenat, E; Guillard, C

2007-07-31

39

Photocatalysis. A multi-faceted concept for green chemistry.  

PubMed

Photocatalysis (by semiconductors, molecules and ions) is used in such diverse applications as water hydrolysis for producing hydrogen as fuel, organic synthesis and the recovery of polluted effluents. This tutorial review discusses the common principles of such applications and their role in green chemistry. PMID:19551179

Ravelli, Davide; Dondi, Daniele; Fagnoni, Maurizio; Albini, Angelo

2009-07-01

40

Role of Nanoparticles in Photocatalysis  

Microsoft Academic Search

The aim of this review paper is to give an overview of the development and implications of nanotechnology in photocatalysis. The topics covered include a detailed look at the unique properties of nanoparticles and their relation to photocatalytic properties. Current applications of and research into the use of nanoparticles as photocatalysts has also been reviewed. Also covered is the utilization

D. Beydoun; R. Amal; G. Low; S. McEvoy

1999-01-01

41

Fuel cell applied research: Electrocatalysis and materials  

NASA Astrophysics Data System (ADS)

The effect of underpotential deposited metal layers on the electrocatalysis of fuel cell reactions is studied. The potential for developing organic compound/air fuel cells using underpotential deposited Pb adatoms to enhance the electrocatalysis of the fuel electrode is explored. The effects of adsorbed layers of Pb, Tl and Bi on formic acid and methanol oxidation on platinum in 85 percent H3PO4 were investigated. The effect of crystal orientation on formic acid oxidation on platinum in 1 M CHlO2 was investigated. The kinetics of the oxygen reduction and evolution reactions at the electrode (metal or oxide) solid electrolyte (yttria stabilized zirconia) interface were investigated using ac and dc techniques.

Srinivasan, S.; Isaacs, H.; McBreen, J.; Ogrady, W. E.; Olender, H.; Olmer, L. J.; Schouler, E. J. L.; Adzic, R. R.

1980-03-01

42

Electrocatalysis of anodic oxidation of ethanol  

NASA Astrophysics Data System (ADS)

The results of fundamental and applied studies in the field of electrocatalysis of anodic oxidation of ethanol in fuel cells are considered. Features of the mechanism of ethanol electrooxidation are discussed as well as the structure and electrochemical properties of the most widely used catalysts of this process. The prospects of further studies of direct ethanol fuel cells with alkaline and acidic electrolytes are outlined. The bibliography includes 166 references.

Tarasevich, M. R.; Korchagin, O. V.; Kuzov, A. V.

2013-11-01

43

TiO 2 photocatalysis and related surface phenomena  

Microsoft Academic Search

The field of photocatalysis can be traced back more than 80 years to early observations of the chalking of titania-based paints and to studies of the darkening of metal oxides in contact with organic compounds in sunlight. During the past 20 years, it has become an extremely well researched field due to practical interest in air and water remediation, self-cleaning surfaces, and

Akira Fujishima; Xintong Zhang; Donald A. Tryk

2008-01-01

44

Photocatalysis Using Semiconductor Nanoclusters.  

National Technical Information Service (NTIS)

We report on experiments using nanosize MoS(sub 2) to photo-oxidize organic pollutants in water using visible light as the energy source. We have demonstrated that we can vary the redox potentials and absorbance characteristics of these small semiconducto...

T. R. Thurston J. P. Wilcoxon

1999-01-01

45

Metal-organic frameworks for artificial photosynthesis and photocatalysis.  

PubMed

Solar energy is an alternative, sustainable energy source for mankind. Finding a convenient way to convert sunlight energy into chemical energy is a key step towards realizing large-scale solar energy utilization. Owing to their structural regularity and synthetic tunability, metal-organic frameworks (MOFs) provide an interesting platform to hierarchically organize light-harvesting antennae and catalytic centers to achieve solar energy conversion. Such photo-driven catalytic processes not only play a critical role in the solar to chemical energy conversion scheme, but also provide a novel methodology for the synthesis of fine chemicals. In this review, we summarize the fundamental principles of energy transfer and photocatalysis and provide an overview of the latest progress in energy transfer, light-harvesting, photocatalytic proton and CO2 reduction, and water oxidation using MOFs. The applications of MOFs in organic photocatalysis and degradation of model organic pollutants are also discussed. PMID:24769551

Zhang, Teng; Lin, Wenbin

2014-07-21

46

HIgh Temperature Photocatalysis over Semiconductors  

NASA Astrophysics Data System (ADS)

Due in large part to in prevalence of solar energy, increasing demand of energy production (from all sources), and the uncertain future of petroleum energy feedstocks, solar energy harvesting and other photochemical systems will play a major role in the developing energy market. This dissertation focuses on a novel photochemical reaction process: high temperature photocatalysis (i.e., photocatalysis conducted above ambient temperatures, T ? 100°C). The overarching hypothesis of this process is that photo-generated charge carriers are able to constructively participate in thermo-catalytic chemical reactions, thereby increasing catalytic rates at one temperature, or maintaining catalytic rates at lower temperatures. The photocatalytic oxidation of carbon deposits in an operational hydrocarbon reformer is one envisioned application of high temperature photocatalysis. Carbon build-up during hydrocarbon reforming results in catalyst deactivation, in the worst cases, this was shown to happen in a period of minutes with a liquid hydrocarbon. In the presence of steam, oxygen, and above-ambient temperatures, carbonaceous deposits were photocatalytically oxidized over very long periods (t ? 24 hours). This initial experiment exemplified the necessity of a fundamental assessment of high temperature photocatalytic activity. Fundamental understanding of the mechanisms that affect photocatalytic activity as a function of temperatures was achieved using an ethylene photocatalytic oxidation probe reaction. Maximum ethylene photocatalytic oxidation rates were observed between 100 °C and 200 °C; the maximum photocatalytic rates were approximately a factor of 2 larger than photocatalytic rates at ambient temperatures. The loss of photocatalytic activity at temperatures above 200 °C is due to a non-radiative multi-phonon recombination mechanism. Further, it was shown that the fundamental rate of recombination (as a function of temperature) can be effectively modeled as a temperature-dependent quantum efficiency term, and is directly driven by bulk photocatalyst crystal parameters: maximum phonon energy and the number of phonons allowed per unit cell. This analysis extends to multiple photocatalysts and can explain experimental observations of photocatalytic oxidation rates with varied reactant concentrations. Lastly, this dissertation applies this knowledge to a thermo-catalytic reaction (CO-oxidation) using a Au/TiO 2 catalyst. The combined photo/thereto-catalytic reaction showed a 10-25% increase in CO conversion during a temperature programmed reaction experiment.

Westrich, Thomas A.

47

Structure sensitivity and nanoscale effects in electrocatalysis.  

PubMed

This review discusses the role of the detailed nanoscale structure of catalytic surfaces on the activity of various electrocatalytic reactions of importance for fuel cells, hydrogen production, and other environmentally important catalytic reactions, such as carbon monoxide oxidation, methanol and ethanol oxidation, ammonia oxidation, nitric oxide reduction, hydrogen evolution, and oxygen reduction. Specifically, results and insights obtained from surface-science single-crystal-based model experiments are linked to experiments on well-defined shape-controlled nanoparticles. A classification of structure sensitive effects in electrocatalysis is suggested, based both on empirical grounds and on quantum-chemical viz. thermochemical considerations. The mutual relation between the two classification schemes is also discussed. The review underscores the relevance of single-crystal modeling of nanoscale effects in catalysis, and points to the special role of two kinds of active sites for electrocatalysis on nanoparticulate surfaces: (i) steps and defects in (111) terraces or facets, and (ii) long-range (100) terraces or facets. PMID:21399781

Koper, Marc T M

2011-05-01

48

Electrocatalysis issues in polymer electrolyte fuel cells  

SciTech Connect

Various electrocatalysis issues of impotance to low platinum loading polymer electrolyte fuel cells (PEFCs) are discussed. Thin film catalyst layer assemblies are used to investigate the effects of CO and CO{sub 2} on the anode as well as efforts to restore performance by oxygen bleeding into the anode feedstream. These electrodes behave differently than ionomer-impregnated E-TEK electrodes because the extra, exposed Pt in the latter case. The tolerance of Pt-Ru alloy thin film anodes to CO and CO{sub 2} are also evaluated. Thin film electrodes are also used to study Pt particle growth in aged electrodes as well as particle size effects on specific activity.

Wilson, M.S.; Derouin, C.R.; Valerio, J.A.; Gottesfeld, S.

1993-06-01

49

Electrocatalysis issues in polymer electrolyte fuel cells  

SciTech Connect

Various electrocatalysis issues of impotance to low platinum loading polymer electrolyte fuel cells (PEFCs) are discussed. Thin film catalyst layer assemblies are used to investigate the effects of CO and CO[sub 2] on the anode as well as efforts to restore performance by oxygen bleeding into the anode feedstream. These electrodes behave differently than ionomer-impregnated E-TEK electrodes because the extra, exposed Pt in the latter case. The tolerance of Pt-Ru alloy thin film anodes to CO and CO[sub 2] are also evaluated. Thin film electrodes are also used to study Pt particle growth in aged electrodes as well as particle size effects on specific activity.

Wilson, M.S.; Derouin, C.R.; Valerio, J.A.; Gottesfeld, S.

1993-01-01

50

REMOVAL OF METHYL TERTIARY BUTYL ETHER (MTBE) FROM GROUNDWATER USING PHOTOCATALYSIS  

EPA Science Inventory

The potential of photocatalysis was determined for treating MTBE-contaminated drinking water supplies. Two liquid-phase systems, a falling film reactor, and a solar degradation system, are being evaluated. We are also conducting a gas-phase treatment method to simulate an integra...

51

Photocatalysis on TiOâ surfaces: Principles, mechanisms, and selected results  

Microsoft Academic Search

In 1972, Fujishima and Honda discovered the photocatalytic splitting of water on TiOâ electrodes. This event marked the beginning of a new era in heterogeneous photocatalysis. Since then, research efforts in understanding the fundamental processes and in enhancing the photocatalytic efficiency of TiOâ have come from extensive research performed by chemists, physicists, and chemical engineers. Such studies are often related

Amy L. Linsebigler; Guangquan. Lu; John T. Yates

1995-01-01

52

Aqueous TiO(sub 2) photocatalysis of metal-EDTA complexes.  

National Technical Information Service (NTIS)

This report describes the results of experiments performed to determine the viability of titanium dioxide photocatalysis towards the treatment of water contaminated with different metal-EDTA complexes. Both the PB-EDTA and Ni-EDTA complexes were chosen fo...

T. Madden A. K. Datye M. R. Prairie B. M. Stange

1995-01-01

53

Microfluidic photoelectrocatalytic reactors for water purification with an integrated visible-light source.  

PubMed

This paper reports experimental studies using the photoelectrocatalytic effect to eliminate a fundamental limit of photocatalysis - the recombination of photo-excited electrons and holes. The fabricated reactor has a planar reaction chamber (10 × 10 × 0.1 mm(3)), formed by a blank indium tin oxide glass slide, an epoxy spacer and a BiVO(4)-coated indium tin oxide glass substrate. A blue light-emitting diode panel (emission area 10 × 10 mm(2)) is mounted on the cover for uniform illumination of the reaction chamber. In the experiment, positive and negative bias potentials were applied across the reaction chamber to suppress the electron/hole recombination and to select either the hole-driven or electron-driven oxidation pathway. The negative bias always exhibits higher performance. It is observed that under -1.8 V the degradation rate is independent of the residence time, showing that the accompanying electrolysis can solve the oxygen deficiency problem. The synergistic effect of photocatalysis and electrocatalysis is observed to reach its maximum under the bias potential of ± 1.5 V. The photoelectrocatalytic microreactor shows high stability and may be scaled up for high-performance water purification. PMID:22930198

Wang, Ning; Zhang, Xuming; Chen, Bolei; Song, Wuzhou; Chan, Ngai Yui; Chan, Helen L W

2012-10-21

54

Advances in selective conversions by heterogeneous photocatalysis.  

PubMed

Selective photocatalytic conversions are offering an alternative green route for replacing environmentally hazardous processes with safe and energy efficient routes. This paper reports the most recent advances in the application of heterogeneous photocatalysis to synthesize valuable compounds by selective oxidation and reduction. PMID:20820526

Palmisano, Giovanni; García-López, Elisa; Marcì, Giuseppe; Loddo, Vittorio; Yurdakal, Sedat; Augugliaro, Vincenzo; Palmisano, Leonardo

2010-10-14

55

A comparison of pilot-scale photocatalysis and enhanced coagulation for disinfection byproduct mitigation.  

PubMed

This study evaluated pilot-scale photocatalysis and enhanced coagulation for their ability to remove or destroy disinfection byproduct (DBP) precursors, trihalomethane (THM) formation potential (FP), and THMs in two Arizona surface waters. Limited photocatalysis (<5 kWh/m(3)) achieved reductions in most of the DBP precursor parameters (e.g., DOC, UV(254), and bromide) but led to increased chlorine demand and THMFP. In contrast, enhanced coagulation achieved reductions in the DBP precursors and THMFP. Extended photocatalysis (<320 kWh/m(3)) decreased THMFP once the energy consumption exceeded 20 kWh/m(3). The photocatalytic energy requirements for THM destruction were considerably lower (EEO=20-60 kWh/m(3)) than when focusing on precursor destruction and THMFP. However, rechlorination increased the total THM (TTHM) concentration well beyond the raw value, thereby negating the energy benefits of this application. Enhanced coagulation achieved consistent 20-30% removals of preformed THMs. Outstanding issues need to be addressed before TiO(2) photocatalysis is considered feasible for DBP mitigation; traditional strategies, including enhanced coagulation, may be more appropriate. PMID:19232668

Gerrity, Daniel; Mayer, Brooke; Ryu, Hodon; Crittenden, John; Abbaszadegan, Morteza

2009-04-01

56

Developments in solar photocatalysis for water purification  

Microsoft Academic Search

Photocatalytic processes in the presence of titanium dioxide provide an interesting route to destroy hazardous organic contaminants, being operational in the UV-A domain with a potential use of solar radiation. In this paper, some specific contaminant classes of interest such as ethylbenzene, ?-lindane and EPTC have been tested at laboratory scale and in the field to determine the feasibility of

Alfonso Vidal

1998-01-01

57

Robust cuprous phenanthroline sensitizer for solar hydrogen photocatalysis.  

PubMed

The Cu(I) metal-to-ligand charge-transfer complex, [Cu(dsbtmp)2](+) (dsbtmp = 2,9-di(sec-butyl)-3,4,7,8-tetramethyl-1,10-phenanthroline), exhibits outstanding stability as a visible-light-absorbing photosensitizer in hydrogen-evolving homogeneous photocatalysis. In concert with the Co(dmgH)2(py)Cl water reduction catalyst and N,N-dimethyl-p-toluidine sacrificial donor in 1:1 H2O:CH3CN, this Cu(I) sensitizer remains active even after 5 days of visible-light-pumped (?ex = 452 ± 10 nm) hydrogen evolution catalysis. Deuteration studies illustrate that the hydrogen produced from this composition does indeed originate from aqueous protons. PMID:24028290

Khnayzer, Rony S; McCusker, Catherine E; Olaiya, Babatunde S; Castellano, Felix N

2013-09-25

58

Combinative sonolysis and photocatalysis for textile dye degradation  

Microsoft Academic Search

The merits of combining two advanced oxidation processes, viz., sonolysis and photocatalysis, have been evaluated by investigating the degradation of an azo dye, naphthol blue black (NBB), using a high-frequency ultrasonic generator and UV-photolysis. An additive effect on the degradation rate of the parent compound is observed when the sonolysis and photocatalysis experiments were carried out in a simultaneous or

Naomi L. Stock; Julie Peller; K. Vinodgopal; Prashant V. Kamat

2000-01-01

59

Novel swirl-flow reactor for kinetic studies of semiconductor photocatalysis  

Microsoft Academic Search

Heterogeneous photocatalysis has received considerable attention in years as an alternative for treating water polluted with hazardous organic chemicals. A new two-phase swirl-flow monolithic-type reactor was designed to study the kinetics of heterogeneous photocatalytic processes on immobilized semiconductor catalysts. True kinetic rate constants for destruction of a textile dye were measured as a function of wavelength of light intensity and

Ajay K. Ray; Antonie A. C. M. Beenackers

1997-01-01

60

Studies on degradation of glyphosate by several oxidative chemical processes: Ozonation, photolysis and heterogeneous photocatalysis  

Microsoft Academic Search

Several different Advanced Oxidation Processes (AOPs) including ozonation at pH 6.5 and 10, photolysis and heterogeneous photocatalysis using TiO2 as semiconductor and dissolved oxygen as electron acceptor were applied to study the degradation of glyphosate (N-phosphonomethyl glycine) in water. The degree of glyphosate degradation, the reactions kinetic and the formation of the major metabolite, aminomethyl phosphonic acid (AMPA), were evaluated.

Marcia R. Assalin; Sandra G. De Moraes; Sonia C. N. Queiroz; Vera L. Ferracini; Nelson Duran

2009-01-01

61

Thermodynamic and kinetic analysis of heterogeneous photocatalysis for semiconductor systems.  

PubMed

Since the report of the Honda-Fujishima effect, heterogeneous photocatalysis has attracted much attention around the world because of its potential energy and environmental applications. Although great progresses have been made in recent years, most were focused on preparing highly-active photocatalysts and investigating visible light utilization. In fact, we are still unclear on the thermodynamic and kinetic nature of photocatalysis to date, which sometimes leads to misunderstandings for experimental results. It is timely to give a review and discussion on the thermodynamics and kinetics of photocatalysis, so as to direct future researches. However, there is an absence of a detailed review on this topic until now. In this article, we tried to review and discuss the thermodynamics and kinetics of photocatalysis. We explained the thermodynamic driving force of photocatalysis, and distinguished the functions of light and heat in photocatalysis. The Langmuir-Hinshelwood kinetic model, the ?OH oxidation mechanism, and the direct-indirect (D-I) kinetic model were reviewed and compared. Some applications of the D-I model to study photocatalytic kinetics were also discussed. The electron transport mode and its importance in photocatalysis were investigated. Finally, the intrinsic relation between the kinetics and the thermodynamics of photocatalytic reactions was discussed. PMID:24675975

Liu, Baoshun; Zhao, Xiujian; Terashima, Chiaki; Fujishima, Akira; Nakata, Kazuya

2014-04-16

62

Bismuth oxyhalide nanomaterials: layered structures meet photocatalysis.  

PubMed

In recent years, layered bismuth oxyhalide nanomaterials have received more and more interest as promising photocatalysts because their unique layered structures endow them with fascinating physicochemical properties; thus, they have great potential photocatalytic applications for environment remediation and energy harvesting. In this article, we explore the synthesis strategies and growth mechanisms of layered bismuth oxyhalide nanomaterials, and propose design principles of tailoring a layered configuration to control the nanoarchitectures for high efficient photocatalysis. Subsequently, we focus on their layered structure dependent properties, including pH-related crystal facet exposure and phase transformation, facet-dependent photoactivity and molecular oxygen activation pathways, so as to clarify the origin of the layered structure dependent photoreactivity. Furthermore, we summarize various strategies for modulating the composition and arrangement of layered structures to enhance the photoactivity of nanostructured bismuth oxyhalides via internal electric field tuning, dehalogenation effect, surface functionalization, doping, plasmon modification, and heterojunction construction, which may offer efficient guidance for the design and construction of high-performance bismuth oxyhalide-based photocatalysis systems. Finally, we highlight some crucial issues in engineering the layered-structure mediated properties of bismuth oxyhalide photocatalysts and provide tentative suggestions for future research on increasing their photocatalytic performance. PMID:24975748

Li, Jie; Yu, Ying; Zhang, Lizhi

2014-07-10

63

Proceedings of the First International Energy Agency Water Electrolysis Workshop.  

National Technical Information Service (NTIS)

The following panel reports are included: aqueous solution water electrolysis, solid polymer electrolyte water electrolysis, solid oxide water electrolysis, and electrocatalysis. Individual papers are abstracted separately. (ERA citation 03:017051)

F. J. Salzano S. inivasan

1975-01-01

64

Titanium dioxide photocatalysis: present situation and future approaches  

Microsoft Academic Search

Scientific studies on photocatalysis started about three decades ago. Titanium dioxide (TiO2), which is one of the most basic materials in our daily life, has emerged as an excellent photocatalyst material for environmental purification. In this short account, we will briefly discuss some fundamental studies on TiO2 photocatalysis, summarize the present commercialization of TiO2-based products, and highlight several points for

Akira Fujishima; Xintong Zhang

2006-01-01

65

Two and three dimensional network polymers for electrocatalysis.  

PubMed

Recently, two and three dimensional network polymers have started to gain traction in the research sphere as scientists look for ways to create materials with more tailored properties. These network polymers show high surface area and specific, sometimes periodic, functionality, providing perfect templates both to host electrocatalytic materials as well as function as electrocatalysts themselves. While doped carbon based materials such as graphene and carbon nanotubes, as well as diamond, have demonstrated their electrocatalytic potential, other network polymers have yet to be synthesized in a manner to optimize their potential. As these polymers are built of a periodic arrangement of appropriately functionalized monomers, an exact arrangement of functional sites should be possible, which combined with potentially high surface areas should lead to very high catalytic activity. This perspective will cover the synthesis and achievements of the mentioned doped carbon materials before taking a look at the strengths, shortcomings, and future goals in electrocatalysis as related to more novel network polymers. PMID:24807465

Filer, Alan; Choi, Hyun-Jung; Seo, Jeong-Min; Baek, Jong-Beom

2014-06-21

66

Modelling and design of microchannel reactor for photocatalysis  

Microsoft Academic Search

Chemical reactions in a microreactor can offer new possibilities for many chemical engineering application fields and have been employed in photocatalysis studies. The purpose of this work is to investigate the photocatalytic degradation of salicylic acid (SA) as a pollutant model, in a continuous flow microchannel reactor in order to evaluate the influence of radial concentration profile on the photocatalytic

Serge Corbel; Guillaume Charles; Nidhal Becheikh; Thibault Roques-Carmes; Orfan Zahraa

2012-01-01

67

CO(2) Sequestration and Recycle by Photocatalysis with Visible Light.  

National Technical Information Service (NTIS)

Visible light-photocatalysis could provide a cost-effective route to recycle CO2 to useful chemicals or fuels. Development of an effective catalyst for the photocatalytic synthesis requires (1) the knowledge of the surface band gap and its relation to the...

S. S. C. Chuang

2001-01-01

68

Organic heterogeneous photocatalysis: chemical conversions sensitized by irradiated semiconductors  

Microsoft Academic Search

Electron-transfer mediated reactions may be initiated by long-wavelength ultraviolet or visible light irradiation of semiconductor particles. The application of this field of photoelectrochemistry to sensitized organic photo-transformations is reviewed. The method has the potential to modify functional groups and to assist in studying heterogeneous photocatalysis and radical ion intermediates.

Marye Anne Fox

1983-01-01

69

Relative photonic efficiencies and quantum yields in heterogeneous photocatalysis  

Microsoft Academic Search

Quantum yield and quantum efficiency (QY) as used in heterogeneous photocatalysis (solid\\/liquid or solid\\/gas systems) have too often been used incorrectly to mean the ratio of the rate of a given event to the rate of incident photons impinging on the (external) rector walls, typically for broadband radiation. There is little accord on how to express process efficiency. At times

Nick Serpone

1997-01-01

70

Organic heterogeneous photocatalysis: chemical conversions sensitized by irradiated semiconductors  

SciTech Connect

Electron-transfer mediated reactions may be initiated by long-wavelength ultraviolet or visible light irradiation of semiconductor particles. The application of this field of photoelectrochemistry to sensitized organic photo-transformations is reviewed. The method has the potential to modify functional groups and to assist in studying heterogeneous photocatalysis and radical ion intermediates.

Fox, M.A.

1983-09-01

71

Dissociative electron transfer to organic chlorides: electrocatalysis at metal cathodes.  

PubMed

The reductive cleavage of a series of organic chlorides, including chloroaromatics, benzyl chlorides, activated chloroalkanes and polychloromethanes, was investigated at Ag, Cu, Pd and glassy carbon (GC) electrodes in CH(3)CN + 0.1 M (C(2)H(5))(4)NClO(4). The silver cathode was either a 2-mm diameter disc, fabricated from Ag wire, or nanoclusters of average diameter d = 304 nm, prepared by electrodeposition on GC. Ag, Cu and Pd electrodes have shown remarkable electrocatalytic properties for the reduction of several compounds. The peak potentials recorded at these electrodes, for example, at upsilon = 0.1 V s(-1) are positively shifted by 0.3-0.8 V with respect to the reduction potentials measured at a non catalytic electrode such as GC. Electrocatalysis is strictly related to the concerted nature of the dissociative electron transfer to the carbon-chlorine bond. No catalysis is observed when the dissociative electron transfer to RCl occurs according to a stepwise mechanism involving the intermediate formation of a radical anion. The catalytic surfaces affect the reaction scheme, offering a more favourable route possibly through the formation of strongly adsorbed activated complexes. PMID:18414732

Isse, Abdirisak A; Gottardello, Silvia; Durante, Christian; Gennaro, Armando

2008-05-01

72

Energy Conversion and Utilization Technologies Program (ECUT) electrocatalysis research  

NASA Technical Reports Server (NTRS)

The general field of electrocatalysis, from both the technical and business standpoints is accessed and research areas and approaches most likely to lead to substantial energy/cost savings are identified. The overall approach was to compile and evaluate available information, relying heavily on inputs/recommendations of research managers and technical personnel in responsible positions in industry and at universities. Some promising approaches identified to date include the use of transition metal compounds as electrocatalysts and the use of the new electrochemical photocapacitance spectroscopy (EPS) technique for electrocatalyst characterization/development. For the first time, an oxygen electrocatalyst based on the K2NiF4 structure was synthesized, investigated and compared with a perovskite analog. Results show that this class of materials, based on Ni(3+), forms very efficient and stable O2 anodes in basic solution and suggest that other structure-types be examined in this regard. The very difficult problem of dinitrogen and carbon dioxide electroreductions is addressed through the use of biological model systems which can mimic the enzyme processes in nature.

Warren, L. F.

1984-01-01

73

Photocatalysis: a promising route for 21st century organic chemistry.  

PubMed

One of the main goals of 21st century chemistry is to replace environmentally hazardous processes with energy efficient routes allowing to totally avoid the use and production of harmful chemicals and to maximise the quantity of raw material that ends up in the final product. Selective photocatalytic conversions will play a major role in this evolution and this account shows how photocatalysis is offering an alternative green route for the production of organics. PMID:17700873

Palmisano, Giovanni; Augugliaro, Vincenzo; Pagliaro, Mario; Palmisano, Leonardo

2007-09-01

74

Degradation of 4-chlorophenol by a microwave assisted photocatalysis method  

Microsoft Academic Search

In this work, the degradation of 4-chlorophenol (4CP) under simultaneous microwave assisted UV (electrodeless discharge lamp) photocatalysis technique (MW\\/UV\\/TiO2) was investigated. Several factors affecting the degradation of 4CP by MW\\/UV\\/TiO2 method, such as the dosage of photocatalysts, the initial pH value of the solutions, gas bubbling, light intensity and addition of H2O2 oxidant, were studied in detail. The synergistic effects

Zhihui Ai; Peng Yang; Xiaohua Lu

2005-01-01

75

Morphologies of zinc oxide particles and their effects on photocatalysis  

Microsoft Academic Search

ZnO powders with different morphologies were synthesized by alkali precipitation, organo-zinc hydrolysis, and spray pyrolysis. Acetaldehyde decomposition was used as a probe reaction to evaluate the photocatalysis of these ZnO powders. We investigated the relationship between photocatalytic activity and crystallinity, surface area, or morphology. Results indicate that the photocatalytic activity of ZnO powder depends on crystallinity rather than surface area

Di Li; Hajime Haneda

2003-01-01

76

Destruction of phenol aqueous solution by photocatalysis or direct photolysis  

Microsoft Academic Search

The photodegradation of phenol has been investigated under a high-pressure mercury lamp with a kind of jacket (glass or quartz) depending on used UV light range and a variety of experimental conditions: UV (?>200 nm) with oxygen or with TiO2 and oxygen or with N2; UV (?>330 nm) with oxygen or with TiO2 and oxygen or with N2. Photocatalysis and

Hu Chun; Wang Yizhong; Tang Hongxiao

2000-01-01

77

Electrocatalysis of anodic and cathodic oxygen-transfer reactions  

SciTech Connect

The electrocatalysis of oxygen-transfer reactions is discussed in two parts. In Part I, the reduction of iodate (IO{sub 3}{sup {minus}}) is examined as an example of cathodic oxygen transfer. On oxide-covered Pt electrodes (PtO), a large cathodic current is observed in the presence of IO{sub 3}{sup {minus}} to coincide with the reduction of PtO. The total cathodic charge exceeds the amount required for reduction of PtO and IO{sub 3}{sup {minus}} to produce an adsorbed product. An electrocatalytic link between reduction of IO{sub 3}{sup {minus}} and reduction of PtO is indicated. In addition, on oxide-free Pt electrodes, the reduction of IO{sub 3}{sup {minus}} is determined to be sensitive to surface treatment. The electrocatalytic oxidation of CN{sup {minus}} is presented as an example of anodic oxygen transfer in Part II. The voltametric response of CN{sup {minus}} is virtually nonexistent at PbO{sub 2} electrodes. The response is significantly improved by doping PbO{sub 2} with Cu. Cyanide is also oxidized effectively at CuO-film electrodes. Copper is concluded to serve as an adsorption site for CN{sup {minus}}. It is proposed that an oxygen tunneling mechanism comparable to electron tunneling does not occur at the electrode-solution interface. The adsorption of CN{sup {minus}} is therefore considered to be a necessary prerequisite for oxygen transfer. 201 refs., 23 figs., 2 tabs.

Wels, B.R.

1990-09-21

78

The combination of heterogeneous photocatalysis with chemical and physical operations: A tool for improving the photoprocess performance  

Microsoft Academic Search

Heterogeneous photocatalysis is a process of great potential for pollutant abatement and waste treatment. In order to improve the overall performance of the photoprocess, heterogeneous photocatalysis is being combined with physical or chemical operations, which affect the chemical kinetics and\\/or the overall efficiency. This review addresses the various possibilities to couple heterogeneous photocatalysis with other technologies to photodegrade organic and

Vincenzo Augugliaro; Marta Litter; Leonardo Palmisano; Javier Soria

2006-01-01

79

A synergistic effect of photocatalysis and ozonation on decomposition of formic acid in an aqueous solution  

Microsoft Academic Search

A synergistic effect of photocatalysis and ozonation on the decomposition of formic acid dissolving in an aqueous solution has been studied. In the photocatalysis over a thin film of titanium oxide immobilized on the inner surface of a glass tube, a 6W blacklight blue fluorescent lamp (wavelength: 300–400nm) was used as a light source. The initial decomposition rates followed a

Shinpon Wang; Fumihide Shiraishi; Katsuyuki Nakano

2002-01-01

80

Roles of cocatalysts in photocatalysis and photoelectrocatalysis.  

PubMed

Since the 1970s, splitting water using solar energy has been a focus of great attention as a possible means for converting solar energy to chemical energy in the form of clean and renewable hydrogen fuel. Approaches to solar water splitting include photocatalytic water splitting with homogeneous or heterogeneous photocatalysts, photoelectrochemical or photoelectrocatalytic (PEC) water splitting with a PEC cell, and electrolysis of water with photovoltaic cells coupled to electrocatalysts. Though many materials are capable of photocatalytically producing hydrogen and/or oxygen, the overall energy conversion efficiency is still low and far from practical application. This is mainly due to the fact that the three crucial steps for the water splitting reaction: solar light harvesting, charge separation and transportation, and the catalytic reduction and oxidation reactions, are not efficient enough or simultaneously. Water splitting is a thermodynamically uphill reaction, requiring transfer of multiple electrons, making it one of the most challenging reactions in chemistry. This Account describes the important roles of cocatalysts in photocatalytic and PEC water splitting reactions. For semiconductor-based photocatalytic and PEC systems, we show that loading proper cocatalysts, especially dual cocatalysts for reduction and oxidation, on semiconductors (as light harvesters) can significantly enhance the activities of photocatalytic and PEC water splitting reactions. Loading oxidation and/or reduction cocatalysts on semiconductors can facilitate oxidation and reduction reactions by providing the active sites/reaction sites while suppressing the charge recombination and reverse reactions. In a PEC water splitting system, the water oxidation and reduction reactions occur at opposite electrodes, so cocatalysts loaded on the electrode materials mainly act as active sites/reaction sites spatially separated as natural photosynthesis does. In both cases, the nature of the loaded cocatalysts and their interaction with the semiconductor through the interface/junction are important. The cocatalyst can provide trapping sites for the photogenerated charges and promote the charge separation, thus enhancing the quantum efficiency; the cocatalysts could improve the photostability of the catalysts by timely consuming of the photogenerated charges, particularly the holes; most importantly, the cocatalysts catalyze the reactions by lowering the activation energy. Our research shows that loading suitable dual cocatalysts on semiconductors can significantly increase the photocatalytic activities of hydrogen and oxygen evolution reactions, and even make the overall water splitting reaction possible. All of these findings suggest that dual cocatalysts are necessary for developing highly efficient photocatalysts for water splitting reactions. PMID:23530781

Yang, Jinhui; Wang, Donge; Han, Hongxian; Li, Can

2013-08-20

81

Particle size, shape and activity for photocatalysis on titania anatase nanoparticles in aqueous surroundings.  

PubMed

TiO(2) nanoparticles have been widely utilized in photocatalysis, but the atomic level understanding on their working mechanism falls much short of expectations. In particular, the correlation between the particle structure and the photocatalytic activity is not established yet, although it was observed that the activity is sensitive to the particle size and shape. This work, by investigating a series of TiO(2) anatase nanoparticles with different size and shape as the photocatalyst for water oxidation, correlates quantitatively the particle size and shape with the photocatalytic activity of the oxygen evolution reaction (OER). Extensive density functional theory (DFT) calculations combined with the periodic continuum solvation model have been utilized to compute the electronic structure of nanoparticles in aqueous solution and provide the reaction energetics for the key elementary reaction. We demonstrate that the equilibrium shape of nanoparticle is sensitive to its size from 1 to 30 nm, and the sharp crystals possess much higher activity than the flat crystals in OER, which in combination lead to the morphology dependence of photocatalytic activity. The conventionally regarded quantum size effect is excluded as the major cause. The physical origin for the shape-activity relationship is identified to be the unique spatial separation/localization of the frontier orbitals in the sharp nanoparticles, which benefits the adsorption of the key reaction intermediate (i.e., OH) in OER on the exposed five-coordinated Ti of {101} facet. The theoretical results here provide a firm basis for maximizing photocatalytic activity via nanostructure engineering and are also of significance for understanding photocatalysis on nanomaterials in general. PMID:21879719

Li, Ye-Fei; Liu, Zhi-Pan

2011-10-01

82

New Electrochemical Methods for Studying Nanoparticle Electrocatalysis and Neuronal Exocytosis  

NASA Astrophysics Data System (ADS)

This dissertation presents the construction and application of micro and nanoscale electrodes for electroanalytical analysis. The studies presented herein encompass two main areas: electrochemical catalysis, and studies of the dynamics of single cell exocytosis. The first portion of this dissertation engages the use of Pt nanoelectrodes to study the stability and electrocatalytic properties of materials. A single nanoparticle electrode (SNPE) was fabricated by immobilizing a single Au nanoparticle on a Pt disk nanoelectrode via an amine-terminated silane cross linker. In this manner we were able to effectively study the electrochemistry and electrocatalytic activity of single Au nanoparticles and found that the electrocatalytic activity is dependent on nanoparticle size. This study can further the understanding of the structure-function relationship in nanoparticle based electrocatalysis. Further work was conducted to probe the stability of Pt nanoelectrodes under conditions of potential cycling. Pt based catalysts are known to deteriorate under such conditions due to losses in electrochemical surface area and Pt dissolution. By using Pt disk nanoelectrodes we were able to study Pt dissolution via steady-state voltammetry. We observed an enhanced dissolution rate and higher charge density on nanoelectrodes than that previously found on macro scale electrodes. The goal of the second portion of this dissertation is to develop new analytical methods to study the dynamics of exocytosis from single cells. The secretion of neurotransmitters plays a key role in neuronal communication, and our studies highlight how bipolar electrochemistry can be employed to enhance detection of neurotransmitters from single cells. First, we developed a theory to quantitatively characterize the voltammetric behavior of bipolar carbon fiber microelectrodes and secondly applied those principles to single cell detection. We showed that by simply adding an additional redox mediator to the back-fill solution of a carbon fiber microelectrode, there is a significant enhancement in detection. Additionally we used solid state nanopores to detect individual phospholipid vesicles in solution. Vesicles are key cellular components that play essential biological roles especially in neurotransmission. This work represents preliminary studies in detection and size determination from vesicles isolated from individual cells.

Cox, Jonathan T.

83

Enantioselective organo-photocatalysis mediated by atropisomeric thiourea derivatives.  

PubMed

Can photocatalysis be performed without electron or energy transfer? To address this, organo-photocatalysts that are based on atropisomeric thioureas and display lower excited-state energies than the reactive substrates have been developed. These photocatalysts were found to be efficient in promoting the [2+2] photocycloaddition of 4-alkenyl-substituted coumarins, which led to the corresponding products with high enantioselectivity (77-96?%?ee) at low catalyst loading (1-10?mol?%). The photocatalytic cycle proceeds by energy sharing via the formation of both static and dynamic complexes (exciplex formation), which is aided by hydrogen bonding. PMID:24740511

Vallavoju, Nandini; Selvakumar, Sermadurai; Jockusch, Steffen; Sibi, Mukund P; Sivaguru, Jayaraman

2014-05-26

84

Friedel-Crafts Amidoalkylation via Thermolysis and Oxidative Photocatalysis  

PubMed Central

Friedel-Crafts amidoalkylation was achieved by oxidation of dialkylamides using persulfate (S2O82?) in the presence of the visible light catalyst, Ru(bpy)3Cl2, at room temperature, via a reactive N-acyliminium intermediate. Alternatively, mild heating of the dialkylamides and persulfate afforded a metal and Lewis acid-free Friedel-Crafts amidoalkylation. Alcohols and electron–rich arenes served as effective nucleophiles, forming new C–O or C–C bonds. In general, photocatalysis provided higher yields and better selectivities.

Dai, Chunhui; Meschini, Francesco; Narayanam, Jagan M. R.; Stephenson, Corey R. J.

2012-01-01

85

A Surface Science Perspective on TiO2 Photocatalysis  

SciTech Connect

The field of surface science provides a unique approach to understanding bulk, surface and interfacial phenomena occurring during TiO2 photochemistry and photocatalysis. This review highlights, from a surface science perspective, recent literature providing molecular-level insights into phonon-initiated events on TiO2 surfaces obtained in seven key scientific issues: (1) photon absorption, (2) charge transport and trapping, (3) electron transfer dynamics, (4) the adsorbed state, (5) mechanisms, (6) poisons and promoters, and (7) phase and form.

Henderson, Michael A.

2011-06-15

86

Study on photocatalysis properties of nanocrystalline titanium dioxide  

Microsoft Academic Search

Nano-TiO2 powders with pure anatase structure were prepared by the method of precipitation-solution-gelation, using H2TiO3, hydrogen peroxide and ammonia as reactants. Active red X-3B dye solution was selected as a model pollutant for the photo-catalysis\\u000a degradation experiments. The effects of grain sizes, dosage and microstructure of nano-TiO2 on its photocatalysis properties were studied. The results show that photo-activity of the

Yi Chen; Xiao-Yan Pan; Xue-Ming Ma; Li-Hui Zhu

2002-01-01

87

Photocatalysis on Fine Powders of Perovskite Oxides  

Microsoft Academic Search

Fine powders of semiconductor oxides have been widely used as photocatalysts for many reactions. Among the various photocatalytic reactions, water splitting has been given much importance, since it is a promising chemical route for solar energy conversion. Perovskite oxides, in particular SrTiO, have been commonly used as photocatalysts because some of them can decompose H,O into H, and 0, without

T. R. N. Kutty; M. Avudaithai

1992-01-01

88

Photocatalysis in water environments using artificial and solar light  

Microsoft Academic Search

This paper presents a review of part of the work done on photocatalytic reactors. Being aware of the comprehensive reports already existing on the chemistry of these reactions [A.M. Braun, L. Jakob, E. Oliveros, C.A. Oller do Nascimento, Adv. Photochem. 18 (1993) 235; O. Legrini, E. Oliveros, A.M. Braun, Chem. Rev. 93 (1993) 671; D. Bahnemann, J. Cunningham, M.A. Fox,

O. M Alfano; D Bahnemann; A. E Cassano; R Dillert; R Goslich

2000-01-01

89

Perovskite-related oxynitrides in photocatalysis.  

PubMed

Over the last decades photocatalytic water splitting has become of increasing importance for fundamental and applied research, since the direct conversion of sunlight into chemical energy via the production of H2 has the potential to contribute to the world's energy needs without CO2 generation. One of the unsolved challenges consists of finding a highly efficient photocatalyst that is cheap, environmentally friendly, contains exclusively abundant elements, is (photo)chemically stable and absorbs visible light. Photocatalytic efficiency is closely connected to both structural properties like crystallinity, particle size and surface area and to electronic properties like the band gap and the quantum efficiency. Hence extensive control over a large parameter field is necessary to design a good photocatalyst. A material class where the structure-composition-property relations and the influence of substitution effects are well studied is the perovskite-type family of compounds. The perovskite-related oxynitrides belong to this very flexible compound family where many of the necessary characteristics for a photocatalyst are already given and some of the intrinsic properties like the band gap can be tuned within the same crystal structure by substitution. In this work we present materials' design concepts to improve the photocatalytic efficiency of a perovskite-type catalyst and describe their effects on the photocatalytic activity. PMID:23574956

Pokrant, Simone; Maegli, Alexandra E; Chiarello, Gian Luca; Weidenkaff, Anke

2013-01-01

90

Electrocatalysis and electroanalysis of nickel, its oxides, hydroxides and oxyhydroxides toward small molecules.  

PubMed

The electrocatalysis toward small molecules, especially small organic compounds, is of importance in a variety of areas. Nickel based materials such as nickel, its oxides, hydroxides as well as oxyhydroxides exhibit excellent electrocatalysis performances toward many small molecules, which are widely used for fuel cells, energy storage, organic synthesis, wastewater treatment, and electrochemical sensors for pharmaceutical, medical, food or environmental analysis. Their electrocatalytic mechanisms are proposed from three aspects such as Ni(OH)2/NiOOH mediated electrolysis, direct electrocatalysis of Ni(OH)2 or NiOOH. Under exposure to air or aqueous solution, two distinct layers form on the Ni surface with a Ni hydroxide layer at the air-oxide interface and an oxide layer between the metal substrate and the outer hydroxide layer. The transformation from nickel or its oxides to hydroxides or oxyhydroxides could be further speeded up in the strong alkaline solution under the cyclic scanning at relatively high positive potential. The redox transition between Ni(OH)2 and NiOOH is also contributed to the electrocatalytic oxidation of Ni and its oxides toward small molecules in alkaline media. In addition, nickel based materials or nanomaterials, their preparations and applications are also overviewed here. PMID:24211454

Miao, Yuqing; Ouyang, Lei; Zhou, Shilin; Xu, Lina; Yang, Zhuoyuan; Xiao, Mingshu; Ouyang, Ruizhuo

2014-03-15

91

TiO{sub 2}-coated carbon nanotubes: A redshift enhanced photocatalysis at visible light  

SciTech Connect

Annealing of carbon nanotubes coated with thin and uniform TiO{sub 2} results in carbon diffusion into oxygen lattices and doping induced redshift is evident by an efficient photocatalysis at visible light. The underlying mechanism is discussed.

Lu, S.-Y.; Tang, C.-W.; Lin, Y.-H.; Kuo, H.-F.; Lai, Y.-C.; Ouyang Hao; Hsu, W.-K. [Department of Materials Science and Engineering, National Tsing-Hua University, HsinChu 30013, Taiwan (China); Tsai, M.-Y. [Instrument Technology Research Center, National Applied Research Laboratories, HsinChu 30076, Taiwan (China)

2010-06-07

92

Platinum nanocatalysts loaded on graphene oxide-dispersed carbon nanotubes with greatly enhanced peroxidase-like catalysis and electrocatalysis activities.  

PubMed

A powerful enzymatic mimetic has been fabricated by employing graphene oxide (GO) nanocolloids to disperse conductive carbon supports of hydrophobic carbon nanotubes (CNTs) before and after the loading of Pt nanocatalysts. The resulting GOCNT-Pt nanocomposites could present improved aqueous dispersion stability and Pt spatial distribution. Unexpectedly, they could show greatly enhanced peroxidase-like catalysis and electrocatalysis activities in water, as evidenced in the colorimetric and electrochemical investigations in comparison to some inorganic nanocatalysts commonly used. Moreover, it is found that the new enzyme mimetics could exhibit peroxidase-like catalysis activity comparable to natural enzymes; yet, they might circumvent some of their inherent problems in terms of catalysis efficiency, electron transfer, environmental stability, and cost effectiveness. Also, sandwiched electrochemical immunoassays have been successfully conducted using GOCNT-Pt as enzymatic tags. Such a fabrication avenue of noble metal nanocatalysts loaded on well-dispersed conductive carbon supports should be tailored for the design of different enzyme mimics promising the extensive catalysis applications in environmental, medical, industrial, and particularly aqueous biosensing fields. PMID:24916053

Wang, Hua; Li, Shuai; Si, Yanmei; Zhang, Ning; Sun, Zongzhao; Wu, Hong; Lin, Yuehe

2014-06-26

93

Visible Light Photocatalysis: The Development of Photocatalytic Radical Ion Cycloadditions  

PubMed Central

Photochemistry has the potential to significantly impact multiple aspects of chemical synthesis, in part because photoinduced reactions can be used to construct molecular architectures that would otherwise be difficult to produce. Nevertheless, organic chemists have been slow to embrace photochemical synthesis because of technical complications associated with the use of ultraviolet light. Our laboratory has been part of an effort to design synthetically useful reactions that utilize visible light. This strategy enables the synthesis of a diverse range of organic structures by generation of a variety of reactive intermediates under exceptionally mild conditions. This Perspective article describes the reasoning that led to the conception of our first experiments in this area, the features of our reaction design that have been most powerful in the discovery of new processes, and a few of the possible future areas in which visible light photocatalysis might have a large impact.

Yoon, Tehshik P.

2013-01-01

94

Epilayer control of photodeposited materials during UV photocatalysis  

SciTech Connect

Epilayer control of photoassisted oxidation and reduction on the ferroelectric PbTiO{sub 3} polar surface was investigated. Photo-oxidation of a AgNO{sub 3} electrolyte resulting in formation of Ag{sub 7}NO{sub 11} particles was observed on the PbTiO{sub 3}/Nb:SrTiO{sub 3} film surface; whereas PbTiO{sub 3}/SrRuO{sub 3}/SrTiO{sub 3} leads to AgNO{sub 3} reduction under UV illumination. The oxidation reaction resulting in the formation of Ag{sub 7}NO{sub 11} is explained in terms of a rectifying interface between PbTiO{sub 3} and Nb:SrTiO{sub 3}, controlling the charge transport during UV photocatalysis.

Takahashi, R.; Dahl, O.; Grepstad, J. K.; Tybell, T. [Department of Electronics and Telecommunications, Norwegian University of Science and Technology, OS Bragstads plass 2A, Trondheim 7491 (Norway); Katayama, M.; Matsumoto, Y. [Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midoriku, Yokohama 226-8503 (Japan)

2009-06-08

95

NASA's Potential Contributions for Using Solar Ultraviolet Radiation in Conjunction with Photocatalysis for Urban Air Pollution Mitigation  

NASA Technical Reports Server (NTRS)

More than 75 percent of the U.S. population lives in urban communities where people are exposed to levels of smog or pollution that exceed the EPA (U.S. Environmental Protection Agency) safety standards. Urban air quality presents a unique problem because of a number of complex variables, including traffic congestion, energy production, and energy consumption activities, all of which can contribute to and affect air pollution and air quality in this environment. In environmental engineering, photocatalysis is an area of research whose potential for environmental clean-up is rapidly developing popularity and success. Photocatalysis, a natural chemical process, is the acceleration of a photoreaction in the presence of a catalyst. Photocatalytic agents are activated when exposed to near UV (ultraviolet) light (320-400 nm) and water. In recent years, surfaces coated with photocatalytic materials have been extensively studied because pollutants on these surfaces will degrade when the surfaces are exposed to near UV light. Building materials, such as tiles, cement, glass, and aluminum sidings, can be coated with a thin film of a photocatalyst. These coated materials can then break down organic molecules, like air pollutants and smog precursors, into environmentally friendly compounds. These surfaces also exhibit a high affinity for water when exposed to UV light. Therefore, not only are the pollutants decomposed, but this superhydrophilic nature makes the surface self-cleaning, which helps to further increase the degradation rate by allowing rain and/or water to wash byproducts away. According to the Clean Air Act, each individual state is responsible for implementing prevention and regulatory programs to control air pollution. To operate an air quality program, states must adopt and/or develop a plan and obtain approval from the EPA. Federal approval provides a means for the EPA to maintain consistency among different state programs and ensures that they comply with the requirements of the Clean Air Act.

Ryan, robert E.; Underwood, Lauren W.

2007-01-01

96

Band-engineered CaTiO3 nanowires for visible light photocatalysis  

NASA Astrophysics Data System (ADS)

We have theoretically investigated the structural, electronic, and optical properties of the perovskite CaTiO3 nanowires for visible light photocatalytic applications using pseudopotential density-functional theory calculations. The electronic structure calculations show that the band gap is greatly modified in the CaTiO3 nanowires compared with that of the bulk. For the TiO2-terminated nanowires, the electronic states on the valence band maxima induced by combining oxygen and calcium atoms on the surface lead to a shift in the valence band toward the conduction band without interference from the edge of the conduction band, which reduces the band gap. On the contrary, the electronic states induced by combining oxygen and calcium atoms on the surface of the CaO-terminated nanowires lead to a shift in the conduction band toward the valence band. The calculated optical results indicate that the absorption edge of the nanowires shifts towards the red-light region. These theoretical results suggest that the perovskite CaTiO3 nanowires are promising candidates for visible light photocatalysis such as solar-assisted water splitting reactions.

Fu, Q.; Li, J. L.; He, T.; Yang, G. W.

2013-03-01

97

Energy positions of oxide semiconductors and photocatalysis with iron complex oxides  

SciTech Connect

Energy position, bandgap, band structure, and their relationships were reviewed for various oxide semiconductors, especially iron oxides, in photoelectrochemistry and photocatalysis, and the photocatalytic reduction of CO{sub 2} on some iron complex oxides was demonstrated. A linear relationship between bandgap and band edge was obtained for almost all the semiconductor oxides. It was pointed out that a bandgap energy higher than about 2.46 eV is necessary for water photolysis without bias voltage. It was found that the energy positions of the band edge can be controlled by the electronegativity of the metal elements constituting the iron complex oxides. The relationship between the band structure and the charge transfer site was also examined. The photocatalytic reduction of CO{sub 2} to CH{sub 2}OH was demonstrated for CaFe{sub 2}O{sub 4} and Fe-Bi-Sr-Pb-O complex oxides. The photocatalytic activity of the latter oxide with a layer structure increased with increased Pb content. The catalytic mechanism was discussed from the point of view of the redox mechanism as well as the energy position of the band edge.

Matsumoto, Yasumichi [Kumamoto Univ. (Japan)] [Kumamoto Univ. (Japan)

1996-11-01

98

A comparison of the degradation of 4-nitrophenol via direct and sensitized photocatalysis in TiO 2 slurries  

Microsoft Academic Search

Sensitized photocatalysis has been demonstrated with colored pollutants such as nitrophenols. With visible light excitation of an adsorbed nitrophenol, charge injection into the conduction band of the semiconductor occurs and subsequent transformation of nitrophenols is possible. This work reports the results of experiments of direct and sensitized photocatalysis of 4-nitrophenol using an annular reactor, TiO2, and an artificial light source.

Melissa S Dieckmann; Kimberly A Gray

1996-01-01

99

Surface Photocatalysis-TPD Spectrometer for Photochemical Kinetics  

NASA Astrophysics Data System (ADS)

A surface photocatalysis-TPD apparatus devoted to studying kinetics and mechanism of photocatalytic processes with various signal crystal surfaces has been constructed. Extremely high vacuum (~0.2 nPa) in the ionization region is obtained by using multiple ultrahigh vacuum pumps. Compared with similar instruments built previously by others, the H2, CH4 background in the ionization region can be reduced by about two orders of magnitude, and other residual gases in the ionization region can be reduced by about an order of magnitude. Therefore, the signal-to-noise ratio for the temperature programmed desorption (TPD) and time of flight (TOF) spectra is substantially enhanced, making experimental studies of photocatalytic processes on surfaces much easier. In this work, we describe the new apparatus in detail and present some preliminary studies on the photo-induced oxygen vacancy defects on TiO2(110) at 266 nm by using the TPD and TOF methods. Preliminary results suggest that the apparatus is a powerful tool for studying kinetics and mechanism of photochemical processes.

Ren, Ze-feng; Guo, Qing; Xu, Chen-biao; Yang, Wen-shao; Xiao, Chun-lei; Dai, Dong-xu; Yang, Xue-ming

2012-10-01

100

Molecular selective photocatalysis by TiO2/nanoporous silica core/shell particulates.  

PubMed

The coating of TiO(2) particles (P25) by a nanoporous silica layer was conducted to impart molecular recognitive photocatalytic ability. TiO(2)/nanoporous silica core/shell particles with varied pore diameters of the shell were synthesized by the reaction of P25 with an aqueous mixture of tetraethoxysilane and alkyltrimethylammonium chloride with varied alkyl chain lengths, followed by calcination. The TEM and nitrogen adsorption/desorption isotherms of the products showed that a nanoporous silica shell with a thickness of ca. 2nm and controlled pore diameter (1.2, 1.6, and 2.7 nm) was deposited on the titania particle when surfactants with different alkyl chain lengths (C12, C16 and C22) were used. The water vapor adsorption/desorption isotherms of the core/shell particles revealed that a larger amount of water adsorbed on the core/shell particles when the pore diameter is larger. The (29)Si MAS NMR spectra of the core/shell particles showed that the amount of surface silanol groups was independent of the water vapor adsorption capacity of the products. The possible molecular recognitive photocatalysis on the products was investigated under UV irradiation using two kinds of aqueous mixtures containing different organic compounds with varied sizes and functional groups: a 4-butylphenol, 4-hexylphenol, and 4-nonylphenol mixture and a 2-nitrophenol, 2-nitro-4-phenylphenol, and 4-nitro-2,6-diphenylphenol mixture. It was found that the core/shell particles exhibited selective adsorption-driven molecular recognitive photocatalytic decomposition of 4-nonylphenol and 2-nitrophenol in the two mixtures. PMID:21419418

Ide, Yusuke; Koike, Yusuke; Ogawa, Makoto

2011-06-01

101

Activating Ag by even more inert Au: a peculiar effect on electrocatalysis toward oxygen reduction in alkaline media.  

PubMed

Combined computational and experimental studies reveal a noble, non-d-band effect on Ag activation and electrocatalysis: upon coating Ag onto the even more inert Au surface, the catalytic activity toward the oxygen reduction reaction in alkaline media can be improved by about half an order of magnitude in comparison to the usual Ag surface. PMID:24067877

Yang, Cuixia; Huang, Bing; Xiao, Li; Ren, Zhandong; Liu, Zilong; Lu, Juntao; Zhuang, Lin

2013-12-01

102

Treatment of formaldehyde by corona plasma cooperated with photo-catalysis  

NASA Astrophysics Data System (ADS)

Formaldehyde, as a main indoor pollutant, is a serious hazard for human health. Here the experimental results of dielectric discharge, together with photo-catalysis to treat formaldehyde, were presented. The modified photocatalyst was loaded onto the electrode surface for degradation of formaldehyde in an artificially enclosed room. The effect of catalyst quantity, inlet rate, temperature, humidity and other process variables were examined in order to explore the relative purification factors of plasma cooperated with photo-catalysis. It is found that formaldehyde degradation efficiency is proportional to photo-catalyst quantity, and reciprocal to gas inlet rate and humidity. Experimental results confirm that plasma discharge combined with photo-catalysis can significantly improve the treatment efficiency of formaldehyde compared to a single plasma discharge. This research may form a basis for practical development of an efficient, low-power-cost, and relatively comprehensive indoor pollutant purification system.

Yue, X. G.; He, Z. H.; Ma, P. Y.; Zhu, L.; Ma, J.; Zhao, H.

2013-03-01

103

Role of water adsorption in photoinduced superhydrophilicity on TiO{sub 2} thin films  

SciTech Connect

The ultraviolet (UV) irradiation of a titanium dioxide (TiO{sub 2}) film surface gives rise to two simultaneous phenomena: photocatalysis and superhydrophilicity. Photocatalysis has been thoroughly studied, but the mechanism governing superhydrophilicity remains controversial. The authors' investigations show the effects induced by UV irradiation on the water adsorption and desorption on the TiO{sub 2} surface. The observations prove that superhydrophilicity cannot be solely induced by the removal of organic contamination via photocatalysis, but is associated with water adsorption most probably due to the appearance of hydroxyl groups on surface defects.

Lee, Fuk Kay; Andreatta, Gaeelle; Benattar, Jean-Jacques [Service de Physique de l'Etat Condense (CNRS URA 2464), DSM/DRECAM/SPEC, CEA Saclay, 91191 Gif sur Yvette Cedex (France)

2007-04-30

104

Recent Progress in Photocatalysis Mediated by Colloidal II-VI Nanocrystals  

PubMed Central

The use of photoexcited electrons and holes in semiconductor nanocrystals as reduction and oxidation reagents is an intriguing way of harvesting photon energy to drive chemical reactions. This review focuses on recent research efforts to understand and control the photocatalytic processes mediated by colloidal II-VI nanocrystalline materials, such as cadmium and zinc chalcogenides. First, we highlight how nanocrystal properties govern the rates and efficiencies of charge-transfer processes relevant to photocatalysis. We then describe the use of nanocrystal catalyst heterostructures for fuel-forming reactions, most commonly H2 generation. Finally, we review the use of nanocrystal photocatalysis as a synthetic tool for metal–semiconductor nano-heterostructures.

Wilker, Molly B; Schnitzenbaumer, Kyle J; Dukovic, Gordana

2012-01-01

105

Carbon Dioxide reduction by non-equilibrium electrocatalysis plasma reactor  

NASA Astrophysics Data System (ADS)

A possible strategy to increase the added value from CCS, is to consider it as a raw material for the production of liquid fuels, or chemical products. The most studied ways related to CO2 reduction, with formation of molecules such as CH3OH or syngas, is the reaction with H2 (exothermic reaction needing catalytic activation), or CH4 (endothermic reaction taking place at high temperature) with the use of a catalyst. The synthesis of CH3OH is performed on Lewis acid type sites (default of electrons) Cu/Zn/Al2O3. However the products of the reaction i.e. the water and methanol molecules, are very polar, resulting in a very low desorption rate. So in this reaction the key step is water desorption (Lewis basis). The increase of temperature in order to increase this desorption rate, leads to a cracking and the deposition of carbon in the catalyst, limiting its lifetime. Plasma driven catalysis allows firstly, a vibrational activation of CO2, H2 or CH4 through electron-molecule collisions, making easier their dissociation at low temperature and secondly expels water from the catalyst sites by supplying electrons (electropolarisation). The results show an increase of the yield in CH3OH with plasma and catalyst, confirming the action of the plasma. However energy consumption remains relatively high.

Amouroux, J.; Cavadias, S.; Doubla, A.

2011-03-01

106

CO2 SEQUESTRATION AND RECYCLE BY PHOTOCATALYSIS WITH VISIBLE LIGHT  

SciTech Connect

Visible light-photocatalysis could provide a cost-effective route to recycle CO{sub 2} to useful chemicals or fuels. Development of an effective catalyst for the photocatalytic synthesis requires (i) the knowledge of the surface band gap and its relation to the surface structure, (ii) the reactivity of adsorbates and their reaction pathways, and (iii) the ability to manipulate the actives site for adsorption, surface reaction, and electron transfer. The objective of this research is to study the photo-catalytic activity of TiO{sub 2}-base catalyst. A series of TiO{sub 2}-supported metal catalysts were prepared for determining the activity and selectivity for the synthesis of methane and methanol. 0.5 wt% Cu/SrTiO{sub 3} was found to be the most active and selective catalyst for methanol synthesis. The activity of the catalyst decreased in the order: Ti silsesquioxane > Cu/SrTiO{sub 3} > Pt/TiO{sub 2} > Cu/TiO{sub 2} > TiO{sub 2} > Rh/TiO{sub 2}. To further increase the number of site for the reaction, we propose to prepare monolayer and multiplayer TiOx on high surface area mesoporous oxides. These catalysts will be used for in situ IR study in the Phase II research project to determine the reactivity of adsorbates. Identification of active adsorbates and sites will allow incorporation of acid/basic sites to alter the nature of CO{sub 2} and H{sub 2}O adsorbates and with Pt/Cu sites to direct reaction pathways of surface intermediates, enhancing the overall activity and selectivity for methanol and hydrocarbon synthesis. The overall goal of this research is to provide a greater predictive capability for the design of visible light-photosynthesis catalysts by a deeper understanding of the reaction kinetics and mechanism as well as by better control of the coordination/chemical environment of active sites.

Steven S.C. Chuang

2001-10-01

107

Degradation of recalcitrant organic contaminants by solar photocatalysis.  

PubMed

Biological pre-treated landfill leachates of Djebel Chakir contains some macromolecular organic substances that are resistant to biological degradation. The aim of the present work is to assess the feasibility of removing refractory organic pollutants in biological pre-treated landfill leachate by solar photocatalyse process. Leachate pollutant contents are studied to assess their contribution to leachate pollution and their treatability by solar photocatalyse process. Phenol is chosen as model of pollutants, to evaluate its removal and the efficiency of the photocatalytic system. The experiments were carried out in suspended photocatalytic reactor, using TiO2 Degussa P25, under sunlight illumination (UV-A: 15-31 W/cm2). Under optimum operational conditions, applied to single reactant (phenol), the system presents a TOC removal of 90% (the degradation follows a first-order kinetic). Based on the TOC removal, the results shows that the degradation of biological pre-treated leachate follows a zero-order kinetic. After 5 h of sunlight exposure, 74% of COT is removed. The TOC removal is the best without any correction of the pH and at the TiO2 concentration of 2.5 g/L. The photocatalytic degradation of organic contaminants as well as the formation and disappearance of the by-products were followed by GC/MS. The solar photocatalysis processes induce several modifications of the matrix leading to more biodegradable forms: all the remaining and new compounds generated after the biological pre-treatment of leachate are degraded and other types of organics appear, mainly carboxylic acid, aliphatic hydrocarbons and phtalic acids. PMID:17674837

Mansouri, L; Bousselmi, L; Ghrabi, A

2007-01-01

108

Desulfurization of Real and Model Liquid Fuels Using Light: Photocatalysis and Photochemistry  

Microsoft Academic Search

Ultra-deep desulfurization of liquid fuels is crucial for the environment, longer lifetime of combustion engines, and emerging “green,” sustainable, carbon-neutral fuels for fuel cell applications. Current interest is towards photocatalysis and photochemistry for production of clean fuels and valuable chemicals. This critical Review provides systematization and analysis of studies on photocatalytic, photosensitized, and photochemical desulfurization of liquid fuels in the

Alexander Samokhvalov

2012-01-01

109

UV and Solar TiO2 Photocatalysis of Brevetoxins (PbTxs)  

PubMed Central

Karenia brevis, the harmful alga associated with red tide, produces brevetoxins (PbTxs). Exposure to these toxins can have a negative impact on marine wildlife and serious human health consequences. The elimination of PbTxs is critical to protect the marine environment and human health. TiO2 photocatalysis under 350 nm and solar irradiation leads to significant degradation of PbTxs via first order kinetics. ELISA results demonstrate TiO2 photocatalysis leads to a significant decrease in the bioactivity of PbTxs as a function of treatment time. Experiments conducted in the presence of synthetic seawater, humic material and a hydroxyl scavenger showed decreased degradation. PbTxs are highly hydrophobic and partition to organic microlayer on the ocean surface. Acetonitrile was employed to probe the influence of an organic media on the TiO2 photocatalysis of PbTxs. Our results indicate TiO2 photocatalysis may be applicable for the degradation of PbTxs.

Khan, Urooj; Benabderrazik, Nadia; Bourdelais, Andrea J.; Baden, Daniel G.; Rein, Kathleen; Gardinali, Piero R.; Arroyo, Luis; O'Shea, Kevin E.

2012-01-01

110

Gas phase vinyl chloride (VC) oxidation using TiO 2-based photocatalysis  

Microsoft Academic Search

Photocatalytic destruction of vinyl chloride (VC) was examined in a laboratory experimental set-up and the results were compared with those obtained from trichloroethylene (TCE) photocatalysis. Granular photocatalyst used in the study consisted of silica support coated with 0.1% titanium dioxide as the main photocatalytically active ingredient. Experimental work involved passing polluted air containing VC or TCE through a UV annular

Madjid Mohseni; Arnaud David

2003-01-01

111

Heterogeneous photocatalysis: fundamentals and applications to the removal of various types of aqueous pollutants  

Microsoft Academic Search

Photocatalysis is based on the double aptitude of the photocatalyst (essentially titania) to simultaneously adsorb both reactants and to absorb efficient photons. The basic fundamental principles are described as well as the influence of the main parameters governing the kinetics (mass of catalyst, wavelength, initial concentration, temperature and radiant flux). Besides the selective mild oxidation of organics performed in gas

Jean-Marie Herrmann

1999-01-01

112

Facilitation of High-Rate NADH Electrocatalysis Using Electrochemically Activated Carbon Materials.  

PubMed

Electrochemical activation of glassy carbon, carbon paper and functionalized carbon nanotubes via high-applied-potential cyclic voltammetry leads to the formation of adsorbed, redox active functional groups and increased active surface area. Electrochemically activated carbon electrodes display enhanced activity toward nicotinamide adenine dinucleotide (NADH) oxidation, and more importantly, dramatically improved adsorption of bioelectrochemically active azine dyes. Adsorption of methylene green on an electroactivated carbon electrode yields a catalyst layer that is 1.8-fold more active toward NADH oxidation than an electrode prepared using electropolymerized methylene green. Stability studies using cyclic voltammetry indicate 70% activity retention after 4000 cycles. This work further facilitates the electrocatalysis of NADH oxidation for bioconversion, biosensor and bioenergy processes. PMID:24780505

Li, Hanzi; Li, Rui; Worden, Robert M; Barton, Scott Calabrese

2014-05-14

113

Application of the colloidal stability of TiO 2 particles for recovery and reuse in solar photocatalysis  

Microsoft Academic Search

TiO2-catalyst suspensions work efficiently in photocatalysis for wastewater treatment. Nevertheless, once photocatalysis is complete, separation of the catalyst from solution becomes the main problem. Catalyst recovery has been enhanced through charge neutralisation and coagulation with electrolytes at lab and pilot-plant scale (40L) to evaluate the potential for its separation after photocatalytic degradation of pollutants. Zeta-potential analysis showed that the isoelectric

P. Fernández-Ibáñez; J. Blanco; S. Malato; F. J. de las Nieves

2003-01-01

114

Water Purification Systems  

NASA Technical Reports Server (NTRS)

A water purification/recycling system developed by Photo-Catalytics, Inc. (PCI) for NASA is commercially available. The system cleanses and recycles water, using a "photo-catalysis" process in which light or radiant energy sparks a chemical reaction. Chemically stable semiconductor powders are added to organically polluted water. The powder absorbs ultraviolet light, and pollutants are oxidized and converted to carbon dioxide. Potential markets for the system include research and pharmaceutical manufacturing applications, as well as microchip manufacture and wastewater cleansing.

1992-01-01

115

Enhanced visible light photocatalysis through fast crystallization of zinc oxide nanorods  

PubMed Central

Summary Hydrothermally grown ZnO nanorods have inherent crystalline defects primarily due to oxygen vacancies that enhance optical absorption in the visible spectrum, opening up possibilities for visible light photocatalysis. Comparison of photocatalytic activity of ZnO nanorods and nanoparticle films on a test contaminant methylene blue with visible light irradiation at 72 kilolux (klx) showed that ZnO nanorods are 12–24% more active than ZnO nanoparticulate films. This can be directly attributed to the increased effective surface area for adsorption of target contaminant molecules. Defects, in the form of interstitials and vacancies, were intentionally created by faster growth of the nanorods by microwave activation. Visible light photocatalytic activity was observed to improve by ?8% attributed to the availability of more electron deficient sites on the nanorod surfaces. Engineered defect creation in nanostructured photocatalysts could be an attractive solution for visible light photocatalysis.

Baruah, Sunandan; Mahmood, Mohammad Abbas; Myint, Myo Tay Zar; Bora, Tanujjal

2010-01-01

116

Removal of silver in photographic processing waste by TiO{sub 2}-based photocatalysis  

SciTech Connect

Treatability data on actual waste show that titania-based photocatalysis can be used to remove silver ions from black and white photoprocessing waste. The silver ion is reduced to its metallic form producing particles comparable in size to the TiO{sub 2} catalyst particles. The mass of silver recovered approaches three times that of the titania. Thiosulfate (the predominant chemical in spent fixer) plays a complicated role in the process of silver ion reduction: (1) as a hole scavenger, it can increase the silver reduction rate; (2) as the chemical that stabilizes silver ion in solution, thiosulfate hinders photocatalysis when present at high concentration. Metallic silver can be separated from titania by the physical process of sonication. We also show that sunlight can be used directly to power the photo-electrochemical silver removal process. 11 refs., 9 figs.

Huang, M.; Tso, E.; Datye, A.K. [Univ. of New Mexico, Albuquerque, NM (United States)] [Univ. of New Mexico, Albuquerque, NM (United States); Prairie, M.R.; Stange, B.M. [Sandia National Lab., ALbuquerque, NM (United States)] [Sandia National Lab., ALbuquerque, NM (United States)

1996-10-01

117

Band gap engineering in BiNbO{sub 4} for visible-light photocatalysis  

SciTech Connect

We have investigated the electronic structure of anionic mono- (S, N, and C) and co-doping (N-N, C-N, S-C, and S-N) on BiNbO{sub 4} for the visible-light photocatalysis. The maximum band gap reduction of pure BiNbO{sub 4} is possible with the (C-S) co-doping and minimum with N mono-doping. The calculated binding energies show that the co-doped systems are more stable than their mono-doped counterparts. Our optical absorption curves indicate that the mono- (C) and co-anionic doped (N-N and C-S) BiNbO{sub 4} systems are promising materials for visible light photocatalysis.

Wang, B. C. [Department of Materials Science and Engineering, Royal Institute of Technology (KTH), S-100 44 Stockholm (Sweden); Nisar, J.; Pathak, B. [Department of Physics and Astronomy, Box 530, Uppsala University, S-751 21 Uppsala (Sweden); Kang, T. W. [QSRC, Department of Physics, Dongguk University, Seoul 100-715 (Korea, Republic of); Ahuja, R. [Department of Materials Science and Engineering, Royal Institute of Technology (KTH), S-100 44 Stockholm (Sweden); Department of Physics and Astronomy, Box 530, Uppsala University, S-751 21 Uppsala (Sweden)

2012-04-30

118

Photocatalytic decolourization of reactive azo dye: A comparison between TiO 2 and us photocatalysis  

Microsoft Academic Search

This study examined the photocatalytic degradation of reactive black 5 (RB5), a reactive azo dye, by TiO2 and US. An aerated semiconductor suspension was illuminated in a batch-lab-scale reactor. Both reactions followed first order kinetics. The effects of initial pH, semiconductor dosage, light intensity, initial dye concentration and temperature were investigated. US photocatalysis of RB5 followed the Langmuir-Hinshelwood equation while

Lars Baetz Reutergådh; Mallika Iangphasuk

1997-01-01

119

Kinetics and mechanism of TNT degradation in TiO 2 photocatalysis  

Microsoft Academic Search

The photocatalytic degradation of TNT in a circular photocatalytic reactor, using a UV lamp as a light source and TiO2 as a photocatalyst, was investigated. The effects of various parameters such as the initial TNT concentration, and the initial pH on the TNT degradation rate of TiO2 photocatalysis were examined. In the presence of both UV light illumination and TiO2

Hyun-Seok Son; So-Jin Lee; Il-Hyoung Cho; Kyung-Duk Zoh

2004-01-01

120

Degradation of nitrogen containing organic compounds by combined photocatalysis and ozonation  

Microsoft Academic Search

The combination of TiO2-assisted photocatalysis and ozonation in the degradation of nitrogen-containing substrates such as alkylamines, alkanolamines, heterocyclic and aromatic N-compounds has been investigated. A laboratory set-up was designed and the influence of the structure of the N-compound, the TiO2 and ozone concentration on the formation of breakdown products were examined. The experimental results showed that a considerable increase in

M. Mare; G. Waldner; R. Bauer; H. Jacobs; J. A. C. Broekaert

1999-01-01

121

TiO2 Photocatalysis: A Historical Overview and Future Prospects  

Microsoft Academic Search

Photocatalysis has recently become a common word and various products using photocatalytic functions have been commercialized. Among many candidates for photocatalysts, TiO2 is almost the only material suitable for industrial use at present and also probably in the future. This is because TiO2 has the most efficient photoactivity, the highest stability and the lowest cost. More significantly, it has been

Kazuhito Hashimoto; Hiroshi Irie; Akira Fujishima

2005-01-01

122

Hole mediated coupling in Sr2Nb2O7 for visible light photocatalysis.  

PubMed

The band gap reduction and effective utilization of visible solar light are possible by introducing the anionic hole-hole mediated coupling in Sr(2)Nb(2)O(7). By using the first principles calculations, we have investigated the mono- and co-anionic doping (S, N and C) in layered perovskite Sr(2)Nb(2)O(7) for the visible-light photocatalysis. Our electronic structure and optical absorption study shows that the mono- (N and S) and co-anionic doped (N-N and C-S) Sr(2)Nb(2)O(7) systems are promising materials for the visible light photocatalysis. The calculated binding energies show that if the hole-hole mediated coupling could be introduced, the co-doped systems would be more stable than their respective mono-doped systems. Optical absorption curves indicate that doping S, (N-N) and (C-S) in Sr(2)Nb(2)O(7) can harvest a longer wavelength of the visible light spectrum as compared to the pure Sr(2)Nb(2)O(7) for efficient photocatalysis. PMID:22389023

Nisar, Jawad; Pathak, Biswarup; Wang, Baochang; Kang, Tae Won; Ahuja, Rajeev

2012-04-14

123

Applicability and costs of nanofiltration in combination with photocatalysis for the treatment of dye house effluents  

PubMed Central

Summary Nanofiltration (NF) is a capable method for the separation of dyes, which can support and even improve the applicability of photocatalysis in effluent-treatment processes. The membrane process usually will need a special pre-treatment to avoid precipitation and fouling on the membrane surface. Conceptually NF can be applied in the pre-treatment prior to the catalytic reactor or in connection with the reactor to separate the liquid phase from the reaction system and to recycle finely suspended catalysts and/or organic compounds. When concerning such reaction systems on a bigger scale, cost figures will prove the usefulness of those concepts. Different applications of photocatalysis on the lab-scale have been published in recent years. Membrane technology is used almost in all those processes and an overview will be given of those recently published systems that have been reported to be potentially useful for a further scale-up. NF membranes are mostly used for the more sophisticated separation step of these processes and the additional costs of the NF treatment, without any associated equipments, will be described and illustrated. The total specific costs of industrial NF treatment processes in usefully adjusted and designed plants range from 1 to 6 US$/m3 treated effluent. Combination concepts will have a good precondition for further development and upscaling, if the NF costs discussed here in detail will be, together with the costs of photocatalysis, economically acceptable.

Samhaber, Wolfgang M

2014-01-01

124

Applicability and costs of nanofiltration in combination with photocatalysis for the treatment of dye house effluents.  

PubMed

Nanofiltration (NF) is a capable method for the separation of dyes, which can support and even improve the applicability of photocatalysis in effluent-treatment processes. The membrane process usually will need a special pre-treatment to avoid precipitation and fouling on the membrane surface. Conceptually NF can be applied in the pre-treatment prior to the catalytic reactor or in connection with the reactor to separate the liquid phase from the reaction system and to recycle finely suspended catalysts and/or organic compounds. When concerning such reaction systems on a bigger scale, cost figures will prove the usefulness of those concepts. Different applications of photocatalysis on the lab-scale have been published in recent years. Membrane technology is used almost in all those processes and an overview will be given of those recently published systems that have been reported to be potentially useful for a further scale-up. NF membranes are mostly used for the more sophisticated separation step of these processes and the additional costs of the NF treatment, without any associated equipments, will be described and illustrated. The total specific costs of industrial NF treatment processes in usefully adjusted and designed plants range from 1 to 6 US$/m(3) treated effluent. Combination concepts will have a good precondition for further development and upscaling, if the NF costs discussed here in detail will be, together with the costs of photocatalysis, economically acceptable. PMID:24778974

Samhaber, Wolfgang M; Nguyen, Minh Tan

2014-01-01

125

Nickel removal by biosorption onto medlar male flowers coupled with photocatalysis on the spinel ZnMn2O4.  

PubMed

Ni2+ is a highly toxic above 0.07 mg/L and its removal is of high significance. The biosorption of Ni2+ onto medlar male flowers (MMF) was studied in relation with the physical parameters like pH, contact time, biosorbent dosage, Ni2+ concentration and temperature. The interaction biosorbent-Ni2+ was examined by the FTIR technique. The equilibrium was achieved within 40 min and the data were well fitted by the Langmuir and Redlich-Peterson (R-P) models. The maximum Ni2+ uptake capacity was 17.073 mg/g at 25°C and the Ni2+ removal follows a pseudo-second order kinetic with activation energy of 13.3 kJ/mol. The thermodynamic parameters: ?S°, ?H° and ?G° showed that the biosorption was spontaneous and endothermic. MMF was used as a post treatment technique and the biosorption was coupled with the visible light driven Ni2+ reduction over the spinel ZnMn2O4. The effect of the pH, ZnMn2O4 loading and light intensity on the photoactivity was investigated. 77.5% of Ni2+ was reduced after ~140 min under optimal conditions. The Ni2+ removal reached a rate conversion of 96% of with the coupled system biosorption/photocatalysis is very promising for the water treatment. PMID:24401700

Chergui, Ahmed; Madjene, Farid; Trari, Mohamed; Khouider, Ali

2014-01-01

126

Nickel removal by biosorption onto medlar male flowers coupled with photocatalysis on the spinel ZnMn2O4  

PubMed Central

Ni2+ is a highly toxic above 0.07 mg/L and its removal is of high significance. The biosorption of Ni2+ onto medlar male flowers (MMF) was studied in relation with the physical parameters like pH, contact time, biosorbent dosage, Ni2+ concentration and temperature. The interaction biosorbent-Ni2+ was examined by the FTIR technique. The equilibrium was achieved within 40 min and the data were well fitted by the Langmuir and Redlich-Peterson (R-P) models. The maximum Ni2+ uptake capacity was 17.073 mg/g at 25°C and the Ni2+ removal follows a pseudo-second order kinetic with activation energy of 13.3 kJ/mol. The thermodynamic parameters: ?S°, ?H° and ?G° showed that the biosorption was spontaneous and endothermic. MMF was used as a post treatment technique and the biosorption was coupled with the visible light driven Ni2+ reduction over the spinel ZnMn2O4. The effect of the pH, ZnMn2O4 loading and light intensity on the photoactivity was investigated. 77.5% of Ni2+ was reduced after ~140 min under optimal conditions. The Ni2+ removal reached a rate conversion of 96% of with the coupled system biosorption/photocatalysis is very promising for the water treatment.

2014-01-01

127

Facile hydrothermal synthesis of TiO2-Bi2WO6 hollow superstructures with excellent photocatalysis and recycle properties.  

PubMed

One-dimensional mesoporous TiO2-Bi2WO6 hollow superstructures are prepared using a hydrothermal method and their photocatalysis and recycle properties are investigated. Experimental results indicate that anatase TiO2 nanoparticles are coupled with hierarchical Bi2WO6 hollow tubes on their surfaces. The TiO2-Bi2WO6 structure has a mesoporous wall and the pores in the wall are on average 21 nm. The hierarchical TiO2-Bi2WO6 heterostructures exhibit the highest photocatalytic activity in comparison with P25, pure Bi2WO6 hollow tube and mechanical mixture of Bi2WO6 tube and TiO2 nanoparticle in the degradation of rhodamine B (RhB) under simulated sunlight irradiation. The as-prepared TiO2-Bi2WO6 heterostructures can be easily recycled through sedimentation and they retains their high photocatalytic activity during the cycling use in the simulated sunlight-driving photodegradation process of RhB. The prepared mesoporous TiO2-Bi2WO6 with hollow superstructure is therefore a promising candidate material for water decontamination use. PMID:24162142

Hou, Ya-Fei; Liu, Shu-Juan; Zhang, Jing-huai; Cheng, Xiao; Wang, You

2014-01-21

128

Conductive carbon nanotube hydrogel as a bioanode for enhanced microbial electrocatalysis.  

PubMed

Enhancing microbial electrocatalysis through new material design is essential to the efficient and stable operation of bio-electrochemical system (BES). In this work, a novel conductive carbon nanotube (CNT) hydrogel was fabricated by electrodepositing both CNT and chitosan onto a carbon paper electrode and used as a BES anode electrode. The microscopic, spectroscopic, and electrochemical analytical results show that the CNT hydrogel exhibited an excellent electrochemical activity. In the BES tests, the current generation and the maximum power density of the MFC with the CNT hydrogel increased by 23% and 65%, respectively, compared with the control. This demonstrates that the utilization of such a hydrogel offers an effective approach to enhance the current generation of BES. The great conductivity of CNT and the high content of oxygen-containing functional groups (C-OH, C?O, etc.) on their surface were found to be responsible for the improvements. Our work provides a facile way to prepare appropriate BES electrodes and offers a straightforward and effective route to enhance the BES performance. PMID:24818709

Liu, Xian-Wei; Huang, Yu-Xi; Sun, Xue-Fei; Sheng, Guo-Ping; Zhao, Feng; Wang, Shu-Guang; Yu, Han-Qing

2014-06-11

129

Techniques and methodologies in modern electrocatalysis: evaluation of activity, selectivity and stability of catalytic materials.  

PubMed

The development and optimisation of materials that promote electrochemical reactions have recently attracted attention mainly due to the challenge of sustainable provision of renewable energy in the future. The need for better understanding and control of electrode-electrolyte interfaces where these reactions take place, however, implies the continuous need for development of efficient analytical techniques and methodologies capable of providing detailed information about the performance of electrocatalysts, especially in situ, under real operational conditions of electrochemical systems. During the past decade, significant efforts in the fields of electrocatalysis and (electro)analytical chemistry have resulted in the evolution of new powerful methods and approaches providing ever deeper and unique insight into complex and dynamic catalytic systems. The combination of various electrochemical and non-electrochemical methods as well as the application of quantum chemistry calculations has become a viable modern approach in the field. The focus of this critical review is primarily set on discussion of the most recent cutting-edge achievements in the development of analytical techniques and methodologies designed to evaluate three key constituents of the performance of electrocatalysts, namely, activity, selectivity and stability. Possible directions and future challenges in the design and elaboration of analytical methods for electrocatalytic research are outlined. PMID:24418971

Bandarenka, Aliaksandr S; Ventosa, Edgar; Maljusch, Artjom; Masa, Justus; Schuhmann, Wolfgang

2014-03-21

130

Low-Coordination Sites in Oxygen-Reduction Electrocatalysis: Their Roles and Methods for Removal  

SciTech Connect

Low-coordination sites, including edges, kinks, and defects, play an important role in oxygen-reduction electrocatalysis. Their role was studied experimentally and theoretically for various Pt surfaces. However, the roughness effect on similar-sized nanoparticles that could elucidate the role of low-coordination sites has attracted much less attention, with no studies on Pd nanoparticles. Here, using Br- adsorption/desorption, we introduce an effective approach to reduce surface roughness, yielding Pd nanoparticles with smoother surfaces and an increased number of (111)-oriented facets. The resulting nanoparticles have a slightly contracted structure and narrow size distribution. Pt monolayer catalysts that contain such nanoparticles as the cores showed a 1.5-fold enhancement in specific and Pt mass activities for the oxygen reduction reaction compared with untreated ones. Furthermore, a dramatic increase in durability was observed with bromide-treated Pd{sub 3}Co cores. These results demonstrate a simple approach to preparing nanoparticles with smooth surfaces and confirm the adverse effect of low-coordination sites on the kinetics of the oxygen-reduction reaction.

Cai, Y.; Ma, C.; Zhu, Y.; Wang, J.X.; Adzic, R.R.

2011-07-05

131

Electrocatalysis for oxygen electrodes in fuel cells and water electrolyzers for space applications  

NASA Technical Reports Server (NTRS)

The lead ruthenate pyrochlore Pb2Ru2O6.5, in both high- and low-area forms, has been characterized using thermogravimetric analysis, X-ray photoelectron spectroscopy, X-ray diffraction, cyclic voltammetry, and O2 reduction and generation kinetic-mechanistic studies. Mechanisms are proposed. Compounds in which part of the Ru is substituted with Ir have also been prepared. They exhibit somewhat better performance for O2 reduction in porous, gas-fed electrodes than the unsubstituted compound. The anodic corrosion resistance of pyrochlore-based porous electrodes was improved by using two different anionically conducting polymer overlayers, which slow down the diffusion of ruthenate and plumbate out of the electrode. The O2 generation performance was improved with both types of electrodes. With a hydrogel overlayer, the O2 reduction performance was also improved.

Prakash, Jai; Tryk, Donald; Yeager, Ernest

1990-01-01

132

Development of a new photocatalytic reactor for water purification  

Microsoft Academic Search

The purification of water by heterogeneous photocatalysis is one of the most rapidly growing areas of interest to both research workers and water purification plants. Recent literature has demonstrated on a laboratory scale the potential of this promising technology to completely destroy organic pollutants dissolved or dispersed in water into harmless substances. However, to date no viable pilot plant exists

Ajay K. Ray; Antonie A. C. M. Beenackers

1998-01-01

133

Transition metal hexacyanoferrates in electrocatalysis of H2O2 reduction: an exclusive property of Prussian Blue.  

PubMed

The ability of Prussian Blue, ferric hexacyanoferrate (FeHCF), to sensitively and selectively detect hydrogen peroxide by its reduction in the presence of oxygen is of high importance for analytical chemistry. Success with Prussian Blue (PB) provided an appearance of contradictory reports concerning electrocatalysis of the other transition metal hexacyanoferrates (HCFs) in H2O2 reduction. Investigating thermodynamics of the catalyzed reactions as well as electrochemical properties of the hexacyanoferrates, we are able to conclude that the noniron hexacyanoferrates themselves are completely electrocatalytically inactive, except for a minor electrocatalysis in the opposite reaction, hydrogen peroxide oxidation, registered for NiHCF. Concerning the most important reaction, H2O2 reduction, the observed electrocatalytic activity (by the way, 100 times decreased compared to PB) is due to the presence of FeHCF (Prussian Blue) as defects in the structure of noniron hexacyanoferrates. This finding, considering other unique properties of transition metal HCFs, will provide a systematic search for sensing materials with improved analytical performance characteristics. PMID:24735447

Sitnikova, Natalya A; Komkova, Maria A; Khomyakova, Irina V; Karyakina, Elena E; Karyakin, Arkady A

2014-05-01

134

Supramolecular photocatalysis: combining confinement and non-covalent interactions to control light initiated reactions.  

PubMed

Using non-bonding interactions to control photochemical reactions requires an understanding of not only thermodynamics and kinetics of ground state and excited state processes but also the intricate interactions that dictate the dynamics within the system of interest. This review is geared towards a conceptual understanding of how one can control the reactivity and selectivity in the excited state by employing confinement and non-covalent interactions. Photochemical reactivity of organic molecules within confined containers and organized assemblies as well as organic templates that interact through H-bonding and/or cation-carbonyl/cation-? interactions is reviewed with an eye towards understanding supramolecular effects and photocatalysis. PMID:24705505

Vallavoju, Nandini; Sivaguru, J

2014-05-27

135

Iron(III)-oxo centers on TiO{sub 2} for visible light photocatalysis.  

SciTech Connect

Isolated iron(III)-oxo clusters were synthesized onto TiO{sub 2} using atomic layer deposition. The Fe{sub x}O{sub y}/TiO{sub 2} nanocomposites have unique properties that enable not only absorption of visible light, but efficient photocatalysis as demonstrated by methylene blue degradation. The localization of photogenerated electrons in core TiO{sub 2} nanocrystallites upon visible light excitation demonstrates coupling of conduction bands of mixed oxides. The redox properties of photogenerated charges in nanocomposites were studied using in situ electron paramagnetic resonance spectroscopy.

Libera, J. A.; Elam, J. W.; Sather, N. F.; Rajh, T.; Dimitrijevic, N. M. (Center for Nanoscale Materials); ( CSE); ( ES)

2009-01-01

136

Solar photo-catalysis to remove paper mill wastewater pollutants  

Microsoft Academic Search

Solar degradation of effluents in board paper industries has been studied using different photo-catalysts: Fenton reagent and TiO2. p-Toluenesulfonic acid was chosen as a model compound for sulfonated pollutants already present in the incoming waters. The abatement of a 0.005M solution of this pollutant after 6h was found to be 47% for photo-Fenton and 27% for TiO2 (pseudo-first-order rate constants

A. M. Amat; A. Arques; F. López; M. A. Miranda

2005-01-01

137

Arsenic removal by photo-catalysis hybrid system  

Microsoft Academic Search

Arsenic is a toxic semi-metallic element that can be fatal to human health. Arsenic pollution in water is found in many parts of the world, especially in developing countries such as Bangladesh, India, Nepal, and Vietnam. Photo-oxidation experiments with titanium dioxide (TiO2) as photo-catalyst showed that photo-oxidation of As(III) to As(V) is possible within minutes. Further, TiO2 can also adsorb

T. V. Nguyen; S. Vigneswaran; H. H. Ngo; J. Kandasamy; H. C. Choi

2008-01-01

138

Application of cetyltrimethylammonium bromide bentonite-titanium dioxide photocatalysis technology for pretreatment of aging leachate.  

PubMed

Organobentonite-photocatalysis technology was applied to pretreat aging leachate containing refractory pollutants. The organobentonite was synthesized by organic modifier cetyltrimethylammonium bromide (CTMAB) and natural bentonite. In characterization experiments, we could confirm that organic functional groups of cetyltrimethylammonium (CTMA(+)) cations were successfully loaded on the surface of bentonite. The combination of CTMAB2.5 adsorption and TiO2 photocatalysis was superior to either running separately. Furthermore, removal efficiency of simultaneously utilizing CTMAB2.5 and TiO2 was better than them in succession. The combination technology was feasible and was optimized by response surface methodology (RSM) with COD and NH3-N removal rate as the target responses. The optimal operation conditions calculated from the regression equations were CTMAB2.5 dosage of 7.5 g/L, pH at 3.5, TiO2 dosage of 1.63 g/L, and reaction time for 60.02 min, which maintained the removal of COD and NH3-N at 82% and 37%, respectively. PMID:24853137

Cai, Fei-Fei; Yang, Zhao-Hui; Huang, Jing; Zeng, Guang-Ming; Wang, Li-Ke; Yang, Jian

2014-06-30

139

Spectroscopic dimensions of silver nanoparticles and clusters in ZnO matrix and their role in bioinspired antifouling and photocatalysis.  

PubMed

Silver doped zinc oxide nanoparticles are synthesized by a solution combustion method. The samples characterized by a variety of spectroscopic and other techniques clearly reveal the presence of silver nanoparticles as well as silver clusters. The silver in the two forms was identified by careful deconvolution of X-ray photoelectron spectral results. Their formation was also confirmed by the presence of plasmons, the concentration and energy of which increase on increasing silver input, indicating the presence of perpendicular excitons since aggregates of clusters are known to shift the plasmon resonances depending on their topologies. Further confirmation of clusters came from EPR (electron paramagnetic resonance), HRSEM (high resolution scanning electron microscopy) and HRTEM (high resolution transmission electron microscopy); direct proof for clusters came from matrix assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectral measurements. The antimicrobial activity of the silver doped zinc oxide polymer nanocomposites as biomedical devices are measured by zone of inhibition. Also, samples coated on paper disk with acacia binder are evaluated by a disk diffusion method. While pure zinc oxide does not show any antimicrobial property, the activity of silver-doped zinc oxide is comparable to that of commercial antibiotics and found to be related to nanoparticulate silver. Similarly, the microbial adherence to the surface of polymer nanocomposite which mimics a biomedical device also was influenced by nanoparticles of silver. The photocatalytic water treatment was carried out using silver carrying nanoparticles with Rhodamine-B and 4-chlorophenol as model pollutants. The increased photocatalytic activity of silver containing zinc oxide as compared to pure zinc oxide nanoparticles is attributed to the synergistic display of the properties of silver nanoparticles and clusters in zinc oxide. This activity depends upon the dispersion of silver nanoparticles over the zinc oxide lattice where charge separation plays a dominant role. The mechanisms for both photocatalysis and antimicrobial activity are discussed. PMID:24671627

Michael, Robin Jude Vimal; Sambandam, Balaji; Muthukumar, Thangavelu; Umapathy, Manickam J; Manoharan, Periakaruppan T

2014-05-14

140

Photocatalysis of 2,2',3,4,4',5'-hexachlorobiphenyl and its intermediates using various catalytical preparing methods.  

PubMed

Four etching solutions used on support materials and two coating methods of TiO(2) were conducted to investigate the effects of catalytical preparing methods on the photocatalysis of 2,2',3,4,4',5'-hexachlorobiphenyl (PCB congener 138). The results of XRD analyses confirmed that various etching solutions used on support substrates did not influence the characteristics of titanium(IV) oxide. The XRD patterns of crystallization for the catalysts before and after purification remained unchanged. Hydrofluoric acid used as an etching solution for the support substrates provided the best adhesion stability for the catalysts that demonstrated the highest photocatalytic efficiency for congener 138. Xenon and ultraviolet lamps were used to compare the irradiation effect on photocatalysis. The shortest half-lives of congener 138 were 7.4 and 12.2 h using xenon and UV reactors, respectively. Lower chlorinated biphenyls (lower congener numbers) were identified through the continuous dechlorination of congener 138. PCB congeners 99, 87, 66, 49, 28, 17, 9, and 7 were detected as a result of dechlorination from higher chlorinated congeners to lower chlorinated congeners along with the extension of exposure times. The concentrations of chloride ion were increased with increasing exposure time through dechlorination, while the concentrations of organic chlorine of congener 138 were decreased. Meta-dechlorination was the most commonly found mechanism for the photocatalysis of PCB 138. The activation energy of the photocatalysis of congener 138 was 70.8 kJ mol(-1). PMID:16494999

Lin, Y J; Chen, Y L; Huang, C Y; Wu, M F

2006-08-25

141

Visible-light-mediated Sr-Bi2O3 photocatalysis of tetracycline: kinetics, mechanisms and toxicity assessment.  

PubMed

Photodegradation of tetracycline (TC) was investigated in aqueous solution by visible-light-driven photocatalyst Sr-doped ?-Bi2O3 (Sr-Bi2O3) prepared via solvothermal synthesis. The decomposition of TC by Sr-Bi2O3 under visible light (?>420nm) irradiation followed pseudo-first-order kinetics, and the removal ratio reached 91.2% after 120min of irradiation. Sr-Bi2O3 photocatalysis is able to break the naphthol ring of TC which decomposes to m-cresol via dislodging hydroxyl group step by step by photogenerated electron. This mechanism was verified by electron spin resonance measurement, the addition of radical scavengers and the intermediate product analysis, indicating that the photogenerated electron acts as a reductant and can be the key to the degradation process. In contrast, in TiO2 photocatalysis the naphthol ring is broken via oxidation by hydroxyl radical, while in direct photolysis the ring remains intact. In addition, the toxicity of photodegradation products was analyzed by bioluminescence inhibition. After 120min of irradiation by Sr-Bi2O3, the toxicity decreases by 90.6%, which is more substantial than direct photolysis (70%) and TiO2 photocatalysis (80%), indicating that the Sr-Bi2O3 photocatalysis is more eco-friendly than the other two methods. PMID:23706401

Niu, Junfeng; Ding, Shiyuan; Zhang, Liwen; Zhao, Jinbo; Feng, Chenghong

2013-09-01

142

Rational design of carbon and TiO2 assembly materials: covered or strewn, which is better for photocatalysis?  

PubMed

The rational design of carbonaceous hybrid nanostructures is very important for obtaining high photoactivity. TiO2 particles strewn with an optimal quantity of carbon nanodots have a much higher photoactivity than that of TiO2 covered with a carbon layer, showing the importance of carbon morphology in the photocatalysis of carbonaceous hybrid nanostructures. PMID:23752661

Cui, Guan-wei; Wang, Wei-liang; Ma, Ming-yue; Zhang, Ming; Xia, Xin-yuan; Han, Feng-yun; Shi, Xi-feng; Zhao, Ying-qiang; Dong, Yu-bin; Tang, Bo

2013-07-21

143

Electrochemical and in situ spectroscopic studies of materials of relevance to energy storage and electrocatalysis  

NASA Astrophysics Data System (ADS)

In situ X-ray absorption (XAS), surface enhanced Raman spectroscopy (SERS) and rotating ring disk electrode techniques have been employed for the characterization of materials of relevance to electrochemical energy storage and electrocatalysis. In particular, analysis of in situ Ir LIII-edge extended X-ray absorption fine structure (EXAFS) of IrO2 films electrodeposited on Au substrates yielded Ir-O bond lengths decreasing in the sequence 2.02, 1.97 and 1.93 A, for Ir3+, Ir4+ and Ir5+ sites, respectively. Although features consistent with the presence of crystalline IrO2 in the highly hydrated films were found from in situ SERS, the lack of intense shells in the FT of the EXAFS function beyond the nearest oxygen neighbors indicates that the films by and large do not display long range order. In similar studies, the Fourier transform of the k3-weighted Ru K-edge EXAFS of electrodeposited RuO2 films recorded in situ were characterized by two shells attributed to Ru-O and Ru-Ru interactions at 1.94(1) and 3.12(2) A, in agreement with results obtained ex situ for Ru4+ in hydrous RuO2, whereas films in the reduced state yielded a single Ru-O interaction shell at 2.02(1) A. Extensions of these in situ XAS to the study of electrocatalysts for the nitrite reduction made it possible to identify and characterize the electronic and structural properties of a nitrosyl iron porphyrin adduct adsorbed on an electrode surface via the analysis of Fe K-edge XAS data. The effects of Se and S ad-atoms on the electrocatalytic activity of Pt electrodes have been examined using RRDE techniques. In acid, within a rather narrow range of coverages, both S- and Se-modified Pt surfaces promote the 2-electron reduction of dioxygen to hydrogen peroxide at ca. 100% faradaic efficiency over a wide potential region. Also developed were methods for immobilizing unsupported dispersed high area Pt particles a glassy carbon (GC) disk of a rotating Pt(ring)/GC(disk) electrode assembly allowing electrochemical measurements to be performed under forced convection with only minimal losses of Pt from the surface.

Mo, Yibo

144

Ultrafast proton-coupled electron transfer in heterogenous photocatalysis  

NASA Astrophysics Data System (ADS)

At metal-oxide/protic-solvent interfaces, partially hydrated or "wet electron" states represent the lowest energy pathway for electron transfer. Here we study the photoinduced charge transfer at the H IIO/TiO II(110) interface by means of timeresolved two-photon photoemission spectroscopy and electronic structure theory. At ~1 monolayer coverage of H IIO on partially hydroxylated TiO II surfaces we find an unoccupied electronic state 2.4+/-0.1 eV above the Fermi level. Density functional theory shows this to be a two-dimensional "wet electron" state, which is distinct from hydrated electrons observed on water-covered metal surfaces. The decay of electrons from the wet electron state by the resonant charge transfer to the conduction band of TiO II occurs in <=15 femtoseconds. Similar unoccupied electronic structure is observed for CH 3OH covered TiO II(110) surfaces; however, the electron dynamics are considerably more complex. The wet electron state dynamics of CH 3OH/TiO II exhibit both energy and population decay. The excited state lifetime is strongly coverage dependent increasing to >100 fs range above 1 ML CH 3OH coverage. Significantly, a pronounced deuterium isotope effect (CH 3OD) indicates a strong correlation between the interfacial electron transfer and the motion of protons in the molecular overlayer.

Zhao, Jin; Onda, Ken; Li, Bin; Petek, Hrvoje

2006-09-01

145

PHOTOELECTROCHEMISTRY AND PHOTOCATALYSIS IN NANOSCALE INORGANIC CHEMICAL SYSTEMS  

SciTech Connect

The goal of our DOE-supported research has been to explore the use of solid state materials as organizing media for, and as active components of, artificial photosynthetic systems. In this work we strive to understand how photoinduced electron and energy transfer reactions occur in the solid state, and to elucidate design principles for using nanoscale inorganic materials in photochemical energy conversion schemes. A unifying theme in this project has been to move beyond the study of simple transient charge separation to integrated chemical systems that can effect permanent charge separation in the form of energy-rich chemicals. This project explored the use of zeolites as organizing media for electron donor-acceptor systems and artificial photosynthetic assemblies. Layer-by-layer synthetic methods were developed using lamellar semiconductors, and multi-step, visible light driven energy/electron transfer cascades were studied by transient specroscopic techniques. By combining molecular photosensitizers with lamellar semiconductors and intercalated catalyst particles, the first non-sacrificial systems for visible light driven hydrogen evolution were developed and studied. Oxygen evolving catalyst particles and semiconductor nanowires were also studied with the goal of achieving photocatalytic water splitting using visible light.

Thomas E. Mallouk

2007-05-27

146

On the genesis of heterogeneous photocatalysis: a brief historical perspective in the period 1910 to the mid-1980s.  

PubMed

The concept Photocatalysis and, of greater import here, Heterogeneous Photocatalysis were first introduced in the second decade (1910-1920) of the 20th century according to the CAPLUS and MEDLINE databases (SciFinder). This review reports a brief historical perspective on the origins of the two concepts, whether implied or explicitly stated, in some detail up to about the mid-1980s when heterogeneous photocatalysis witnessed the beginning of an exponential growth, with particular emphasis on the use of nanosized TiO(2) particles in powdered form as the (so-called) photocatalyst of choice in environmental applications because of its inherent properties of abundance and chemical stability in acidic and alkaline aqueous media (in the dark), in contrast to ZnO that had been the metal oxide of choice in the early days. The early workers in this area often used the term photosensitization rather than the current popular term photocatalysis, used since the early 1980s. The term Photocatalysis appeared in the literature as early as 1910 in a book by Plotnikow (Russia) and a few years later it was introduced in France by Landau. The review also reports on contributions during the early years by Terenin at the University of St. Petersburg (previously Leningrad, Soviet Union), and in the decade spanning 1975-1985 contributions by Bard's group at the University of Texas at Austin (USA) as well as those of other groups. Some activities into the conversion of light energy to chemical fuels (e.g. H(2)) during the 1975-1985 decade are also considered. PMID:22488180

Serpone, N; Emeline, A V; Horikoshi, S; Kuznetsov, V N; Ryabchuk, V K

2012-07-01

147

[Preparation, characterization and photocatalysis of Bi2WO6 nanocrystals].  

PubMed

In the present study, bismuth tungstate (Bi2WO6) nanocrystals were prepared by the hydrothermal method using bismuth nitrate (Bi(NO3)3 x 5H2O) and sodium tungstate (Na2WO4 x 2H2O) as raw materials at 150 degrees C for 24 h. The powder X-ray diffraction (XRD) pattern shows that the Bi2WO6 nanocrystals belong to the orthorhombic phase with calculated lattice constants a = 5.457 angstroms, b = 16.435 angstroms and c = 5.438 angstroms. The X-ray photoelectron spectra (XPS) indicate that the obtained Bi2WO6 was pure. The photocatalytic activity of the nanocrystal prepared by using water, N, N-dimethyl formamide (DMF) and ethylene glycol (EG) as the solvent respectively were studied for the degradation of rhodamine B under visible light irradiation. The results show that Bi2WO6 sample obtained in EG has the best photocatalytic activity mainly owing to good dispersion, small particle size and broader spectrum response for visible light. In addition, the influence of pH and surfactant on the Bi2WO6 photocatalytic activity was also studied. The results show that Bi2WO6 sample has better photocatalytic activity when prepared at 150 degrees C and pH 1.0 with sodium dodecylsulfate (SDS) as the surfactant. The photoluminescence (PL) spectra of the prepared Bi2WO6 reveal that the recombination of photo-generated electrons and holes was inhibited over Bi2WO6 prepared with SDS and thus its photocatalytic ability was enhanced. PMID:23905341

Xia, Jia-Wei; Zhang, Yue; Lu, Lei; Han, Qiao-Feng

2013-05-01

148

Enhancement of titanium dioxide photocatalysis with polyhydroxy fullerenes  

NASA Astrophysics Data System (ADS)

Semiconductor photocatalysts, particularly TiO2, are attracting extensive research for destruction of environmentally hazardous chemicals (e.g., organic pollutants, greenhouse gases) and hazardous bioparticulates (e.g., bacterial endospores, emerging pathogens) because they can achieve complete mineralization without generation of toxic byproducts. Several attempts have been made to improve the quantum efficiency of TiO2 by conjugating it with conductors such as metals and organic molecules for scavenging the photo-generated electrons. Another class of materials well known for their electron accepting properties is carbon nanotubes and fullerenes. TiO2 (anatase polymorph) was coated on multi-wall carbon nanotubes by sol-gel coating and the resulting nanocomposites were found to inactivate bacterial endospores two times faster than Degussa P25 (gold standard), but were ineffective against Escherichia coli. This was attributed to their high aspect ratio, which prevented contact with the fimbriae covered cell-wall of E. coli. Water-soluble and non-toxic polyhydroxy fullerenes (PHF) were employed as alternate to the TiO2 coated MWNT. Adsorption of PHF molecules onto TiO2 by electrostatic interaction was demonstrated. PHF-TiO 2 nanocomposites enhanced the photocatalytic activity of TiO2 for dye degradation and E. coli inactivation. Surface coverage of TiO2 nanoparticles by PHF molecules determined the extent of enhancement, with an optimum at 2--7% surface coverage. The rate of photocatalytic dye degradation by the TiO2-PHF nanocomposite was 2.6 times the rate found with TiO2 alone. The hypothesis that scavenging of photo-generated electrons and therefore higher generation of hydroxyl radicals is the mechanism for the observed enhancement was validated. The concentration of hydroxyl radicals generated by PHF-TiO 2 nanocomposite was up to 60% greater than the concentration obtained with TiO2 alone as determined with EPR. Influence of functional groups of PHF on its electron scavenging ability and stability was determined. Fresh and aged forms of PHF were characterized by MS, FTIR, XPS and TGA. Higher concentrations of impure groups were detrimental to stability and electron scavenging ability of PHF. A ratio of impure groups to hydroxyl groups of 0.27 was associated with successful enhancement by PHF, whereas a ratio of 1.66 was associated with no enhancement. Guidelines for effective formulation of PHF-TiO2 nanocomposites were developed.

Krishna, Vijay B.

149

The Adsorption of BiIII/Pt Nanocomposites at Platinum Electrode with Highly Enhanced Electrocatalysis Toward Glucose  

NASA Astrophysics Data System (ADS)

In this paper, we first fabricated a nanoPt modified platinum electrode. Then through a simple method, the electrode surface was introduced with a submonolayer of bismuth that acted as an effective promoter. Cyclic voltammetry and other characterizations were employed. The obtained BiIII/nanoPt/Pt electrode exhibited two greatly increased oxidation peaks at negative and positive potential areas, respectively. The signals were far larger than that of platinum electrode because of the large true surface area of nanoparticles and the catalysis of bismuth adsorbed on platinum. In the presence of bismuth, the platinum active sites could combine with more OH- from bismuth hydroxyl to form a new active site for the oxidation of glucose. The prepared BiIII/nanoPt/Pt electrode given high sensitivity and excellent linearship to glucose detection and showed the potential application in the areas of electrocatalysis or electroanalysis.

Yang, Zhuoyuan; Miao, Yuqing; Wang, Tianrui; Xiao, Mingshu; Liang, Xiaocai; Yang, Yang; Li, Weiwei

2014-05-01

150

Growth of non-phototrophic microorganisms using solar energy through mineral photocatalysis.  

PubMed

Phototrophy and chemotrophy are two dominant modes of microbial metabolism. To date, non-phototrophic microorganisms have been excluded from the solar light-centered phototrophic metabolism. Here we report a pathway that demonstrates a role of light in non-phototrophic microbial activity. In lab simulations, visible light-excited photoelectrons from metal oxide, metal sulfide, and iron oxide stimulated the growth of chemoautotrophic and heterotrophic bacteria. The measured bacterial growth was dependent on light wavelength and intensity, and the growth pattern matched the light absorption spectra of the minerals. The photon-to-biomass conversion efficiency was in the range of 0.13-1.90‰. Similar observations were obtained in a natural soil sample containing both bacteria and semiconducting minerals. Results from this study provide evidence for a newly identified, but possibly long-existing pathway, in which the metabolisms and growth of non-phototrophic bacteria can be stimulated by solar light through photocatalysis of semiconducting minerals. PMID:22473012

Lu, Anhuai; Li, Yan; Jin, Song; Wang, Xin; Wu, Xiao-Lei; Zeng, Cuiping; Li, Yan; Ding, Hongrui; Hao, Ruixia; Lv, Ming; Wang, Changqiu; Tang, Yueqin; Dong, Hailiang

2012-01-01

151

Nanostructure sensitization of transition metal oxides for visible-light photocatalysis  

PubMed Central

Summary To better utilize the sunlight for efficient solar energy conversion, the research on visible-light active photocatalysts has recently attracted a lot of interest. The photosensitization of transition metal oxides is a promising approach for achieving effective visible-light photocatalysis. This review article primarily discusses the recent progress in the realm of a variety of nanostructured photosensitizers such as quantum dots, plasmonic metal nanostructures, and carbon nanostructures for coupling with wide-bandgap transition metal oxides to design better visible-light active photocatalysts. The underlying mechanisms of the composite photocatalysts, e.g., the light-induced charge separation and the subsequent visible-light photocatalytic reaction processes in environmental remediation and solar fuel generation fields, are also introduced. A brief outlook on the nanostructure photosensitization is also given.

Chen, Hongjun

2014-01-01

152

The inactivation of phages MS2, ?X174 and PR772 using UV and solar photocatalysis.  

PubMed

The photolytic and photocatalytic disinfection of three bacteriophages (MS2, ?X174 and PR772) under both artificial UV irradiation and natural sunlight was studied. A large variation was seen in the relative responses of phages to the two light sources, while solar photocatalysis showed promising disinfection capabilities for all three phages. Under artificial UV, the resistance of phages to both photolytic and artificial treatment was found to decrease in the following order: PR772>?X174>MS2. Indeed, 3-log inactivation of PR772 was not achieved after 25 h of illumination in either the absence or presence of catalyst. Under solar treatment, PR772 was inactivated far more readily, 3-log inactivation being achieved within an hour in the presence of catalyst in two trials. It is thought that the variation in solar intensity during the trials had a major effect on disinfection rates, as kinetics for phages varied considerably under different weather conditions. PMID:22218135

Misstear, David B; Gill, Laurence W

2012-02-01

153

The photocatalysis and mechanism of new SrTiO3/TiO2  

NASA Astrophysics Data System (ADS)

The SrTiO3/TiO2 was obtained via hydrothermal and sol-gel method and the optimal proportion (5wt %) was confirmed. The compounds have been characterized by XRD, UV-vis DRS, TEM and XPS. The photocatalytic degradation toward gas-phase benzene is almost 40% under UV irradiation, much better than pure TiO2 and SrTiO3. Besides, the SrTiO3/TiO2 also possessed outstanding performance toward methyl orange in liquid-phase testing. Finally, the electro-chemistry and electron spin-resonance spectroscopy (ESR) provided evidence that the improved photocatalysis is attributed to (1) the matching energy band which can transfer charge carriers efficiently and (2) enhanced generation of photo-electron and free radicals.

Wang, Lei; Wang, Zhijun; Wang, Donghui; Shi, Xicheng; Song, Hua; Gao, Xiaoqiang

2014-05-01

154

Dielectric Barrier Discharge Plasma-Induced Photocatalysis and Ozonation for the Treatment of Wastewater  

NASA Astrophysics Data System (ADS)

The physicochemical processes of dielectric barrier discharge (DBD) such as in-situ formation of chemically active species and emission of ultraviolet (UV)/visible light were utilized for the treatment of a simulated wastewater formed with Acid Red 4 as the model organic contaminant. The chemically active species (mostly ozone) produced in the DBD reactor were well distributed in the wastewater using a porous gas diffuser, thereby increasing the gas-liquid contact area. For the purpose of making the best use of the light emission, a titanium oxide-based photocatalyst was incorporated in the wastewater treating system. The experimental parameters chosen were the voltage applied to the DBD reactor, the initial pH of the wastewater, and the concentration of hydrogen peroxide added to the wastewater. The results have clearly shown that the present system capable of degrading organic contaminants in two ways (photocatalysis and ozonation) may be a promising wastewater treatment technology.

Mok, Young Sun; Jo, Jin-Oh; Lee, Heon-Ju

2008-02-01

155

Fundamental aspects of electrocatalysis of the hydrogen electrode reaction and oxygen electrode reaction on platinum  

NASA Astrophysics Data System (ADS)

This dissertation work studies the fundamental aspects of the electrocatalysis of the hydrogen electrode reaction (HER) and oxygen electrode reaction (OER) on platinum over a wide temperature range from ambient up to 220°C. Previously, the majority of the work reported was restricted to temperatures below 70°C due to apparatus constraints, whereas the current operation temperature for proton exchange membrane fuel cells is around 100oC and is envisioned to operate at even higher temperatures. In this work, a special apparatus for controlled hydrodynamic study was constructed, which can keep the system in a single aqueous phase at elevated temperatures. The growth kinetics and mechanism of the anodic oxide film on platinum are studied under potential sweep conditions. By fitting the current equation derived based on the framework of the point defect model (PDM) on the linear polarization curves, the kinetic parameters for film growth and dissolution are extracted, which agree well with other findings. The kinetics and mechanism of the HER are investigated both at ambient temperature with a rotating ring disk electrode and at elevated temperatures with a platinized nickel electrode. Ambient results by micropolarization analysis agree well with findings in literature, and yield an exchange current density on the order of mA/cm2. An activation energy of 17.3kJ/mol is determined. This is comparable with that of a bulk platinum electrode, and is lower than sputtered platinum and single crystal platinum electrodes in alkaline solutions. Surprisingly, the apparent Tafel slope of the hydrogen evolution reaction is almost temperature independent. The most probable reason is that two parallel reactions with different activation energy and transfer coefficients are occurring at the interface. The OER on platinum is also studied by potential sweep method and potentiostatic polarization method. The sluggish nature of this reaction is postulated to be due to the existence of a thin oxide layer on the electrode surface so that the electrons resides in the metal have to quantum mechanically tunnel (QMT) through this layer in order to reach the oxygen species in the solution or adsorbed on the surface. The exponential decay of the current with potential (the inverse Tafel's law) upon the formation of an oxide film can be accounted for by combining QMT theory for charge transfer across an interface and the PDM for film growth and dissolution. A new method for extremely thin oxide film thickness measurement is also developed by combining these two theories. This method employs the tunneling current of the hydrogen oxidation reaction as a probe and is demonstrated to be a very sensitive and convenient in situ technique. However, currently the thickness range that can be measured is limited to 1-2nm, since the passive current of platinum imposing a lower limit of the tunneling current that can be measured. The tunneling constant, which defines the blocking character of the film, is measured to be (0.57 +/- 0.035) x 108cm-1, and is temperature independent. A barrier height of 0.31eV at the film/solution interface is then yielded. Theoretical interpretation is implemented by developing a model for the electronic structure of the metal/barrier layer/solution interphase utilizing the Boltzmann's distribution law for the distribution of the energy states of the redox species in the solution phase and by noting that the barrier layer is a highly doped (and probably degenerate) defect (oxygen vacancy) semiconductor, having a Debye length that is the same order as the thickness of the film.

Bao, Jianer

156

Intimate coupling of photocatalysis and biodegradation in a photocatalytic circulating-bed biofilm reactor.  

PubMed

Coupling advanced oxidative pretreatment with subsequent biodegradation demonstrates potential for treating wastewaters containing biorecalcitrant and inhibitory organic constituents. However, advanced oxidation is indiscriminate, producing a range of products that can be too oxidized, unavailable for biodegradation, or toxic themselves. This problem could be overcome if advanced oxidation and biodegradation occurred together, an orientation called intimate coupling; then, biodegradable organics are removed as they are formed, focusing the chemical oxidant on the non-biodegradable fraction. Intimate coupling has seemed impossible because the conditions of advanced oxidation, for example, hydroxyl radicals and sometimes UV-light, are severely toxic to microorganisms. Here, we demonstrate that a novel photocatalytic circulating-bed biofilm reactor (PCBBR), which utilizes macro-porous carriers to protect biofilm from toxic reactants and UV light, achieves intimate coupling. We demonstrate the viability of the PCBBR system first with UV only and acetate, where the carriers grew biofilm and sustained acetate biodegradation despite continuous UV irradiation. Images obtained by scanning electron microscopy and confocal laser scanning microscopy show bacteria living behind the exposed surface of the cubes. Second, we used slurry-form Degussa P25 TiO2 to initiate photocatalysis of inhibitory 2,4,5-trichlorophenol (TCP) and acetate. With no bacterial carriers, photocatalysis and physical processes removed TCP and COD to 32% and 26% of their influent levels, but addition of biofilm carriers decreased residuals to 2% and 4%, respectively. Biodegradation alone could not remove TCP. Photomicrographs clearly show that biomass originally on the exterior of the carriers was oxidized (charred), but biofilm a short distance within the carriers was protected. Finally, we coated TiO2 directly onto the carrier surface, producing a hybrid photocatalytic-biological carrier. These carriers likewise demonstrated the concept of photocatalytic degradation of TCP coupled with biodegradation of acetate, but continued TCP degradation required augmentation with slurry-form TiO2. PMID:18512737

Marsolek, Michael D; Torres, César I; Hausner, Martina; Rittmann, Bruce E

2008-09-01

157

Mono- and co-doped NaTaO3 for visible light photocatalysis.  

PubMed

Electronic structures of doped NaTaO3 compounds are of significant interest to visible light photocatalysis. This work involves the study of the band gap, band edge potentials, and thermodynamic stability of certain mono-doped and co-doped NaTaO3 systems, using DFT-PBE as well as hybrid (PBE0) functional calculations. Doping of certain non-magnetic cations (Ti, V, Cu, Zn, W, In, Sn, Sb, Ce, and La), certain anions (N, C, and I), and certain co-dopant pairs (W-Ti, W-Ce, N-I, N-W, La-C, Pb-I, and Cu-Sn) is investigated. Our calculations suggest that substitutional doping of Cu at the Ta site, Cu at the Na site, and C at the O site narrows the band gap of NaTaO3 to 2.3, 2.8, and 2.1 eV, respectively, inducing visible light absorption. Additionally, passivated co-doping of Pb-I and N-W narrows the band gap of NaTaO3 to the visible region, while maintaining the band potentials at favorable positions. Hybrid density of states (DOS) accurately describe the effective band potentials and the location of mid-gap states, which shed light on the possible mechanism of photoexcitation in relation to the photocatalysis reactions. Furthermore, the thermodynamic stability of the doped systems and defect pair binding energies of co-doped systems are discussed in detail. The present results provide useful insights into designing new photocatalysts based on NaTaO3. PMID:24965846

Kanhere, Pushkar; Shenai, Prathamesh; Chakraborty, Sudip; Ahuja, Rajeev; Zheng, Jianwei; Chen, Zhong

2014-07-01

158

Molecular-Level Insights into Photocatalysis from Scanning Probe Microscopy Studies on TiO2(110)  

SciTech Connect

The field of heterogeneous photocatalysis has grown considerably in the decades since Fujishima and Honda's ground-breaking publications of photoelectrochemistry on TiO2. Numerous review articles continue to point to both progress made in the use of heterogeneous materials (such as TiO2) to perform photoconversion processes, and the many opportunities and challenges in heterogeneous photocatalysis research such as solar energy conversion and environmental remediation. The past decade has also seen an increase in the use of molecular-level approaches applied to model single crystal surfaces in an effort to obtain new insights into photocatalytic phenomena. In particular, scanning probe techniques (SPM) have enabled researchers to take a ‘nanoscale’ approach to photocatalysis that includes interrogation of the reactivities of specific sites and adsorbates on a model photocatalyst surface. The rutile TiO2(110) surface has become the prototypical oxide single crystal surface for fundamental studies of many interfacial phenomena. In particular, TiO2(110) has become an excellent model surface for probing photochemical and photocatalytic reactions at the molecular level. A variety of experimental approaches have emerged as being ideally suited for studying photochemical reactions on TiO2(110), including desorption-oriented approaches and electronic spectroscopies, but perhaps the most promising techniques for evaluating site-specific properties are those of SPM. In this review, we highlight the growing use of SPM techniques in providing molecular-level insights into surface photochemistry on the model photocatalyst surface of rutile TiO2(110). Our objective is to both illustrate the unique knowledge that scanning probe techniques have already provided the field of photocatalysis, and also to motivate a new generation of effort into the use of such approaches to obtain new insights into the molecular level details of photochemical events occurring at interfaces. Discussion will start with an examination of how scanning probe techniques are being used to characterize the TiO2(110) surface in ways that are relevant to photocatalysis. We will then discuss specific classes of photochemical reaction on TiO2(110) for which SPM has proven indispensible in providing unique molecular-level insights, and conclude with discussion of future areas in which SPM studies may prove valuable to photocatalysis on TiO2. This work was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. I.L. was partially supported by a Pacific Northwest National Laboratory (PNNL) Chemical Imaging Initiative project. PNNL is a multiprogram national laboratory operated for DOE by Battelle.

Henderson, Michael A.; Lyubinetsky, Igor

2013-06-12

159

Heterogeneous photocatalysis  

Microsoft Academic Search

The presence of transition metal ions in photocatalytic reactions is reviewed according to two main approaches: (a) the influence of transition metal ions on the rate of photocatalytic reactions (mainly oxidation) and (b) the transformation of the ions to less toxic species or their deposition on the semiconductor catalyst surface for recovery of expensive and useful metals. Most of the

Marta I. Litter

1999-01-01

160

MUTAGENICITY ASSESSMENT OF PRODUCED WATER DURING PHOTOELECTROCATALYTIC DEGRADATION  

Microsoft Academic Search

Oilfield produced water was treated by photocatalysis, electro-oxidation, and photoelectrocatalysis, respectively. The chemical composition and toxicity of the raw effluent and treated products were assessed by chemical and mutagenicity analysis. The raw effluent exhibited mutagenic activity in both strains of Salmonella typhimurium. The lowest concentration of the dichlo- romethane extract capable of inducing a positive response in strains TA98 and

Guiying Li; Taicheng An; Xiangping Nie; Guoying Sheng; Xiangying Zeng; Jiamo Fu; Zheng Lin; Eddy Y. Zeng

2007-01-01

161

Size-tunable fabrication of multifunctional Bi2O3 porous nanospheres for photocatalysis, bacteria inactivation and template-synthesis  

NASA Astrophysics Data System (ADS)

Multifunctional Bi2O3 porous nanospheres (PNs) with tunable size have been successfully synthesized via a facile solvothermal method. The obtained Bi2O3 porous nanospheres demonstrate outstanding performance in visible-light-driven photocatalysis for Cr(vi) and organic dye removal, inactivation of Gram-negative and Gram-positive bacteria, as well as template-synthesis for fabrication of bismuth-related hollow nanostructures.Multifunctional Bi2O3 porous nanospheres (PNs) with tunable size have been successfully synthesized via a facile solvothermal method. The obtained Bi2O3 porous nanospheres demonstrate outstanding performance in visible-light-driven photocatalysis for Cr(vi) and organic dye removal, inactivation of Gram-negative and Gram-positive bacteria, as well as template-synthesis for fabrication of bismuth-related hollow nanostructures. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr06870f

Qin, Fan; Zhao, Huiping; Li, Guangfang; Yang, Hao; Li, Ju; Wang, Runming; Liu, Yunling; Hu, Juncheng; Sun, Hongzhe; Chen, Rong

2014-04-01

162

Laser-enhanced photocatalytic degradation of organic pollutants from water using ZnO semiconductor catalyst  

Microsoft Academic Search

Wastewater contaminated with organic pollutants creates serious environmental problems. Laser induced photocatalysis has been investigated for removal of organic pollutant like phenol from water. The important mechanism for degradation of phenol by UV laser irradiation is redox reactions triggered by semiconductor catalyst in presence of water. In this study the potential of a ZnO semiconductor catalyst has been explored as

Mohammed A. Gondal; Mohammad N. Sayeed

2007-01-01

163

Summary of engineering-scale experiments for the Solar Detoxification of Water project  

Microsoft Academic Search

This report contains a summary of large-scale experiments conducted at Sandia National Laboratories under the Solar Detoxification of Water project. The objectives of the work performed were to determine the potential of using solar radiation to destroy organic contaminants in water by photocatalysis and to develop the process and improve its performance. For these experiments, we used parabolic troughs to

J. E. Pacheco; L. Yellowhorse

1992-01-01

164

Size-tunable fabrication of multifunctional Bi2O3 porous nanospheres for photocatalysis, bacteria inactivation and template-synthesis.  

PubMed

Multifunctional Bi2O3 porous nanospheres (PNs) with tunable size have been successfully synthesized via a facile solvothermal method. The obtained Bi2O3 porous nanospheres demonstrate outstanding performance in visible-light-driven photocatalysis for Cr(VI) and organic dye removal, inactivation of Gram-negative and Gram-positive bacteria, as well as template-synthesis for fabrication of bismuth-related hollow nanostructures. PMID:24710180

Qin, Fan; Zhao, Huiping; Li, Guangfang; Yang, Hao; Li, Ju; Wang, Runming; Liu, Yunling; Hu, Juncheng; Sun, Hongzhe; Chen, Rong

2014-05-21

165

A decade of heterogeneous photocatalysis in our laboratory: Pure and applied studies in energy production and environmental detoxification  

Microsoft Academic Search

Heterogeneous Photocatalysis (HP) has been examined and explored as a potentially viable alternative technology to classical\\u000a “best” technologies in both environmental detoxification and in energy production. Both fundamental and applied investigations\\u000a have been pursued over the last decade (1983–1993). This novel technology employs illuminated semiconductor materials as photocatalysts\\u000a such as CdS and TiO2 to produce both reducing and highly oxidizing

Nick Serpone

1994-01-01

166

The study of photocatalysis under ultraviolet + visible two-beam light irradiation using undoped nano-titanium dioxide  

Microsoft Academic Search

The nano-TiO2 powder was synthesized using wet chemical method and characterized by X-ray diffraction (XRD), Raman spectroscopy, Brunauer–Emmett–Teller (BET), and transmission electron microscope (TEM). The photodegradation of aqueous methyl orange and phenol under the irradiation of visible, ultraviolet (UV), and UV+visible lights was used to evaluate the photocatalytic activity of nano-TiO2 powder prepared. It is found that the photocatalysis under

Baoshun Liu; Liping Wen; Xiujian Zhao

2008-01-01

167

Hybrid processes coupling photocatalysis and membranes for degradation of organic pollutants in water  

Microsoft Academic Search

Tests of degradation in a photocatalytic membrane system with the lamp immersed in the suspension inside the photoreactor have been carried out by using polycrystalline TiO2 (Degussa P25) as catalyst and humic acids, organic dyes, 4-nitrophenol as pollutants. The influence of the type of nanofiltration membrane, initial concentration of pollutant and pH on the photodegradation rate was investigated in discontinuous

Raffaele Molinari; Michelangelo Borgese; Enrico Drioli; Leonardo Palmisano; Mario Schiavello

2002-01-01

168

UV\\/VIS LIGHT-ENHANCED PHOTOCATALYSIS FOR WATER TREATMENT AND PROTECTION  

Microsoft Academic Search

Applied research data on advanced photocatalytic methods aimed at treatment of contaminated aqueous phase is presented. Phenol\\u000a and chloroorganic pesticides (as model compounds) besides actual wastewater samples were UVphotodegraded using suspended TiO2 or UV\\/H2O2\\/air systems. Titanium dioxide catalysts modified with non-metal elements were used to photodegrade phenols in visible light.\\u000a Laboratory and pilot scale reactors were used and the effect

Jan Hupka; Adriana Zaleska; Marcin Janczarek; Ewa Kowalska; Paulina Górska; Robert Aranowski

169

Comparative evaluation of acute toxicity by Vibrio fischeri and fern spore based bioassays in the follow-up of toxic chemicals degradation by photocatalysis.  

PubMed

The development of efficient bioassays is a necessary step for cost-effective environmental monitoring and evaluation of novel decontamination technologies. Marine Vibrio fischeri kits have demonstrated to be extremely sensitive but lack of ecological relevance, especially when assessing impacts on freshwater higher organisms. A novel riparian are fern spore microbioassay could merge higher ecological relevance and reduced costs. The aim of this work is the comparative evaluation of the V. fischeri and fern spore bioassays for the follow up of detoxification processes of water contaminated with cyanide and phenol by advanced oxidation technologies, using heterogeneous photocatalysis as example. In both cases, EC(50) values differed significantly for V. fischeri commercial kit, V. fischeri lab cultures and Polystichum setiferum fern spores (1.9, 16 and 101 mg cyanide L(-1) and 27.0, 49.3 and 1440 mg phenol L(-1), respectively). Whereas V. fischeri bioassays are extremely sensitive and dilution series must be prepared, toxicant solutions can be directly applied to spores. Spore microbioassay was also useful in the follow up of photoxidation processes of cyanide and phenol, also reflecting the formation of intermediate degradation by-products even more toxic than phenol. We conclude that this new microbioassay is a promising cost-effective tool for the follow up of decontamination processes. PMID:22341980

Marugán, Javier; Bru, David; Pablos, Cristina; Catalá, Myriam

2012-04-30

170

NF-TiO? photocatalysis of amitrole and atrazine with addition of oxidants under simulated solar light: emerging synergies, degradation intermediates, and reusable attributes.  

PubMed

In order to investigate sustainable alternatives to current water treatment methods, the effect of NF-titania film thickness and subsequent photocatalysis in combination with oxidants was examined under simulated solar light. Such a combination presents a theoretical possibility for a synergistic interaction between the photocatalyst and the oxidant (activation of the oxidant by the catalyst under conditions under which it may not conventionally be activated). To investigate, peroxymonosulfate (PMS) and persulfate (PS) were used as oxidants, and two pesticides, amitrole and atrazine, were used as target contaminants. In the absence of a film, activation of PMS under simulated solar conditions is demonstrated by removal of atrazine, whereas PS provided minimal removal, suggesting inefficient activation. Combining photocatalytic films with PMS and PS manifested synergies for both oxidants. The effect was most pronounced for PS since PMS already underwent significant activation without the photocatalyst. Amitrole degradation results indicated a lack of removal of amitrole by activated PS alone, suggesting that this sulfate radical-based treatment technology may be ineffective for the removal of amitrole. The NF-TiO? films demonstrated reusability under solar light both with and without oxidants. Finally, the degradation intermediates were analyzed, and a new intermediate appeared upon incorporating oxidants into the system. PMID:23811632

Andersen, Joel; Pelaez, Miguel; Guay, Lisa; Zhang, Zhaohong; O'Shea, Kevin; Dionysiou, Dionysios D

2013-09-15

171

TiO2 Hollow Spheres: One-Pot Synthesis and Enhanced Photocatalysis  

NASA Astrophysics Data System (ADS)

Hollow TiO2 microspheres were successfully fabricated by metal salts with low solubility in ethanol acting as intelligent templates using a simple one-pot solvothermal method. Hollow spheres with large diameter were obtained using CuSO4?5H2O as templates while small ones were obtained using Sr(NO3)2 as templates. It is found that titanium precursor plays an important role for the morphology of samples. Solid TiO2 microspheres were prepared by using titanium tetrabutoxide (TBT). In contrast, bowl-like hollow microspheres were obtained by using titanium tetrachloride (TiCl4). Furthermore, the amount of H2O can stimulate the hydrolysis rate of TiCl4 to form solid spheres. Compared with solid microspheres, hollow TiO2 microspheres depending on their interior cavity structure exhibited enhanced photocatalysis efficiency for the UV-light photodegradation of methyl orange. Quantificationally, the apparent photocatalytic degradation pseudo-first-rate constant of the hollow microspheres is 1.25 times of that of the solid ones.

Jia, Changchao; Cao, Yongqiang; Yang, Ping

2013-06-01

172

Synthesis of nanotitania decorated few-layer graphene for enhanced visible light driven photocatalysis.  

PubMed

We report a simple method for decorating carboxyl functionalized few-layer graphene with titania (TiO2) nanoparticles by sonication and stirring under room temperature. The nanocomposites showed a remarkable improvement in visible light driven photocatalysis. From Raman and XRD analysis the number of layers of graphene was found to be 3. The TiO2 decorated few-layer graphene (FLG) sheets were characterized by electron microscopy, Raman spectroscopy, infrared spectroscopy, XRD and UV-vis spectroscopy. Titania nanoparticles were uniformly decorated on FLG matrix. The incorporation of titania on FLG enhanced the visible light photocatalytic activity of titania, lowered the electron hole recombination and improved the electron hole mobility. The enhanced life time of the charge carriers was confirmed from the photocurrent measurements. Compared to bare TiO2 nanoparticles the FLG-TiO2 nanocomposites exhibited rapid degradation of Rhodamine B (Rhd B) under solar radiation. It was found that adsorption of dye molecules and the rate of degradation have been greatly enhanced in the FLG decorated with TiO2. The rapid degradation of Rhd B using carboxyl functionalized FLG-TiO2 within 8min under solar radiation and 20min under 30W UV tube with very low concentration (0.01wt.%) of the photocatalyst is the highlight of the present report. The mechanism of degradation and charge separation ability of the nanocomposite are also explored. PMID:24910056

Thomas, Reny Thankam; Abdul Rasheed, P; Sandhyarani, N

2014-08-15

173

Heterogeneous photo-catalysis system for the degradation of azo dye Reactive Black 5 (RB5).  

PubMed

This study investigated a heterogeneous photo-catalysis system by introducing a novel brick supported iron oxide (denoted as B1) for the heterogeneous photoassisted degradation of Reactive Black 5 (RB5) at pH value from 3 to 7 in a three-phase (gas-liquid-solid) fluidized bed reactor (3P-FBR). Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD) and N(2) adsorption/desorption were used to characterize the B1 catalyst. The in situ formation of hydrogen peroxide and the depletion of oxalic acid by photochemical cycle of Fe(III)-oxalate complex under UVA light (? = 365 nm) were studied. The effects of the solution pH and the concentration of oxalic acid on the degradation of RB5 are elucidated. About 90% decolourization was measured and 80% of the total organic carbon (TOC) was eliminated at pH 5.0 after 120 min for 20 mg/L RB5 in presence of 10 g/L B1 catalyst, 30 mg/L oxalic acid under 15 W UVA light. A mechanism for the photocatalytic degradation of RB5 over B1 catalyst is proposed. PMID:22233898

Huang, Yao-Hui; Wei, Hau-Cheng; Chen, Hung-Ta

2012-01-01

174

Crystalline metallic Au nanoparticle-loaded ?-Bi2O3 microrods for improved photocatalysis.  

PubMed

Crystalline metallic Au nanoparticles were loaded on ?-Bi(2)O(3) microrods (Au/?-Bi(2)O(3)) using an Au deposition-precipitation method. The prepared samples were characterized by scanning electron and transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and UV-vis diffuse reflectance spectroscopy. Upon visible light irradiation, the Au/?-Bi(2)O(3) exhibits much higher photocatalytic activities than the pure ?-Bi(2)O(3) for the degradation of Rhodamine B and 2,4-dichlorophenol in aqueous solution. The role of the Au and the paths of electron transport in the photocatalysis of the Au/?-Bi(2)O(3) were investigated and discussed in detail based on the analysis of the photo-generated hydroxyl radicals (?OH) and hydrogen peroxide (H(2)O(2)) in the visible light irradiated suspension of pure ?-Bi(2)O(3) and Au/?-Bi(2)O(3). The result reveals that the Au loaded on ?-Bi(2)O(3) plays a critical role in the separation of the electron and hole pairs by accumulating the electrons from the excited ?-Bi(2)O(3), which is responsible for the enhanced photocatalytic activity. PMID:22868636

Jiang, Hai-Ying; Cheng, Kun; Lin, Jun

2012-09-21

175

Silver decorated titanate/titania nanostructures for efficient solar driven photocatalysis  

NASA Astrophysics Data System (ADS)

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.

Gong, Dangguo; Ho, Weng Chye Jeffrey; Tang, Yuxin; Tay, Qiuling; Lai, Yuekun; Highfield, James George; Chen, Zhong

2012-05-01

176

Reduction of hexavalent chromium: photocatalysis and photochemistry and their application in wastewater remediation.  

PubMed

Hexavalent chromium present in wastewater discharge of galvanic industries is toxic to most microorganisms and potentially harmful to human health. This work examines the photochemical reduction of Cr(VI) with ethanol under ultraviolet (UV) and visible radiation, and photocatalytic reduction of Cr(VI) with TiO2 in the presence of ethanol under UV radiation. By means of different experimental designs, this study investigates the influence of the initial pH, ethanol amount, catalyst concentration and initial Cr(VI) concentration on total Cr(VI) reduction. The results obtained showed that photochemistry with ethanol under UV radiation (96.10%) was more efficient than photochemistry with ethanol under visible light (48.07%). Furthermore, photocatalysis with TiO2 in the presence of ethanol under UV radiation showed high values of total Cr(VI) reduction: 94.15%, under the optimal conditions established by the experimental design. Finally, experiments were carried out with wastewater discharge from an electroplating plant in its original concentration, and higher values of total Cr(VI) reduction were observed. PMID:25026579

Machado, Tiele Caprioli; Lansarin, Marla Azário; Matte, Natália

2014-01-01

177

The investigation of the LED-activated FeFNS-TiO2 nanocatalyst for photocatalytic degradation and mineralization of organophosphate pesticides in water.  

PubMed

This study evaluated the preparation and characterization of an efficient doped TiO2 as a novel catalyst for degradation of diazinon model pesticide using LED-activated photocatalysis. TiO2 was doped using N, NS, FeNS, and FeFNS. The FeFNS-doped TiO2 showed the highest catalytic activity in LED/photocatalysis. FeFNS-doped TiO2 is a mesoporous nanocrystal powder with a mean pore diameter of 10.2 nm, a specific surface area of 104.4 m(2)/g and a crystallite size of 6.7 nm. LED/photocatalysis using FeFNS-doped TiO2 improved diazinon degradation by 52.3% over that of as-made plain TiO2 at an optimum solution pH of 7. The diazinon degradation in LED/photocatalysis using FeFNS-doped TiO2 increased from 44.8% to 96.3% when the catalyst concentration increased from 25% to 300%at a reaction time of 100 min. The degradation and mineralization of diazinon during LED/photocatalysis with FeFNS-doped TiO2 catalyst followed the pseudo-first-order reaction model with the rate constants of 0.973 h(-1) and 0.541 h(-1), respectively. The FeFNS-doped TiO2 was found to be an efficient catalyst that was photoactivated using UV-LED lamps. LED/photocatalysis with FeFNS-doped TiO2 catalyst is a promising alternative to conventional UV/TiO2photocatalysis for producing free OH radicals for use in the degradation and mineralization of water toxic contaminants. PMID:24793111

Hossaini, Hiwa; Moussavi, Gholamreza; Farrokhi, Mehrdad

2014-08-01

178

Enhanced near-infrared photocatalysis of NaYF4:Yb, Tm/CdS/TiO2 composites.  

PubMed

The previous works by our group (Chem. Commun., 2010, 46, 2304-2306; ACS Catal., 2013, 3, 405-412; Phys. Chem. Chem. Phys., 2013, 15, 14681-14688) have reported the near-infrared-driven photocatalysis of broadband semiconductor TiO2 or ZnO that was combined with upconverting luminescence particles to form a core-shell structure. However, the photocatalytic efficiency is low for this new type of photocatalysts. In this work, NaYF4:Yb,Tm/CdS/TiO2 composites for NIR photocatalysis were prepared by linking CdS and TiO2 nanocrystals on the NaYF4:Yb,Tm microcrystal surfaces. CdS and TiO2 were well interacted to form a heterojunction structure. The energy transfer between NaYF4:Yb,Tm and the semiconductors CdS and TiO2 was investigated by steady-state and dynamic fluorescence spectroscopy. The photocatalytic activities of the as-prepared composites were evaluated by the degradation of methylene blue in aqueous solution upon NIR irradiation. Significantly, it was found that the united adhesions of CdS and TiO2 on the NaYF4:Yb,Tm particle surfaces showed much higher catalytic activities than the individual adhesion of CdS or TiO2 on the NaYF4:Yb,Tm surfaces. This was attributed mainly to the effective separation of the photogenerated electron-hole pairs due to the charge transfer across the CdS-TiO2 interface driven by the band potential difference between them. The presented composite structure of upconverting luminescence materials coupled with narrow/wide semiconductor heterojunctions provides a new model for improved NIR photocatalysis. PMID:24162269

Guo, Xingyuan; Di, Weihua; Chen, Changfeng; Liu, Chunxu; Wang, Xue; Qin, Weiping

2014-01-21

179

Superiority of solar Fenton oxidation over TiO2 photocatalysis for the degradation of trimethoprim in secondary treated effluents.  

PubMed

The overall aim of this work was to examine the degradation of trimethoprim (TMP), which is an antibacterial agent, during the application of two advanced oxidation process (AOP) systems in secondary treated domestic effluents. The homogeneous solar Fenton process (hv/Fe(2+)/H2O2) and heterogeneous photocatalysis with titanium dioxide (TiO2) suspensions were tested. It was found that the degradation of TMP depends on several parameters such as the amount of iron salt and H2O2, concentration of TiO2, pH of solution, solar irradiation, temperature and initial substrate concentration. The optimum dosages of Fe(2+) and H2O2 for homogeneous ([Fe(2+)] = 5 mg L(-1), [H2O2] = 3.062 mmol L(-1)) and TiO2 ([TiO2] = 3 g L(-1)) for heterogeneous photocatalysis were established. The study indicated that the degradation of TMP during the solar Fenton process is described by a pseudo-first-order reaction and the substrate degradation during the heterogeneous photocatalysis by the Langmuir-Hinshelwood kinetics. The toxicity of the treated samples was evaluated using a Daphnia magna bioassay and was finally decreased by both processes. The results indicated that solar Fenton is more effective than the solar TiO2 process, yielding complete degradation of the examined substrate within 30 min of illumination and dissolved organic carbon (DOC) reduction of about 44% whereas the respective values for the TiO2 process were ?70% degradation of TMP within 120 min of treatment and 13% DOC removal. PMID:23508150

Michael, I; Hapeshi, E; Michael, C; Fatta-Kassinos, D

2013-01-01

180

Design, modelling and experimentation of a new large-scale photocatalytic reactor for water treatment  

Microsoft Academic Search

Recent literature has demonstrated on a laboratory scale the potential of semiconductor photocatalysis technology to completely destroy organic pollutants present in water. However, to date no viable pilot plant exists using this technology. In this paper, a new reactor design is presented that addresses the two most important parameters, namely, light distribution inside the reactor and high specific surface area

Ajay K. Ray

1999-01-01

181

TiO2-Based Advanced Oxidation Nanotechnologies For Water Purification And Reuse  

EPA Science Inventory

TiO2 photocatalysis, one of the UV-based advanced oxidation technologies (AOTs) and nanotechnologies (AONs), has attracted great attention for the development of efficient water treatment and purification systems due to the effectiveness of TiO2 to generate ...

182

Self-doping and surface plasmon modification induced visible light photocatalysis of BiOCl  

NASA Astrophysics Data System (ADS)

In this study we demonstrate that self-doping and surface plasmon resonance could endow a wide-band-gap ternary semiconductor BiOCl with remarkable visible light driven photocatalytic activity on the degradation of organic pollutants and photocurrent generation properties. The self-doped BiOCl with plasmonic silver modification was synthesized by a facile one-pot nonaqueous approach and systematically characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-visible diffuse reflectance spectra, electron spin resonance, and X-ray photoelectron spectroscopy. The photocurrent enhancement was found to be intimately dependent on the irradiation wavelength and matched well with the intensity of the absorption of the Ag nanoparticles. Reactive species trapping experiments and electron spin resonance spectroscopy with 5,5-dimethyl-1-pyrroline-N-oxide spin-trapping adducts confirmed that more oxidative species could be generated from the photogenerated electrons due to the plasmon-excitation of the metallic Ag in the self-doped BiOCl with plasmonic silver modification, which is responsible for the great enhancement of photocatalytic activity and photocurrent. Surface photovoltage spectroscopy and time-resolved photoluminescence spectroscopy results revealed the transfer of plasmon-band-induced electrons from Ag nanoparticles into BiOCl and the acceleration effect of surface plasmon resonance-induced intense oscillating electric fields on this electron transfer. This study would not only provide direct evidence of plasmonic photocatalysis, but also shed light on the design of highly efficient metal-semiconductor composite photocatalysts.In this study we demonstrate that self-doping and surface plasmon resonance could endow a wide-band-gap ternary semiconductor BiOCl with remarkable visible light driven photocatalytic activity on the degradation of organic pollutants and photocurrent generation properties. The self-doped BiOCl with plasmonic silver modification was synthesized by a facile one-pot nonaqueous approach and systematically characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-visible diffuse reflectance spectra, electron spin resonance, and X-ray photoelectron spectroscopy. The photocurrent enhancement was found to be intimately dependent on the irradiation wavelength and matched well with the intensity of the absorption of the Ag nanoparticles. Reactive species trapping experiments and electron spin resonance spectroscopy with 5,5-dimethyl-1-pyrroline-N-oxide spin-trapping adducts confirmed that more oxidative species could be generated from the photogenerated electrons due to the plasmon-excitation of the metallic Ag in the self-doped BiOCl with plasmonic silver modification, which is responsible for the great enhancement of photocatalytic activity and photocurrent. Surface photovoltage spectroscopy and time-resolved photoluminescence spectroscopy results revealed the transfer of plasmon-band-induced electrons from Ag nanoparticles into BiOCl and the acceleration effect of surface plasmon resonance-induced intense oscillating electric fields on this electron transfer. This study would not only provide direct evidence of plasmonic photocatalysis, but also shed light on the design of highly efficient metal-semiconductor composite photocatalysts. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03597b

Jiang, Jing; Zhang, Lizhi; Li, Hao; He, Weiwei; Yin, Jun Jie

2013-10-01

183

Dramatic activities of vanadate intercalated bismuth doped LDH for solar light photocatalysis.  

PubMed

To harvest solar energy efficiently, a series of Zn/Bi layered double hydroxide (LDH) photocatalysts with different molar ratios of Zn/Bi (2?:?1, 3?:?1, 4?:?1) has been synthesized by a coprecipitation method at constant pH. All the Bi doped LDH samples displayed hydrotalcite-like structure with interlayer carbonate, in which crystallinity decreases as the bismuth content increases. The Zn/Bi (4?:?1) LDH with a small amount of bismuth in the brucite layer and possessing high crystallinity was further modified hydrothermally by intercalating decavanadate and it showed high photochemical stability and photocatalytic activity for the degradation of different organic pollutants for practical applications under solar light irradiation. The structural integrity of the materials has been successfully characterized by studying their structural, morphological, electronic and optical properties by various physico-chemical techniques. The present study provided an insight into oxo-bridged MMCT of the LDH and established that the Zn(ii)-O-Bi(iii) units resulted in the generation of superoxide radicals which is clearly observed by the EPR technique. The ?OH radicals formed during photocatalysis were revealed by means of the terephthalic acid fluorescence probe method. The photoelectrochemical measurement confirmed that the intercalated vanadate anion was crucial to obtain an optimal synergistic effect for the degradation of organic pollutants. The prolonged lifetime of photogenerated charges and improved charge transfer capability were confirmed by time-resolved fluorescence emission spectra. Furthermore, a detailed mechanism for the enhanced photocatalytic activity was discussed. PMID:25005613

Mohapatra, Lagnamayee; Parida, K M

2014-07-23

184

Energy recovery during advanced wastewater treatment: simultaneous estrogenic activity removal and hydrogen production through solar photocatalysis.  

PubMed

Simultaneous estrogenic activity removal and hydrogen production from secondary effluent were successfully achieved using TiO(2) microspheres modified with both platinum nanoparticles and phosphates (P-TiO(2)/Pt) for the first time. The coexistence of platinum and phosphate on the surface of TiO(2) microspheres was confirmed by transmission electron microscope, energy-dispersive X-ray and X-ray photoelectron spectroscopy analyses. P-TiO(2)/Pt microspheres showed a significantly higher photocatalytic activity than TiO(2) microspheres and TiO(2) powders (P25) for the removal of estrogenic activity from secondary effluent with the removal ratio of 100%, 58.2% and 48.5% in 200 min, respectively. Moreover, the marked production of hydrogen (photonic efficiency: 3.23 × 10(-3)) was accompanied by the removal of estrogenic activity only with P-TiO(2)/Pt as photocatalysts. The hydrogen production rate was increasing with decreased DO concentration in secondary effluent. Results of reactive oxygen species (ROS) evaluation during P-TiO(2)/Pt photocatalytic process showed that O(2)(-)and OH were dominant ROS in aerobic phase, while OH was the most abundant ROS in anoxic phase. Changes of effluent organic matter (EfOM) during photocatalysis revealed that aromatic, hydrophobic, and high molecular weight fractions of EfOM were preferentially transformed into non-humic, hydrophilic, and low MW fractions (e.g. aldehydes and carboxylic acids), which were continuously utilized as electron donors in hydrogen production process. PMID:23269320

Zhang, Wenlong; Li, Yi; Wang, Chao; Wang, Peifang; Wang, Qing

2013-03-01

185

Silver decorated titanate/titania nanostructures for efficient solar driven photocatalysis  

SciTech Connect

Photocatalysis has attracted significant interest to solve both the energy crisis and effectively combat environmental contamination. However, as the most widely used photocatalyst, titania (TiO{sub 2}) 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 Degree-Sign C) do not show significant activity under our conditions, while the one annealed at 450 Degree-Sign C shows fast-degradation of methyl orange (MO) under visible light irradiation. The detailed mechanisms are also discussed. - Graphical abstract: Silver nanoparticles decorated titanate/titania as visible light active photocatalysts: silver nanoparticles could be excited by visible light due to its surface plasmon effect and excited electrons could be transferred to the conduction band of the semiconductor, where the reduction process occurs. Highlights: Black-Right-Pointing-Pointer Uniform Ag nanoparticles are photo-reduced onto titanate and titania nanostructures. Black-Right-Pointing-Pointer Titania crystal is formed by annealing hydrogen titanate at different temperatures. Black-Right-Pointing-Pointer Best visible-light activity is achieved by Ag-loaded titania annealed at 450 Degree-Sign C. Black-Right-Pointing-Pointer The visible light activity is attributed to the surface plasmonic resonance effect.

Gong, Dangguo [School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Heterogeneous Catalysis Technology, Institute of Chemical and Engineering Sciences, 1 Pesek Road, Singapore 627833 (Singapore); Ho, Weng Chye Jeffrey; Tang Yuxin; Tay Qiuling; Lai Yuekun [School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Highfield, James George, E-mail: james_highfield@ices.a-star.edu.sg [Heterogeneous Catalysis Technology, Institute of Chemical and Engineering Sciences, 1 Pesek Road, Singapore 627833 (Singapore); Chen Zhong, E-mail: aszchen@ntu.edu.sg [School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)

2012-05-15

186

Preparation of cuprous oxides with different sizes and their behaviors of adsorption, visible-light driven photocatalysis and photocorrosion  

NASA Astrophysics Data System (ADS)

Cuprous oxide (Cu 2O) nanoparticles and microparticles have been prepared by liquid phase chemical synthesis. The samples were characterized by means of SEM, XRD, UV/DRS and XPS. It was presented that as-prepared Cu 2O nanoparticles are substantially stable in ambient atmosphere and the Cu + as main state exists on the surface of Cu 2O nanoparticles. As-prepared Cu 2O microparticles can exist stably as a Cu 2O/CuO core/shell structure; and the Cu 2+ as main state exists on the surface of Cu 2O microparticles. The behaviors of adsorption, photocatalysis and photocorrosion of Cu 2O particles with different sizes were investigated in detail. The results show that Cu 2O nanoparticles are very easy to photocorrosion during the photocatalytic reaction, which cannot be used as photocatalyst directly to degrade organic compound, although as-prepared Cu 2O nanoparticles exhibit special property of adsorption. Cu 2O microparticles have a higher photocatalytic activity than Cu 2O nanoparticles because of its slower photocorrosion rate, although Cu 2O microparticles have much lower adsorption capacity than Cu 2O nanoparticles. The mechanisms of photocatalysis and photocorrosion for Cu 2O under visible light were also discussed.

Huang, Lei; Peng, Feng; Yu, Hao; Wang, Hongjuan

2009-01-01

187

Mesoporous TiO2 nanocrystals grown in situ on graphene aerogels for high photocatalysis and lithium-ion batteries.  

PubMed

TiO2/graphene composites have been well studied as a solar light photocatalysts and electrode materials for lithium-ion batteries (LIBs). Recent reports have shown that ultralight 3D-graphene aerogels (GAs) can better adsorb organic pollutants and can provide multidimensional electron transport pathways, implying a significant potential application for photocatalysis and LIBs. Here, we report a simple one-step hydrothermal method toward in situ growth of ultradispersed mesoporous TiO2 nanocrystals with (001) facets on GAs. This method uses glucose as the dispersant and linker owing to its hierarchically porous structure and a high surface area. The TiO2/GAs reported here exhibit a highly recyclable photocatalytic activity for methyl orange pollutant and a high specific capacity in LIBs. The strong interaction between TiO2 and GAs, the facet characteristics, the high electrical conductivity, and the three-dimensional hierarchically porous structure of these composites results in highly active photocatalysis, a high rate capability, and stable cycling. PMID:24712676

Qiu, Bocheng; Xing, Mingyang; Zhang, Jinlong

2014-04-23

188

Decomposition of hydrazine by an organic fullerene-phthalocyanine p-n bilayer photocatalysis system over the entire visible-light region.  

PubMed

An organic p-n bilayer photocatalysis system successfully induced the oxidative decomposition of hydrazine (N2H4) into N2 and simultaneously yielded H2 from H(+). This demonstrates the first instance of the stoichiometric decomposition of N2H4 under visible-light irradiation. PMID:24409454

Abe, Toshiyuki; Taira, Naohiro; Tanno, Yoshinori; Kikuchi, Yuko; Nagai, Keiji

2014-02-25

189

Development of an FTIR in situ reactor for real time study of surface reactions in photocatalysis  

NASA Astrophysics Data System (ADS)

For many years, photocatalysis has been proposed as one of the promising techniques to abate environmental pollutants. To improve the catalytic efficiency, it is vital to know the reaction mechanisms of the photocatalytic degradation. Different methods are therefore described in literature to study these mechanisms at the gaseous phase/photocatalyst interface with Fourier transform infrared (FTIR) spectroscopy as a commonly used method. The reactors described in literature and/or available on the market experience some technical and scientific difficulties. Generally, the catalyst can only be investigated after the reactions have occurred, or it is only possible to look at the changes in the gas phase concentrations while the reactions are taking place. It is thus a major challenge to develop a reactor which makes it possible to detect changes on the catalyst surface at the moment the reactions are happening. In this work, a new reactor is developed that makes it possible to study the catalytic surface at the moment the reactions occur, by means of transmission-absorption FTIR spectroscopy. Moreover, by using UV LEDs, it was possible to install the UV light inside the reactor area, so that no harmful UV light can leave the reactor, inherently making it a safer method. It was also opted to construct the reactor in a modular way, so that every part was interchangeable and could easily be replaced according to the needs of the researcher. A special screw cap is designed to hold the UV LEDs on a printed circuit board and to fit in every standard FTIR spectrometer. This study provides exciting new insights in the photocatalytic degradation mechanism of ethylene and acetaldehyde. It is for instance found that OH radicals are used as the oxidising agents to abate these pollutants. For ethylene it was proven that the molecular orbitals play an important role, resulting in the formation of both formaldehyde and formic acid as intermediates before complete mineralisation could be achieved. In the case of acetaldehyde, new insights in the adsorption behaviour were provided. It was found that acetic acid, formaldehyde and formic acid are intermediate products, necessary to obtain mineralisation.

Hauchecorne, Birger

190

Excited state properties of diiron dithiolate hydrides: implications in the unsensitized photocatalysis of H2 evolution.  

PubMed

Density functional theory (DFT) and time-dependent DFT (TDDFT) have been used to investigate how visible light photons can excite an asymmetrically substituted diiron hydride, [Fe2(pdt)(?-H)(CO)4dppv](+) (1(+), dppv = cis-1,2-C2H2(PPh2)2; pdt = 1,3-propanedithiolate), as well as the symmetric species [Fe2(pdt)(?-H)(CO)4(PMe3)2](+) (2(+)), which are the first photocatalysts of proton reduction operating without employing sensitizers (Wang, W.; Rauchfuss, T. B.; Bertini, L.; Zampella, G.; J. Am. Chem. Soc., 2012, 134, 4525). Theoretical results illustrate that the peculiar reactivity associated to the excited states of 1(+) and 2(+) is compatible with three different scenarios: (i) it can arise from the movement of the hydride ligand from fully bridging to semibridging/terminal coordination, which is expected to be more reactive toward protons; (ii) reactivity could be related to cleavage of a Fe-S bond, which implies formation of a transient Fe penta-coordinate species that would trigger a facile turnstile hydride isomerization, if lifetime excitation is long enough; (iii) also in line with a Fe-S bond cleavage is the possibility that after excited state decay, a highly basic S center is protonated so that a species simultaneously containing S-H(?+) and Fe-H(?-) moieties is formed and, once reduced by a suitable electron donor, it can readily afford H2 plus an unprotonated form of the FeFe complex. This last possibility is consistent with (31)P NMR and IR solution data. All the three possibilities are compatible with the capability of 1(+) and 2(+) to perform photocatalysis of hydrogen evolving reaction (HER) without sensitizer. Moreover, even though it turned out difficult to discriminate among the three scenarios, especially because of the lack of experimental excitation lifetimes, it is worth underscoring that all of the three pathways represent a novelty regarding diiron carbonyl photoreactivity, which is usually associated with CO loss. Results provide also a rationale to the experimental observations which showed that the simultaneous presence of donor ligands (dppv in the case of 1(+)) and a H ligand in the coordination environment of diiron complexes is a key factor to prevent CO photodissociation and catalyze HER. Finally, the comparison of photoexcitation behavior of 1(+) and 2(+) allows a sort of generalization about the functioning of such hydride species. PMID:23952259

Bertini, Luca; Fantucci, Piercarlo; De Gioia, Luca; Zampella, Giuseppe

2013-09-01

191

Study of photocatalytic degradation of tributyltin, dibutylin and monobutyltin in water and marine sediments.  

PubMed

This study reports on the first assessment of the treatment of sediments contaminated by organotin compounds using heterogeneous photocatalysis. Photocatalysis of organotins in water was carried out under realistic concentration conditions (?gL(-1)). Degradation compounds were analyzed by GC-ICP-MS; a quasi-complete degradation of tributyltin (TBT) in water (99.8%) was achieved after 30min of photocatalytic treatment. The degradation by photolysis was about (10%) in the same conditions. For the first time decontamination of highly polluted marine sediments (certified reference material and harbor sediments) by photocatalysis proves that the use of UV and the production of hydroxyl radicals are an efficient way to treat organotins adsorbed onto marine sediment despite the complexity of the matrix. In sediment, TBT degradation yield ranged from 32% to 37% after only 2h of irradiation (TiO2-UV) and the by-products: dibutyltin (DBT) and monobutyltin (MBT) were degraded very rapidly in comparison with TBT. It was shown that during photocatalysis of organotins in sediments, the hydroxyl radical attack and photolysis are the two ways for the degradation of adsorbed TBT. PMID:24613444

Brosillon, Stephan; Bancon-Montigny, Chrystelle; Mendret, Julie

2014-08-01

192

The atomic AXAFS and Delta(mu) XANES techniques as applied to heterogeneous catalysis and electrocatalysis.  

PubMed

X-Ray absorption spectroscopy (XAFS) is an attractive in situ and in operando technique. In recent years, the more conventional extended X-ray absorption fine structure (EXAFS) data analysis technique has been complemented by two newer analysis methods: the 'atomic' XAFS (AXAFS) technique, which analyzes the scattering from the absorber atom itself, and the Delta(mu) XANES technique, which uses a difference method to isolate the changes in the X-ray absorption near edge structure (XANES) due to adsorbates on a metal surface. With AXAFS it is possible to follow the electronic effect a support has on a metal particle; with Delta(mu) XANES it is possible to determine the adsorbate, the specific adsorption sites and adsorbate coverage on a metal catalyst. This unprecedented new information helps a great deal to unravel the complex kinetic mechanisms operating in working reactors or fuel cell systems. The fundamental principles and methodology for applying the AXAFS and Delta(mu) XANES techniques are given here, and then specific applications are summarized, including H adsorption on supported Pt in the gas phase, water activation at a Pt cathode and methanol oxidation at a Pt anode in an electrochemical cell, sulfur oxidation on Pt, and oxygen reduction on a Au/SnO(x) cathode. Finally, the future outlook for time and/or space resolved applications of these techniques is contemplated. PMID:20442940

Ramaker, D E; Koningsberger, D C

2010-06-01

193

Treatment of Heterogeneous Electrocatalysis in Modeling Transport-Reaction Phenomena in PEFCs  

NASA Astrophysics Data System (ADS)

Thermal and water management is a critical issue in PEFCs. In this research, the thermal behavior of PEFC is focused. The objective is to understand the influence of heat on cell performance both by experiment and theoretical analysis, as well as improving cell performance and reliability. In order to investigate the theoretical behavior, especially in the catalyst layer where the electrochemical reactions occur, a detailed modeling of heterogeneous surface reaction coupled with reactant transport is needed. In this paper, a theoretical model that improves the dependency of the exchange current density with reactant concentrations by applying data from a known surface reaction steps found in catalysis is developed. Further, we compared the results of calculation model with the experimental results. The results of calculation model showed good agreement with the experimental results, especially at low current densities and the model can estimate several properties in PEFC e.g. solid phase potential distribution, electron flow vector in GDL, hydrogen and oxygen mole fraction distribution at the membrane?catalyst layer interface. The calculation model served as a preliminary step before the thermal-electrochemical behavior of a PEFC can be fully understood.

Hasmady, Saiful; Hatakeyama, Tomoyuki; Wacker, Manuel Philipp; Fushinobu, Kazuyoshi; Okazaki, Ken

194

Near-infrared photocatalysis of ?-NaYF4:Yb3+,Tm3+@ZnO composites.  

PubMed

A novel near-infrared (NIR)-responsive photocatalyst, ?-NaYF4:Yb(3+),Tm(3+)@ZnO composites, was prepared by a two-step high temperature thermolysis method. In the NIR-responsive photocatalysis, ?-NaYF4:Yb,Tm served as a NIR-to-UV upconverter and provided "UV light" or "necessary energy" to the ZnO catalyst. The energy transfer in the composites and the mixtures of ?-NaYF4:Yb,Tm and ZnO was studied by using steady-state and dynamic fluorescence spectroscopy. The NIR photocatalytic activities were investigated by the decomposition of Rhodamine B. It was found that the energy transfer processes dominated the overall photocatalytic activities, and the generation of hydroxyl radicals was the origin of organic pollutant decomposition under NIR irradiation. PMID:23897044

Guo, Xingyuan; Song, Weiye; Chen, Changfeng; Di, Weihua; Qin, Weiping

2013-09-21

195

Facile one-pot synthesis of flower-like AgCl microstructures and enhancing of visible light photocatalysis  

NASA Astrophysics Data System (ADS)

Flower-like AgCl microstructures with enhanced visible light-driven photocatalysis are synthesized by a facile one-pot hydrothermal process for the first time. The evolution process of AgCl from dendritic structures to flower-like octagonal microstructures is investigated quantitatively. Furthermore, the flower-like AgCl microstructures exhibit enhanced ability of visible light-assisted photocatalytic degradation of methyl orange. The enhanced photocatalytic activity of the flower-like AgCl microstructure is attributed to its three-dimensional hierarchical structure exposing with [100] facets. This work provides a fresh view into the insight of electrochemical process and the application area of visible light photocatalysts.

Li, Meicheng; Yu, Hang; Huang, Rui; Bai, Fan; Trevor, Mwenya; Song, Dandan; Jiang, Bing; Li, Yingfeng

2013-10-01

196

Facile one-pot synthesis of flower-like AgCl microstructures and enhancing of visible light photocatalysis.  

PubMed

Flower-like AgCl microstructures with enhanced visible light-driven photocatalysis are synthesized by a facile one-pot hydrothermal process for the first time. The evolution process of AgCl from dendritic structures to flower-like octagonal microstructures is investigated quantitatively. Furthermore, the flower-like AgCl microstructures exhibit enhanced ability of visible light-assisted photocatalytic degradation of methyl orange. The enhanced photocatalytic activity of the flower-like AgCl microstructure is attributed to its three-dimensional hierarchical structure exposing with [100] facets. This work provides a fresh view into the insight of electrochemical process and the application area of visible light photocatalysts. PMID:24153176

Li, Meicheng; Yu, Hang; Huang, Rui; Bai, Fan; Trevor, Mwenya; Song, Dandan; Jiang, Bing; Li, Yingfeng

2013-01-01

197

Substrate Fermi level effects in photocatalysis on oxides: Properties of ultrathin TiO{sub 2}/Si films  

SciTech Connect

Photocatalysis has widespread applications from solar cells to photolithography. We studied the photocatalytic properties of TiO{sub 2} films of thicknesses down to 2 nm, grown on n-type and p-type silicon wafers, using the oxidation of isopropanol as a model system. Direct in vacuo mass spectrometry measurements were performed under irradiation above the TiO{sub 2} bandgap. We present a model consistent with our experimental results, which indicate that only near-surface electron-hole pair generation is relevant and that the reaction rate can be controlled by varying the substrate Fermi level in going from n-type to p-type silicon, by approximately a factor of 2.

Kazazis, D.; Zaslavsky, A. [Division of Engineering, Brown University, Providence, Rhode Island 02912 (United States); Guha, S.; Bojarczuk, N. A. [IBM T. J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Kim, H.-C. [IBM Almaden Research Center, San Jose, California 95120 (United States)

2009-08-10

198

Facile one-pot synthesis of flower-like AgCl microstructures and enhancing of visible light photocatalysis  

PubMed Central

Flower-like AgCl microstructures with enhanced visible light-driven photocatalysis are synthesized by a facile one-pot hydrothermal process for the first time. The evolution process of AgCl from dendritic structures to flower-like octagonal microstructures is investigated quantitatively. Furthermore, the flower-like AgCl microstructures exhibit enhanced ability of visible light-assisted photocatalytic degradation of methyl orange. The enhanced photocatalytic activity of the flower-like AgCl microstructure is attributed to its three-dimensional hierarchical structure exposing with [100] facets. This work provides a fresh view into the insight of electrochemical process and the application area of visible light photocatalysts.

2013-01-01

199

Photocatalytic membrane reactors for water treatment from organic pollutants  

Microsoft Academic Search

The current status of research in the field of development and application of photocatalytic membrane reactors for water treatment\\u000a from organic pollutants has been analyzed. The main types of these reactors and the construction techniques and properties\\u000a of catalytically active membranes were discussed. The combination of photocatalysis and the membrane methods was shown to\\u000a facilitate the effective removal of different

V. M. Kochkodan; E. A. Rolya; V. V. Goncharuk

2009-01-01

200

Solar photocatalytic degradation of some hazardous water-soluble pesticides at pilot-plant scale.  

PubMed

The technical feasibility and performance of photocatalytic degradation of six water-soluble pesticides (cymoxanil, methomyl, oxamyl, dimethoate, pyrimethanil and telone) have been studied at pilot-plant scale in two well-defined systems which are of special interest because natural solar UV light can be used: heterogeneous photocatalysis with titanium dioxide and homogeneous photocatalysis by photo-Fenton. TiO(2) photocatalysis tests were performed in a 35L solar pilot plant with three Compound Parabolic Collectors (CPCs) under natural illumination and a 75L solar pilot plant with four CPC units was used for homogeneous photocatalysis tests. The initial pesticide concentration studied was 50 mg L(-1) and the catalyst concentrations employed were 200 mg L(-1) of TiO(2) and 20 mg L(-1) of iron. Both toxicity (Vibrio fischeri, Biofix) and biodegradability (Zahn-Wellens test) of the initial pesticide solutions were also measured. Total disappearance of the parent compounds and nearly complete mineralization were attained with all pesticides tested. Treatment time, hydrogen peroxide consumption and release of heteroatoms are discussed. PMID:16839679

Oller, I; Gernjak, W; Maldonado, M I; Pérez-Estrada, L A; Sánchez-Pérez, J A; Malato, S

2006-12-01

201

Water  

MedlinePLUS

... to drink more water Other drinks How much water do you need? top Water is very important, ... you probably need more water. What about bottled water? top Some people like bottled water for its ...

202

Distant protonated pyridine groups in water-soluble iron porphyrin electrocatalysts promote selective oxygen reduction to water  

SciTech Connect

Fe(III)-meso-tetra(pyridyl)porphines are selective electrocatalysts for the reduction of dioxygen to water in aqueous acidic solution. The 2-pyridyl derivatives, both the triflate and chloride salts, are more selective than the isomeric 4-pyridyl complexes. The improved selectivity of is ascribed to the inward-pointing pyridinium groups acting as intramolecular proton relays. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

Matson, Benjamin D.; Carver, Colin T.; Von Ruden, Amber L.; Yang, Jenny Y.; Raugei, Simone; Mayer, James M.

2012-11-08

203

Degradation of diclofenac by TiO 2 photocatalysis: UV absorbance kinetics and process evaluation through a set of toxicity bioassays  

Microsoft Academic Search

In the present study the degradation kinetics and mineralization of diclofenac (DCF) by the TiO2 photocatalysis were investigated in terms of UV absorbance and COD measurements for a wide range of initial DCF concentrations (5–80mgL?1) and photocatalyst loadings (0.2–1.6gTiO2L?1) in a batch reactor system. A set of bioassays (Daphnia magna, Pseudokirchneriella subcapitata and Artemia salina) was performed to evaluate the

L. Rizzo; S. Meric; D. Kassinos; M. Guida; F. Russo; V. Belgiorno

2009-01-01

204

Degradation and reduction of acute toxicity of environmentally persistent perfluorooctanoic acid (PFOA) using VUV photolysis and TiO2 photocatalysis in acidic and basic aqueous solutions  

Microsoft Academic Search

Degradation and toxicity reduction of perfluorooctanoic acid (PFOA) were investigated using TiO2 adsorption, vacuum ultraviolet (VUV) photolysis, and VUV\\/TiO2 photocatalysis in acidic and basic aqueous solutions. Chemical analyses of PFOA and its selected by-products and an acute toxicity assessment using the luminescent bacteria Vibrio fischeri (Microtox®) were conducted during and after the various treatment methods. PFOA was found to be

Il-Hyoung Cho

2011-01-01

205

In situ controllable synthesis platinum nanocrystals on TiO2 by novel polyol-process combined with light induced photocatalysis oxidation.  

PubMed

Clean Pt/TiO(2) with highly dispersed controlled Pt nanocrystals was prepared by a novel approach combining an in situ polyol process with light induced photocatalysis oxidation. The interaction between TiO(2) and Pt under the assistance of surfactants hinders the agglomeration. The preference to form three dimensional clusters as the cluster size increases enables the formation of controlled Pt nanocrystals. PMID:22910980

Jiang, Zhi; Guo, Hongyan; Jiang, Zheng; Chen, Guosheng; Xia, Longfei; Shangguan, Wenfeng; Wu, Xiaojun

2012-10-01

206

Effects of Photocatalysis and Decrease of Electrical Resistivity under UV Irradiation on TiO2 Thin Films by RF Magnetron Sputtering Method  

Microsoft Academic Search

In this paper, the authors clarified effects of photocatalysis and decrease of electrical resistivity under UV irradiation on TiO2 thin films prepared under Ar+O2 atmosphere by RF magnetron sputtering method. From the result of XRD, thin films prepared under Ar+10˜50%O2 atmosphere formed structure of anatase, and films with structures of anatase and rutile were formed under Ar+60˜80%O2 atmosphere. For TiO2

Takahiro Hayakawa; Kiyozumi Niizuma; Yoshio Utsushikawa

2006-01-01

207

Coupling of solar photoelectro-Fenton with a BDD anode and solar heterogeneous photocatalysis for the mineralization of the herbicide atrazine.  

PubMed

Here, the synergetic effect of coupling solar photoelectro-Fenton (SPEF) and solar heterogeneous photocatalysis (SPC) on the mineralization of 200mL of a 20mg L(-1) atrazine solution, prepared from the commercial herbicide Gesaprim, at pH 3.0 was studied. Uniform, homogeneous and adherent anatase-TiO2 films onto glass spheres of 5mm diameter were prepared by the sol-gel dip-coating method and used as catalyst for SPC. However, this procedure yielded a poor removal of the substrate because of the low oxidation ability of positive holes and OH formed at the catalyst surface to destroy it. Atrazine decay was improved using anodic oxidation (AO), electro-Fenton (EF), SPEF and coupled SPEF-SPC at 100mA. The electrolytic cell contained a boron-doped diamond (BDD) anode and H2O2 was generated at a BDD cathode fed with an air flow. The removal and mineralization of atrazine increased when more oxidizing agents were generated in the sequence AOwater oxidation at the BDD anode in AO, along with OH formed from Fenton's reaction between added Fe(2+) and generated H2O2 in EF. In SPEF, solar radiation produced higher amounts of OH induced from the photolysis of Fe(III) species and photodecomposed intermediates like Fe(III)-carboxylate complexes. The synergistic action of sunlight in the most potent coupled SPEF-SPC was ascribed to the additional quick removal of several intermediates with the oxidizing agents formed at the TiO2 surface. After 300min of this treatment, 80% mineralization, 9% mineralization current efficiency and 1.93kWhg(-1) TOC energy cost were obtained. The mineralization of atrazine was inhibited by the production of cyanuric acid, which was the main byproduct detected at the end of the coupled SPEF-SPC process. PMID:24231044

Garza-Campos, Benjamín R; Guzmán-Mar, Jorge Luis; Reyes, Laura Hinojosa; Brillas, Enric; Hernández-Ramírez, Aracely; Ruiz-Ruiz, Edgar J

2014-02-01

208

Highly efficient indoor air purification using adsorption-enhanced-photocatalysis-based microporous TiO2 at short residence time.  

PubMed

A short residence time is a key design parameter for the removal of organic pollutants in catalyst-based indoor air purification systems. In this study, we synthesized a series of TiO2 with different micropore volumes and studied their removal efficiency of indoor carbonyl pollutants at a short residence time. Our results indicated that the superior adsorption capability of TiO2 with micropores improved its performance in the photocatalytic degradation of cyclohexanone, while the photocatalytic removal of the pollutant successfully kept porous TiO2 from becoming saturated. When treated with 1 mg m(-3) cyclohexanone at a relatively humidity of 18%, the adsorption amount on microporous TiO2 was 5.4-7.9 times higher than that on P25. Removal efficiency via photocatalysis followed'the same order as the adsorption amount: TiO2-5 > TiO2-20 > TiO2-60 > TiO2-180 > P25. The advantage of microporous TiO2 over P25 became more pronounced when the residence time declined from 0.072 to 0.036 s. Moreover, as the concentration of cyclohexanone deceased from 1000 ppb to 500 ppb, removal efficiency by microporous TiO2 increased more rapidly than P25. PMID:24191478

Lv, Jinze; Zhu, Lizhong

2013-01-01

209

Photochemical preparation of CdS hollow microspheres at room temperature and their use in visible-light photocatalysis  

NASA Astrophysics Data System (ADS)

CdS hollow microspheres have been successfully prepared by a photochemical preparation technology at room temperature, using polystyrene latex particles as templates, CdSO 4 as cadmium source and Na 2S 2O 3 as both sulphur source and photo-initiator. The process involved the deposition of CdS nanoparticles on the surface of polystyrene latex particles under the irradiation of an 8 W UV lamp and the subsequent removal of the latex particles by dispersing in dichloromethane. Photochemical reactions at the sphere/solution interface should be responsible for the formation of hollow spheres. The as-prepared products were characterized by X-ray diffraction, transmission electron microscopy and scanning electron microscopy. Such hollow spheres could be used in photocatalysis and showed high photocatalytic activities in photodegradation of methyl blue (MB) in the presence of H 2O 2. The method is green, simple, universal and can be extended to prepare other sulphide and oxide hollow spheres.

Huang, Yuying; Sun, Fengqiang; Wu, Tianxing; Wu, Qingsong; Huang, Zhong; Su, Heng; Zhang, Zihe

2011-03-01

210

Hematoporphyrin-ZnO nanohybrids: twin applications in efficient visible-light photocatalysis and dye-sensitized solar cells.  

PubMed

Light-harvesting nanohybrids (LHNs) are systems composed of an inorganic nanostructure associated with an organic pigment that have been exploited to improve the light-harvesting performance over individual components. The present study is focused on developing a potential LHN, attained by the functionalization of dense arrays of ZnO nanorods (NRs) with a biologically important organic pigment hematoporphyrin (HP), which is an integral part of red blood cells (hemoglobin). Application of spectroscopic techniques, namely, Fourier transform infrared spectroscopy (FTIR) and Raman scattering, confirm successful monodentate binding of HP carboxylic groups to Zn(2+) located at the surface of ZnO NRs. Picosecond-resolved fluorescence studies on the resulting HP-ZnO nanohybrid show efficient electron migration from photoexcited HP to the host ZnO NRs. This essential photoinduced event activates the LHN under sunlight, which ultimately leads to the realization of visible-light photocatalysis (VLP) of a model contaminant Methylene Blue (MB) in aqueous solution. A control experiment in an inert gas atmosphere clearly reveals that the photocatalytic activity is influenced by the formation of reactive oxygen species (ROS) in the media. Furthermore, the stable LHNs prepared by optimized dye loading have also been used as an active layer in dye-sensitized solar cells (DSSCs). We believe these promising LHNs to find their dual applications in organic electronics and for the treatment of contaminant wastewater. PMID:23186038

Sarkar, Soumik; Makhal, Abhinandan; Bora, Tanujjal; Lakhsman, Karthik; Singha, Achintya; Dutta, Joydeep; Pal, Samir Kumar

2012-12-01

211

COD removal and toxicity decrease from tannery wastewater by zinc oxide-assisted photocatalysis: a case study.  

PubMed

This work reports the optimization of degradation conditions and toxicity decrease in the tannery wastewater, collected in the retanning and dyeing steps. This effluent was filtered, diluted in a 1:200 proportion, and investigated as a case study on a bench scale by heterogeneous photocatalysis. These conditions were attained when the suspension, containing 1 g L-1 of ZnO and effluent, was irradiated for 4h at pH 8.0 and 30 degrees C. Physico-chemical parameters such as chemical oxygen demand (COD) decreased from 15,023 to 350 mg O2 L-1; fifth-day biochemical oxygen demand (BODs) from 4374 to 10 mg O2 L-1; total solids from 28,500 to 188 mg L-1; total organic carbon (TOC) from 4685 to 4.93 mg L-1, and turbidity from 331 to 1.15NTU after 4h of irradiation. The LC50 increase from 14.90% to 56.82% in the lethality assay of Artemia salina L. microcrustacean as well as the dissolved oxygen of 6.45mg L-1 indicated efficiency in this treatment. PMID:24956748

Hasegawa, Maria Claudia; Daniel, Juliana Feijó de Souza; Takashima, Keiko; Batista, Gisselma A; da Silva, Sandra M C P

2014-08-01

212

Improvement of gaseous pollutant photocatalysis with WO3/TiO2 heterojunctional-electrical layered system.  

PubMed

Since the photogenerated holes play a much more important role than electrons in gas-phase photocatalysis, it is better to enrich the holes in the surface of a material system. Here, a novel [interdigital electrode/WO(3)/TiO(2)] heterojunctional-electrical layered (HEL) system is proposed to realize this attempt. The HEL system consists of interdigital electrode, WO(3) layer and TiO(2) layer, and they are orderly printed onto the alumina substrate from bottom to top using the technology of screen printing. It is surprise that the synergistic effect of layered heterojunction and external low bias can strengthen the separation of electron-hole pairs in both TiO(2) and WO(3), and enrich the TiO(2) surface layer with photogenerated holes to degrade the gaseous pollutants. In comparison with the pure TiO(2) film, a 6-fold enhancement in photocatalytic activity was observed using the HEL system by applying a very low bias of 0.2V. Furthermore, the results also showed that the remarkable improvement could not be obtained when either the WO(3) layer or the low external bias was absent. PMID:21924831

Liu, Yuan; Xie, Changsheng; Li, Huayao; Chen, Hao; Zou, Tao; Zeng, Dawen

2011-11-30

213

Zinc ions surface-doped titanium dioxide nanotubes and its photocatalysis activity for degradation of methyl orange in water  

Microsoft Academic Search

Zn ions surface-doped TiO2 nanotubes were synthesized via an assembly process based on ligand exchange reaction and with additional thermal treatment. First the ligand exchange reaction between zinc acetylacetonate and hydroxide radicals on TiO2 surface introduced the Zn ions onto the surface of TiO2 nanotubes, then the Zn(acac)2 assembled TiO2 nanotubes were calcined at an optimal temperature (400°C) to eliminate

Ji-Chuan Xu; Mei Lu; Xin-Yong Guo; Hu-Lin Li

2005-01-01

214

NASA's Potential Contributions for Remediation of Retention Ponds Using Solar Ultraviolet Radiation and Photocatalysis  

NASA Technical Reports Server (NTRS)

This Candidate Solution uses NASA Earth science research on atmospheric ozone and aerosols data (1) to help improve the prediction capabilities of water runoff models that are used to estimate runoff pollution from retention ponds, and (2) to understand the pollutant removal contribution and potential of photocatalytically coated materials that could be used in these ponds. Models (the EPA's SWMM and the USGS SLAMM) exist that estimate the release of pollutants into the environment from storm-water-related retention pond runoff. UV irradiance data acquired from the satellite mission Aura and from the OMI Surface UV algorithm will be incorporated into these models to enhance their capabilities, not only by increasing the general understanding of retention pond function (both the efficacy and efficiency) but additionally by adding photocatalytic materials to these retention ponds, augmenting their performance. State and local officials who run pollution protection programs could then develop and implement photocatalytic technologies for water pollution control in retention ponds and use them in conjunction with existing runoff models. More effective decisions about water pollution protection programs could be made, the persistence and toxicity of waste generated could be minimized, and subsequently our natural water resources would be improved. This Candidate Solution is in alignment with the Water Management and Public Health National Applications.

Underwood, Lauren W.; Ryan, Robert E.

2007-01-01

215

New insights into electrocatalysis based on plasmon resonance for the real-time monitoring of catalytic events on single gold nanorods.  

PubMed

Gold nanoparticles (GNPs) have been widely applied in industrial catalysis and electrocatalysis. Owing to their wide variety of shapes, sizes, and compositions, a range of different catalytic properties is possible. Thus, it is important to monitor catalytic processes and their mechanisms on single GNP surfaces to avoid averaging effects in bulk systems. Therefore, a novel method based on dark-field scattering spectroscopy was developed to monitor, in real-time, the electrocatalytic oxidation of hydrogen peroxide on a single gold nanoparticle surface. The catalytic mechanism was revealed via the plasmon resonance scattering spectral shift of single gold nanorod with the elimination of bulk effect. Moreover, we found that the presence of chloride ions could block the catalytic activity of nanorods for the oxidation of H2O2. Most importantly, it was discovered that individual nanoparticles have variable properties with different spectra shifts during the catalytic process. The obtained optical signals from individual nanorods not only offer versatile information regarding the reaction but also improve the understanding of electrochemistry and the catalysis mechanism of single nanoparticles. PMID:24766541

Jing, Chao; Rawson, Frankie James; Zhou, Hao; Shi, Xin; Li, Wen-Hui; Li, Da-Wei; Long, Yi-Tao

2014-06-01

216

Water  

MedlinePLUS

... to groundwater (the fresh water found under the Earth’s surface that supplies wells and springs). Everything that ... body is water. 4. How much of the earth’s surface is water? About 80 percent of the ...

217

Solar-based detoxification of phenol and p-nitrophenol by sequential TiO 2 photocatalysis and photosynthetically aerated biological treatment  

Microsoft Academic Search

Simulated solar UV\\/TiO2 photocatalysis was efficient to detoxify a mixture of 100mgphenoll?1 and 50mgp-nitrophenol (PNP) l?1 and allow the subsequent biodegradation of the remaining pollutants and their photocatalytic products under photosynthetic aeration with Chlorella vulgaris. Photocatalytic degradation of phenol and PNP was well described by pseudo-first order kinetics (r2>0.98) with removal rate constants of 1.9×10?4 and 2.8×10?4min?1, respectively, when the

Tamer Essam; Magdy Aly Amin; Ossama El Tayeb; Bo Mattiasson; Benoit Guieysse

2007-01-01

218

Graphene oxide/?-Bi(2)O(3) composites for visible-light photocatalysis, chemical catalysis, and solar energy conversion.  

PubMed

The growing challenges of environmental purification by solar photocatalysis, precious-metal-free catalysis, and photocurrent generation in photovoltaic cells receive the utmost global attention. Here we demonstrate a one-pot, green chemical synthesis of a new stable heterostructured, ecofriendly, multifunctional microcomposite that consists of ?-Bi2 O3 microneedles intercalated with anchored graphene oxide (GO) microsheets (1.0?wt?%) for the above-mentioned applications on a large economical scale. The bare ?-Bi2 O3 microneedles display two times better photocatalytic activities than commercial TiO2 (Degussa-P25), whereas the GO-hybridized composite exhibits approximately four to six times enhanced photocatalytic activities than the neat TiO2 photocatalyst in the degradation of colored aromatic organic dyes (crystal violet and rhodamine 6G) under visible-light irradiation (300?W tungsten lamp). The highly efficient activity is associated with the strong surface adsorption ability of GO for aromatic dye molecules, the high carrier acceptability, and the efficient electron-hole pair separation in Bi2 O3 by individual adjoining GO sheets. The introduction of Ag nanoparticles (2.0?wt?%) further enhances the photocatalytic performance of the composite over eightfold because of a plasmon-induced electron-transfer process from Ag nanoparticles through the GO sheets into the conduction band of Bi2 O3 . The new composites are also catalytically active and catalyze the reduction of 4-nitrophenol to 4-aminophenol in the presence of borohydride ions. Photoanodes assembled from GO/?-Bi2 O3 and Ag/GO/?-Bi2 O3 composites display an improved photocurrent response (power conversion efficiency ?20?% higher) over those prepared without GO in dye-sensitized solar cells. PMID:24578169

Som, Tirtha; Troppenz, Gerald V; Wendt, R Robert; Wollgarten, Markus; Rappich, Jörg; Emmerling, Franziska; Rademann, Klaus

2014-03-01

219

Combination of photocatalysis and HC/SCR for improved activity and durability of DeNOx catalysts.  

PubMed

A photocatalytic HC/SCR system has been developed and its high deNOx performance (54.0-98.6% NOx conversion) at low temperatures (150-250 °C) demonstrated by using a representative diesel fuel hydrocarbon (dodecane) as the reductant over a hybrid SCR system of a photocatalytic reactor (PCR) and a dual-bed HC/SCR reactor. The PCR generates highly active oxidants such as O3 and NO2 from O2 and NO in the feed stream, followed by the subsequent formation of highly efficient reductants such as oxygenated hydrocarbon (OHC), NH3, and organo-nitrogen compounds. These reductants are the key components for enhancing the low temperature deNOx performance of the dual-bed HC/SCR system containing Ag/Al2O3 and CuCoY in the front and rear bed of the reactor, respectively. The OHCs are particularly effective for both NOx reduction and NH3 formation over the Ag/Al2O3 catalyst, while NH3 and organo-nitrogen compounds are effective for NOx reduction over the CuCoY catalyst. The hybrid HC/SCR system assisted by photocatalysis has shown an overall deNOx performance comparable to that of the NH3/SCR, demonstrating its potential as a promising alternative to the current urea/SCR and LNT technologies. Superior durability of HC/SCR catalysts against coking by HCs has also been demonstrated by a PCR-assisted regeneration scheme for deactivating catalysts. PMID:23586945

Heo, Iljeong; Kim, Mun Kyu; Sung, Samkyung; Nam, In-Sik; Cho, Byong K; Olson, Keith L; Li, Wei

2013-04-16

220

Photochemical preparation of CdS hollow microspheres at room temperature and their use in visible-light photocatalysis  

SciTech Connect

CdS hollow microspheres have been successfully prepared by a photochemical preparation technology at room temperature, using polystyrene latex particles as templates, CdSO{sub 4} as cadmium source and Na{sub 2}S{sub 2}O{sub 3} as both sulphur source and photo-initiator. The process involved the deposition of CdS nanoparticles on the surface of polystyrene latex particles under the irradiation of an 8 W UV lamp and the subsequent removal of the latex particles by dispersing in dichloromethane. Photochemical reactions at the sphere/solution interface should be responsible for the formation of hollow spheres. The as-prepared products were characterized by X-ray diffraction, transmission electron microscopy and scanning electron microscopy. Such hollow spheres could be used in photocatalysis and showed high photocatalytic activities in photodegradation of methyl blue (MB) in the presence of H{sub 2}O{sub 2}. The method is green, simple, universal and can be extended to prepare other sulphide and oxide hollow spheres. -- Graphical abstract: Taking polystyrene spheres dispersed in a precursor solution as templates, CdS hollow microspheres composed of nanoparticles were successfully prepared via a new photochemical route at room temperature. Display Omitted Research highlights: {yields} Photochemical method was first employed to prepare hollow microspheres. {yields} CdS hollow spheres were first prepared at room temperature using latex spheres. {yields} The polystyrene spheres used as templates were not modified with special groups. {yields}The CdS hollow microspheres showed high visible-light photocatalytic activities.

Huang Yuying [School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Sun Fengqiang, E-mail: fengqiangsun@yahoo.c [School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); Key Laboratory of Electrochemical Technology on Energy Storage and Power Generation in GuangDong Universities, Guangzhou 510006 (China); Engineering Research Center of Materials and Technology for Electrochemical Energy Storage (Ministry of Education), South China Normal University, Guangzhou 510006 (China); Wu Tianxing; Wu Qingsong; Huang Zhong; Su Heng; Zhang Zihe [School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China)

2011-03-15

221

Interaction between E. coli inactivation and DBP-precursors — dihydroxybenzene isomers — in the photocatalytic process of drinking-water disinfection with TiO 2  

Microsoft Academic Search

The common drinking water disinfection procedures lead to the formation of disinfection by-products (DBPs), which come mainly from naturally occurring organic compounds disinfection by-products precursors (DBPPs). Solar disinfection by photocatalysis is a promising method, which could be applied to a drinking water treatment process in order to destroy a bacterial population and DBPPs as well.The complete E. coli inactivation by

Angela G. Rincón; Cesar Pulgarin; Nevenka Adler; Paul Peringer

2001-01-01

222

Simultaneous monitoring of photocatalysis of three pharmaceuticals by immobilized TiO2 nanoparticles: Chemometric assessment, intermediates identification and ecotoxicological evaluation  

NASA Astrophysics Data System (ADS)

In this study, the photocatalytic degradation of a mixture of three pharmaceuticals, Metronidazole (MET), Atenolol (ATL) and Chlorpromazine (CPR), was quantified simultaneously during the UV/TiO2 process. The investigated TiO2 was Millennium PC-500 immobilized on ceramic plates by sol-gel based method. The partial least squares modeling was successfully applied for the multivariate calibration of the spectrophotometric data. The central composite design was applied to model and optimize the UV/TiO2 process. Predicted values of removal efficiency were found to be in good agreement with experimental values for MET, ATL and CPR (R2 = 0.947 and Adj-R2 = 0.906, R2 = 0.977 and Adj-R2 = 0.960 and R2 = 0.982 and Adj-R2 = 0.969, respectively). The optimum initial concentration of pharmaceuticals, reaction time and UV light intensity was found to be 10 mg L-1, 150 min and 38.45 W m-2, respectively. The main degradation intermediates of pharmaceuticals produced in this process were identified by GC-MS technique. The chronic ecotoxicity of pharmaceuticals was evaluated using aquatic species Spirodela polyrrhiza prior to and after photocatalysis. The TOC results (90% removal after 16 h) and ecotoxicological experiments revealed that the photocatalysis process could effectively mineralize and reduce the ecotoxicity of the pharmaceuticals from their aqueous solutions.

Khataee, A. R.; Fathinia, M.; Joo, S. W.

2013-08-01

223

Simultaneous monitoring of photocatalysis of three pharmaceuticals by immobilized TiO2 nanoparticles: chemometric assessment, intermediates identification and ecotoxicological evaluation.  

PubMed

In this study, the photocatalytic degradation of a mixture of three pharmaceuticals, Metronidazole (MET), Atenolol (ATL) and Chlorpromazine (CPR), was quantified simultaneously during the UV/TiO2 process. The investigated TiO2 was Millennium PC-500 immobilized on ceramic plates by sol-gel based method. The partial least squares modeling was successfully applied for the multivariate calibration of the spectrophotometric data. The central composite design was applied to model and optimize the UV/TiO2 process. Predicted values of removal efficiency were found to be in good agreement with experimental values for MET, ATL and CPR (R(2)=0.947 and Adj-R(2)=0.906, R(2)=0.977 and Adj-R(2)=0.960 and R(2)=0.982 and Adj-R(2)=0.969, respectively). The optimum initial concentration of pharmaceuticals, reaction time and UV light intensity was found to be 10 mg L(-1), 150 min and 38.45 W m(-2), respectively. The main degradation intermediates of pharmaceuticals produced in this process were identified by GC-MS technique. The chronic ecotoxicity of pharmaceuticals was evaluated using aquatic species Spirodela polyrrhiza prior to and after photocatalysis. The TOC results (90% removal after 16 h) and ecotoxicological experiments revealed that the photocatalysis process could effectively mineralize and reduce the ecotoxicity of the pharmaceuticals from their aqueous solutions. PMID:23659949

Khataee, A R; Fathinia, M; Joo, S W

2013-08-01

224

Applications of real-time infrared spectroscopy to electrocatalysis at bimetallic surfaces. I. Electrooxidation of formic acid and methanol on bismuth-modified Pt(111) and Pt(100)  

NASA Astrophysics Data System (ADS)

The influence of predosed bismuth upon the electro-oxidation of formic acid and methanol to CO 2 on Pt(111) and (100) in 0.1M HClO 4 is examined by means of voltammetry combined with real-time infrared spectroscopy. The substantial (up to 30-40-fold) enhancement of the formic acid electro-oxidation rates observed in the presence of bismuth on Pt(100) are observed to be due primarily to the attenuation in the degree of CO poison formation as discerned from FTIR. The adsorbed CO formation, which reaches near-saturation coverages in the absence of bismuth, is essentially eliminated for bismuth coverages above ca. 0.2. The production of terminal CO is triggered by the onset of formic acid oxidation, suggesting that it forms from a reactive intermediate rather than from formic acid itself. The bismuth-induced electrocatalysis of formic acid oxidation observed on Pt(111) apparently also arises in a similar manner, although the major poison in this case is not adsorbed CO. These electrocatalytic influences of bismuth are consistent with an "ensemble effect", whereby poison formation is suppressed to a markedly greater degree than is the reactive precursor. In contrast, the electro-oxidation rates of methanol on Pt(100) and especially Pt(111) are diminished in the presence of predosed bismuth. In addition, the terminal CO coverages formed during methanol electro-oxidation correlate directly with the variation in the reaction rates by altering either the reactant concentration or the bismuth coverage. These results suggest that CO can act as a reaction intermediate for methanol electro-oxidation under these conditions. A consistency is observed in the degree of dissociation of formic acid and methanol to yield adsorbed CO on Pt(111) and Pt(100) in electrochemical versus UHV surface environments.

Chang, Si-Chung; Ho, Yeunghaw; Weaver, Michael J.

1992-04-01

225

Combining TiO2-photocatalysis and wetland reactors for the efficient treatment of pesticides.  

PubMed

In the present work the photocatalytic and biological degradation of two commercial mixtures of pesticides (Folimat and Ronstar) and two fungicides (pyrimethanil and triadimenol) has been studied. The evolution of some components of these commercial products (dicofol, tetradifon and oxadiazon) and that of the two fungicides has been monitored by means of HPLC, GC-MS, TOC and toxicity (Lemna minor toxicity test) measurements. The photocatalytic method was able to degrade dicofol, tetradifon, pyrimethanil, triadimenol and the components of Ronstar with the exception of oxadiazon. In addition to this, the photocatalytic method eliminated pyrimethanil toxicity and reduced that of triadimenol by a 90%, Ronstar by a 78% and Folimat by an 87%. Nevertheless, the wetland reactors alone could reduce the toxicity of only the former. Finally, the proper dosage of the water containing the pesticides to a photocatalytic reactor followed by a wetland reactor resulted to be the most successful strategy for the detoxification of the studied compounds and their mixtures. PMID:18023844

Araña, J; Garriga I Cabo, C; Fernández Rodríguez, C; Herrera Melián, J A; Ortega Méndez, J A; Doña Rodríguez, J M; Pérez Peña, J

2008-03-01

226

Prolonged hot electron dynamics in plasmonic-metal/semiconductor heterostructures with implications for solar photocatalysis.  

PubMed

Ideal solar-to-fuel photocatalysts must effectively harvest sunlight to generate significant quantities of long-lived charge carriers necessary for chemical reactions. Here we demonstrate the merits of augmenting traditional photoelectrochemical cells with plasmonic nanoparticles to satisfy these daunting photocatalytic requirements. Electrochemical techniques were employed to elucidate the mechanics of plasmon-mediated electron transfer within Au/TiO2 heterostructures under visible-light (?>515?nm) irradiation in solution. Significantly, we discovered that these transferred electrons displayed excited-state lifetimes two orders of magnitude longer than those of electrons photogenerated directly within TiO2 via UV excitation. These long-lived electrons further enable visible-light-driven H2 evolution from water, heralding a new photocatalytic paradigm for solar energy conversion. PMID:24920227

DuChene, Joseph S; Sweeny, Brendan C; Johnston-Peck, Aaron C; Su, Dong; Stach, Eric A; Wei, Wei David

2014-07-21

227

Molecular electrocatalysis of the oxygen reduction at a polarised interface between two immiscible electrolyte solutions by Co(II) tetraphenylporphyrin  

Microsoft Academic Search

Cyclic voltammetry and the interfacial tension measurements are used to study electrochemistry and adsorption of 5,10,15,20-tetraphenyl-21H, 23H-porphine cobalt(II) (CoTPP) at the polarized water?1,2-dichloroethane (1,2-DCE) interface. It is shown that CoTPP facilitates the successive transfer of two protons from water to 1,2-DCE, and that the formation of its protonated forms (CoTPPH+, CoTPPH22+) gives rise to an enhancement of the interfacial tension

Antonín Trojánek; Vladimír Mare?ek; Hana Jänchenová; Zden?k Samec

2007-01-01

228

Band-engineered SrTiO{sub 3} nanowires for visible light photocatalysis  

SciTech Connect

We have theoretically investigated the structural, electronic, and optical properties of perovskite SrTiO{sub 3} nanowires for use in visible light photocatalytic applications using pseudopotential density-functional theory calculations. The electronic structure calculations show that the band gap is modified in the SrTiO{sub 3} nanowires compared with that of the bulk. For TiO{sub 2}-terminated nanowires, the mid-band states induced by the combination of oxygen and strontium atoms on the surface lead to a shift in the valence band toward the conduction band without interference from the edge of the conduction band, which reduces the band gap. On the contrary, the electronic states induced by the combination of oxygen and strontium atoms on the surface of SrO-terminated nanowires lead to a shift in the conduction band toward the valence band. The calculated optical results indicate that the absorption edge of the nanowires shift towards the red-light region. These theoretical results suggest that perovskite SrTiO{sub 3} nanowires are promising candidates for use in visible light photocatalytic processes such as solar-assisted water splitting reactions.

Fu, Q.; He, T.; Li, J. L.; Yang, G. W. [State Key Laboratory of Optoelectronic Materials and Technologies, Institute of Optoelectronic and Functional Composite Materials, Nanotechnology Research Center, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275, Guangdong (China)

2012-11-15

229

Band-engineered SrTiO3 nanowires for visible light photocatalysis  

NASA Astrophysics Data System (ADS)

We have theoretically investigated the structural, electronic, and optical properties of perovskite SrTiO3 nanowires for use in visible light photocatalytic applications using pseudopotential density-functional theory calculations. The electronic structure calculations show that the band gap is modified in the SrTiO3 nanowires compared with that of the bulk. For TiO2-terminated nanowires, the mid-band states induced by the combination of oxygen and strontium atoms on the surface lead to a shift in the valence band toward the conduction band without interference from the edge of the conduction band, which reduces the band gap. On the contrary, the electronic states induced by the combination of oxygen and strontium atoms on the surface of SrO-terminated nanowires lead to a shift in the conduction band toward the valence band. The calculated optical results indicate that the absorption edge of the nanowires shift towards the red-light region. These theoretical results suggest that perovskite SrTiO3 nanowires are promising candidates for use in visible light photocatalytic processes such as solar-assisted water splitting reactions.

Fu, Q.; He, T.; Li, J. L.; Yang, G. W.

2012-11-01

230

Fe doped TiO2-graphene nanostructures: synthesis, DFT modeling and photocatalysis.  

PubMed

In this work, Fe-doped TiO2 nanoparticles ranging from a 0.2 to 1 weight % were grown from the surface of graphene sheet templates containing -COOH functionalities using sol-gel chemistry in a green solvent, a mixture of water/ethanol. The assemblies were characterized by a variety of analytical techniques, with the coordination mechanism examined theoretically using the density functional theory (DFT). Scanning electron microscopy and transmission electron microscopy images showed excellent decoration of the Fe-doped TiO2 nanoparticles on the surface of the graphene sheets >5 nm in diameter. The surface area and optical properties of the Fe-doped photocatalysts were measured by BET, UV and PL spectrometry and compared to non-graphene and pure TiO2 analogs, showing a plateau at 0.6% Fe. Interactions between graphene and Fe-doped anatase TiO2 were also studied theoretically using the Vienna ab initio Simulation Package based on DFT. Our first-principles theoretical investigations validated the experimental findings, showing the strength in the physical and chemical adsorption between the graphene and Fe-doped TiO2. The resulting assemblies were tested for photodegradation under visible light using 17?-estradiol (E2) as a model compound, with all investigated catalysts showing significant enhancements in photocatalytic activity in the degradation of E2. PMID:25002220

Farhangi, Nasrin; Ayissi, Serge; Charpentier, Paul A

2014-08-01

231

Investigations of the effects of photocatalysis on the molecular assembly behavior of titanium alkoxide materials  

NASA Astrophysics Data System (ADS)

The present work focuses on the use of engineered, photoactive metal alkoxide precursors in the sol-gel processing of metal-oxide materials. The strategy under investigation seeks to integrate photoinduced structural modification with conventional sol-gel chemical preparations to enable the selective photo-activation of reaction points about the metal center during material formation. The approach thus has the potential to influence the development of intermolecular bonding geometry and to provide an opportunity to enforce or bias longer range structural development processes and resulting network topology. This ability to bias the long range structural development has been shown to provide opportunities both for photoinduced material formation and the potential to control multi-length scale structural characteristics of these materials. The response of a mononuclear, heteroleptic titanium alkoxide (OPy) 2Ti(4MP)2 [where OPy = pyridine carbinoxide and 4MP = 4-mercaptophenoxide] to ultraviolet (UV) irradiation in dilute solution and in solid-state samples has been measured. Vibrational spectroscopy (FTIR absorption and Raman scattering) was used to monitor changes in molecular structure upon exposure to 337.1 and 365 nm light. Assignment of spectral features to vibrational modes of the molecule was aided by a normal-mode analysis of the energy-minimized molecular structure within a density functional theory (DFT) framework. Photoinduced decreases in peak areas were observed in both FTIR spectra of the precursor solutions and Raman data collected from solution-cast films of the precursor material. These changes were associated with vibrational modes localized at the 4MP ligands. Conversely, no significant modification of vibrational structure associated with the OPy moiety was observed under the excitation conditions examined. Excitation, with 248 nm light, of a solution of (OPy)2Ti(TAP) 2 [where OPy = pyridine carbinoxide and TAP = 2,4,6 tris(dimethylamino)phenoxide] in watercontaining pyridine has been shown to create an insoluble photoproduct in the region of the incident laser beam. Analysis of the photoproduct by Raman spectroscopy indicates the presence of hydrolysis and condensation products as well as features consistent with the unreacted metal alkoxide, indicating destabilization of the alkoxide material that leads to intermolecular linking reactions. Further analysis indicates that it is excitations resonant with the pi -- pi* transitions in the aromatic ligands, as well as in the solvent, that provide this destabilization rather than excitations resonant with the charge transfer band in the molecule. These fundamental studies of the intrinsic molecular-level response of (OPy)2Ti(TAP)2 to ultraviolet irradiation have lead to the development of a novel thin film deposition process wherein the film is deposited directly from solution onto a substrate only in the regions in which it is exposed to ultraviolet light. The nanoscale porosity of films deposited from solution using this technique was found to be dependent on the chemistry of the precursor solution used, with a 1 part addition of water to the precursor producing films with 100 nm diameter surface pores, and an 8 part addition of water to the precursor producing films with no visible surface porosity. Post-deposition thermal treatments have been explored as a means to modify the as-deposited chemistry and nanostructure of the photodeposited films. Films that were fired to 350°C under an oxygen atmosphere no longer showed FTIR features corresponding to ligand-based vibrational modes, with the Raman spectrum of the material showing an increase in the wavenumber range that is indicative of Ti-O-Ti bonding, leading to the conclusion that the residual alkoxide ligands had been removed. In contrast films fired to this temperature under argon showed Raman features assigned to graphite-like structures, indicating that the reducing atmosphere led to the retention of the phenyl moieties in the fired films. The experimental results obtained from optical spectroscopy

Musgraves, Jonathan David

232

Reactions of oxygen-containing molecules on transition metal carbides: Surface science insight into potential applications in catalysis and electrocatalysis  

NASA Astrophysics Data System (ADS)

Historically the interest in the catalytic properties of transition metal carbides (TMC) has been inspired by their “Pt-like” properties in the transformation reactions of hydrocarbon molecules. Recent studies, however, have revealed that the reaction pathways of oxygen-containing molecules are significantly different between TMCs and Pt-group metals. Nonetheless, TMCs demonstrate intriguing catalytic properties toward oxygen-containing molecules, either as the catalyst or as the catalytically active substrate to support metal catalysts, in several important catalytic and electrocatalytic applications, including water electrolysis, alcohol electrooxidation, biomass conversion, and water gas shift reactions. In the current review we provide a summary of theoretical and experimental studies of the interaction of TMC surfaces with oxygen-containing molecules, including both inorganic (O2, H2O, CO and CO2) and organic (alcohols, aldehydes, acids and esters) molecules. We will discuss the general trends in the reaction pathways, as well as future research opportunities in surface science studies that would facilitate the utilization of TMCs as catalysts and electrocatalysts.

Stottlemyer, Alan L.; Kelly, Thomas G.; Meng, Qinghe; Chen, Jingguang G.

2012-09-01

233

Reactions of oxygen-containing molecules on transition metal carbides: Surface science insight into potential applications in catalysis and electrocatalysis  

NASA Astrophysics Data System (ADS)

Historically the interest in the catalytic properties of transition metal carbides (TMC) has been inspired by their "Pt-like" properties in the transformation reactions of hydrocarbon molecules. Recent studies, however, have revealed that the reaction pathways of oxygen-containing molecules are significantly different between TMCs and Pt-group metals. Nonetheless, TMCs demonstrate intriguing catalytic properties toward oxygen-containing molecules, either as the catalyst or as the catalytically active substrate to support metal catalysts, in several important catalytic and electrocatalytic applications, including water electrolysis, alcohol electrooxidation, biomass conversion, and water gas shift reactions. In the current review we provide a summary of theoretical and experimental studies of the interaction of TMC surfaces with oxygen-containing molecules, including both inorganic (O2, H2O, CO and CO2) and organic (alcohols, aldehydes, acids and esters) molecules. We will discuss the general trends in the reaction pathways, as well as future research opportunities in surface science studies that would facilitate the utilization of TMCs as catalysts and electrocatalysts.

Stottlemyer, Alan L.; Kelly, Thomas G.; Meng, Qinghe; Chen, Jingguang G.

2012-09-01

234

Photocatalytic degradation of pesticides in pure water and a commercial agricultural solution on TiO2 coated media.  

PubMed

Heterogeneous photocatalysis of pesticides is an effective process for removing pesticides from pure water. With a view to treating real agricultural effluents, this paper deals with the degradation of the chlortoluron and cyproconazole pesticides in pure water and the treatment of commercial solutions by photocatalysis on TiO2 coated media. The process was effective in degrading and mineralizing the pesticides. The changes of the fate of heteroatoms showed that during irradiation of the chlortoluron and cyproconazole, NH4+ and NO3(-) ions were produced. A release of chloride ions was observed from the beginning of the irradiation and stoichiometry was achieved. The photodegradation of chlortoluton and cyproconazole in commercial solutions was studied. For the degradation of chlortoluton in a commercial solution, the mineralization was completely achieved whereas in the case of the commercial cyproconazole solution, the degradation kinetic was lower. These results highlight the fact that the chemical nature of the additives in the commercial pesticide solutions does significantly affect the degradation yield of the target compound by photocatalysis. PMID:17709129

Lhomme, L; Brosillon, S; Wolbert, D

2008-01-01

235

Visible-Light Organic Photocatalysis for Latent Radical-Initiated Polymerization via 2e(-)/1H(+) Transfers: Initiation with Parallels to Photosynthesis.  

PubMed

We report the latent production of free radicals from energy stored in a redox potential through a 2e(-)/1H(+) transfer process, analogous to energy harvesting in photosynthesis, using visible-light organic photoredox catalysis (photocatalysis) of methylene blue chromophore with a sacrificial sterically hindered amine reductant and an onium salt oxidant. This enables light-initiated free-radical polymerization to continue over extended time intervals (hours) in the dark after brief (seconds) low-intensity illumination and beyond the spatial reach of light by diffusion of the metastable leuco-methylene blue photoproduct. The present organic photoredox catalysis system functions via a 2e(-)/1H(+) shuttle mechanism, as opposed to the 1e(-) transfer process typical of organometallic-based and conventional organic multicomponent photoinitiator formulations. This prevents immediate formation of open-shell (radical) intermediates from the amine upon light absorption and enables the "storage" of light-energy without spontaneous initiation of the polymerization. Latent energy release and radical production are then controlled by the subsequent light-independent reaction (analogous to the Calvin cycle) between leuco-methylene blue and the onium salt oxidant that is responsible for regeneration of the organic methylene blue photocatalyst. This robust approach for photocatalysis-based energy harvesting and extended release in the dark enables temporally controlled redox initiation of polymer syntheses under low-intensity short exposure conditions and permits visible-light-mediated synthesis of polymers at least 1 order of magnitude thicker than achievable with conventional photoinitiated formulations and irradiation regimes. PMID:24786755

Aguirre-Soto, Alan; Lim, Chern-Hooi; Hwang, Albert T; Musgrave, Charles B; Stansbury, Jeffrey W

2014-05-21

236

Surface-Mediated Photocatalysis.  

National Technical Information Service (NTIS)

Three areas have been investigated: (1) application of esr spectroscopy and time-resolved diffuse reflectance absorption and emission spectroscopy to establish mechanisms in photocatalytic oxidative degradations of organic molecules; (2) exploration of co...

M. A. Fox

1992-01-01

237

Surface Mediated Photocatalysis.  

National Technical Information Service (NTIS)

Sensitized interfacial photoreactivity has been investigated as a means for accomplishing unique chemical transformations. Photoreactions on heteropolyoxoanions, on clays on native and modified form, and on zeolites of varying size, selectivity and cataly...

M. A. Fox

1987-01-01

238

Photocatalysis in microreactors  

Microsoft Academic Search

A photocatalytic microreactor with immobilized titanium dioxide as photocatalyst and illuminated by UV-A light emitting diodes was constructed and tested for the degradation of the model substance 4-chlorophenol. The microreactor consisted of 19 channels with a cross-section of approximately 200?m×300?m. Intrinsic kinetic parameters of the reaction could be determined and mass-transfer limitations for the employed operating conditions could be excluded

Roger Gorges; Susann Meyer; Günter Kreisel

2004-01-01

239

Water  

NSDL National Science Digital Library

This section of the Windows to the Universe website provides information and images about water, including detailed information about lakes, rivers, ocean, the water cycle, and tides. Windows to the Universe is a user-friendly learning system pertaining to the Earth and Space sciences. The objective of this project is to develop an innovative and engaging website that includes a rich array of documents, including images, movies, animations, and data sets that explore the Earth and Space sciences and the historical and cultural ties between science, exploration and the human experience. Links at the top of each page allow users to navigate between beginner, intermediate and advanced levels.

Johnson, Roberta

2000-07-01

240

Origin of visible-light-driven photocatalysis: A comparative study on N\\/F-doped and N–F-codoped TiO 2 powders by means of experimental characterizations and theoretical calculations  

Microsoft Academic Search

An overall comparative study was carried out on N-doped, F-doped, and N–F-codoped TiO2 powders (NTO, FTO, NFTO) synthesized by spray pyrolysis in order to elucidate the origin of their visible-light-driven photocatalysis. The comparisons in their experimentally obtained characteristics were based on the analysis of XPS, UV–Vis, PL, NH3-TPD and ESR spectra. The comparisons in their theoretically predicted properties were based

Di Li; Naoki Ohashi; Shunichi Hishita; Taras Kolodiazhnyi; Hajime Haneda

2005-01-01

241

Surface nanostructures in photocatalysts for visible-light-driven water splitting.  

PubMed

Overall water splitting to form hydrogen and oxygen over a heterogeneous (particulate) photocatalyst with solar energy is a promising process for clean and recyclable hydrogen production on a large-scale. In recent years, numerous attempts have been made for the development of photocatalysts that work under visible-light to utilize solar energy efficiently. This chapter describes recent research progress on heterogeneous photocatalysis for water splitting with visible light, particularly focusing on the development of nanostructured cocatalysts made by the authors' group. PMID:21516390

Maeda, Kazuhiko; Domen, Kazunari

2011-01-01

242

La(0.8)Sr(0.2)MnO(3-?) decorated with Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-?): a bifunctional surface for oxygen electrocatalysis with enhanced stability and activity.  

PubMed

Developing highly active and stable catalysts based on earth-abundant elements for oxygen electrocatalysis is critical to enable efficient energy storage and conversion. In this work, we took advantage of the high intrinsic oxygen reduction reaction (ORR) activity of La(0.8)Sr(0.2)MnO(3-?) (LSMO) and the high intrinsic oxygen evolution reaction (OER) activity of Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-?) (BSCF) to develop a novel bifunctional catalyst. We used pulsed laser deposition to fabricate well-defined surfaces composed of BSCF on thin-film LSMO grown on (001)-oriented Nb-doped SrTiO3. These surfaces exhibit bifunctionality for oxygen electrocatalysis with enhanced activities and stability for both the ORR and OER that rival the state-of-the-art single- and multicomponent catalysts in the literature. PMID:24649849

Risch, Marcel; Stoerzinger, Kelsey A; Maruyama, Shingo; Hong, Wesley T; Takeuchi, Ichiro; Shao-Horn, Yang

2014-04-01

243

Hydrogen electrocatalysis: A basic solution  

NASA Astrophysics Data System (ADS)

Hydrogen-oxygen alkaline fuel cells are promising devices for the 'hydrogen economy' but their oxidation of hydrogen fuel is slow compared with that of acidic fuel cells. More efficient electrocatalysts have now been prepared in which the adsorption of hydroxyl groups onto the electrode surface is controlled through suitable promoters.

Koper, Marc T. M.

2013-04-01

244

The reactivity of perovskites with water  

SciTech Connect

The interaction of oxides with water plays a critical role in understanding the surface functionality for environmental, geological, and technological applications (1, 2). Oxides are important geological constituents of rocks and soils, impact the quality of natural drinking water (3), and are used heavily in a wide range of industrial applications, including gas sensing (4) and separation (5), photoelectrochemistry (6), and electrocatalysis (7, 8). Performance in many applications is influenced by the oxide s affinity towards hydroxylation and the coverage of surface adsorbates (9, 10), which can lead to a change in its reactivity and adsorptive properties (11, 12). The subsequent wetting of materials, either by thin water films in ambient air or liquid water in an aqueous environment, also plays an important role in many properties of the surface, such as electrical and ionic conductivity (13). Consequently, the surface reactivity and chemical changes upon wetting of oxide surfaces in humid environments is key to a more fundamental understanding of oxides for environmental and technological applications.

Stoerzinger, Kelsey [Massachusetts Institute of Technology (MIT)] [Massachusetts Institute of Technology (MIT); Hong, W. [Harvard University] [Harvard University; Crumlin, Ethan [Massachusetts Institute of Technology (MIT)] [Massachusetts Institute of Technology (MIT); Biegalski, Michael D [ORNL] [ORNL; Azimi, Gisele [Massachusetts Institute of Technology (MIT)] [Massachusetts Institute of Technology (MIT); Varanasi, Kripa [Massachusetts Institute of Technology (MIT)] [Massachusetts Institute of Technology (MIT); Bluhm, Hendrik [Massachusetts Institute of Technology (MIT)] [Massachusetts Institute of Technology (MIT); Shao-Horn, Yang [Massachusetts Institute of Technology (MIT)] [Massachusetts Institute of Technology (MIT)

2012-01-01

245

Solar-chemical treatment of groundwater contaminated with petroleum at gas station sites: ex situ remediation using solar/TiO(2) photocatalysis and Solar Photo-Fenton.  

PubMed

Groundwater samples contaminated by BTEX (benzene, toluene, ethylbenzene, xylene isomers and TPHs (total petroleum hydrocarbons) were treated with advanced oxidation processes (AOPs), such as TiO(2) photocatalysis and Fe(2+)/H(2)O(2) exposed to solar light (37 degrees N and 128 degrees E) with an average intensity of 1.7 mW/cm(2) at 365 nm. These AOP processes showed feasibility in the treatment of groundwater contaminated with BTEX, TPH and TOC (Total Organic Carbon). Outdoor field tests showed that the degradation efficiency of each contaminant was higher in the Fe(2+)/H(2)O(2) system without solar light compared to the TiO(2)/solar light and H(2)O(2)/solar light systems. However, the TiO(2)/solar light and the Fe(2+)/H(2)O(2)/solar light systems showed significantly enhanced efficiencies in the degradation of BTEX, TPH and TOC with the additional use of H(2)O(2). Near complete degradation of BTEX and TPH was observed within 2 and 4 hrs, respectively, however, that of TOC was slower. Without pretreatment of the groundwater, fouling of the TiO(2), due to the ionic species present, was observed within 1 hr of operation, which resulted in the inhibition of further BTEX, TPH and TOC destruction. The degradation rate of n-alkanes with carbon numbers ranging from C10 to C15 was relatively greater than that of n-alknaes with carbon numbers ranging from C16 to C20. From this work, the AOP process (Fe(2+)/H(2)O(2)/solar light and TiO(2)/H(2)O(2)/solar light) illuminated with solar light was identified as an effective ex situ technique in the remediation of groundwater contaminated with petroleum. PMID:16484076

Cho, Ii-Hyoung; Kim, Young-Gyu; Yang, Jae-Kyu; Lee, Nae-Hyun; Lee, Seung-Mok

2006-01-01

246

Photocatalysis: effect of light-activated nanoscale formulations of TiO(2) on Xanthomonas perforans and control of bacterial spot of tomato.  

PubMed

Protection of crops from bacterial diseases presents a continuing challenge, mandating the development of novel agents and approaches. Photocatalysis is a process where chemically reactive oxygen species are catalytically generated by certain minerals in the presence of light. These reactive oxygen species have the capacity to destroy organic molecular structures critical to pathogen viability. In this study, the antibacterial potential of photocatalytic nanoscale titanium dioxide (TiO(2)), nanoscale TiO(2) doped (incorporation of other materials into the structure of TiO(2)) with silver (TiO(2)/Ag), and nanoscale TiO(2) doped with zinc (TiO(2)/Zn; AgriTitan) was evaluated against Xanthomonas perforans, the causal agent for bacterial spot disease of tomato. In vitro experiments on photocatalytic activity and dose dependency were conducted on glass cover slips coated with the nanoscale formulations by adding a known population of X. perforans strain Xp-F7 and illuminating the cover slips under a visible light source. TiO(2)/Ag and TiO(2)/Zn had high photocatalytic activity against X. perforans within 10 min of exposure to 3 × 10(4) lux. Greenhouse studies on naturally and artificially infected transplants treated with TiO(2)/Zn at ?500 to 800 ppm significantly reduced bacterial spot severity compared with untreated and copper control. Protection was similar to the grower standard, copper + mancozeb. The use of TiO(2)/Zn at ?500 to 800 ppm significantly reduced disease incidence in three of the four trials compared with untreated and copper control, and was comparable to or better than the grower standard. The treatments did not cause any adverse effects on tomato yield in any of the field trials. PMID:23190116

Paret, Mathews L; Vallad, Gary E; Averett, Devron R; Jones, Jeffrey B; Olson, Stephen M

2013-03-01

247

Photolytic and photocatalytic degradation of quinclorac in ultrapure and paddy field water: identification of transformation products and pathways.  

PubMed

Quinclorac (QNC) is an effective but rather persistent herbicide commonly used in rice production. This herbicide presents a mean persistence in the environment so its residues are considered of environmental relevance. However, few studies have been conducted to investigate its environmental behavior and degradation. In the present work, direct photolysis and TiO(2) photocatalysis of the target compound in ultrapure and paddy field water were investigated. After 10h photolysis in ultrapure water, the concentration of QNC declined 26% and 54% at 250 and 700 W m(-2), respectively. However, the amount of quinclorac in paddy field water remained almost constant under the same irradiation conditions. QNC dissipated completely after 40 min of TiO(2) photocatalysis in ultrapure water, whereas 130 min were necessary to degrade 98% of the initial concentration in paddy field water. Possible QNC photolytic and photocatalytic degradation pathways are proposed after structure elucidation of the main transformation products, through liquid chromatography-electrospray ionization-quadrupole time-of-flight mass spectrometry and exact mass measurements. Pyridine ring hydroxylation at C-9 followed by ring opening and/or oxidative dechlorination were the key steps of QNC degradation. PMID:22316588

Pareja, Lucía; Pérez-Parada, Andrés; Agüera, Ana; Cesio, Verónica; Heinzen, Horacio; Fernández-Alba, Amadeo R

2012-05-01

248

Interplay between Water and TiO2 Anatase (101) Surface with Subsurface Oxygen Vacancy  

NASA Astrophysics Data System (ADS)

The interaction between water and the TiO2 anatase (101) surface with a subsurface VO is studied using first-principles calculations. Upon water adsorption, the relative stability of the subsurface and surface VO reverses. The surface VO becomes energetically more stable than its subsurface counterpart, which induces VO to migrate from the subsurface to the surface with a very low energy barrier. Then the adsorbed water molecule can easily dissociate through a barrierless pathway facilitated by surface VO. This reaction pathway has a similar energy barrier with another pathway under which water dissociates with the presence of subsurface VO followed by VO migration from the subsurface layer to the surface layer, indicating that subsurface VO can facilitate water dissociation directly, or, via surface VO indirectly. This novel interplay between the adsorbate and substrate defects may provide a new way to explain the origin of the activity of anatase (101) in photocatalysis in aqueous surroundings.

Li, Yadong; Gao, Yi

2014-05-01

249

Synthesis and visible light photocatalysis water splitting property of Cu-doped NaInS{sub 2} synthesized by a hydrothermal method  

SciTech Connect

Graphical abstract: Display Omitted Highlights: ? Cu-doped NaInS{sub 2} powders were prepared by the solvethermal method. ? The samples were characterized by XRD, SEM, and DRS (diffuse reflection spectra). ? The effects of Cu doping ion on the photocatalytic activity were studied. ? The effects of Pt loading on the photocatalytic activity were investigated. -- Abstract: Copper-doped NaInS{sub 2} with hexagonal blocks morphology was prepared by a one-step hydrothermal method and the photocatalytic activity was investigated. The as-synthesized products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–vis spectroscopy. XRD patterns show that the Cu ions doping has no effect on the crystal structure of NaInS{sub 2}. UV–vis diffuse reflectance spectra show that the absorption wavelength of Cu-doped NaInS{sub 2} occurs red-shift which originated from Cu3d orbital forming impurity level. The photocatalytic activity was increased by Cu doping. The optimal doping amount of Cu{sup 2+} is 1.5 ml.

Zhang, HongJie, E-mail: mis-hongjie@163.com [Department of Chemistry, Harbin Institute of Technology, XiDa Straight Street 92, Harbin 150001 (China)] [Department of Chemistry, Harbin Institute of Technology, XiDa Straight Street 92, Harbin 150001 (China); Chen, Gang, E-mail: gchen@hit.edu.cn [Department of Chemistry, Harbin Institute of Technology, XiDa Straight Street 92, Harbin 150001 (China)] [Department of Chemistry, Harbin Institute of Technology, XiDa Straight Street 92, Harbin 150001 (China); He, Xiaodong [School of Astronautics, Harbin Institute of Technology, XiDa Straight Street 92, Harbin 150001 (China)] [School of Astronautics, Harbin Institute of Technology, XiDa Straight Street 92, Harbin 150001 (China); Xu, Jing [Heilongjiang Institute of Technology, Department of Materials and Chemistry Engineering, Harbin 150001 (China)] [Heilongjiang Institute of Technology, Department of Materials and Chemistry Engineering, Harbin 150001 (China)

2012-12-15

250

Destruction of Trace Organics in Otherwise Ultra Pure Water  

SciTech Connect

A number of experiments were conducted to determine the economic viability of applying various ultraviolet (UV) oxidation processes to a waste water stream containing approximately 12 mg/L total organic carbon (TOC), predominately ethylene glycol. In all experiments, a test solution was illuminated with either near-UV or a far-UV light alone or in combination with a variety of photocatalysts and oxidants. Based upon the outcomes of this project, both UV/photocatalysis and UV/ozone processes are capable of treating the water sample to below detection capabilities of TOC. However, the processes are fairly energy intensive; the most efficient case tested required 11 kWh per order of magnitude reduction in TOC per 1000 L. If energy consumption rates of 5-10 kWh/1000 L are deemed reasonable, then further investigation is recommended.

Prairie, M. R.; Stange, B. M.; Showalter, S. K.; Magrini, K. A.

1995-12-01

251

Destruction of trace organics in otherwise ultra pure water  

SciTech Connect

A number of experiments were conducted to determine the economic viability of applying various ultraviolet (UV) oxidation processes to a waste water stream containing approximately 12 mg/L total organic carbon (TOC), predominately ethylene glycol. In all experiments, a test solution was illuminated with either near-UV or a far-UV light alone or in combination with a variety of photocatalysts and oxidants. Based upon the outcomes of this project, both UV/photocatalysis and UV/ozone processes are capable of treating the water sample to below detection capabilities of TOC. However, the processes are fairly energy intensive; the most efficient case tested required 11 kWh per order of magnitude reduction in TOC per 1000 L. If energy consumption rates of 5-10 kWh/1000 L are deemed reasonable, then further investigation is recommended.

Prairie, M.R.; Stange, B.M.; Showalter, S.K. [Sandia National Labs., Albuquerque, NM (United States); Magrini, K.A. [National Renewable Energy Laboratory, Golden, CO (United States)

1995-12-01

252

Photolysis and photocatalysis of ibuprofen in aqueous medium: characterization of by-products via liquid chromatography coupled to high-resolution mass spectrometry and assessment of their toxicities against Artemia salina.  

PubMed

The degradation of the pharmaceutical compound ibuprofen (IBP) in aqueous solution induced by direct photolysis (UV-A and UV-C radiation) and photocatalysis (TiO2 /UV-A and TiO2 /UV-C systems) was evaluated. Initially, we observed that whereas photocatalysis (both systems) and direct photolysis with UV-C radiation were able to cause an almost complete removal of IBP, the mineralization rates achieved for all the photodegradation processes were much smaller (the highest value being obtained for the TiO2 /UV-C system: 37.7%), even after an exposure time as long as 120?min. Chemical structures for the by-products formed under these oxidative conditions (11 of them were detected) were proposed based on the data from liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) analyses. Taking into account these results, an unprecedented route for the photodegradation of IBP could thus be proposed. Moreover, a fortunate result was achieved herein: tests against Artemia salina showed that the degradation products had no higher ecotoxicities than IBP, which possibly indicates that the photocatalytic (TiO2 /UV-A and TiO2 /UV-C systems) and photolytic (UV-C radiation) processes can be conveniently employed to deplete IBP in aqueous media. PMID:24464542

da Silva, Júlio César Cardoso; Teodoro, Janaina Aparecida Reis; Afonso, Robson José de Cássia Franco; Aquino, Sérgio Francisco; Augusti, Rodinei

2014-02-01

253

Novel Au/La-SrTiO3 microspheres: Superimposed Effect of Gold Nanoparticles and Lanthanum Doping in Photocatalysis.  

PubMed

Novel multielement Au/La-SrTiO3 microspheres were synthesized by a solvothermal method using monodisperse gold and La-SrTiO3 nanocrystals as building blocks. The porous Au/La-SrTiO3 microspheres had a large surface area of 94.6?m(2) ?g(-1) . The stable confined Au nanoparticles demonstrated strong surface plasmon resonance effect, leading to enhanced absorption in a broad UV/Vis/NIR range. Doping of rare-earth metal La also broadened the absorption band to the visible region. Both the conduction and valence bands of Au/La-SrTiO3 microspheres thus show favorable potential for proton reduction under visible light. The superimposed effect of Au nanoparticles and La doping in Au/La-SrTiO3 microspheres led to high photocurrent density in photoelectrochemical water splitting and good photocatalytic activity in photodegradation of rhodamine?B. The photocatalytic activities are in the order of the following: Au/La-SrTiO3 microspheres>Au/SrTiO3 microspheres>La-SrTiO3 microspheres>SrTiO3 microspheres. PMID:24817580

Wang, Guannan; Wang, Pei; Luo, He-Kuan; Hor, T S Andy

2014-07-01

254

Syntheses, structures, photoluminescence, photocatalysis, and photoelectronic effects of 3D mixed high-connected metal-organic frameworks based on octanuclear and dodecanuclear secondary building units.  

PubMed

Four novel metal-organic frameworks (MOFs) based on high-nuclear metal carboxylate clusters, namely, [Zn(4)(L)(2)(?(3)-OH)(2)(H(2)O)(1.5)]·2H(2)O (1), [Zn(5)Na(L)(2)(?(3)-OH)(4)(CH(3)CH(2)O)(H(2)O)(2)] (2), [Cd(4)(L)(2)(BIME)(0.5)(?(3)-OH)(2)(H(2)O)(1.5)]·2H(2)O (3), and [Zn(4)(L)(2)(BET)(0.5)(?(3)-OH)(2)(H(2)O)] (4), where H(3)L = (3,5-dicarboxyl-phenyl)-(4-(2'-carboxyl-phenyl)-benzyl)ether, BET = 1,1'-(2'-oxybis(ethane-2,1-diyl))bis(1,2,4-triazol-1-yl), BIME = 1,2-bis(imidazol-1-yl)ethane, have been synthesized under hydrothermal conditions. In 1, each planar octanuclear zinc cluster [Zn(8)(?(3)-OH)(8)(CO(2))(12)(H(2)O)(3)] is linked by twelve L anions to give an unusual (3,12)-connected framework with (4(3))(2)(4(20)·6(28)·8(18)) topology. In 2, dodecanuclear heterometallic clusters [Zn(10)Na(2)(?(3)-OH)(8)(CO(2))(12)(CH(3)CH(2)O)(2)(H(2)O)(4)] are surrounded by twelve L anions to form a (3,12)-connected net with the same topology as 1. However, 3 exhibits a rare (3,14)-connected (4(3))(3(2)4)(3(4)·4(20)·5(14)·6(34)·7(11)·8(8)) net based on octanuclear cadmium cluster [Cd(8)(BIME)(2)(?(3)-OH)(4)(CO(2))(12)(H(2)O)(4)]·2H(2)O as a 14-connected node and H(3)L as a 3-connected node. In 4, each octanuclear zinc cluster [Zn(8)(BET)(2)(?(3)-OH)(4)(CO(2))(12)(H(2)O)(2)] is linked by twelve L anions to furnish a (3,14)-connected net with the same topology as 3. The optical energy gaps and photoluminescence were investigated for the compounds. Moreover, compounds 1-4 exhibit good photocatalytic activities for degradation of methylene blue (MB) under UV irradiation and show good stability towards UV photocatalysis. In addition, 1 and 4 display a photocurrent density under several on-off cycles of illumination. PMID:23138531

Du, Peng; Yang, Yan; Yang, Jin; Liu, Bing-Kun; Ma, Jian-Fang

2013-02-01

255

A novel copper(II) complex constructed with mixed ligands of biphenyl-4,4'-dicarboxylic acid (H 2bpdc) and dipyrido[3,2-d:2',3'-f]quinoxaline (Dpq): Synthesis, structure, electrochemistry and electrocatalysis  

NASA Astrophysics Data System (ADS)

A novel metal-organic framework [Cu 2(bpdc) 2(Dpq) 2(H 2O)]·H 2O ( 1) has been obtained from hydrothermal reaction of copper chloride with the mixed ligands [biphenyl-4,4'-dicarboxylic acid (H 2bpdc) and dipyrido[3,2-d:2',3'-f]quinoxaline (Dpq)], and structurally characterized by elemental analysis, IR, TG and single-crystal X-ray diffraction analysis. The unique feature is that there simultaneously exist two kinds of one-dimensional (1-D) zigzag polymeric chains in complex 1. Moreover, the 1-D polymeric chains are ultimately packed into a three-dimensional (3-D) supramolecular framework through two different hydrogen bonding interactions. The adjacent different chains are linked by C-H⋯O hydrogen bonding interactions, and the same kind chains are further connected through C-H⋯? stacking interactions. Additionally, the complex 1 was used as solid bulk-modifier to fabricate renewable carbon paste electrode (Cu-CPE) by the direct mixing method. The electrochemical behavior and electrocatalysis of Cu-CPE have been studied in detail. The results indicate that Cu-CPE give one-electron quasi-reversible redox waves in potential range of 400 to -300 mV due to the metal copper ion Cu(II)/Cu(I). The Cu-CPE showed good electrocatalytic activity toward the reduction of the bromate, nitrite and hydrogen peroxide. The electrocatalytic reduction peak currents of KBrO 3, KNO 2 and H 2O 2 showed a linear dependence on their concentrations. All of the results revealed that the Cu-CPE had a good reproducibility, remarkable long-term stability and especially good surface renewability by simple mechanical polishing in the event of surface fouling, which is important for practical application.

Lin, HongYan; Wang, XiuLi; Hu, HaiLiang; Chen, BaoKuan; Liu, GuoCheng

2009-03-01

256

Enzymatic conversion of carbon dioxide to methanol: Enhanced methanol production in silica sol-gel matrices  

Microsoft Academic Search

Strategies for effective conversion of atmospheric COâ to methanol offer promising new technologies not only for recycling of the greenhouse gas but also for an efficient production of fuel alternatives. Partial hydrogenation of carbon dioxide has been accomplished by means of heterogeneous catalysis, electrocatalysis, and photocatalysis. Oxide-based catalysts are predominantly used for industrial fixation of carbon dioxide. A unique approach

Robyn Obert; Bakul C. Dave

1999-01-01

257

Fabrication of TiO2 film with different morphologies on Ni anode and application in photoassisted water electrolysis  

NASA Astrophysics Data System (ADS)

The anode of an alkaline electrolytic cell for water electrolysis was modified by TiO2 photocatalysts with different morphologies. The water electrolysis was coupled with photocatalytic decomposition of water by irradiation of UV light on the modified anode. And a feasible process for the hydrogen production of water electrolysis assisted by photocatalysis (WEAP) was proposed and experimentally confirmed. The results show that the highly ordered, vertically oriented tubular arrays structure on Ni anode surface has better hydrogen production performance than random TiO2. In WEAP process, the maximum rate of hydrogen production is 2.77 ml/(h*cm2) when the anode modified by ordered TiO2 nanotube arrays, compared to traditional alkaline electrolytic cell for water electrolysis with Ni anode, H2-production rate increased by 139%.

He, Hongbo; Chen, Aiping; Lv, Hui; Dong, Haijun; Chang, Ming; Li, Chunzhong

2013-02-01

258

Cu2ZnSnS4-Pt and Cu2ZnSnS4-Au Heterostructured Nanoparticles for Photocatalytic Water Splitting and Pollutant Degradation.  

PubMed

Cu2ZnSnS4, based on abundant and environmental friendly elements and with a direct band gap of 1.5 eV, is a main candidate material for solar energy conversion through both photovoltaics and photocatalysis. We detail here the synthesis of quasi-spherical Cu2ZnSnS4 nanoparticles with unprecedented narrow size distributions. We further detail their use as seeds to produce CZTS-Au and CZTS-Pt heterostructured nanoparticles. Such heterostructured nanoparticles are shown to have excellent photocatalytic properties toward degradation of Rhodamine B and hydrogen generation by water splitting. PMID:24946131

Yu, Xuelian; Shavel, Alexey; An, Xiaoqiang; Luo, Zhishan; Ibáñez, Maria; Cabot, Andreu

2014-07-01

259

Photocatalysis on TiO{sub 2} surfaces investigated by atomic force microscopy: Photodegradation of partial and full monolayers of stearic acid on TiO{sub 2}(110)  

SciTech Connect

The photocatalytic properties of TiO{sub 2} are of practical significance in applications ranging from solar energy conversion through environmental remediation to antibacterial, self-cleaning, and antifogging functions. The authors have studied the nature and surface morphological changes associated with the photodegradation of stearic acid LB films on TiO{sub 2}(110). Interestingly, submonolayers of stearic acid consisted of circular domains of various sizes--a feature very attractive for monitoring TiO{sub 2} photocatalysis by AFM. The authors noted that there was no bulk differential reactivity at island edges compared to the interior. This suggests that the rate of photodegradation of the stearic acid molecules is independent of their location in the island. Accordingly, the overall surface reactivity trends were similar for both partial films and complete films. Likewise, the observed inhomogeneous reactivity patterns appear to be a reflection of the transient distribution of the reaction centers.

Sawunyama, P. [Kanagawa Academy of Science and Technology, Atsugi, Kanagawa (Japan). Dept. of Applied Chemistry] [Kanagawa Academy of Science and Technology, Atsugi, Kanagawa (Japan). Dept. of Applied Chemistry; Fujishima, Akira; Hashimoto, Kazuhito [Kanagawa Academy of Science and Technology, Atsugi, Kanagawa (Japan). Dept. of Applied Chemistry] [Kanagawa Academy of Science and Technology, Atsugi, Kanagawa (Japan). Dept. of Applied Chemistry; [Univ. of Tokyo (Japan)

1999-05-11

260

Selective isolation of the electron or hole in photocatalysis: ZnO-TiO2 and TiO2-ZnO core-shell structured heterojunction nanofibers via electrospinning and atomic layer deposition  

NASA Astrophysics Data System (ADS)

Heterojunctions are a well-studied material combination in photocatalysis studies, the majority of which aim to improve the efficacy of the catalysts. Developing novel catalysts begs the question of which photo-generated charge carrier is more efficient in the process of catalysis and the associated mechanism. To address this issue we have fabricated core-shell heterojunction (CSHJ) nanofibers from ZnO and TiO2 in two combinations where only the `shell' part of the heterojunction is exposed to the environment to participate in the photocatalysis. Core and shell structures were fabricated via electrospinning and atomic layer deposition, respectively which were then subjected to calcination. These CSHJs were characterized and studied for photocatalytic activity (PCA). These two combinations expose electrons or holes selectively to the environment. Under suitable illumination of the ZnO-TiO2 CSHJ, e/h pairs are created mainly in TiO2 and the electrons take part in catalysis (i.e. reduce the organic dye) at the conduction band or oxygen vacancy sites of the `shell', while holes migrate to the core of the structure. Conversely, holes take part in catalysis and electrons diffuse to the core in the case of a TiO2-ZnO CSHJ. The results further revealed that the TiO2-ZnO CSHJ shows ~1.6 times faster PCA when compared to the ZnO-TiO2 CSHJ because of efficient hole capture by oxygen vacancies, and the lower mobility of holes.Heterojunctions are a well-studied material combination in photocatalysis studies, the majority of which aim to improve the efficacy of the catalysts. Developing novel catalysts begs the question of which photo-generated charge carrier is more efficient in the process of catalysis and the associated mechanism. To address this issue we have fabricated core-shell heterojunction (CSHJ) nanofibers from ZnO and TiO2 in two combinations where only the `shell' part of the heterojunction is exposed to the environment to participate in the photocatalysis. Core and shell structures were fabricated via electrospinning and atomic layer deposition, respectively which were then subjected to calcination. These CSHJs were characterized and studied for photocatalytic activity (PCA). These two combinations expose electrons or holes selectively to the environment. Under suitable illumination of the ZnO-TiO2 CSHJ, e/h pairs are created mainly in TiO2 and the electrons take part in catalysis (i.e. reduce the organic dye) at the conduction band or oxygen vacancy sites of the `shell', while holes migrate to the core of the structure. Conversely, holes take part in catalysis and electrons diffuse to the core in the case of a TiO2-ZnO CSHJ. The results further revealed that the TiO2-ZnO CSHJ shows ~1.6 times faster PCA when compared to the ZnO-TiO2 CSHJ because of efficient hole capture by oxygen vacancies, and the lower mobility of holes. Electronic supplementary information (ESI) available: Additional SEM image of the CSHJ, XPS spectra and mechanism demonstrating PCA at the surface of pure TiO2. See DOI: 10.1039/c3nr06665g

Kayaci, Fatma; Vempati, Sesha; Ozgit-Akgun, Cagla; Donmez, Inci; Biyikli, Necmi; Uyar, Tamer

2014-05-01

261

Overview of Photocatalysis, Photocatalytic Surface Materials Studies, and Demonstration of Self-Cleaning Materials for Space and Terrestrial Based Applications at the Infinity Science Center at NASA Stennis Space Center  

NASA Technical Reports Server (NTRS)

Research into photocatalytic technology has been progressing for over three decades in the early 1990s Japanese and European companies initiate research into photocatalytic technology. In the 1996 specific focus on the technology with the first large-scale application: the construction of a church in Rome (Jubilee Church). And in 2000 Europe and Japan research into the benefits of photocatalytic technology. Currently, photocatalytic technology continues to improve, and with time development is becoming more efficient and effective. What is Photocatalysis? Photo: phenomenon induced by the light, having specifically a wavelength around 320-400 nm (artificial or natural sunlight). Catalyst: a material that induces a reaction but is not consumed or transformed by it. The catalyst remains constantly available. In this case, the catalyst is made with nano-particles of titanium oxide (Ti02).

Underwood, Lauren W.

2012-01-01

262

Effect of the structure of imidazolium cations in [BF 4] ?-type ionic liquids on direct electrochemistry and electrocatalysis of horseradish peroxidase in Nafion films  

Microsoft Academic Search

The direct electrochemistry and bioelectrocatalysis of horseradish peroxidase (HRP) in Nafion films at glassy carbon electrode (GCE) was investigated in three [BF4]?-type room-temperature ionic liquids (ILs) to understand the structural effect of imidazolium cations. The three ILs are 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim][BF4]), 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) and 1-hexyl-3-methylimidazolium tetrafluoroborate ([Hmim][BF4]). A small amount of water in the three ILs is indispensable for

Lu Lu; Xirong Huang; Yinbo Qu

2011-01-01

263

Selective isolation of the electron or hole in photocatalysis: ZnO-TiO2 and TiO2-ZnO core-shell structured heterojunction nanofibers via electrospinning and atomic layer deposition.  

PubMed

Heterojunctions are a well-studied material combination in photocatalysis studies, the majority of which aim to improve the efficacy of the catalysts. Developing novel catalysts begs the question of which photo-generated charge carrier is more efficient in the process of catalysis and the associated mechanism. To address this issue we have fabricated core-shell heterojunction (CSHJ) nanofibers from ZnO and TiO2 in two combinations where only the 'shell' part of the heterojunction is exposed to the environment to participate in the photocatalysis. Core and shell structures were fabricated via electrospinning and atomic layer deposition, respectively which were then subjected to calcination. These CSHJs were characterized and studied for photocatalytic activity (PCA). These two combinations expose electrons or holes selectively to the environment. Under suitable illumination of the ZnO-TiO2 CSHJ, e/h pairs are created mainly in TiO2 and the electrons take part in catalysis (i.e. reduce the organic dye) at the conduction band or oxygen vacancy sites of the 'shell', while holes migrate to the core of the structure. Conversely, holes take part in catalysis and electrons diffuse to the core in the case of a TiO2-ZnO CSHJ. The results further revealed that the TiO2-ZnO CSHJ shows ?1.6 times faster PCA when compared to the ZnO-TiO2 CSHJ because of efficient hole capture by oxygen vacancies, and the lower mobility of holes. PMID:24664354

Kayaci, Fatma; Vempati, Sesha; Ozgit-Akgun, Cagla; Donmez, Inci; Biyikli, Necmi; Uyar, Tamer

2014-06-01

264

A review on catalytic applications of Au/TiO2 nanoparticles in the removal of water pollutant.  

PubMed

Nanomaterials are showing great potential for the improvement of water treatment technologies. In recent years, catalysis and photocatalysis processes using gold nanoparticles (Au-NPs) have received great attention due to their effectiveness in degrading and mineralizing organic compounds. This paper aims to review and summarize the recently published works and R & D progress in the field of photocatalytic oxidation of various water pollutants such as toxic organic compounds (i.e. azo dyes and phenols) by Au-NPs/TiO2 under solar, visible and UV irradiation. Extensive research which has focused on the enhancement of photocatalysis by modification of TiO2 employing Au-NPs is also reviewed. Moreover, the effects of various operating parameters on the photocatalytic activity of these catalysts, such as size and loading amount of Au-NPs, pH and calcination, are discussed. The support type, loading amount and particle size of deposited Au-NPs are the most important parameters for Au/TiO2 catalytic activity. Our study showed in particular that the modification of TiO2, including semiconductor coupling, can increase the photoactivity of Au/TiO2. In contrast, doping large gold NPs can mask or block the TiO2 active sites, reducing photocatalytic activity. The optimized loading amount of Au-NP varied for each experimental condition. Finally, research trends and prospects for the future are briefly discussed. PMID:24560285

Ayati, Ali; Ahmadpour, Ali; Bamoharram, Fatemeh F; Tanhaei, Bahareh; Mänttäri, Mika; Sillanpää, Mika

2014-07-01

265

Effect of the structure of imidazolium cations in [BF4](-)-type ionic liquids on direct electrochemistry and electrocatalysis of horseradish peroxidase in Nafion films.  

PubMed

The direct electrochemistry and bioelectrocatalysis of horseradish peroxidase (HRP) in Nafion films at glassy carbon electrode (GCE) was investigated in three [BF(4)](-)-type room-temperature ionic liquids (ILs) to understand the structural effect of imidazolium cations. The three ILs are 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim][BF(4)]), 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF(4)]) and 1-hexyl-3-methylimidazolium tetrafluoroborate ([Hmim][BF(4)]). A small amount of water in the three ILs is indispensable for maintaining the electrochemical activity of HRP in Nafion films, and the optimum water contents decrease with the increase of alkyl chain length on imidazole ring. Analysis shows that the optimum water contents are primarily determined by the hydrophilicity of ILs used. In contrast to aqueous medium, ILs media facilitate the direct electron transfer of HRP, and the electrochemical parameters obtained in different ILs are obviously related to the nature of ILs. The direct electron transfer between HRP and GCE is a surface-confined quasi-reversible single electron transfer process. The apparent heterogeneous electron transfer rate constant decreases gradually with the increase of alkyl chain length on imidazole ring, but the changing extent is relatively small. The electrocatalytic reduction current of H(2)O(2) at the present electrode decreases obviously with the increase of alkyl chain length, and the mass transfer of H(2)O(2) via diffusion in ILs should be responsible for the change. In addition, the modified electrode has good stability and reproducibility; the ability to tolerate high levels of F(-) has been greatly enhanced due to the use of Nafion film. When an appropriate mediator is included in the sensing layer, a sensitive nonaqueous biosensor could be fabricated. PMID:21632219

Lu, Lu; Huang, Xirong; Qu, Yinbo

2011-10-01

266

A Current Perspective on Photocatalysis  

Microsoft Academic Search

The efficient conversion of solar photons into solar electricity and solar fuels is one of the most important scientific challenges of this century owing to dwindling fossil fuel reserves and the need for clean energy. While research in the direct conversion of solar energy to electricity in the areas of low-cost photovoltaic (PV) systems based on all-inorganic semiconductors, dye-sensitized solar

E. Fujita; J. T. Muckerman; K. Domen

2011-01-01

267

The application of novel spindle-like polypyrrole hollow nanocapsules containing Pt nanoparticles in electrocatalysis oxidation of nicotinamide adenine dinucleotide (NADH).  

PubMed

Novel spindle-like polypyrrole hollow nanocapsules containing Pt nanoparticles (Pt NPs/PPy composite hollow nanospindles) were successfully prepared by using beta-akaganeite (?-Fe(3+)O(OH,Cl)) nanospindles as templates and methanoic acid as a reducing agent. The ?-Fe(3+)O(OH,Cl) templates can be easily obtained in ethanol/water mixing solution in the presence of thiophene and FeCl(3)·6H(2)O, and after coating by PPy shell, they can be gradually and completely etched during the reduction of H(2)PtCl(6) into Pt nanoparticles (Pt NPs) with the average size of 3.6 nm on spindle-like polypyrrole hollow nanocapsules, which could still keep their integrality of morphologies with the thickness of PPy shell of 18-20 nm. The investigation of Pt NPs/PPy composite hollow nanospindles modified glassy carbon electrode (GCE) for the application to detect nicotinamide adenine dinucleotide (NADH) with cyclic voltammetry (CV) and amperometry indicated good linearity and sensitivity of responses in the certain range of NADH concentration. The influence of Pt NPs content to the NADH oxidation current was also studied. This new kind of unique spindle-like noble metal/conducting polymer hollow nanostructured complex can be acted as a good steady electrode material for electrocatalytic oxidation of NADH. PMID:21310424

Mao, Hui; Li, Yongxin; Liu, Xincai; Zhang, Wanjin; Wang, Ce; Al-Deyab, Salem S; El-Newehy, Mohamed

2011-04-15

268

Rapid synthesis, structure and photocatalysis of pure bismuth A-site perovskite of Bi(Mg3/8Fe2/8Ti3/8)O3.  

PubMed

Bi(Mg3/8Fe2/8Ti3/8)O3, a member of a small group of pure Bi(3+) A site perovskites, exhibiting a high ferroelectric Curie point (Tc), was rapidly synthesized by a sample method of molten salt synthesis. The purity of Bi(Mg3/8Fe2/8Ti3/8)O3 samples is directly affected by the reaction conditions such as the soaking temperature, and the heating and cooling rates. The as-prepared Bi(Mg3/8Fe2/8Ti3/8)O3 particles are well-formed, cube-shaped single-crystals with sizes ranging from 200-300 nm. The chemical states of Bi and Fe ions are Bi(3+) and Fe(3+) in Bi(Mg3/8Fe2/8Ti3/8)O3. UV-vis diffuse reflectance spectra and preliminary photocatalytic experiments indicate that the pure Bi(3+) A site perovskite of Bi(Mg3/8Fe2/8Ti3/8)O3 has a suitable energy bandgap (1.86 eV) and shows obvious photocatalytic activity for the decolorization of methyl blue under visible-light irradiation. The present work suggests potential future applications of Bi(Mg3/8Fe2/8Ti3/8)O3 in photocatalysis and ferroelectric photovoltaic effects. PMID:24818220

Zhang, Wenjuan; Chen, Jun; An, Xiaoxin; Wang, Qi; Fan, Longlong; Wang, Fangfang; Deng, Jinxia; Yu, Ranbo; Xing, Xianran

2014-06-28

269

Perovskite oxides: Oxygen electrocatalysis and bulk structure  

NASA Technical Reports Server (NTRS)

Perovskite type oxides were considered for use as oxygen reduction and generation electrocatalysts in alkaline electrolytes. Perovskite stability and electrocatalytic activity are studied along with possible relationships of the latter with the bulk solid state properties. A series of compounds of the type LaFe(x)Ni1(-x)O3 was used as a model system to gain information on the possible relationships between surface catalytic activity and bulk structure. Hydrogen peroxide decomposition rate constants were measured for these compounds. Ex situ Mossbauer effect spectroscopy (MES), and magnetic susceptibility measurements were used to study the solid state properties. X ray photoelectron spectroscopy (XPS) was used to examine the surface. MES has indicated the presence of a paramagnetic to magnetically ordered phase transition for values of x between 0.4 and 0.5. A correlation was found between the values of the MES isomer shift and the catalytic activity for peroxide decomposition. Thus, the catalytic activity can be correlated to the d-electron density for the transition metal cations.

Carbonio, R. E.; Fierro, C.; Tryk, D.; Scherson, D.; Yeager, Ernest

1987-01-01

270

Perovskite oxides: Oxygen electrocatalysis and bulk structure  

NASA Astrophysics Data System (ADS)

Perovskite type oxides were considered for use as oxygen reduction and generation electrocatalysts in alkaline electrolytes. Perovskite stability and electrocatalytic activity are studied along with possible relationships of the latter with the bulk solid state properties. A series of compounds of the type LaFe(x)Ni1(-x)O3 was used as a model system to gain information on the possible relationships between surface catalytic activity and bulk structure. Hydrogen peroxide decomposition rate constants were measured for these compounds. Ex situ Mossbauer effect spectroscopy (MES), and magnetic susceptibility measurements were used to study the solid state properties. X ray photoelectron spectroscopy (XPS) was used to examine the surface. MES has indicated the presence of a paramagnetic to magnetically ordered phase transition for values of x between 0.4 and 0.5. A correlation was found between the values of the MES isomer shift and the catalytic activity for peroxide decomposition. Thus, the catalytic activity can be correlated to the d-electron density for the transition metal cations.

Carbonio, R. E.; Fierro, C.; Tryk, D.; Scherson, D.; Yeager, Ernest

1987-09-01

271

Photocatalyzed destruction of water contaminants  

Microsoft Academic Search

Heterogeneous photocatalysis is a process in which the illumination of an oxide semiconductor, usually the anatase form of titanium dioxide, produces photoexcited electrons (e⁻) and holes (h{sup +}). These can migrate to the oxide surface and participate in half-cell reactions that are part of a closed, catalytic cycle. In the aqueous phase, the illuminated surface is widely regarded as a

David F. Ollis; Ezio Pelizzetti; Nick Serpone

1991-01-01

272

Plasmon-enhanced water splitting on TiO2-passivated GaP photocatalysts.  

PubMed

Integrating plasmon resonant nanostructures with photocatalytic semiconductors shows great promise for high efficiency photocatalytic water splitting. However, the electrochemical instability of most III-V semiconductors severely limits their applicability in photocatalysis. In this work, we passivate p-type GaP with a thin layer of n-type TiO2 using atomic layer deposition. The TiO2 passivation layer prevents corrosion of the GaP, as evidenced by atomic force microscopy and photoelectrochemical measurements. In addition, the TiO2 passivation layer provides an enhancement in photoconversion efficiency through the formation of a charge separating pn-region. Plasmonic Au nanoparticles deposited on top of the TiO2-passivated GaP further increases the photoconversion efficiency through local field enhancement. These two enhancement mechanisms are separated by systematically varying the thickness of the TiO2 layer. Because of the tradeoff between the quickly decaying plasmonic fields and the formation of the pn-charge separation region, an optimum performance is achieved for a TiO2 thickness of 0.5 nm. Finite difference time domain (FDTD) simulations of the electric field profiles in this photocatalytic heterostructure corroborate these results. The effects of plasmonic enhancement are distinguished from the natural catalytic properties of Au by evaluating similar photocatalytic TiO2/GaP structures with catalytic, non-plasmonic metals (i.e., Pt) instead of Au. This general approach of passivating narrower band gap semiconductors enables a wider range of materials to be considered for plasmon-enhanced photocatalysis for high efficiency water splitting. PMID:24401904

Qiu, Jing; Zeng, Guangtong; Pavaskar, Prathamesh; Li, Zhen; Cronin, Stephen B

2014-02-21

273

LC/MS/MS structure elucidation of reaction intermediates formed during the TiO2 photocatalysis of microcystin-LR  

EPA Science Inventory

Microcystin-LR (MC-LR), a cyanotoxin and emerging drinking water contaminant, was treated with TiO(2) photocatalysts immobilized on stainless steel plates as an alternative to nanoparticles in slurry. The reaction intermediates of MC-LR were identified with mass spectrometry (MS)...

274

Cost-effective and eco-friendly synthesis of novel and stable N-doped ZnO/g-C3N4 core-shell nanoplates with excellent visible-light responsive photocatalysis.  

PubMed

N-doped ZnO/g-C3N4 hybrid core-shell nanoplates have been successfully prepared via a facile, cost-effective and eco-friendly ultrasonic dispersion method for the first time. HRTEM studies confirm the formation of the N-doped ZnO/g-C3N4 hybrid core-shell nanoplates with an average diameter of 50 nm and the g-C3N4 shell thickness can be tuned by varying the content of loaded g-C3N4. The direct contact of the N-doped ZnO surface and g-C3N4 shell without any adhesive interlayer introduced a new carbon energy level in the N-doped ZnO band gap and thereby effectively lowered the band gap energy. Consequently, the as-prepared hybrid core-shell nanoplates showed a greatly enhanced visible-light photocatalysis for the degradation of Rhodamine B compare to that of pure N-doped ZnO surface and g-C3N4. Based on the experimental results, a proposed mechanism for the N-doped ZnO/g-C3N4 photocatalyst was discussed. Interestingly, the hybrid core-shell nanoplates possess high photostability. The improved photocatalytic performance is due to a synergistic effect at the interface of the N-doped ZnO and g-C3N4 including large surface-exposure area, energy band structure and enhanced charge-separation properties. Significantly, the enhanced performance also demonstrates the importance of evaluating new core-shell composite photocatalysts with g-C3N4 as shell material. PMID:24664127

Kumar, Santosh; Baruah, Arabinda; Tonda, Surendar; Kumar, Bharat; Shanker, Vishnu; Sreedhar, B

2014-05-01

275

Noble metals can have different effects on photocatalysis over metal-organic frameworks (MOFs): a case study on M/NH?-MIL-125(Ti) (M=Pt and Au).  

PubMed

M-doped NH2-MIL-125(Ti) (M=Pt and Au) were prepared by using the wetness impregnation method followed by a treatment with H2 flow. The resultant samples were characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS) analyses, N2-sorption BET surface area, and UV/Vis diffuse reflectance spectroscopy (DRS). The photocatalytic reaction carried out in saturated CO2 with triethanolamine (TEOA) as sacrificial agent under visible-light irradiations showed that the noble metal-doping on NH2-MIL-125(Ti) promoted the photocatalytic hydrogen evolution. Unlike that over pure NH2-MIL-125(Ti), in which only formate was produced, both hydrogen and formate were formed over Pt- and Au-loaded NH2-MIL-125(Ti). However, Pt and Au have different effects on the photocatalytic performance for formate production. Compared with pure NH2-MIL-125(Ti), Pt/NH2-MIL-125(Ti) showed an enhanced activity for photocatalytic formate formation, whereas Au has a negative effect on this reaction. To elucidate the origin of the different photocatalytic performance, electron spin resonance (ESR) analyses and density functional theory (DFT) calculations were carried out over M/NH2-MIL-125(Ti).The photocatalytic mechanisms over M/NH2-MIL-125(Ti) (M=Pt and Au) were proposed. For the first time, the hydrogen spillover from the noble metal Pt to the framework of NH2-MIL-125(Ti) and its promoting effect on the photocatalytic CO2 reduction is revealed. The elucidation of the mechanism on the photocatalysis over M/NH2-MIL-125(Ti) can provide some guidance in the development of new photocatalysts based on MOF materials. This study also demonstrates the potential of using noble metal-doped MOFs in photocatalytic reactions involving hydrogen as a reactant, like hydrogenation reactions. PMID:24644131

Sun, Dengrong; Liu, Wenjun; Fu, Yanghe; Fang, Zhenxing; Sun, Fangxiang; Fu, Xianzhi; Zhang, Yongfan; Li, Zhaohui

2014-04-14

276

Water, Water Everywhere  

ERIC Educational Resources Information Center

Everybody knows that children love water and how great water play is for children. The author discusses ways to add water to one's playscape that fully comply with health and safety regulations and are still fun for children. He stresses the importance of creating water play that provides children with the opportunity to interact with water.

Keeler, Rusty

2009-01-01

277

Water, Water Everywhere  

NSDL National Science Digital Library

This is a short NASA video on the water cycle. The video shows the importance of the water cycle to nearly every natural process on Earth and illustrates how tightly coupled the water cycle is to climate.

Nasa

278

Water effect on the surface morphology of TiO2 thin film modified by polyethylene glycol  

NASA Astrophysics Data System (ADS)

Water effect on the surface morphology of TiO2 thin film was investigated by using PEG-6000 as a template to form the porous structure. The porous TiO2 thin films were characterized by thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), n&k Analyzer, UV-vis spectrophotometer, field-emission scanning electron microscopy (FE-SEM), and atomic forced microscopy (AFM) as a function of water content in the preparation of TiO2 thin film. The various water contents result in the TiO2 thin films possessing different surface structures, grain sizes, and thicknesses. The grain sizes were varied with changing the water content, and the thickness increased with increasing water content due to the enhancement of the cross-linking speed. In addition, the cratered surface structure transformed into cracked surface structure upon the water content beyond stoichiometric quantity because the excess water causes the aggregation of polyethylene glycol (PEG-6000). The photocatalysis has been performed by the degradation of methyl blue with corresponding structural characteristics of the TiO2 thin film. The best photocatalytic activity has been obtained when the ratio of water to titanium precursor is equal to 2 referred as TiO2-W2.

Wang, Sheng-Hung; Wang, Kuo-Hua; Dai, Yong-Ming; Jehng, Jih-Mirn

2013-01-01

279

Water, Water Everywhere  

NSDL National Science Digital Library

In this activity, learners estimate how much water they think can be found in various locations on the Earth in all its states (solid, liquid, and gas) to discover the different water ratios in the Earth's total water supply. Learners divide 1000 ml of water (representing the total amount of water on Earth) amongst eight beakers as they predict the various ratios. Then learners measure the amounts of water that reflect the actual ratios and compare their predictions to reality. Learners will be surprised to find out that most of Earth's water is found in the ocean. This resource also includes information about flash floods and flood safety.

Service, National W.

2012-06-26

280

Graphene-analogue carbon nitride: novel exfoliation synthesis and its application in photocatalysis and photoelectrochemical selective detection of trace amount of Cu2+  

NASA Astrophysics Data System (ADS)

Graphene-analogue nanostructures defined as a new kind of promising materials with unique electronic, surface and optical properties have received much attention in the fields of catalysis, energy storage, sensing and electronic devices. Due to the distinctive structure characteristics of the graphene-analogue materials, they brought novel and amazing properties. Herein, graphene-analogue carbon nitride (GA-C3N4) was synthesized by high-yield, large-scale thermal exfoliation from the graphitic C3N4-based intercalation compound. Graphene-analogue carbon nitride exhibited 2D thin-layer structure with 6-9 atomic thickness, a high specific surface area of 30.1 m2 g-1, increased photocurrent responses and improved electron transport ability, which could give rise to enhancing the photocatalytic activity and stability. The graphene-analogue carbon nitride had a new features that could make it suitable as a sensor for Cu2+ determination. So GA-C3N4 is a new but promising candidate for heavy metal ions (Cu2+) determination in water environment. The photocatalytic mechanism and photoelectrochemical selective sensing of Cu2+ were also discussed.Graphene-analogue nanostructures defined as a new kind of promising materials with unique electronic, surface and optical properties have received much attention in the fields of catalysis, energy storage, sensing and electronic devices. Due to the distinctive structure characteristics of the graphene-analogue materials, they brought novel and amazing properties. Herein, graphene-analogue carbon nitride (GA-C3N4) was synthesized by high-yield, large-scale thermal exfoliation from the graphitic C3N4-based intercalation compound. Graphene-analogue carbon nitride exhibited 2D thin-layer structure with 6-9 atomic thickness, a high specific surface area of 30.1 m2 g-1, increased photocurrent responses and improved electron transport ability, which could give rise to enhancing the photocatalytic activity and stability. The graphene-analogue carbon nitride had a new features that could make it suitable as a sensor for Cu2+ determination. So GA-C3N4 is a new but promising candidate for heavy metal ions (Cu2+) determination in water environment. The photocatalytic mechanism and photoelectrochemical selective sensing of Cu2+ were also discussed. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr04759h

Xu, Hui; Yan, Jia; She, Xiaojie; Xu, Li; Xia, Jiexiang; Xu, Yuanguo; Song, Yanhua; Huang, Liying; Li, Huaming

2014-01-01

281

Synthesis and visible light photocatalysis of Fe-doped TiO{sub 2} mesoporous layers deposited on hollow glass microbeads  

SciTech Connect

Nano-composite of Fe-doped anatase TiO{sub 2} nanocrystals loaded on the hollow glass microbeads was prepared by co-thermal hydrolysis deposition and calcining treatment. The adherence of TiO{sub 2} mesoporous layers to the surfaces of hollow glass microbeads prevented the aggregation of TiO{sub 2} nanoparticles and benefited to their catalytic activity. The doping of Fe ions makes the absorption edge of the TiO{sub 2} based nano-composite red-shifted into the visible region. An effective photodegradation of the methyl orange aqueous solution was achieved under visible light (lambda>420 nm) irradiation, revealing the potential applicability of such nano-composite in some industry fields, such as air and water purifications. - Graphical abstract: Nano-composite of Fe-doped anatase TiO{sub 2} nanocrystals loaded on the hollow glass microbeads was prepared by co-thermal hydrolysis deposition. Photodegradation of the methyl orange was achieved under visible light irradiation, revealing the potential applicability of such nano-composite in some industry fields.

Cui Lifeng [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences and Graduate School of Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Wang Yuansheng, E-mail: yswang@fjirsm.ac.c [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences and Graduate School of Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Niu Mutong; Chen Guoxin; Cheng Yao [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences and Graduate School of Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China)

2009-10-15

282

Graphene-analogue carbon nitride: novel exfoliation synthesis and its application in photocatalysis and photoelectrochemical selective detection of trace amount of Cu²?.  

PubMed

Graphene-analogue nanostructures defined as a new kind of promising materials with unique electronic, surface and optical properties have received much attention in the fields of catalysis, energy storage, sensing and electronic devices. Due to the distinctive structure characteristics of the graphene-analogue materials, they brought novel and amazing properties. Herein, graphene-analogue carbon nitride (GA-C?N?) was synthesized by high-yield, large-scale thermal exfoliation from the graphitic C?N?-based intercalation compound. Graphene-analogue carbon nitride exhibited 2D thin-layer structure with 6-9 atomic thickness, a high specific surface area of 30.1 m(2) g(-1), increased photocurrent responses and improved electron transport ability, which could give rise to enhancing the photocatalytic activity and stability. The graphene-analogue carbon nitride had a new features that could make it suitable as a sensor for Cu(2+) determination. So GA-C?N? is a new but promising candidate for heavy metal ions (Cu(2+)) determination in water environment. The photocatalytic mechanism and photoelectrochemical selective sensing of Cu(2+) were also discussed. PMID:24309635

Xu, Hui; Yan, Jia; She, Xiaojie; Xu, Li; Xia, Jiexiang; Xu, Yuanguo; Song, Yanhua; Huang, Liying; Li, Huaming

2014-01-16

283

One-pot solvothermal synthesis of ZnSe·xN2H4/GS and ZnSe/N-GS and enhanced visible-light photocatalysis.  

PubMed

Doped-graphene has attracted considerable attention in many fields because doping element can alter the electrical properties of graphene. In this paper, we synthesized ZnSe·xN2H4/graphene (ZnSe·xN2H4/GS) and ZnSe/nitrogen-doped graphene (ZnSe/N-GS) nanocomposites with p-n junctions via one-pot solvothermal process. The structure, morphologies and catalytic performance of the ZnSe·xN2H4/GS and ZnSe/N-GS are characterized by X-ray diffraction pattern (XRD), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy (RS), X-ray photoelectron spectroscopy (XPS), and cathodoluminescence spectrum (CL), respectively. Our experiments show that the as-prepared nanocomposites ZnSe·xN2H4/GS and ZnSe/N-GS exhibit remarkably enhanced photocatalytic activities for methylene blue (MB) dye under visible light irradiation. Even importantly, ZnSe/N-GS would make this degradation process more effective. Overall, this facile and catalyst-free synthesize method in this work could provide new insights into the fabrication of other composites based on doped graphene with high performance photocatalysts, which show their potential applications in producing of hydrogen through water splitting, environmental protection issues. PMID:23945131

Liu, Bitao; Tian, Liangliang; Wang, Yuhua

2013-09-11

284

Preparation of magnetic Fe{sub 3}O{sub 4}/SiO{sub 2}/Bi{sub 2}WO{sub 6} microspheres and their application in photocatalysis  

SciTech Connect

Graphical abstract: Display Omitted Highlights: ? We described the preparation and characterization of the Fe{sub 3}O{sub 4}/SiO{sub 2}/Bi{sub 2}WO{sub 6} magnetic microspheres composites. ? The photocatalytic activities of the composites were also investigated. ? With the combination of photocatalysts and Fe{sub 3}O{sub 4}/SiO{sub 2}, good stability and magnetic separability can be achieved. ? And to the best of our knowledge, this is the first report concerning Bi{sub 2}WO{sub 6} nanoparticles loaded on Fe{sub 3}O{sub 4}/SiO{sub 2} particles. -- Abstract: Magnetic Fe{sub 3}O{sub 4}/SiO{sub 2}/Bi{sub 2}WO{sub 6} microspheres with photocatalytic properties have been synthesized using a silica layer for “bonding” (adhering Bi{sub 2}WO{sub 6} to Fe{sub 3}O{sub 4}). The morphology, composition and magnetic properties of the Fe{sub 3}O{sub 4}/SiO{sub 2}/Bi{sub 2}WO{sub 6} composites were characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, vibrating sample magnetometry, and BET surface area analysis. The activity of the material in photocatalytic decoloration of aqueous rhodamine B (RhB) solution under visible light was evaluated. The results showed that Bi{sub 2}WO{sub 6} combined well with the magnetic Fe{sub 3}O{sub 4}/SiO{sub 2} nanoparticles. The Fe{sub 3}O{sub 4}/SiO{sub 2}/Bi{sub 2}WO{sub 6} composites were spherical in shape, having a mean size of 2 ?m. The spent catalyst could be recycled with only slight decline in catalytic activity. It is envisaged that the stability, reusability, and magnetic nature of the Fe{sub 3}O{sub 4}/SiO{sub 2}/Bi{sub 2}WO{sub 6} catalyst warrants its application in photocatalysis.

Chen, Su-Hua; Yin, Zhen [Key Laboratory of Jiangxi Province for Ecological Diagnosis-Remediation and Pollution Control, Nanchang Hangkong University, Nanchang 330063 (China)] [Key Laboratory of Jiangxi Province for Ecological Diagnosis-Remediation and Pollution Control, Nanchang Hangkong University, Nanchang 330063 (China); Luo, Sheng-Lian, E-mail: sllou@hnu.edu.cn [Key Laboratory of Jiangxi Province for Ecological Diagnosis-Remediation and Pollution Control, Nanchang Hangkong University, Nanchang 330063 (China)] [Key Laboratory of Jiangxi Province for Ecological Diagnosis-Remediation and Pollution Control, Nanchang Hangkong University, Nanchang 330063 (China); Au, Chak-Tong [Key Laboratory of Jiangxi Province for Ecological Diagnosis-Remediation and Pollution Control, Nanchang Hangkong University, Nanchang 330063 (China) [Key Laboratory of Jiangxi Province for Ecological Diagnosis-Remediation and Pollution Control, Nanchang Hangkong University, Nanchang 330063 (China); Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong (China); Li, Xue-Jun [Key Laboratory of Jiangxi Province for Ecological Diagnosis-Remediation and Pollution Control, Nanchang Hangkong University, Nanchang 330063 (China)] [Key Laboratory of Jiangxi Province for Ecological Diagnosis-Remediation and Pollution Control, Nanchang Hangkong University, Nanchang 330063 (China)

2013-02-15

285

Environmentally Responsible Use of Nanomaterials for the Photocatalytic Reduction of Nitrate in Water  

NASA Astrophysics Data System (ADS)

Nitrate is the most prevalent water pollutant limiting the use of groundwater as a potable water source. The overarching goal of this dissertation was to leverage advances in nanotechnology to improve nitrate photocatalysis and transition treatment to the full-scale. The research objectives were to (1) examine commercial and synthesized photocatalysts, (2) determine the effect of water quality parameters (e.g., pH), (3) conduct responsible engineering by ensuring detection methods were in place for novel materials, and (4) develop a conceptual framework for designing nitrate-specific photocatalysts. The key issues for implementing photocatalysis for nitrate drinking water treatment were efficient nitrate removal at neutral pH and by-product selectivity toward nitrogen gases, rather than by-products that pose a human health concern (e.g., nitrite). Photocatalytic nitrate reduction was found to follow a series of proton-coupled electron transfers. The nitrate reduction rate was limited by the electron-hole recombination rate, and the addition of an electron donor (e.g., formate) was necessary to reduce the recombination rate and achieve efficient nitrate removal. Nano-sized photocatalysts with high surface areas mitigated the negative effects of competing aqueous anions. The key water quality parameter impacting by-product selectivity was pH. For pH < 4, the by-product selectivity was mostly N-gas with some NH4 +, but this shifted to NO2- above pH = 4, which suggests the need for proton localization to move beyond NO2 -. Co-catalysts that form a Schottky barrier, allowing for localization of electrons, were best for nitrate reduction. Silver was optimal in heterogeneous systems because of its ability to improve nitrate reduction activity and N-gas by-product selectivity, and graphene was optimal in two-electrode systems because of its ability to shuttle electrons to the working electrode. "Environmentally responsible use of nanomaterials" is to ensure that detection methods are in place for the nanomaterials tested. While methods exist for the metals and metal oxides examined, there are currently none for carbon nanotubes (CNTs) and graphene. Acknowledging that risk assessment encompasses dose-response and exposure, new analytical methods were developed for extracting and detecting CNTs and graphene in complex organic environmental (e.g., urban air) and biological matrices (e.g. rat lungs).

Doudrick, Kyle

286

Heterogeneous photocatalytic disinfection of wash waters from the fresh-cut vegetable industry.  

PubMed

The effectiveness of photocatalytic disinfection for control of natural and potentially pathogenic microflora in wash waters used for fresh-cut vegetables was evaluated. Wash waters for lettuce, escarole, chicory, carrot, onion, and spinach from a fresh-cut vegetable processing plant were treated with a titanium dioxide (TiO2) photocatalytic system. The vegetable wash waters were impelled out with a pump at a flow rate of 1,000 liters/h and conducted through a stainless steel circuit to the filtration system to reach the TiO2 photocatalyst fiber, which was illuminated with a 40-W UV-C lamp. The microbial and physicochemical qualities of the wash water were analyzed. Heterogeneous photocatalysis was an effective disinfection method, reducing counts of bacteria, molds, and yeasts. Most of the treated wash waters had total bacteria reductions of 4.1 +/- 1.3 to 4.8 +/- 0.4 log CFU/ml after 10 min of treatment when compared with untreated water. Higher decontamination efficacy was observed in carrot wash water (6.2 +/- 0.1-log reductions), where turbidity and organic matter were lower than those in the wash waters for other vegetables. The tested heterogeneous photocatalytic system also was effective for reducing water turbidity, although chemical oxygen demand was unaffected after the treatments. The efficacy of the photocatalytic system for reducing microbial load depended on the physicochemical characteristics of the wash water, which depended on the vegetable being washed. The conclusions derived from this study illustrate that implementation of a heterogeneous photocatalytic system in the fresh-cut vegetable washing processes could allow the reuse of wash water. PMID:18326177

Selma, María Victoria; Allende, Ana; López-Gálvez, Francisco; Conesa, María Angeles; Gil, María Isabel

2008-02-01

287

Water 2: Disappearing Water  

NSDL National Science Digital Library

In this lesson, students will observe the amount of water in an open container vs a closed container over time. This lesson is the second in a three-part series that addresses a concept that is central to the understanding of the water cycle: that water is able to take many forms but is still water. In this second lesson, students will focus on the concept that water can go back and forth from one form to another and the amount of water will remain the same.

288

Role(s) of adsorbed water in the surface chemistry of environmental interfaces.  

PubMed

The chemistry of environmental interfaces such as oxide and carbonate surfaces under ambient conditions of temperature and relative humidity is of great interest from many perspectives including heterogeneous atmospheric chemistry, heterogeneous catalysis, photocatalysis, sensor technology, corrosion science, and cultural heritage science. As discussed here, adsorbed water plays important roles in the reaction chemistry of oxide and carbonate surfaces with indoor and outdoor pollutant molecules including nitrogen oxides, sulfur dioxide, carbon dioxide, ozone and organic acids. Mechanisms of these reactions are just beginning to be unraveled and found to depend on the details of the reaction mechanism as well as the coverage of water on the surface. As discussed here, adsorbed water can: (i) alter reaction pathways and surface speciation relative to the dry surface; (ii) hydrolyze reactants, intermediates and products; (iii) enhance surface reactivity by providing a medium for ionic dissociation; (iv) inhibit surface reactivity by blocking sites; (v) solvate ions; (vi) enhance ion mobility on surfaces and (vii) alter the stability of surface adsorbed species. In this feature article, drawing on research that has been going on for over a decade on the reaction chemistry of oxide and carbonate surfaces under ambient conditions of temperature and relative humidity, a number of specific examples showing the multi-faceted roles of adsorbed water are presented. PMID:23417201

Rubasinghege, Gayan; Grassian, Vicki H

2013-04-18

289

Water, Water Everywhere! Research the Water Cycle  

NSDL National Science Digital Library

Water, Water Everywhere! Research the Water Cycle asks students to conduct their own research on the water cycle (hydrologic cycle). Working collaboratively in small groups, students will research and write about the relationships between stages in the water cycle and the three states of matter relating to water. After completing this lesson, students will be prepared to create a model of the water cycle.

Bale, Regina

2012-07-17

290

Water, water everywhere  

Microsoft Academic Search

The first part of this article describes the current understanding of the dynamic interaction between protein folding and function and water, dependent on the polarity of water. The second part examines the role of water in converting organic matter into oil and coal by summarizing the history and result of experiments done over the last 13 years by Exxon researchers.

Pennisi

1993-01-01

291

Healthy Water  

MedlinePLUS

... and safe drinking water is critical to sustain human life and without it waterborne illness can be a serious problem. Water, which is necessary for recreational water activities like swimming, also helps promote healthy living. Often, water’s vital ...

292

Visible light photocatalytic water disinfection and its kinetics using Ag-doped titania nanoparticles.  

PubMed

The UN estimated about five million deaths every year due to water-borne diseases, accounting from four billion patients. Keeping in view, the ever increasing health issues and to undermine this statistics, a reliable and sustainable water-treatment method has been developed using visible light for water treatment. titania nanoparticles (NPs) have been synthesized successfully by a more applicable method Viz: liquid impregnation (LI) method. The bacterial death rate by photocatalysis under visible light was studied by employing a typical fluorescent source and was found to follow pseudo first-order reaction kinetics. The nanoparticles were characterized using X-ray diffraction (XRD), scanning electron microscopy, and energy-dispersive X-ray spectroscopy to deduce their size range, surface morphology, and elemental compositions, respectively. Among all the prepared grades, 1% Ag-TiO2 was found to be a very effective photocatalytic agent against Escherichia coli. The resulted photoinactivated data were also evaluated by different empirical kinetic models for bacterial inactivation. Hom, Hom-power, Rational, and Selleck models were not able to explain the disinfection kinetics but modified-Hom model fitted best with the experimentally obtained data by producing a shoulder, log-linear, and a tail region. PMID:23872896

Younas, Hassan; Qazi, Ishtiaq A; Hashmi, Imran; Awan, M Ali; Mahmood, Asif; Qayyum, Hafiz Adil

2014-01-01

293

Thick titanium dioxide films for semiconductor photocatalysis  

Microsoft Academic Search

Thick paste TiO2 films are prepared and tested for photocatalytic and photoinduced superhydrophilic (PSH) activity. The films are effective photocatalysts for the destruction of stearic acid using near or far UV and all the sol–gel films tested exhibited a quantum yield for this process of typically 0.15%. These quantum yields are significantly greater (4–8-fold) than those for titania films produced

Andrew Mills; George Hill; Sharan Bhopal; Ivan P. Parkin; Shane A. O’Neill

2003-01-01

294

Photocatalysis with Large-Scale Trough Collectors.  

National Technical Information Service (NTIS)

Sandia National Laboratories' part in the Department of Energy's Solar Detoxification of Hazardous Waste Initiative is focused on conducting large-scale solar photocatalytic experiments. Sandia's efforts support fundamental laboratory research performed b...

J. E. Pacheco

1991-01-01

295

Photoelectrosynthesis and Photocatalysis at Semiconductor Electrodes.  

National Technical Information Service (NTIS)

The principles and applications of semiconductor electrodes in photoelectrochemical (PEC) cells for carrying out useful chemical reactions are described. The factors in the design of efficient and stable systems and semiconductor particulate systems const...

A. J. Bard

1981-01-01

296

Bactericidal mode of titanium dioxide photocatalysis  

Microsoft Academic Search

When exposed to near-UV light, titanium dioxide (TiO2) exhibits a strong bactericidal activity. However, the killing mechanism(s) underlying the TiO2 photocatalytic reaction is not yet well understood. The aim of the present study is to investigate the cellular damage sites and their contribution to cell death. A sensitive approach using o-nitrophenol ?-d–galactopyranosideside (ONPG) as the probe and Escherichia coli as

Zheng Huang; Pin-Ching Maness; Daniel M. Blake; Edward J. Wolfrum; Sharon L. Smolinski; William A. Jacoby

2000-01-01

297

Catalyst Deactivation in Gas–Solid Photocatalysis  

Microsoft Academic Search

Photocatalyst lifetime is potentially important in process economics, as it sets maximum run times between catalyst regeneration or replacement. This note surveys the literature of photocatalytic air treatment and purification in order to identify the emerging photocatalyst deactivation issue. For each pertinent paper, the authors evaluate the total number of molecules converted by a photocatalyst over time and compare this

Michael L. Sauer; David F. Ollis

1996-01-01

298

Water, Water, Everywhere.  

ERIC Educational Resources Information Center

The brain needs energy, oxygen, and water to operate. Access to the bathroom pass can become a major conflict between teachers and students and has great potential for disrupting classes. The classroom can be humanized by granting more bathroom passes and allowing water bottles. (MLH)

Fahey, John A.

2000-01-01

299

Water, Water, Everywhere.  

ERIC Educational Resources Information Center

Water is a major component in many consumer products. Azeotropic distillation of products such as detergents and foodstuffs to form a two-phase distillate is a simple experimental method to determine the percentage of water in the product. (Author/GA)

Selinger, Ben

1979-01-01

300

Water law  

SciTech Connect

The author pays particular attention to recent amendments to the Clean Water Act, Safe Drinking Water Act, and hazardous waste statutes. Concludes with a new chapter on regional land-use controls to safeguard water quality. This book is revised to explain the nature of law and the relationships among water law, science, water uses, water rights, and water resources management.

Goldfarb, W.

1988-01-01

301

Ground Water  

NSDL National Science Digital Library

Ground Water: USGS Water Science for Schools explaines the uses of ground water in the United States. The main uses of ground water include "irrigation uses, drinking-water and other public uses, and for supplying domestic water to people who do not receive public-supply water." Check out this site to learn more.

2008-05-28

302

TiO2Based Heterogeneous Photocatalytic Water Treatment Combined with Ozonation  

Microsoft Academic Search

The degradations of aliphatic carboxylic acids (formic acid, acetic acid, and propionic acid) were investigated by a combination of TiO2-based photocatalysis and ozonation at pH = 2. The carboxylic acids were analyzed by high-performance liquid chromatography (HPLC), while the mineralization process was characterized by measuring the dissolved organic carbon (DOC) content. The efficiency of heterogeneous photocatalysis combined with ozonation was

István Ilisz; Attila Bokros; András Dombi

2004-01-01

303

Water, water everywhere  

SciTech Connect

The first part of this article describes the current understanding of the dynamic interaction between protein folding and function and water, dependent on the polarity of water. The second part examines the role of water in converting organic matter into oil and coal by summarizing the history and result of experiments done over the last 13 years by Exxon researchers. Water under pressure and at high temperatures (300 C) can act as a solvent, a catalyst, and a reagent. Organic molecules can be fragmented by high temperature, but water and brine can also fragment them, sometimes more effectively. The actual mechanism by which water works is still a matter of active investigation, but the fact that it can be involved in oil formation could weak havoc on established ideas. Among the possibilities in the immediate future using hot water include the following: introducing hydrogen to coal for easier liquefaction and cost reduction; add hydrogen to low quality oil deposits for better quality and easier extraction; increasing the efficiency of isopropyl alcohol production; breaking down petroleum based wastes to reduce environmental contamination.

Pennisi, E.

1993-02-20

304

Identifying active surface phases for metal oxide electrocatalysts: a study of manganese oxide bi-functional catalysts for oxygen reduction and water oxidation catalysis.  

PubMed

Progress in the field of electrocatalysis is often hampered by the difficulty in identifying the active site on an electrode surface. Herein we combine theoretical analysis and electrochemical methods to identify the active surfaces in a manganese oxide bi-functional catalyst for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). First, we electrochemically characterize the nanostructured ?-Mn(2)O(3) and find that it undergoes oxidation in two potential regions: initially, between 0.5 V and 0.8 V, a potential region relevant to the ORR and, subsequently, between 0.8 V and 1.0 V, a potential region between the ORR and the OER relevant conditions. Next, we perform density function theory (DFT) calculations to understand the changes in the MnO(x) surface as a function of potential and to elucidate reaction mechanisms that lead to high activities observed in the experiments. Using DFT, we construct surface Pourbaix and free energy diagrams of three different MnO(x) surfaces and identify 1/2 ML HO* covered Mn(2)O(3) and O* covered MnO(2), as the active surfaces for the ORR and the OER, respectively. Additionally, we find that the ORR occurs through an associative mechanism and that its overpotential is highly dependent on the stabilization of intermediates through hydrogen bonds with water molecules. We also determine that OER occurs through direct recombination mechanism and that its major source of overpotential is the scaling relationship between HOO* and HO* surface intermediates. Using a previously developed Sabatier model we show that the theoretical predictions of catalytic activities match the experimentally determined onset potentials for the ORR and the OER, both qualitatively and quantitatively. Consequently, the combination of first-principles theoretical analysis and experimental methods offers an understanding of manganese oxide oxygen electrocatalysis at the atomic level, achieving fundamental insight that can potentially be used to design and develop improved electrocatalysts for the ORR and the OER and other important reactions of technological interest. PMID:22990481

Su, Hai-Yan; Gorlin, Yelena; Man, Isabela C; Calle-Vallejo, Federico; Nørskov, Jens K; Jaramillo, Thomas F; Rossmeisl, Jan

2012-10-28

305

Water Works.  

ERIC Educational Resources Information Center

Describes a two-day field trip, along with follow-up classroom activities and experiments which relate to water resources and water quality. Discusses how trips to a lake and water treatment facilities can enhance appreciation of water. (TW)

Van De Walle, Carol

1988-01-01

306

Water Safety  

MedlinePLUS

... best measure of protection. Back Continue Making Kids Water Wise It's important to teach your kids proper ... water during bad weather, especially lightning. Back Continue Water Park Safety Water parks can be a lot ...

307

Water, Water Everywhere!  

ERIC Educational Resources Information Center

Describes how problems with water drainage on the playground, and the resulting puddles, provided a wealth of learning opportunities, children's fun, family-school communication, and challenges for one early childhood program. (KB)

Sible, Kathleen P.

2000-01-01

308

Photocatalytic degradation of hexazinone and its determination in water via UPLC-MS/MS.  

PubMed

Degradation of hexazinone has been investigated by means of photocatalysis of mixed-phase crystal nano-TiO(2). Influences of adsorption, amount of nano-TiO(2), pH and irradiation time on the photocatalytic process are studied. Results show that hexazinone is totally degraded within 40min of irradiation under pH neutral conditions. This compares favorably with Degussa P25 TiO(2) when conducted under the same experimental conditions. Preliminary photocatalytic kinetic information for hexazinone degradation is proposed. First order kinetics is obtained for the adsorption and photocatalytic degradation reactions, which fit the Langmuir-Hinshelwood model. A rapid, sensitive and accurate UPLC-MS/MS technique is developed and utilized to determine the level of hexazinone in water in support of the degradation kinetics study. The results indicate a limit of detection (LOD) at 0.05?g/l and the recoveries between 90.2 and 98.5% with relative standard deviations (RSD) lower than 12%. A LC-MS/MS technique is used to trace the degradation process. Complete degradation is achieved into final products including nontoxic water, carbon dioxide and urea. A probable pathway for the total photocatalytic degradation of hexazinone is proposed. PMID:22551636

Mei, Mei; Du, Zhenxia; Xu, Ruifen; Chen, Yun; Zhang, Haojie; Qu, Shuping

2012-06-30

309

Porous SiC nanowire arrays as stable photocatalyst for water splitting under UV irradiation  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Arrays of porous SiC nanowires prepared by a facile in situ carbonizing method. Black-Right-Pointing-Pointer Utilizing the SiC nanowire arrays as photocatalysis for water splitting. Black-Right-Pointing-Pointer Excellent photocatalytic performance under the UV irradiation. Black-Right-Pointing-Pointer Very high stability of the SiC nanowire photocatalyst. -- Abstract: In this study, we report the fabrication and photocatalytic properties of the oriented arrays of SiC nanowires on the Si substrate. The SiC nanowire arrays were prepared by carbonizing the Si nanowire arrays with the graphite powder at 1250 Degree-Sign C. The as-prepared SiC nanowires are highly porous, which endows them with a high surface-to-volume ratio. Considering the large surface areas and the high stability, the porous SiC nanowire arrays were used as photocatalyst for water splitting under UV irradiation. It was found that such porous SiC structure exhibited an enhanced and extremely stable photocatalytic performance.

Liu, Hailong [Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)] [Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); She, Guangwei, E-mail: shegw@mail.ipc.ac.cn [Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)] [Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Mu, Lixuan [Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)] [Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Shi, Wensheng, E-mail: shiws@mail.ipc.ac.cn [Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)] [Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)

2012-03-15

310

Ultrasound (US), Ultraviolet light (UV) and combination (US+UV) assisted semiconductor catalysed degradation of organic pollutants in water: Oscillation in the concentration of hydrogen peroxide formed in situ.  

PubMed

Application of Advanced Oxidation Processes (AOP) such as sono, photo and sonophoto catalysis in the purification of polluted water under ambient conditions involve the formation and participation of Reactive Oxygen Species (ROS) like OH, HO2, O2(-), H2O2 etc. Among these, H2O2 is the most stable and is also a precursor for the reactive free radicals. Current investigations on the ZnO mediated sono, photo and sonophoto catalytic degradation of phenol pollutant in water reveal that H2O2 formed in situ cannot be quantitatively correlated with the degradation of the pollutant. The concentration of H2O2 formed does not increase corresponding to phenol degradation and reaches a plateau or varies in a wave-like fashion (oscillation) with well defined crests and troughs, indicating concurrent formation and decomposition. The concentration at which decomposition overtakes formation or formation overtakes decomposition is sensitive to the reaction conditions. Direct photolysis of H2O2 in the absence of catalyst or the presence of pre-equilibrated (with the adsorption of H2O2) catalyst in the absence of light does not lead to the oscillation. The phenomenon is more pronounced in sonocatalysis, the intensity of oscillation being in the order sonocatalysis>photocatalysis?sonophotocatalysis while the degradation of phenol follows the order sonophotocatalysis>photocatalysis>sonocatalysis>sonolysis>photolysis. In the case of sonocatalysis, the oscillation continues for some more time after discontinuing the US irradiation indicating that the reactive free radicals as well as the trapped electrons and holes which interact with H2O2 have longer life time (memory effect). PMID:24731472

Jyothi, K P; Yesodharan, Suguna; Yesodharan, E P

2014-09-01

311

Ground Water  

NSDL National Science Digital Library

USGS Water Science for Schools explaines the uses of ground water in the United States. The main uses of ground water include "irrigation uses, drinking-water and other public uses, and for supplying domestic water to people who do not receive public-supply water." Check out this site to learn more.

2008-05-28

312

Search for the ANSER (A "Life at the Frontiers of Energy Research" contest entry from the 2011 Energy Frontier Research Centers (EFRCs) Summit and Forum  

ScienceCinema

'Search for the ANSER' was submitted by the Argonne-Northwestern Solar Energy Research Center (ANSER) to the 'Life at the Frontiers of Energy Research' video contest at the 2011 Science for Our Nation's Energy Future: Energy Frontier Research Centers (EFRCs) Summit and Forum. Twenty-six EFRCs created short videos to highlight their mission and their work. ANSER, an EFRC directed by Michael Wasielewski at Argonne National Laboratory is a partnership of scientists from five institutions: Argonne National Laboratory, Northwestern University, University of Chicago, University of Illinois at Urbana-Champaign, and Yale. The Office of Basic Energy Sciences in the U.S. Department of Energy's Office of Science established the 46 Energy Frontier Research Centers (EFRCs) in 2009. These collaboratively-organized centers conduct fundamental research focused on 'grand challenges' and use-inspired 'basic research needs' recently identified in major strategic planning efforts by the scientific community. The overall purpose is to accelerate scientific progress toward meeting the nation's critical energy challenges. At ANSER, the mission is 'to revolutionize our understanding of molecules, materials and methods necessary to create dramatically more efficient technologies for solar fuels and electricity production.' Research topics are: catalysis (water), electrocatalysis, photocatalysis, photoelectrocatalysis, solar photovoltaic, solar fuels, solar electrodes, photosynthesis, transportation fuels, bio-inspired, spin dynamics, hydrogen (fuel), ultrafast physics, interfacial characterization, matter by design, novel materials synthesis, charge transport, and self-assembly.

Wasielewski, Michael R. (Director, Argonne-Northwestern Solar Energy Research Center); ANSER Staff

2011-11-02

313

UNC EFRC: Fuels from Sunlight (A "Life at the Frontiers of Energy Research" contest entry from the 2011 Energy Frontier Research Centers (EFRCs) Summit and Forum)  

ScienceCinema

'Fuels from Sunlight' was submitted by the University of North Carolina (UNC) EFRC: Solar Fuels and Next Generation Photovoltaics to the 'Life at the Frontiers of Energy Research' video contest at the 2011 Science for Our Nation's Energy Future: Energy Frontier Research Centers (EFRCs) Summit and Forum. Twenty-six EFRCs created short videos to highlight their mission and their work. The UNC EFRC directed by Thomas J. Meyer is a partnership of scientists from six institutions: UNC (lead), Duke University, University of Florida, North Caroline Central University, North Carolina State University, and the Research Triangle Institute. The Office of Basic Energy Sciences in the U.S. Department of Energy's Office of Science established the 46 Energy Frontier Research Centers (EFRCs) in 2009. These collaboratively-organized centers conduct fundamental research focused on 'grand challenges' and use-inspired 'basic research needs' recently identified in major strategic planning efforts by the scientific community. The overall purpose is to accelerate scientific progress toward meeting the nation's critical energy challenges. The mission of Solar Fuels and Next Generation Photovoltaics is 'to combine the best features of academic and translational research to study light/matter interactions and chemical processes for the efficient collection, transfer, and conversion of solar energy into chemical fuels and electricity.' Research topics are: catalysis (CO{sub 2}, hydrocarbons, water), electrocatalysis, photocatalysis, photoelectrocatalysis, solar photovoltaic, solar fuels, photonic, solar electrodes, photosynthesis, fuel cells, CO{sub 2} (convert), greenhosue gas, hydrogen (fuel), interfacial characterization, novel materials synthesis, charge transport, and self-assembly.

Meyer, Thomas J. (Director, UNC EFRC: Solar Fuels and Next Generation Photovoltaics); UNC EFRC Staff

2011-11-02

314

[Drinking water].  

PubMed

Water is essential for life. Thirst is a pressing need which always has to be satisfied. Infants need 3 times more water than adults if the requirements is calculated according to body weight. A correct balance in the sensory, physical, chemical and bacteriological qualities of water make it drinkable. Two laws have been passed recently concerning drinking water in France: one deals with water for human consumption (January 3 1989 decree), and the other deals with drinkable bottled mineral water (June 3 1989 decree). Tap water and bottled water are under strict vigilance. For babies under 4 months of age, it is better to use bottled water with a low mineral content (nitrates less than 15 mg/l). Hard water is safe; water softeners are useful only for hot water. Fluorination supplies of water is good for dental health at a concentration of 1 mg/l. Plastic bottles are as safe as glass ones. PMID:1662352

Dartois, A M; Casamitjana, F

1991-01-01

315

Water, Water Everywhere, But...  

ERIC Educational Resources Information Center

Materials for teaching a unit on water pollution are provided in this teaching package. These materials include: (1) a student reading booklet; (2) a reference booklet listing a variety of popular chemical, biological, and physical tests which can be performed on a local waterway and providing information about the environmental effects and toxic…

Jacobson, Cliff

316

Ground Water  

NSDL National Science Digital Library

This USGS site contains very useful descriptions about many aspects of ground water. The major topics include Ground Water, How Ground Water Occurs, Quality of Ground Water, Appraising the Nation's Ground-Water Resources, and a Glossary. This is a non-technical site, designed for use by the general public. Several charts and diagrams are also included in this site.

2002-02-15

317

Water Artists.  

ERIC Educational Resources Information Center

Discusses how experiences with water provide children with opportunities to be artists. Describes different types of water play for children. Believes that experiences with water introduce children to the principles of painting. (CMK)

Szekely, George

2003-01-01

318

Water Properties  

NSDL National Science Digital Library

This simple description of the chemical and physical properties of water was produced by the U.S. Geological Survey. It includes a brief quiz to assess prior knowledge, diagrams of water molecules, and important numerical data about water.

2009-11-04

319

Water ingestion during water recreation  

Microsoft Academic Search

Quantitative risk assessments have estimated health risks of water recreation. One input to risk assessment models is the rate of water ingestion. One published study estimated rates of water ingestion during swimming, but estimates of water ingestion are not available for common limited contact water recreation activities such as canoeing, fishing, kayaking, motor boating, and rowing. In the summer of

Samuel Dorevitch; Suraj Panthi; Yue Huang; Hong Li; Angela M. Michalek; Preethi Pratap; Meredith Wroblewski; Li Liu; Peter A. Scheff; An Li

2011-01-01

320

Special Topics in Water Science (Water Pollution)  

MedlinePLUS

... Site map Help Home Water Basics Water Properties Water Cycle Surface Water Groundwater Water Quality Water Use Activities ... saline water, watersheds, runoff, and hydrology. Investigate the water cycle (in many languages!) Accessibility FOIA Privacy Policies and ...

321

Efficient Solar Energy Conversion Systems for Hydrogen Production from Water using Semiconductor Photoelectrodes and Photocatalysts  

NASA Astrophysics Data System (ADS)

Efficient solar energy conversion system for hydrogen production from water, solar-hydrogen system, is one of most important technologies for genuinely sustainable development of the society in the world wide scale. However, there are many problems to breakthrough such as low solar-to-H2 efficiency (STH), high cost, low stability, etc in order to realize the system practically and economically. The solar-hydrogen systems using semiconductors are mainly classified as follows; solar cell-electrolysis system, semiconductor photoelectrode system, and photocatalyst system. There are various merits and demerits in each system. The solar cell-electrolysis system is very efficient but is very high cost. The photocatalyst system is very simple and relatively low cost, but the efficiency is still very low. On the other hand, various semiconductor systems with high efficiency have been investigated. A high STH more than 10% was reported using non-oxide semiconductor photoelectrodes such as InGaP, while the preparation methods were costly. In a European project, some simple oxide semiconductor photoelectrodes such as Fe2O3 and WO3 are mainly studied. Here, we investigated various photoelectrodes using mixed metal oxide especially on BiVO4 semiconductor, and a high throughput screening system of new visible light responsible semiconductors for photoelectrode and photocatalyst. Moreover, photocatalysis-electrolysis hybrid system for economical H2 production is studied to overcome the demerit of photocatalyst system on the gas separation and low efficiency.

Sayama, K.; Arai, T.

2008-02-01

322

Photoinactivation of virus on iron-oxide coated sand: enhancing inactivation in sunlit waters.  

PubMed

Adsorption onto iron oxides can enhance the removal of waterborne viruses in constructed wetlands and soils. If reversible adsorption is not coupled with inactivation, however, infective viruses may be released when changes in solution conditions cause desorption. The goals of this study were to investigate the release of infective bacteriophages MS2 and ?X174 (two human viral indicators) after adsorption onto an iron oxide coated sand (IOCS), and to promote viral inactivation by exploiting the photoreactive properties of the IOCS. The iron oxide coating greatly enhanced viral adsorption (adsorption densities up to ? 10(9) infective viruses/g IOCS) onto the sand, but had no affect on infectivity. Viruses that were adsorbed onto IOCS under control conditions (pH 7.5, 10 mM Tris, 1250 ?S/cm) were released into solution in an infective state with increases in pH and humic acid concentrations. The exposure of IOCS-adsorbed MS2 to sunlight irradiation caused significant inactivation via a photocatalytic mechanism in both buffered solutions and in wastewater samples (4.9 log(10) and 3.3 log(10) inactivation after 24-h exposure, respectively). Unlike MS2, ?X174 inactivation was not enhanced by photocatalysis. In summary, IOCS enhanced the separation of viruses from the water column, and additionally provided a photocatalytic mechanism to promote inactivation of one of the surrogates studied. These qualities make it an attractive option for improving viral control strategies in constructed wetlands. PMID:22264797

Pecson, Brian M; Decrey, Loïc; Kohn, Tamar

2012-04-15

323

Water Quality  

MedlinePLUS

What is in that water that you just drank? Is it just hydrogen and oxygen atoms? Is it safe for drinking? All water is of a certain "quality" (and you can't tell by just looking), but what does "water quality" really mean? Water full of dirt and ...

324

WATER USAGE  

NSDL National Science Digital Library

DESK Standard: Understand how the water cycle relates to the water supply in your community. Thirstin Glass DATES: You can begin this activity on September 18. You should complete it by September 22. OBJECTIVE: We have been learning about water and the water cycle in class. It is important for you to understand the impact you have on this cycle. Each person uses ...

Hughes, Mr.

2006-02-11

325

Water Ways  

ERIC Educational Resources Information Center

In many communities, schools are among the largest facilities and house the highest concentrations of daytime population. They create a huge demand for water. Even in regions with abundant water supplies, an increase in demand stresses local capacity, and water becomes more expensive. However, with the help of innovative products that reduce water…

Jahrling, Peter

2007-01-01

326

Photocatalysis and promoted photocatalysis during photocrosslinking of multifunctional acrylates in composite membranes immobilizing titanium dioxide  

Microsoft Academic Search

The photocatalytic activities of semiconductor titanium dioxide (added to a standard titanium dioxide pigment) and five organometallic coordination compounds (containing cobalt(III) and vanadium(V) as central atoms) have been investigated during the photopolymerization and photocrosslinking of acrylic monomers, employed for the preparation of composite membranes by photografting onto a non-woven polyester support. By partly or wholly substituting the 30 wt.% titanium

Ignazio Renato Bellobono; Roberto Morelli; Claudia Maria Chiodaroli

1997-01-01

327

Water Phases  

NSDL National Science Digital Library

Every day, we encounter water in its three phases: liquid water, solid ice, and water vapor, an invisible gas. Most other substances can exist in these three phases as well, but water is unique because it is the only substance that can exist in all three phases at Earth's ordinary temperature conditions. This slide show provides examples of water in each of its three phases.

328

Water Systems  

NSDL National Science Digital Library

Water cycle concepts and basics including the distribution of water on the planet in oceans, rivers and lakes, glaciers and atmosphere. Defines basic terms: states of water, evaporation, transpiration, condensation, precipitation, melting. Good illustrations, maps and photos. Excellent list itemizes human uses and impacts on water and the water cycle. Links to more detailed references are provided, case studies illustrate current concerns and issues in Ontario, Canada.

329

Thin-film fixed-bed reactor for solar photocatalytic inactivation of Aeromonas hydrophila: influence of water quality  

PubMed Central

Background Controlling fish disease is one of the major concerns in contemporary aquaculture. The use of antibiotics or chemical disinfection cannot provide a healthy aquaculture system without residual effects. Water quality is also important in determining the success or failure of fish production. Several solar photocatalytic reactors have been used to treat drinking water or waste water without leaving chemical residues. This study has investigated the impact of several key aspects of water quality on the inactivation of the pathogenic bacterium Aeromonas hydrophila using a pilot-scale thin-film fixed-bed reactor (TFFBR) system. Results The level of inactivation of Aeromonas hydrophila ATCC 35654 was determined using a TFFBR with a photocatalytic area of 0.47 m2 under the influence of various water quality variables (pH, conductivity, turbidity and colour) under high solar irradiance conditions (980–1100 W m-2), at a flow rate of 4.8 L h-1 through the reactor. Bacterial enumeration were obtained through conventional plate count using trypticase soy agar media, cultured in conventional aerobic conditions to detect healthy cells and under ROS-neutralised conditions to detect both healthy and sub-lethally injured (oxygen-sensitive) cells. The results showed that turbidity has a major influence on solar photocatalytic inactivation of A. hydrophila. Humic acids appear to decrease TiO2 effectiveness under full sunlight and reduce microbial inactivation. pH in the range 7–9 and salinity both have no major effect on the extent of photoinactivation or sub-lethal injury. Conclusions This study demonstrates the effectiveness of the TFFBR in the inactivation of Aeromonas hydrophila under the influence of several water quality variables at high solar irradiance, providing an opportunity for the application of solar photocatalysis in aquaculture systems, as long as turbidity remains low.

2012-01-01

330

Earth's Water:Ground Water  

NSDL National Science Digital Library

This USGS site contains graphs, tables, and charts for the following ground water topics: What is ground water, ground water flow diagrams, importance of groundwater, and trends in ground-water use. Ground water quality, pesticides, aquifers, waterwells, artesian wells, sinkholes, and land subsidence are also covered. There are a variety of links within all of the above topics and a very complete glossary, as well as numerous charts, maps, photographs and illustrations.

331

Water Purifier  

NASA Technical Reports Server (NTRS)

The Floatron water purifier combines two space technologies - ionization for water purification and solar electric power generation. The water purification process involves introducing ionized minerals that kill microorganisms like algae and bacteria. The 12 inch unit floats in a pool while its solar panel collects sunlight that is converted to electricity. The resulting current energizes a specially alloyed mineral electrode below the waterline, causing release of metallic ions into the water. The electrode is the only part that needs replacing, and water purified by the system falls within EPA drinking water standards.

1992-01-01

332

Valuable water  

NASA Astrophysics Data System (ADS)

In some places, money flows with water. Studying both the water quality and property values around 22 lakes in south-central Maine, Kevin Boyle and Holly James of the University of Maine and Roy Bouchard of the Maine Department of Environmental Protection have found that good water quality makes waterfront property even more valuable. To gauge water quality, the researchers used Secchi disks to measure the clarity of the water at depth. They also reviewed 543 lakefront property sales between 1990 and 1994 to determine how values correlated with changing water conditions. The group also considered such factors as lake frontage, sizes of the houses and lots, and size of the lake.

Carlowicz, Michael

333

Branding water.  

PubMed

Branding is a key strategy widely used in commercial marketing to make products more attractive to consumers. With the exception of bottled water, branding has largely not been adopted in the water context although public acceptance is critical to the implementation of water augmentation projects. Based on responses from 6247 study participants collected between 2009 and 2012, this study shows that (1) different kinds of water - specifically recycled water, desalinated water, tap water and rainwater from personal rainwater tanks - are each perceived very differently by the public, (2) external events out of the control of water managers, such as serious droughts or floods, had a minimal effect on people's perceptions of water, (3) perceptions of water were stable over time, and (4) certain water attributes are anticipated to be more effective to use in public communication campaigns aiming at increasing public acceptance for drinking purposes. The results from this study can be used by a diverse range of water stakeholders to increase public acceptance and adoption of water from alternative sources. PMID:24742528

Dolnicar, Sara; Hurlimann, Anna; Grün, Bettina

2014-06-15

334

Branding water  

PubMed Central

Branding is a key strategy widely used in commercial marketing to make products more attractive to consumers. With the exception of bottled water, branding has largely not been adopted in the water context although public acceptance is critical to the implementation of water augmentation projects. Based on responses from 6247 study participants collected between 2009 and 2012, this study shows that (1) different kinds of water – specifically recycled water, desalinated water, tap water and rainwater from personal rainwater tanks – are each perceived very differently by the public, (2) external events out of the control of water managers, such as serious droughts or floods, had a minimal effect on people's perceptions of water, (3) perceptions of water were stable over time, and (4) certain water attributes are anticipated to be more effective to use in public communication campaigns aiming at increasing public acceptance for drinking purposes. The results from this study can be used by a diverse range of water stakeholders to increase public acceptance and adoption of water from alternative sources.

Dolnicar, Sara; Hurlimann, Anna; Grun, Bettina

2014-01-01

335

Fluoridated Water  

MedlinePLUS

... more other elements. Fluorides are present naturally in water and soil at varying levels. In the 1940s, scientists discovered that people who lived where drinking water supplies had naturally occurring fluoride levels of approximately ...

336

Bending Water  

NSDL National Science Digital Library

In this activity, bend water with the help of static electricity. Discover how a comb can cause water flowing out of a faucet to bend in a unique direction. This activity guide includes a step-by-step instructional video.

Center, Saint L.

2013-02-25

337

Water Chemistry.  

National Technical Information Service (NTIS)

Contents: Water - its chemical nature; The three states of matter; Water and the engineer; Equilibrium product constants dissociation constants; Equilibrium constants solubility product constants; pH and hydrogen ion concentration; Acids and bases; Buffer...

G. R. Seidel

1976-01-01

338

Water resources  

NASA Technical Reports Server (NTRS)

The application of ERTS-1 imagery to the conservation and control of water resources is discussed. The effects of exisiting geology and land use in the water shed area on the hydrologic cycle and the general characteristics of runoff are described. The effects of floods, snowcover, and glaciers are analyzed. The use of ERTS-1 imagery to map surface water and wetland areas to provide rapid inventorying over large regions of water bodies is reported.

Salomonson, V. V.; Rango, A.

1973-01-01

339

Extraterrestrial Water  

Microsoft Academic Search

Life as we know it, i.e., carbon-based organisms that rely on RNA and DNA for information storage and transfer, requires liquid water. Thus, the search for life elsewhere in the universe generally begins with a search for liquid water. In our own Solar System, Earth is the only planet (or moon) that has liquid water at its surface. Mars and

J. F. Kasting

2002-01-01

340

Water Conservation  

NSDL National Science Digital Library

Students study the availability of fresh water on Earth and the methods that can be used to purify and conserve it. They also assess how much water they and their families typically use, and think about ways to reduce water usage.

Foundation, Wgbh E.

2005-12-17

341

Electrocatalysis of fuel cell reactions: Investigation of alternate electrolytes  

NASA Technical Reports Server (NTRS)

Oxygen reduction and transport properties of the electrolyte in the phosphoric acid fuel cell are studied. The areas covered were: (1) development of a theoretical expression for the rotating ring disk electrode technique; (2) determination of the intermediate reaction rate constants for oxygen reduction on platinum in phosphoric acid electrolyte; (3) determination of oxygen reduction mechanism in trifluoreomethanesulfonic acid (TFMSA) which was considered as an alternate electrolyte for the acid fuel cells; and (4) the measurement of transport properties of the phosphoric acid electrolyte at high concentrations and temperatures.

Chin, D. T.; Hsueh, K. L.; Chang, H. H.

1984-01-01

342

Electrocatalysis of Oxygen Reduction by the Tungsten Bronzes.  

National Technical Information Service (NTIS)

Capacitances measured on tungsten bronze electrodes have provided new information about the electronic properties of the semiconducting surface layer. Both the donor concentration and the flat bond potential are altered by platinum doping. Further evidenc...

J. McHardy J. O. Bockris

1971-01-01

343

Improved microbial electrocatalysis with neutral red immobilized electrode  

Microsoft Academic Search

Efficient electron transfer (ET) between microbes and electrodes is a key factor for electricity generation in microbial fuel cell (MFC). The utilization of reversible redox electron-mediator can enhance such extracellular ET but could result in environmental contamination and low cost-effectiveness. These limitations may be overcome by immobilizing electron-mediator molecules on electrode surface. In this paper, we present a stepwise amidation

Kaipeng Wang; Yuwen Liu; Shengli Chen

2011-01-01

344

Block copolymer lithography of rhodium nanoparticles for high temperature electrocatalysis.  

PubMed

We present a method for forming ordered rhodium nanostructures on a solid support. The approach makes use of a block copolymer to create and assemble rhodium chloride nanoparticles from solution onto a surface; subsequent plasma and thermal processing are employed to remove the polymer and fully convert the nanostructures to metallic rhodium. Films cast from a solution of the triblock copolymer poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) dissolved in toluene with rhodium(III) chloride hydrate were capable of producing a monolayer of rhodium nanoparticles of uniform size and interparticle spacing. The nanostructures were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. The electrocatalytic performance of the nanoparticles was investigated with AC impedance spectroscopy. We observed that the addition of the particles to a model solid oxide fuel cell anode provided up to a 14-fold improvement in the anode activity as evidenced by a decrease in the AC impedance resistance. Examination of the anode after electrochemical measurement revealed that the basic morphology and distribution of the particles were preserved. PMID:23713545

Boyd, David A; Hao, Yong; Li, Changyi; Goodwin, David G; Haile, Sossina M

2013-06-25

345

Solvothermal synthesis of platinum alloy nanoparticles for oxygen reduction electrocatalysis.  

PubMed

Platinum alloy nanoparticles show great promise as electrocatalysts for the oxygen reduction reaction (ORR) in fuel cell cathodes. We report here on the use of N,N-dimethylformamide (DMF) as both solvent and reductant in the solvothermal synthesis of Pt alloy nanoparticles (NPs), with a particular focus on Pt-Ni alloys. Well-faceted alloy nanocrystals were generated with this method, including predominantly cubic and cuboctahedral nanocrystals of Pt(3)Ni, and octahedral and truncated octahedral nanocrystals of PtNi. X-ray diffraction (XRD) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), coupled with energy dispersive spectroscopy (EDS), were used to characterize crystallite morphology and composition. ORR activities of the alloy nanoparticles were measured with a rotating disk electrode (RDE) technique. While some Pt(3)Ni alloy nanoparticle catalysts showed specific activities greater than 1000 ?A/cm(2)(Pt), alloy catalysts prepared with a nominal composition of PtNi displayed activities close to 3000 ?A/cm(2)(Pt), or almost 15 times that of a state-of-the-art Pt/carbon catalyst. XRD and EDS confirmed the presence of two NP compositions in this catalyst. HAADF-STEM examination of the PtNi nanoparticle catalyst after RDE testing revealed the development of hollows in a number of the nanoparticles due to nickel dissolution. Continued voltage cycling caused further nickel dissolution and void formation, but significant activity remained even after 20,000 cycles. PMID:22524269

Carpenter, Michael K; Moylan, Thomas E; Kukreja, Ratandeep Singh; Atwan, Mohammed H; Tessema, Misle M

2012-05-23

346

Beyond the volcano limitations in electrocatalysis - oxygen evolution reaction.  

PubMed

Oxygen evolution catalysis is restricted by the interdependence of adsorption energies of the reaction intermediates and the surface reactivity. The interdependence reduces the number of degrees of freedom available for catalyst optimization. Here it is demonstrated that this limitation can be removed by active site modification. This can be achieved on ruthenia by incorporation of Ni or Co into the surface, which activates a proton donor-acceptor functionality on the conventionally inactive bridge surface sites. This enhances the actual measured oxygen evolution activity of the catalyst significantly compared to conventional ruthenia. PMID:24671166

Halck, Niels Bendtsen; Petrykin, Valery; Krtil, Petr; Rossmeisl, Jan

2014-07-21

347

Characterizing nano-scale electrocatalysis during partial oxidation of methane  

PubMed Central

Electrochemical analysis allows in situ characterization of solid oxide electrochemical cells (SOCs) under operating conditions. However, the SOCs that have been analyzed in this way have ill-defined or uncommon microstructures in terms of porosity and tortuosity. Therefore, the nano-scale characterization of SOCs with respect to three-phase boundaries has been hindered. We introduce novel in situ electrochemical analysis for SOCs that uses combined solid electrolyte potentiometry (SEP) and impedance measurements. This method is employed to investigate the oscillatory behavior of a porous Ni-yttria-stabilized zirconia (YSZ) anode during the partial oxidation of methane under ambient pressure at 800°C. The cyclic oxidation and reduction of nickel induces the oscillatory behavior in the impedance and electrode potential. The in situ characterization of the nickel surface suggests that the oxidation of the nickel occurs predominantly at the two-phase boundaries, whereas the nickel at the three-phase boundaries remains in the metallic state during the cyclic redox reaction.

Lee, Daehee; Kim, Dongha; Kim, Joosun; Moon, Jooho

2014-01-01

348

Electrocatalysis of Fuel Cell Reactions: Investigation of Alternate Electrolytes.  

National Technical Information Service (NTIS)

Oxygen reduction and transport properties of the electrolyte in the phosphoric acid fuel cell are studied. A theoretical expression for the rotating ring-disk electrode technique; the intermediate reaction rate constants for oxygen reduction on platinum i...

D. T. Chin H. H. Chang K. L. Hsueh

1983-01-01

349

Electrocatalysis of fuel cell reactions: Investigation of alternate electrolytes  

NASA Astrophysics Data System (ADS)

Oxygen reduction and transport properties of the electrolyte in the phosphoric acid fuel cell are studied. A theoretical expression for the rotating ring-disk electrode technique; the intermediate reaction rate constants for oxygen reduction on platinum in phosphoric acid electrolyte; oxygen reduction mechanism in trifluoromethanesulfonic acid (TFMSA), considered as an alternate electrolyte for the acid fuel cells; and transport properties of the phosphoric acid electrolyte at high concentrations and temperatures are covered.

Chin, D. T.; Hsueh, K. L.; Chang, H. H.

350

Volcano plots in hydrogen electrocatalysis - uses and abuses  

PubMed Central

Summary Sabatier’s principle suggests, that for hydrogen evolution a plot of the rate constant versus the hydrogen adsorption energy should result in a volcano, and several such plots have been presented in the literature. A thorough examination of the data shows, that there is no volcano once the oxide-covered metals are left out. We examine the factors that govern the reaction rate in the light of our own theory and conclude, that Sabatier’s principle is only one of several factors that determine the rate. With the exception of nickel and cobalt, the reaction rate does not decrease for highly exothermic hydrogen adsorption as predicted, because the reaction passes through more suitable intermediate states. The case of nickel is given special attention; since it is a 3d metal, its orbitals are compact and the overlap with hydrogen is too low to make it a good catalyst.

Quaino, Paola; Juarez, Fernanda; Santos, Elizabeth

2014-01-01

351

Constant chemical potential approach for quantum chemical calculations in electrocatalysis  

PubMed Central

Summary In order to simulate electrochemical reactions in the framework of quantum chemical methods, density functional theory, methods can be devised that explicitly include the electrochemical potential. In this work we discuss a Grand Canonical approach in the framework of density functional theory in which fractional numbers of electrons are used to represent an open system in contact with an electrode at a given electrochemical potential. The computational shortcomings and the additional effort in such calculations are discussed. An ansatz for a SCF procedure is presented, which can be applied routinely and only marginally increases the computational effort of standard constant electron number approaches. In combination with the common implicit solvent models this scheme can become a powerful tool, especially for the investigation of omnipresent non-faradaic effects in electrochemistry.

Schneider, Wolfgang B

2014-01-01

352

Perovskite-type oxides - Oxygen electrocatalysis and bulk structure  

NASA Technical Reports Server (NTRS)

Perovskite type oxides were considered for use as oxygen reduction and generation electrocatalysts in alkaline electrolytes. Perovskite stability and electrocatalytic activity are studied along with possible relationships of the latter with the bulk solid state properties. A series of compounds of the type LaFe(x)Ni1(-x)O3 was used as a model system to gain information on the possible relationships between surface catalytic activity and bulk structure. Hydrogen peroxide decomposition rate constants were measured for these compounds. Ex situ Mossbauer effect spectroscopy (MES), and magnetic susceptibility measurements were used to study the solid state properties. X ray photoelectron spectroscopy (XPS) was used to examine the surface. MES has indicated the presence of a paramagnetic to magnetically ordered phase transition for values of x between 0.4 and 0.5. A correlation was found between the values of the MES isomer shift and the catalytic activity for peroxide decomposition. Thus, the catalytic activity can be correlated to the d-electron density for the transition metal cations.

Carbonio, R. E.; Fierro, C.; Tryk, D.; Scherson, D.; Yeager, E.

1988-01-01

353

Perovskite-type oxides: Oxygen electrocatalysis and bulk structure  

NASA Astrophysics Data System (ADS)

Perovskite-type oxides have been considered for use as oxygen reduction and generation electrocatalysts in alkaline electrolytes. This paper is concern Perovskite oxides have not been found, in general, to be very active for oxygen reduction, although substantial catalytic activity for hydrogen peroxid A series of compounds of the type LaFe xNi 1- xO 3 has been used as a model system to gain information on the possible relationships be MES also shows that the introduction of Ni into the FE(III) matrix of LaFeO 3 forces some of the FE(III) into the unusual FE(IV) state, while part o The hydrogen peroxide decomposition rates have been found to undergo a substantial change in the range 0.25 < x < 0.5. A correlation has been f

Carbonio, R. E.; Fierro, C.; Tryk, D.; Scherson, D.; Yeager, E.

354

Microfluidic platforms and fundamental electrocatalysis studies for fuel cell applications  

NASA Astrophysics Data System (ADS)

The fabrication and testing of a planar membraneless microchannel fuel cell, based on a silicon microchannel, is described in detail. Laminar flow of fuel and oxidant streams, one on top of the other, prevents fuel crossover while allowing ionic transport at the interface between the two solutions. By employing laminar flow, the useful functions of a membrane are retained, while bypassing its inherent limitations. The planar design maximizes the anode and cathode areas, and elimination of the membrane affords broad flexibility in the choice of fuel and oxidant. Fuels including formic acid, methanol, ethanol, sodium borohydride and hydrogen were tested along with oxidants such as oxygen, hydrogen peroxide and potassium permanganate. Steps taken to improve voltage, current density, and overall power output have been addressed, including the testing of a dual electrolyte system and the use of micro-patterned electrode surfaces to enhance fuel utilization. As the complexity of the fuels studied in the microchannel fuel cell increased, it was imperative to characterize these fuels using electrochemical techniques prior to utilization in the fuel cell. The oxidation pathway of the liquid fuel methanol was studied rigorously because of its importance for micro-fuel cell applications. Activation energies for methanol oxidation at a Ptpoly surface were determined using electrochemical techniques, providing a benchmark for the comparison of activation energies of other Pt-based electrocatalysts for methanol oxidation at a given potential. A protocol to obtain Ea values was established in three different electrolytes and experimental parameters that influence the magnitude of these values are discussed in detail. The oxidation pathways of sodium borohydride were also examined at Au, Pt, and Pd surfaces using cyclic voltammetry, chronoamperometry, and rotating disk electrode voltammetry. In addition to studies on bulk Ptpoly surfaces, new bulk intermetallic catalysts were characterized for their electrocatalytic activity in formic acid. These intermetallics, including Pt2Ta, Pt3Ta, and PtTi, were compared to Pt in terms of onset of oxidation potential and current density at a given potential. The intermetallic PtPb was also extensively characterized in nine different fuels at room temperature, and at 70°C, and compared to Ptpoly.

Cohen, Jamie Lee

355

Redox active iron nitrosyl units in proton reduction electrocatalysis.  

PubMed

Base metal, molecular catalysts for the fundamental process of conversion of protons and electrons to dihydrogen, remain a substantial synthetic goal related to a sustainable energy future. Here we report a diiron complex with bridging thiolates in the butterfly shape of the 2Fe2S core of the [FeFe]-hydrogenase active site but with nitrosyl rather than carbonyl or cyanide ligands. This binuclear [(NO)Fe(N2S2)Fe(NO)2](+) complex maintains structural integrity in two redox levels; it consists of a (N2S2)Fe(NO) complex (N2S2=N,N'-bis(2-mercaptoethyl)-1,4-diazacycloheptane) that serves as redox active metallodithiolato bidentate ligand to a redox active dinitrosyl iron unit, Fe(NO)2. Experimental and theoretical methods demonstrate the accommodation of redox levels in both components of the complex, each involving electronically versatile nitrosyl ligands. An interplay of orbital mixing between the Fe(NO) and Fe(NO)2 sites and within the iron nitrosyl bonds in each moiety is revealed, accounting for the interactions that facilitate electron uptake, storage and proton reduction. PMID:24785411

Hsieh, Chung-Hung; Ding, Shengda; Erdem, Ozlen F; Crouthers, Danielle J; Liu, Tianbiao; McCrory, Charles C L; Lubitz, Wolfgang; Popescu, Codrina V; Reibenspies, Joseph H; Hall, Michael B; Darensbourg, Marcetta Y

2014-01-01

356

ELECTROCATALYSIS ON SURFACES MODIFIED BY METAL MONOLAYERS DEPOSITED AT UNDERPOTENTIALS.  

SciTech Connect

The remarkable catalytic properties of electrode surfaces modified by monolayer amounts of metal adatoms obtained by underpotential deposition (UPD) have been the subject of a large number of studies during the last couple of decades. This interest stems from the possibility of implementing strictly surface modifications of electrocatalysts in an elegant, well-controlled way, and these bi-metallic surfaces can serve as models for the design of new catalysts. In addition, some of these systems may have potential for practical applications. The UPD of metals, which in general involves the deposition of up to a monolayer of metal on a foreign substrate at potentials positive to the reversible thermodynamic potential, facilitates this type of surface modification, which can be performed repeatedly by potential control. Recent studies of these surfaces and their catalytic properties by new in situ surface structure sensitive techniques have greatly improved the understanding of these systems.

ADZIC,R.

2000-12-01

357

Volcano plots in hydrogen electrocatalysis - uses and abuses.  

PubMed

Sabatier's principle suggests, that for hydrogen evolution a plot of the rate constant versus the hydrogen adsorption energy should result in a volcano, and several such plots have been presented in the literature. A thorough examination of the data shows, that there is no volcano once the oxide-covered metals are left out. We examine the factors that govern the reaction rate in the light of our own theory and conclude, that Sabatier's principle is only one of several factors that determine the rate. With the exception of nickel and cobalt, the reaction rate does not decrease for highly exothermic hydrogen adsorption as predicted, because the reaction passes through more suitable intermediate states. The case of nickel is given special attention; since it is a 3d metal, its orbitals are compact and the overlap with hydrogen is too low to make it a good catalyst. PMID:24991521

Quaino, Paola; Juarez, Fernanda; Santos, Elizabeth; Schmickler, Wolfgang

2014-01-01

358

Water Conditioner  

NASA Technical Reports Server (NTRS)

The Aqualizer is designed to cleanse water with minimal use of chemicals by stabilizing the ions in the water. Its applications are both recreational and industrial. A non-electrical passive device, the Aqualizer operates on the principle of catalytic water conditioning. It consists of a stainless steel pipe length with a helical core and is offered in a variety of sizes depending on the quantity of water to be treated. The device is based on NASA silver ionization technology used to purify drinking water aboard the Apollo spacecraft.

1994-01-01

359

Drinking Water and Ground Water: Kids' Stuff  

MedlinePLUS

... Kids Drinking Water & Ground Water Kids' Stuff Drinking Water & Ground Water Kids' Stuff Kids' Home Games & Activities Other Kids' ... to you. Submit Your Artwork from Thirstin's Wacky Water Adventure Activity Book Here Area Navigation Water Home ...

360

Water Resources Data Utah, Water Year 2001.  

National Technical Information Service (NTIS)

Water-resources data for the year 2001 water year for Utah consist of records of stage, discharge, and water quality of streams; stage and contents of lakes and reservoirs; and water levels and water quality of ground water.

D. E. Wilberg J. R. Tibbetts L. R. Herbert

2002-01-01

361

Evaluation of a photocatalytic reactor membrane pilot system for the removal of pharmaceuticals and endocrine disrupting compounds from water.  

PubMed

A photocatalytic reactor membrane pilot system, employing UV/TiO(2) photocatalysis, was evaluated for its ability to remove thirty-two pharmaceuticals, endocrine disrupting compounds, and estrogenic activity from water. Concentrations of all compounds decreased following treatment, and removal followed pseudo-first-order kinetics as a function of the amount of treatment. Twenty-nine of the targeted compounds in addition to total estrogenic activity were greater than 70% removed while only three compounds were less than 50% removed following the highest level of treatment (4.24 kW h/m(3)). No estrogenically active transformation products were formed during treatment. Additionally, the unit was operated in photolytic mode (UV only) and photolytic plus H(2)O(2) mode (UV/H(2)O(2)) to determine the relative amount of energy required. Based on the electrical energy per order (EEO), the unit achieved the greatest efficiency when operated in photolytic plus H(2)O(2) mode for the conditions tested. PMID:19269667

Benotti, Mark J; Stanford, Benjamin D; Wert, Eric C; Snyder, Shane A

2009-04-01

362

Ground Water  

USGS Publications Warehouse

Some water underlies the Earth's surface almost everywhere, beneath hills, mountains,plains, and deserts. It's not always accessible, or fresh enough for use without treatment, and it's sometimes difficult to locate or to measure and descri be. This water may occur close to the land surface, as in a marsh, or it may lie many hundreds of feet below the surface, as in some arid areas of the West. Water at very shallow depths might be just a few hours old ; at moderate depth, it may be 100 years old; and at great depth or after having flowed long distances from places of entry, water may be several thousands of years old . Water under the Earth's surface is called ground water.

U.S. Geological Survey

1986-01-01

363

Water Cycle  

NSDL National Science Digital Library

Students will use this short interactive activity to check their understanding on what they learned about the water cycle Do you drink the same water as your great grandparents did? Check this website then answer the following questions. COLLECTION 1. How many times does water go through the cycle? 2. Explain each part of the cycle and why it is important. 3. Construct a model or diagram based off the information from this ...

Peterson, Lori

2009-09-28

364

Water Purifiers  

NASA Technical Reports Server (NTRS)

Technology developed to purify the water aboard manned spacecraft has led to a number of spinoff applications. One of them is the Ambassador line of bacteriostatic water treatment systems, which employ high grade, high absorption media to inhibit bacteria growth and remove the medicinal taste and odor of chlorine. Company President, Ray Ward, originally became interested in the technology because of the "rusty" taste of his water supply.

1992-01-01

365

Water Quality  

NSDL National Science Digital Library

In this online interactive, learners explore the various types of life that live in fresh water systems and how the presence of these organisms is an indication of the overall health of the water. Learners perform a water quality test that simulates tests performed in the field and use the data to determine the pollution level of three different streams. This activity also introduces learners to macroinvertebrates (animals without backbones).

Service, National P.

2011-08-20

366

Water Animation  

NSDL National Science Digital Library

This Flash animation provides a detailed explanation of the chemistry and properties of water. Animated diagrams accompanied by written explanations show the configuration of the water molecule, how water molecules link together, what the crystal structure of ice looks like, and how acids and bases are formed. There is also an animated diagram of the pH scale showing the range in which most cellular processes occur and the approximate pH of some common substances. A French translation is available.

Kyrk, John

367

Synthesis of Pt doped Bi2O3/RuO2 photocatalysts for hydrogen production from water splitting using visible light.  

PubMed

This study was focused on the preparation of modified bismuth oxide photocatalysts, including Ru and Pt doped Bi2O3, using sonochemically assisted method to enhance their photocatalytic activity. The crystalline phase composition and surface structure of Bi2O3 photocatalysts were examined using SEM, XRD, UV-visible spectroscopy, and XPS. Optical characterizations have indicated that the Bi2O3 presents the photoabsorption properties shifting from UV light region into visible light which is approaching towards the edge of 470 nm. According to the experimental results, visible-light-driven photocatalysis for water splitting with the addition of 0.3 M Na2SO3 and 0.03 M H2C2O4 as sacrificing agents demonstrates that Pt/Bi2O3-RuO2 catalyst could increase the amount of hydrogen evolution, which is around 11.6 and 14.5 micromol g(-1) h(-1), respectively. Plausible formation mechanisms of modified bismuth oxide and reaction mechanisms of photocatalytic water splitting have been proposed. PMID:22966683

Hsieh, S H; Lee, G J; Chen, C Y; Chen, J H; Ma, S H; Horng, T L; Chen, K H; Wu, J J

2012-07-01

368

Ground water  

USGS Publications Warehouse

Some water underlies the Earth's surface almost everywhere, beneath hills, mountains, plains, and deserts. It is not always accessible, or fresh enough for use without treatment, and it's sometimes difficult to locate or to measure and describe. This water may occur close to the land surface, as in a marsh, or it may lie many hundreds of feet below the surface, as in some arid areas of the West. Water at very shallow depths might be just a few hours old; at moderate depth, it may be 100 years old; and at great depth or after having flowed long distances from places of entry, water may be several thousands of years old.

U.S. Geological Survey

1999-01-01

369

Water Filters  

NASA Technical Reports Server (NTRS)

The Aquaspace H2OME Guardian Water Filter, available through Western Water International, Inc., reduces lead in water supplies. The filter is mounted on the faucet and the filter cartridge is placed in the "dead space" between sink and wall. This filter is one of several new filtration devices using the Aquaspace compound filter media, which combines company developed and NASA technology. Aquaspace filters are used in industrial, commercial, residential, and recreational environments as well as by developing nations where water is highly contaminated.

1993-01-01

370

Incorporation of Water-Oxidation Catalysts into Photoinduced Electron Transfer Systems: Toward Solar Fuel Generation via Artificial Photosynthesis  

NASA Astrophysics Data System (ADS)

A key goal of artificial photosynthesis is to mimic the photochemistry of photosystem II and oxidize water using light energy, with the ultimate aim of using the liberated electrons for reductive, fuel-forming reactions. One of the more recent challenges in the field of solar fuels chemistry is the efficient activation of molecular water-oxidation catalysts with photoinduced electron transfer, an effort that would benefit from detailed knowledge of the energetics and kinetics of each electron transfer step in a light-driven catalytic cycle. The focus of this thesis is the synthesis and photophysical characterization of covalent assemblies comprising a redox-active organic chromophore and the iridium(III)-based water-oxidation catalyst Cp*Ir(ppy)Cl (ppy = 2-phenylpyridine), and the rates and pathways for photogeneration of higher-valence states of the catalyst are determined with femtosecond transient absorption spectroscopy and other time-resolved spectroscopic techniques. In linking the photooxidant perylene-3,4:9,10-bis (dicarboximide) (PDI) to the Ir(III) catalyst, fast photoinduced electron transfer from the metal complex to PDI outcompetes heavy-atom quenching of the dye excited state, and the catalytic integrity of the complex is retained, as determined by electrocatalysis experiments. Long-lived higher-valence states of the catalyst are necessary for the accumulation of oxidizing equivalents for oxygen evolution, and the lifetime of photogenerated Ir(IV) has been extended by over two orders of magnitude by catalyst incorporation into a covalent electron acceptor--chromophore--catalyst triad, in which the dye is perylene-3,4-dicarboximide (PMI). Time resolved X-ray absorption studies of the triad confirm the photogeneration of an Ir(IV) metal center, a species that is too unstable to observe with chemical or electrochemical oxidation methods. This approach to preparing higher-valence states of water-oxidation catalysts has great promise for deducing catalytic mechanisms and probing highly-reactive intermediates, and it also establishes a basis in systems design for photodriving catalytic processes. Covalent dye-catalyst assemblies have been gaining recognition as a useful motif for incorporation into dye-sensitized photoanodes for photoelectrochemical water-splitting cells, and the PMI-Ir catalyst unit is well-poised, both in the energetics and kinetics of its electron transfer properties, to improve upon current solar-driven fuel-forming devices.

Vagnini, Michael Thomas

371

Highly dispersed TiO6 units in a layered double hydroxide for water?splitting.  

PubMed

A family of photocatalysts for water splitting into hydrogen was prepared by distributing TiO(6) units in an MTi-layered double hydroxide matrix (M = Ni, Zn, Mg) that displays largely enhanced photocatalytic activity with an H(2)-production rate of 31.4??mol? h(-1) as well as excellent recyclable performance. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) mapping and XPS measurement reveal that a high dispersion of TiO(6) octahedra in the layered doubled hydroxide (LDH) matrix was obtained by the formation of an M(2+)-O-Ti network, rather different from the aggregation state of TiO(6) in the inorganic layered material K(2)Ti(4)O(9). Both transient absorption and photoluminescence spectra demonstrate that the electron-hole recombination process was significantly depressed in the Ti-containing LDH materials relative to bulk Ti oxide, which is attributed to the abundant surface defects that serve as trapping sites for photogenerated electrons verified by positron annihilation and extended X-ray absorption fine structure (EXAFS) techniques. In addition, a theoretical study on the basis of DFT calculations demonstrates that the electronic structure of the TiO(6) units was modified by the adjacent MO(6) octahedron by means of covalent interactions, with a much decreased bandgap of 2.1?eV, which accounts for its superior water-splitting behavior. Therefore, the dispersion strategy for TiO(6) units within a 2D inorganic matrix can be extended to fabricate other oxide or hydroxide catalysts with greatly enhanced performance in photocatalysis and energy conversion. PMID:22927368

Zhao, Yufei; Chen, Pengyun; Zhang, Bingsen; Su, Dang Sheng; Zhang, Shitong; Tian, Lei; Lu, Jun; Li, Zhuoxin; Cao, Xingzhong; Wang, Baoyi; Wei, Min; Evans, David G; Duan, Xue

2012-09-17

372

Source Water Protection  

MedlinePLUS

... Drinking Water Source Water Source Water Protection Source Water Protection The drinking water we receive from our ... communities, resource managers and the public. My Source Water Basic Information Frequent Questions Source Water Pocket Guide ( ...

373

Water Pollution  

MedlinePLUS

We all need clean water. People need it to grow crops and to operate factories, and for drinking and recreation. Fish and wildlife depend on ... and phosphorus make algae grow and can turn water green. Bacteria, often from sewage spills, can pollute ...

374

Virginia's Waters.  

ERIC Educational Resources Information Center

This booklet describes the water resources in Virginia. Main sections included are: (1) "Introduction" (providing a general overview of the richness and diversity of Virginia's water resources both economic and recreational); (2) "River Basins" (illustrating the area drained by nine rivers and their tributaries); (3) "Bays" (including the…

Sevebeck, Kathryn P.; And Others

375

Water Filter  

NSDL National Science Digital Library

In this engineering activity, challenge learners to invent a water filter that cleans dirty water. Learners construct a filter device out of a 2-liter bottle and then experiment with different materials like gravel, sand, and cotton balls to see which is the most effective. Safety note: An adult's help is needed for this activity.

Boston, Wgbh

2002-01-01

376

Water Science for Schools: USGS Water Information  

NSDL National Science Digital Library

This site offers information on many aspects of water, including text, pictures, data, maps, and an interactive center where users can offer opinions and test their water knowledge. Main topics include: water basics, Earth's water, water use, and special topics such as acid rain, saline water and other water-quality issues. Links to other water-related sites are also provided.

2001-07-02

377

Ground water. [Water pollution control  

Microsoft Academic Search

There is growing evidence that the Nation's ground water is contaminated by a variety of sources. These include unprotected industrial, municipal, and radioactive disposal sites, petroleum exploration and mining activities, agricultural operations such as insecticide spraying, high de-icing salts and others. As of March 1980, more than 8000 chemical tests have been performed on well water, with chlorinated organic solvents

Costle

1980-01-01

378

Water 1: Water and Ice  

NSDL National Science Digital Library

In this lesson, students will explore what happens to water as it goes from solid to liquid and back again; in addition, they will use observation, measurement, and communication skills to describe change. This lesson is the first in a three-part series that addresses a concept that is central to the understanding of the water cycle: that water is able to take many forms but is still water. This series of lessons is designed to prepare students to understand that most substances may exist as solids, liquids, or gases depending on the temperature, pressure, and nature of that substance. This knowledge is critical to understanding that water in our world is constantly cycling as a solid, liquid, or gas.

379

Cleaning Water  

NSDL National Science Digital Library

In this activity, students design and build their own water filtering system and collect data to compare water quality before and after filtering. They will conclude by developing a conclusion based upon their results and comparing individual results to class results to look for patterns. The activity is designed to accompany the Kids' Science News Network (KSNN) 21st Century Explorer 30-second news break entitled 'Where would a space explorer find water and oxygen?' The activity includes a teacher's guide and instructions for students, and a Spanish translation is available.

380

Montana Water  

NSDL National Science Digital Library

Provided by the Montana University System Water Center at Montana State University-Bozeman, this impressive site offers a wealth of information regarding issues related to water in Montana and nationally. A mix of political (regarding recent legislation), educational, research, and funding/employment "water information" is posted at this Website, under several section headings: Information, Featured Programs, Policy & Legislation, Learning Resources, and Montana Watersheds. In addition, a substantial collection of links to related organizations and resources assists users in finding further online information.

2000-01-01

381

Water Purification  

NASA Technical Reports Server (NTRS)

The Vision Catalyst Purifier employs the basic technology developed by NASA to purify water aboard the Apollo spacecraft. However, it also uses an "erosion" technique. The purifier kills bacteria, viruses, and algae by "catalytic corrosion." A cartridge contains a silver-impregnated alumina bed with a large surface area. The catalyst bed converts oxygen in a pool of water to its most oxidative state, killing over 99 percent of the bacteria within five seconds. The cartridge also releases into the pool low levels of ionic silver and copper through a controlled process of erosion. Because the water becomes electrochemically active, no electricity is required.

1994-01-01

382

Water Filters  

NASA Technical Reports Server (NTRS)

Seeking to find a more effective method of filtering potable water that was highly contaminated, Mike Pedersen, founder of Western Water International, learned that NASA had conducted extensive research in methods of purifying water on board manned spacecraft. The key is Aquaspace Compound, a proprietary WWI formula that scientifically blends various types of glandular activated charcoal with other active and inert ingredients. Aquaspace systems remove some substances; chlorine, by atomic adsorption, other types of organic chemicals by mechanical filtration and still others by catalytic reaction. Aquaspace filters are finding wide acceptance in industrial, commercial, residential and recreational applications in the U.S. and abroad.

1988-01-01

383

WATER ANALYSIS  

EPA Science Inventory

This review covers developments in water analysis from November 1996 to the end of October 1998, as found in the Chemical Abstracts Service CA Selects for gas chromatography, mass spectrometry, inorganic analytical chemistry, and pollution monitoring. In addition, because develop...

384

Water Fountain  

NSDL National Science Digital Library

In this activity, learners explore how a hydraulic pump works. Learners work in teams to design and build a unique water fountain that employs a hydraulic pump. This lesson also contains a demonstration of a hydraulic pump in action.

Ieee

2013-07-08

385

Healthy Waters  

NSDL National Science Digital Library

This activity is an mock investigation into different macroinvertebrates found in the streams in your local city. Students will record and analyze data that will lead them to learn if the water quality is good or bad in their backyard.

Voss, Jason

386

WATER QUALITY  

EPA Science Inventory

This manual was develped to provide an overview of microfiltration and ultrafiltration technology for operators, administrators, engineers, scientists, educators, and anyone seeking an introduction to these processes. Chapters on theory, water quality, applications, design, equip...

387

Water Walk  

NSDL National Science Digital Library

The purpose of this resource is to become familiar with the hydrology of your locale. Students will study and visit the Hydrology Study Site, conduct a visual survey to discover information about local land cover, water quality, and document their findings. They will use this initial investigation to raise questions about local land cover and/or water chemistry issues that may require further investigation.

The GLOBE Program, UCAR (University Corporation for Atmospheric Research)

2003-08-01

388

Water Resources Georgia  

NSDL National Science Digital Library

Water Resources Georgia: From the USGS web site comes the Georgia Water Information Network (GWIN)which offers water information for thousands of surface-water, ground-water, and water-quality measurement sites in Georgia.

2008-05-28

389

Total Water Management - slides  

EPA Science Inventory

Total Water Management (TWM) examines urban water systems in an interconnected manner. It encompasses reducing water demands, increasing water recycling and reuse, creating water supply assets from stormwater management, matching water quality to end-use needs, and achieving envi...

390

ESW 2009: Water, Water Everywhere  

NASA Video Gallery

Water is all around us, and its importance to nearly every natural process on earth cannot be underestimated. It is vital to life, but it is also tightly coupled to climate, helping to carry heat f...

391

Field solar degradation of pesticides and emerging water contaminants mediated by polymer films containing titanium and iron oxide with synergistic heterogeneous photocatalytic activity at neutral pH.  

PubMed

Photocatalytic degradation of phenol, nalidixic acid, mixture of pesticides, and another of emerging contaminants in water was mediated by TiO(2) and iron oxide immobilized on functionalized polyvinyl fluoride films (PVF(f)-TiO(2)-Fe oxide) in a compound parabolic collector (CPC) solar photoreactor. During degradation, little iron leaching (<0.2mgL(-1)) was observed. Phenol was efficiently degraded and mineralized at operational pH<5 and nalidixic acid degradation was complete even at pH 7, but mineralization stopped at 35%. Pesticide mixture was slowly degraded (50%) after 150min of irradiation. Degradation of the emergent contaminant mixture was successful for eight compounds and less efficient for six other compounds. The significant reactivity differences between tested compounds were assigned to the differences in structure namely that the presence of complexing or chelating groups enhanced the rates. PVF(f)-TiO(2)-Fe oxide photoactivity gradually increased during 20 days of experiments. X-ray photoelectron spectroscopy (XPS) measurements revealed significant changes on the catalyst surface. These analyses confirm that during photocatalysis mediated by PVF(f)-TiO(2)-Fe oxide, some iron leaching led to enlargement of the TiO(2) surface exposed to light, increasing its synergy with iron oxides and leading to enhanced pollutant degradation. PMID:20362319

Mazille, F; Schoettl, T; Klamerth, N; Malato, S; Pulgarin, C

2010-05-01

392

Water law  

SciTech Connect

Water law overlaps a number of legal fields beyond the narrow scope the term implies. These include environmental law, natural resources law, real property law, and tort law. This diversity can pose problems for those water resource administrators, consultants, and other professionals who need access to the latest legal decisions, but who cannot find the needed information in one single, convenient, and easily understood form. This new book is designed to present recent developments in water law on a level that can be easily understood, with a minimum of ''legalese.'' No prior knowledge of the law or legal system is necessary to understand the material, and all legal terms are explained in the text.

Goldfarb, W.

1984-01-01

393

Study of the photolytic and photocatalytic transformation of amiloride in water.  

PubMed

The diffusion of drug residues in wastewaters and surface waters as rivers and streams may constitute a problem for the environment, with consequences on the ecosystem and also on the human health. This paper deals with the study of the photo-induced transformation of amiloride, an orally administered diuretic agent, under simulated solar light. Direct photolysis and photocatalyzed degradation processes, using titanium dioxide as a photocatalyst, were investigated. The study involved the monitoring of the drug decomposition, the identification of intermediate compounds of the decomposition, the assessment of mineralization, as well as the evaluation of the toxicity associated to the degradation products. Amiloride underwent complete degradation within 30min of irradiation (heterogeneous photocatalysis) or 4h (homogeneous photolysis). HPLC coupled to HRMS, via ESI interface, demonstrated to be a powerful tool to identify and measure degradation products of the studied drug. By considering the photocatalytic process, the identified intermediates are formed through: (1) dechlorination and hydroxylation of the heteroaromatic ring; (2) the detachment of the guanidinic moiety; (3) cleavage of the heteroaromatic ring. The drug photomineralization was a rather slow process and after 4h of irradiation 25% of the total organic carbon (TOC) was still present. Chlorine was stoichiometrically released as chloride ions within the considered irradiation times (4h), while nitrogen was only partially converted into ammonium ions. This was due to the formation of guanidine, known to be hardly mineralized photocatalytically, and some other small molecules still containing the nitrogen. Acute toxicity, measured with a Vibrio fischery assay, showed that amiloride transformation proceeded through the formation of toxic compounds. PMID:18291610

Calza, P; Massolino, C; Monaco, G; Medana, C; Baiocchi, C

2008-09-29

394

Visible Light Responsive Catalysts Using Quantum Dot-Modified Ti02 for Air and Water Purification  

NASA Technical Reports Server (NTRS)

The method of photocatalysis utilizing titanium dioxide, TiO2, as the catalyst has been widely studied for trace contaminant control for both air and water applications because of its low energy consumption and use of a regenerable catalyst. Titanium dioxide requires ultraviolet light for activation due to its band gap energy of 3.2 eV. Traditionally, Hg-vapor fluorescent light sources are used in PCO reactors and are a setback for the technology for space application due to the possibility of Hg contamination. The development of a visible light responsive (VLR) TiO2-based catalyst could lead to the use of solar energy in the visible region (approx.45% of the solar spectrum lies in the visible region; > 400 nm) or highly efficient LEDs (with wavelengths > 400 nm) to make PCO approaches more efficient, economical, and safe. Though VLR catalyst development has been an active area of research for the past two decades, there are few commercially available VLR catalysts; those that are available still have poor activity in the visible region compared to that in the UV region. Thus, this study was aimed at the further development of VLR catalysts by a new method - coupling of quantum dots (QD) of a narrow band gap semiconductor (e.g., CdS, CdSe, PbS, ZnSe, etc.) to the TiO2 by two preparation methods: 1) photodeposition and 2) mechanical alloying using a high-speed ball mill. A library of catalysts was developed and screened for gas and aqueous phase applications, using ethanol and 4-chlorophenol as the target contaminants, respectively. Both target compounds are well studied in photocatalytic systems serve as model contaminants for this research. Synthesized catalysts were compared in terms of preparation method, type of quantum dots, and dosage of quantum dots.

Coutts, Janelle L.; Levine, Lanfang H.; Richards, Jeffrey T.; Hintze, paul; Clausen, Christian

2012-01-01

395

Reuse of Regenerated Waters Under Water Scarcity  

Microsoft Academic Search

\\u000a Mediterranean countries face water supply challenges due to water scarcity. Water regeneration, recycling and reuse address\\u000a these challenges by resolving water resource issues and creating new sources of high-quality water supplies. Among others,\\u000a industrial activities worldwide account for about a quarter of all water consumption and there is hardly any industry that\\u000a does not use large amounts of water. Water

I. Ortiz; R. Ibáñez; A. M. Urtiaga; P. Gómez

396

Mass Production and High Photocatalytic Activity of ZnS Nanoporous Nanoparticles  

Microsoft Academic Search

Environmental problems associated with organic pollutants and toxic water pollutants provide the impetus for sustained fundamental and applied research in the area of environ- mental remediation. Semiconductor photocatalysis offers the potential for complete elimination of toxic chemicals through its efficiency and potentially broad applicability.(1) Various new compounds and materials for photocatalysis have been synthesized in the past few decades. A

Jin-Song Hu; Ling-Ling Ren; Yu-Guo Guo; An-Min Cao; Li-Jun Wan; Chun-Li Bai; Angewandte Chemie

2005-01-01

397

Ground water contamination  

SciTech Connect

This book covers: Ground water contamination and basic concepts of water law; Federal law governing water contamination and remediation; Ground water flow and contaminant migration; Ground water cleanup under CERCLA; Technical methods of remediation and prevention of contamination; Liability for ground water contamination; State constraints on contamination of ground water; Water quantity versus water quality; Prevention of use of contaminated ground water as an alternative to remediation; Economic considerations in liability for ground water contamination; and Contamination, extraction, and injection issues.

Not Available

1991-01-01

398

Water Sampling  

USGS Multimedia Gallery

On April 20, 2010, the Deepwater Horizon Drilling Platform exploded and sank, causing an enormous oil spill in the Gulf of Mexico. U.S. Geological Survey field offices responded immediately by organizing teams to take pre-spill sediment and water samples in order to establish a baseline survey. This...

2010-06-04

399

Water Spout  

ERIC Educational Resources Information Center

During the AAPT summer meeting at Creighton University in 2011, Vacek Miglus and I took pictures of early apparatus at the Creighton physics department. The apparatus in the left-hand picture, shown with the spigot closed, appeared to be a liquid-level device: the water level was the same in both the narrow tube and the flaring glass vase.…

Greenslade, Thomas B., Jr.

2013-01-01

400

Water Detectives  

NSDL National Science Digital Library

In this introductory classroom activity, students exercise their scientific skills of observation and deduction as they use their senses and simple laboratory assays, such as pH indicator paper, to identify mystery pollutants in water samples. Activity includes a student worksheet. This is a learning activity within the Hydrology chapter, GLOBE Teacher's Guide.

401

Water Quality  

NSDL National Science Digital Library

In this problem-based learning module, students work in teams to examine a broad array of information related to water quality in Lower Wheeling Creek and the Wheeling Creek watersheds in Wheeling, West Virginia. This module is part of Exploring the Environment.

402

Energetic Water  

NSDL National Science Digital Library

In this activity, learners explore how hot and cold water move. Learners observe that temperature and density affect how liquids rise and fall. Learners also discover that although they can't see molecules with their eyes, they can demonstrate that molecules are always moving.

Workshop, Mission S.

2013-01-01

403

Water world  

Microsoft Academic Search

We reproduced a beautiful sea and animals in the ocean by the latest software technology. They show their life in the great water world. Wave, splash, bubble and all fluid movement were created by our original fluid simulator to bling realistic and correct expression. In the beautiful ocean, dolphins, whale sharks, great white sharks, humpback whales and other beautiful animals

Makoto Chiba

2010-01-01

404

Troubling Waters  

NSDL National Science Digital Library

One of the world's richest deltas has been radically replumbed, its ecosystem is collapsing, and Californians are realizing their water supply is tapped out. Despite decades of efforts--and some positive trends--solutions may not be any closer. Downstream, the San Francisco Bay looks good by comparison.

Carolyn J. Strange (freelance writer;)

2008-12-01

405

Water watch  

SciTech Connect

In this issue of Water Watch, a summary of precipitation, drought, and streamflow conditions during the summer is presented. In addition, short-term streamflow forecasts (through October) for each region are given. For purposes of reporting, the US is divided into six regions. The data presented can be used to observe how weather conditions affected hydro generation in July.

Not Available

1991-10-01

406

Thirstin's Water Cycle  

NSDL National Science Digital Library

The representation is an animation of the water cycle. The user can select individual parts, such as: rain, water vapor, water storage and clouds. The user can observe water as it cycles through the various parts of the water cycle.

407

Earth's Water  

NSDL National Science Digital Library

The total amount of water on Earth, the places in which it is found and the percentages of fresh vs. salt are examined in this lesson. A short demonstration allows students to visualize the percentage differences and a coloring exercise illustrates locations. This lesson uses the 5E instructional model. All background information, student worksheets and images/photographs/data are included in these downloadable sections: Teacher's Guide, Student Capture Sheet and PowerPoint Presentation.

408

Troubled Waters  

NSDL National Science Digital Library

In this activity, students explore the influences of different parameters on the environmental quality of a river system. They will run a computer model of a river system, interpret graphs, and adjust model parameters such as wind speed, sewage load, and other variables to determine their effects on water quality. For teachers, there are additional background materials, teaching tips, evaluation methods, and links to national standards.

Farmer, John

409

Water characteristics  

SciTech Connect

Recent research on water characteristics is cited in this review article. Acid precipitation has been noted as one of the major environmental problems of the current decade. It poses a serious challenge to national and international bodies to protect water quality. Considerable interest was voiced in 1980 over the causes and effects, prevention and control of acid rain. One study estimated that acid rain was causing an estimated annual $5 billion loss in crop, forest, and aquatic yields. Several conferences were held during 1980 on acid rain problems. Groundwater contamination from acid rain was cited as one of the many current and anticipated problems in maintaining a clean and healthful water supply. Acid rain and vegetation interactions were studied in depth, as were the effects of acid precipitation on aquatic organisms. A procedure was developed which may be useful in the quantification of acid rain via isolated precipitation events. Acid precipitation was studied in forest environments. Two efforts assessed the potential for acid rain to leach into the soil. 154 references.

Smith, E.D.

1981-06-01

410

Water resources data, Louisiana, water year 2004  

USGS Publications Warehouse

Water resources data for the 2004 water year for Louisiana consist of records of stage, discharge, and water quality of streams; stage, contents, and water quality of lakes and reservoirs; and water levels and water quality of ground water. This report contains records for water discharge at 77 gaging stations; stage only for 86 gaging stations and 7 lakes; water quality for 60 surface-water stations (including 42 gaging stations) and 112 wells; and water levels for 304 observation wells. Also included are data for 158 crest-stage and flood-profile partial-record stations. Additional water data were collected at various sites not included in the systematic data-collection program, and are published as miscellaneous measurements. These data represent that part of the National Water Data System operated by the U.S. Geological Survey and cooperating State and Federal agencies in Louisiana.

Baumann, Todd; Goree, B. B.; Lovelace, W. M.; Montogmery, P. A.; Resweber, J. C.; Ross, Garron B.; Ward, Aub N.; Walters, David J.

2005-01-01

411

The Fluid Interface Reactions Structures and Transport (FIRST) EFRC (A "Life at the Frontiers of Energy Research" contest entry from the 2011 Energy Frontier Research Centers (EFRCs) Summit and Forum)  

ScienceCinema

'The Fluid Interface Reactions Structures and Transport (FIRST) EFRC' was submitted by FIRST to the 'Life at the Frontiers of Energy Research' video contest at the 2011 Science for Our Nation's Energy Future: Energy Frontier Research Centers (EFRCs) Summit and Forum. Twenty-six EFRCs created short videos to highlight their mission and their work. FIRST, an EFRC directed by David J. Wesolowski at the Oak Ridge National Laboratory is a partnership of scientists from nine institutions: Oak Ridge National Laboratory (lead), Argonne National Laboratory, Drexel University, Georgia State University, Northwestern University, Pennsylvania State University, Suffolk University, Vanderbilt University, and University of Virginia. The Office of Basic Energy Sciences in the U.S. Department of Energy's Office of Science established the 46 Energy Frontier Research Centers (EFRCs) in 2009. These collaboratively-organized centers conduct fundamental research focused on 'grand challenges' and use-inspired 'basic research needs' recently identified in major strategic planning efforts by the scientific community. The overall purpose is to accelerate scientific progress toward meeting the nation's critical energy challenges. The mission of Fluid Interface Reactions, Structures and Transport Center is 'to develop quantitative and predictive models of the unique nanoscale environment at fluid-solid interfaces that will enable transformational advances in electrical energy storage and heterogeneous catalysis for solar fuels.' Research topics are: catalysis (biomass, CO{sub 2}, water), electrocatalysis, photocatalysis, photoelectrocatalysis, solar fuels, solar electrodes, electrical energy storage, batteries, capacitors, battery electrodes, electrolytes, extreme environment, CO{sub 2} (convert), greenhouse gas, microelectromechanical systems (MEMS), interfacial characterization, matter by design, novel materials synthesis, and charge transport.

Wesolowski, David J. (Director, FIRST - Fluid Interface Reactions, Structures, and Transport Center); FIRST Staff

2011-11-02

412

Water Wise: A Water Use Handbook.  

ERIC Educational Resources Information Center

This guide for elementary school students deals with the importance of and the uses of water, especially in the western United States. Topics covered include the importance of water as a resource; the need for conservation; water storage through dams and reservoirs; irrigation; the lack of water in the old West; the uses of water for cities and…

Bureau of Reclamation (Dept. of Interior), Washington, DC.

413

Principles of Water Quality  

SciTech Connect

CONTENTS: Introduction to Water Quality Concepts. Natural Environmental Processes. Toxic Metals as Factors in Water Quality. Refractory Organic Compounds. Nutrients, Productivity, and Eutrophication. Microbes and Water Quality. Thermal Effects and Water Quality. Air Quality. Water Quality Interactions. Introduction to Water Quality Modeling. Water Quality Standards, and Management Approaches.

Waite, T.D.

1984-01-01

414

Water Source Books  

NSDL National Science Digital Library

Online curriculum guides for K-12 with over 324 activities related to wetlands, coastal waters, and water resources. Each grade section (K-2, 3-5, 5-8, and 9-12) is divided into five chapters: Introduction to Water, Drinking Water and Wastewater Treatment, Surface Water Resources, Ground Water Resources, and Wetlands and Coastal Waters.

415

Be Water Wise.  

ERIC Educational Resources Information Center

Various topics on water and water conservation are discussed, each general topic followed by a student activity. Topics include: (1) importance of water; (2) water in the environment; (3) getting water to and from homes (making water usable; treating wastewater; on-site systems, including water wells and septic tanks); (4) relationship between…

Birch, Sandra K.; Pettus, Alvin M.

416

Water Purification  

NASA Technical Reports Server (NTRS)

Silver ionization water purification technology was originally developed for Apollo spacecraft. It was later used to cleanse swimming pools and has now been applied to industrial cooling towers and process coolers. Sensible Technologies, Inc. has added two other technologies to the system, which occupies only six square feet. It is manufactured in three capacities, and larger models are custom built on request. The system eliminates scale, corrosion, algae, bacteria and debris, and because of the NASA technology, viruses and waterborne bacteria are also destroyed. Applications include a General Motors cooling tower, amusement parks, ice manufacture and a closed-loop process cooling system.

1992-01-01

417

Fresh Water  

NSDL National Science Digital Library

You will use online resources to learn about freshwater ecosystems, the critters that live in them and the effect we have on them. You may choose to print this page out to assist you in answering questions. In studying fresh water, we will be looking at three different ecosystems: Streams and Rivers; Ponds and Lakes; and Wetlands. The following site contains information about all 3. Answer the questions on loose-leaf or in an MS Word document, to be printed. Freshwater Ecosystems (title provided or enhanced by cataloger) After clicking the link above, click on "Rivers ...

Bionagy

2008-10-25

418

Water Conservation Devices: Residential Water Conservation.  

National Technical Information Service (NTIS)

A consumer-oriented capsule report highlights findings of research projects funded through the Office of Water Research and Technology which treat the significance, economics, and application of water conservation. Water conservation measures and devices,...

1977-01-01

419

Photocatalysis and photoelectrochemical properties of tungsten trioxide nanostructured films.  

PubMed

Tungsten trioxide (WO?) possesses a small band gap energy of 2.4-2.8?eV and is responsive to both ultraviolet and visible light irradiation including strong absorption of the solar spectrum and stable physicochemical properties. Thus, controlled growth of one-dimensional (1D) WO? nanotubular structures with desired length, diameter, and wall thickness has gained significant interest. In the present study, 1D WO? nanotubes were successfully synthesized via electrochemical anodization of tungsten (W) foil in an electrolyte composed of 1?M of sodium sulphate (Na?SO?) and ammonium fluoride (NH?F). The influence of NH?F content on the formation mechanism of anodic WO? nanotubular structure was investigated in detail. An optimization of fluoride ions played a critical role in controlling the chemical dissolution reaction in the interface of W/WO?. Based on the results obtained, a minimum of 0.7?wt% of NH?F content was required for completing transformation from W foil to WO? nanotubular structure with an average diameter of 85?nm and length of 250?nm within 15?min of anodization time. In this case, high aspect ratio of WO? nanotubular structure is preferred because larger active surface area will be provided for better photocatalytic and photoelectrochemical (PEC) reactions. PMID:24782669

Lai, Chin Wei

2014-01-01

420

Green Photocatalysis for Degradation of Organic Contaminants: A Review  

EPA Science Inventory

Many organic pesticides that were banned a few decades ago, as well as those that are currently in use in many parts of the world, pose some serious threat to human life and the ecosystem because of their persistent and bioaccumulative nature. In the recent years advanced oxidati...

421

Photocatalysis and Photoelectrochemical Properties of Tungsten Trioxide Nanostructured Films  

PubMed Central

Tungsten trioxide (WO3) possesses a small band gap energy of 2.4–2.8?eV and is responsive to both ultraviolet and visible light irradiation including strong absorption of the solar spectrum and stable physicochemical properties. Thus, controlled growth of one-dimensional (1D) WO3 nanotubular structures with desired length, diameter, and wall thickness has gained significant interest. In the present study, 1D WO3 nanotubes were successfully synthesized via electrochemical anodization of tungsten (W) foil in an electrolyte composed of 1?M of sodium sulphate (Na2SO4) and ammonium fluoride (NH4F). The influence of NH4F content on the formation mechanism of anodic WO3 nanotubular structure was investigated in detail. An optimization of fluoride ions played a critical role in controlling the chemical dissolution reaction in the interface of W/WO3. Based on the results obtained, a minimum of 0.7?wt% of NH4F content was required for completing transformation from W foil to WO3 nanotubular structure with an average diameter of 85?nm and length of 250?nm within 15?min of anodization time. In this case, high aspect ratio of WO3 nanotubular structure is preferred because larger active surface area will be provided for better photocatalytic and photoelectrochemical (PEC) reactions.

Lai, Chin Wei

2014-01-01

422

The use of plastic optical fibers in photocatalysis of trichloroethylene  

Microsoft Academic Search

In this study, plastic optical fibers (POFs) were considered as light-transmitting media and substrates for the potential use in photocatalytic environmental purification system and the performance of POFs was also compared with that of quartz optical fibers (QOFs). After the characteristic of POFs in terms of light transmittance was determined in the beginning, detailed investigation was further conducted through the

Hyunku Joo; Heerok Jeong; Myungseok Jeon; Il Moon

2003-01-01

423

Removal of toxic metal ions from wastewater by semiconductor photocatalysis  

Microsoft Academic Search

Semiconductor photocatalytic reduction is a relatively new technique for the removal of dissolved metal ions in wastewater. In this paper, physical adsorption and photocatalytic reduction of eight environmentally significant metal ions in TiO2 suspensions of Degussa P25 and Hombikat UV100 were investigated. Critical scrutiny of the potential versus pC and pH diagrams reveals that any particular oxidation or reduction reaction

Dingwang Chen; Ajay K. Ray

2001-01-01

424

Heterogeneous photocatalysis: an emerging discipline involving multiphase systems  

Microsoft Academic Search

The influence of the various parameters which govern the kinetics (mass of catalyst, wavelength, initial concentration, temperature, radiant flux, modification of the photocatalyst) has been analyzed. The knowledge of these parameters enables one to determine the best conditions for an optimum quantum yield. The photon appears as a reactant and the light flux as an additional phase (the ‘electromagnetic phase’).

J.-M. Herrmann

1995-01-01

425

Photocatalysis on Modified Semiconductor Surfaces and on Bipolar Photoelectrodes,  

National Technical Information Service (NTIS)

Selective photo induced redox chemistry can be achieved on irradiated semiconductor surfaces configured as unmodified particles, as chemically modified powders, single crystals, or films, as components of multielement membrane systems, or as surfaces of b...

M. A. Fox

1987-01-01

426

Augmentation for Research Training: Surface-Mediated Photocatalysis.  

National Technical Information Service (NTIS)

Three areas have been investigated: application of ESR spectroscopy and time-resolved reflectance absorption and emission spectroscopy to establish mechanisms in photocatalytic oxidative degradations of organic molecules; exploration of controlled oxidati...

M. A. Fox

1994-01-01

427

Novel TiO 2 CVD films for semiconductor photocatalysis  

Microsoft Academic Search

A novel CVD film of titanium(IV) oxide has been prepared on glass, via the reaction of titanium(IV) chloride and ethyl acetate, using a CVD technique. The film is clear, very robust mechanically and comprised of a thin (24nm) layer of nanocrystalline anatase titania that absorbs light of ?<360nm. The film is active in terms of photo-induced superhydrophilicity, and thus its

Andrew Mills; Nicholas Elliott; Ivan P. Parkin; Shane A. O’Neill; R. J. Clark

2002-01-01

428

Sol–gel preparation and photocatalysis of titanium dioxide  

Microsoft Academic Search

Titanium dioxide (TiO2) is extensively used as a photocatalyst due to the strong oxidizing power of its holes, high photostability and redox selectivity. In the present work, the microstructural and chemical properties of TiO2, obtained by a sol–gel procedure, were investigated. TiO2 sols were prepared by the hydrolysis and condensation of titanium (IV) n-butoxide in iso-propyl alcohol. The particle dimensions

C. Su; B.-Y. Hong; C.-M. Tseng

2004-01-01

429

Kinetic study of acetaminophen degradation by visible light photocatalysis.  

PubMed

In this work, a novel photocatalyst K3[Fe(CN)6]/TiO2 synthesized via a simple sol-gel method was utilized to degrade acetaminophen (ACT) under visible light with the use of blue and green LED lights. Parameters (medium pH, initial concentration of reactant, catalyst concentration, temperature, and number of blue LED lights) affecting photocatalytic degradation of ACT were also investigated. The experimental result showed that compared to commercially available Degussa P-25 (DP-25) photocatalyst, K3[Fe(CN)6]/TiO2 gave higher degradation efficiency and rate constant (kapp) of ACT. The degradation efficiency or kapp decreased with increasing initial ACT concentration and temperature, but increased with increased number of blue LED lamps. Additionally, kapp increased as initial pH was increased from 5.6 to 6.9, but decreased at a high alkaline condition (pH 8.3). Furthermore, the degradation efficiency and kapp of ACT increased as K3[Fe(CN)6]/TiO2 loading was increased to 1 g L(-1) but decreased and eventually leveled off at photocatalyst loading above this value. Photocatalytic degradation of ACT in K3[Fe(CN)6]/TiO2 catalyst system follows a pseudo-first-order kinetics. The Langmuir-Hinshelwood equation was also satisfactorily used to model the degradation of ACT in K3[Fe(CN)6]/TiO2 catalyst system indicated by a satisfactory linear correlation between 1/kapp and Co, with kini = 6.54 × 10(-4) mM/min and KACT = 17.27 mM(-1). PMID:24766590

Gotostos, Mary Jane N; Su, Chia-Chi; De Luna, Mark Daniel G; Lu, Ming-Chun

2014-07-01

430

Photocatalysis of 4-nitrophenol using zinc phthalocyanine complexes  

Microsoft Academic Search

Photodegradation of 4-nitrophenol (4-Np) in the presence of zinc tetrasulfophthalocyanine (ZnPcS4), zinc octacarboxyphthalocyanine (ZnPc(COOH)8) and a sulfonated ZnPc containing a mixture of differently sulfonated derivatives (ZnPcSmix), as photocatalysts is reported. ZnPcSmix is the most effective catalyst in terms of a high quantum yield for 4-Np degradation and the stability of the catalyst. However ZnPc(COOH)8 degrades readily during the catalysis, but

Eloïse Marais; Rosalyn Klein; Edith Antunes; Tebello Nyokong

2007-01-01

431

Water resources data, Nebraska, water year 2004  

USGS Publications Warehouse

The Nebraska water resources data report for water year 2004 includes records of stage, discharge, and water quality of streams; water elevation and/or contents of lakes and reservoirs; and water levels and quality of ground water in wells. This report contains records of stream stage for 3 stations; stream discharge for 101 continuous and 5 crest-stage gaging stations, and 6 miscellaneous sites; stream water quality for 7 gaging stations and 40 miscellaneous sites; water elevation and/or contents for 2 lakes and 1 reservoir; ground-water levels for 74 observation wells; and ground-water quality for 200 wells. These data represent that part of the National Water Data System collected in and near Nebraska by the U.S. Geological Survey and cooperating Federal, State, and local agencies.

compiled by Hitch, D. E.; Soensken, P. J.; Sebree, S. K.; Wilson, K. E.; Walczyk, V. C.; Drudik, R. A.; Miller, J. D.; Hull, S. H.

2005-01-01

432

Water Resources Data, Nebraska, Water Year 2003  

USGS Publications Warehouse

The Nebraska water resources data report for water year 2003 includes records of stage, discharge, and water quality of streams; water elevation and/or contents of lakes and reservoirs; and water levels and quality of ground water in wells. This report contains records of stream stage for 3 stations; stream discharge for 103 continuous and 5 crest-stage gaging stations, and 5 miscellaneous sites; stream water quality for 14 gaging stations and 5 miscellaneous sites; water elevation and/or contents for 2 lakes and 1 reservoir; ground-water levels for 40 observation wells; and ground-water quality for 132 wells. These data represent that part of the National Water Data System collected in and near Nebraska by the U.S. Geological Survey and cooperating local, State, and Federal agencies.

Hitch, D. E.; Hull, S. H.; Walczyk, V. C.; Miller, J. D.; Drudik, R. A.

2004-01-01

433

Water resources data, Kansas, water year 2004  

USGS Publications Warehouse

Water-resources data for the 2004 water year for Kansas consist of records of stage, discharge, and water quality of streams; elevation and contents of lakes and reservoirs; and water levels of ground-water wells. This report contains records for water discharge at 155 complete-record gaging stations; elevation and contents at 17 lakes and reservoirs; water-quality records at 2 precipitation stations, water-level data at 14 observation wells; and records of specific conductance, pH, water temperature, dissolved oxygen, and turbidity at 16 gaging stations and 2 lakes with water-quality monitors. Also included are discharge data for 29 high-flow partial-record stations. These data represent that part of the National Water Information System collected by the U.S. Geological Survey in cooperation with local, State, and Federal agencies in Kansas.

Putnam, J. E.; Schneider, D. R.

2005-01-01

434

Water Sensors  

NASA Technical Reports Server (NTRS)

Mike Morris, former Associate Director of STAC, formed pHish Doctor, Inc. to develop and sell a pH monitor for home aquariums. The monitor, or pHish Doctor, consists of a sensor strip and color chart that continually measures pH levels in an aquarium. This is important because when the level gets too high, ammonia excreted by fish is highly toxic; at low pH, bacteria that normally break down waste products stop functioning. Sales have run into the tens of thousands of dollars. A NASA Tech Brief Technical Support Package later led to a salt water version of the system and a DoE Small Business Innovation Research (SBIR) grant for development of a sensor for sea buoys. The company, now known as Ocean Optics, Inc., is currently studying the effects of carbon dioxide buildup as well as exploring other commercial applications for the fiber optic sensor.

1992-01-01

435

Water Safety Quiz  

MedlinePLUS

Water Safety Quiz Trivia quiz loading... Please enable javascript. Stay Safe around Water Download water safety tips in English or Spanish and share them with your friends. Make Water Safety a Priority Contact your local Red Cross ...

436

Lead and tap water  

MedlinePLUS

Water contaminated with lead ... The Environmental Protection Agency (EPA) monitors drinking water and requires water suppliers to produce annual water quality reports. These reports, which include information about lead amounts, are available to consumers. For ...

437

Water Science School  

MedlinePLUS

The USGS Water Science School The USGS Water Science School Welcome to the U.S. Geological Survey's ( USGS ) Water Science School. We offer information on many aspects of water, along with pictures, ...

438

Water: Consumer Information  

MedlinePLUS

... EPA's (PDF) page to learn more. Your Drinking Water Quality Water On Tap: What You Need to ... Drinking Water Sources (PDF) (2 pp, 563K) Drinking Water Emergencies Learn what to do in the event ...

439

Build a Kit: Water  

MedlinePLUS

... your family’s needs during an emergency. How Much Water Do I Need? You should store at least ... of water per person. How Should I Store Water? It is recommended you purchase commercially bottled water, ...

440

Learn about Water  

MedlinePLUS

... Search Contact Us Learn the Issues Learn about Water When the water in our rivers, lakes, and ... swim and fish. See all water resources . Our Waters Wetlands Oceans, Coasts, Estuaries and Beaches Watersheds More ...

441

Private Ground Water Wells  

MedlinePLUS

... Water Healthy Water Home Share Compartir Private Ground Water Wells Many people in the United States receive ... answers to frequently asked questions about wells . Ground Water and Wells When rain falls, much of it ...

442

Important Water Quality Factors  

NSDL National Science Digital Library

This site provides basic information about factors commonly analyzed in water quality studies of drinking water, waste water and natural water. The factors are listed alphabetically with descriptions and explanations about what the results of measurements mean in environmental terms.

443

Water Contamination Demonstration  

NSDL National Science Digital Library

Summary: Misplaced Matter and Water Pollution The drinking water pollution demonstration provides a very simple but dramatic way to get students to think about water contamination and drinking water standards, ...

444

Radon in Drinking Water  

MedlinePLUS

... are here: EPA Home Air Indoor Air Radon Health Risks Drinking Water Radon in Drinking Water Public Health ... States and community water systems for reducing radon health risks in both drinking water and indoor air quality, ...

445

Weather and Water.  

National Technical Information Service (NTIS)

The importance of water in the world today is emphasized and the hydrological cycle described. Aspects of hydrology - damming, irrigation, water loss, water supply - are noted, and the role of WMO, particularly in developing countries, in water resources ...

1977-01-01

446

Virtual water trade and world water resources.  

PubMed

Global virtual water trade was quantitatively estimated and evaluated. The basic idea of how to estimate unit requirement of water resources to produce each commodity is introduced and values for major agricultural and stock products are presented. The concept of virtual water and the quantitative estimates can help in assessing a more realistic water scarcity index in each country, projecting future water demand for food supply, increasing public awareness on water, and identifying the processes wasting water in the production. Really required water in exporting countries is generally smaller than virtually required water in importing countries, reflecting the comparative advantage of water use efficiency, and it is estimated to be 680 km3/y for 2000. On the contrary the virtually required water for the same year is estimated to be 1,130 km3/y, and the difference of 450 km3/y is virtually saved by global trade. However, solely virtual water should not be used for any decision making since the idea of virtual water implies only the usage and influence of water and no concerns on social, cultural, and environmental implications. Virtual water trade also does not consider other limiting factors than water. PMID:15195440

Oki, T; Kanae, S

2004-01-01

447

Everyone into the Water!  

ERIC Educational Resources Information Center

As the days grow longer and warmer with the approach of summer, everyone's thoughts turn to the outdoors and the clear blue of water sports. While recreational choices range from in-the-water activities like water polo to under-the-water sports like free diving, and on-the-water diversions like water skiing, this article focuses on print, video,…

Hennessey, Christina L.

2007-01-01

448

China's water scarcity  

Microsoft Academic Search

China has been facing increasingly severe water scarcity, especially in the northern part of the country. China's water scarcity is characterized by insufficient local water resources as well as reduced water quality due to increasing pollution, both of which have caused serious impacts on society and the environment. Three factors contribute to China's water scarcity: uneven spatial distribution of water

Yong Jiang

2009-01-01

449

The Water Cycle  

NSDL National Science Digital Library

Students will understand and explain parts of the water cycle. First watch the video to get a background about the water cycle: water cycle video Draw and explain the water cycle in your own words (include the terms: evaporation, condensation, precipitation, at least 3 bodies of water, the sun). Before reading the experiment record your predictions: If you put a small amount of water ...

Amanda, Miss

2011-02-14

450

Testing the Waters.  

ERIC Educational Resources Information Center

Provides information about home drinking water treatment systems to address concerns about the safety and quality of drinking water. Discusses water testing, filtration, product options and selection, water testing resources, water treatment device guidelines, water analysis terminology, and laboratory selection. (MCO)

Finks, Mason

1993-01-01

451

Physiological Water Model Development.  

National Technical Information Service (NTIS)

The water of the human body can be categorized as existing in two main compartments: intracellular water and extracellular water. The intracellular water consists of all the water within the cells and constitutes over half of the total body water. Since r...

S. Doty

1993-01-01

452

Minimal Proton Channel Enables H2 Oxidation and Production with a Water-Soluble Nickel-Based Catalyst  

SciTech Connect

Hydrogenase enzymes efficiently interconvert H2 and H+ using first row transition metals with low overpotentials and high rates in aqueous solution. The development of efficient electrocatalysts mimicking the properties of hydrogenase enzymes for fuel and electrolysis cells based upon abundant and inexpensive metals could enable the widespread use of renewable fuels such as solar and wind. However, molecular electrocatalysts are typically unable to operate bidirectionally and are notably unable to meet the overall efficiency of the enzyme in either direction. Here we show that introducing an amino acid residue in the outer coordination sphere of a Ni-based complex Ni(PCy2NGlycine2)2 creates an electrocatalyst that is active and efficient for hydrogen oxidation (5-8 s-1, overpotential=44-250 mV) over a range of moderate pH values (3.5-9.0). Hydrogen production can be achieved from the same complex under identical solution conditions (>1200 s-1). Proton transfer from the amino acid carboxylates in the outer coordination sphere to the pendant amines in the second coordination sphere is observed by NMR and IR, signifying a plausible role of the carboxylate groups in creating a proton channel for proton removal and delivery during the catalytic cycle. These results with this first generation water soluble Ni(PR2NR’2)2 complex indicate that fast, bidirectional (hydrogen production/oxidation) catalysis for molecular catalysts is achievable. This work was funded by the Office of Science Early Career Research Program through the USDOE, BES (AD, SL, WJS), and the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US DOE, Office of Science, Office of BES (JH, JASR). Part of the research was conducted at the W.R. Wiley Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by U.S. DOE’s Office of Biological and Environmental Research (BER) program located at Pacific Northwest National Laboratory (PNNL). PNNL is operated by Battelle for the U.S. Department of Energy.

Dutta, Arnab; Lense, Sheri; Hou, Jianbo; Engelhard, Mark H.; Roberts, John A.; Shaw, Wendy J.

2013-11-08

453

Magnificent Ground Water Connection  

NSDL National Science Digital Library

The Magnificent Ground Water Connection is a compilation of ground water-related activities for teaching and learning purposes. The teacher's activity guide is applicable to a wide range of subject matter and the ground water theme is integrated into stories, songs, math, social studies, art and writing. The topics include basic concepts of the water cycle, water distribution, treatment and stewardship. Other subjects include the water cycle and water conservation, New England's ground water resources, ground water contamination and protection. Sections are also available for wetlands, ground water, marine debris, waster, air quality, acid rain, and energy. Users can also access an on-line lending library for educational materials and videos.