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1

WATER TREATMENT BY HETEROGENEOUS PHOTOCATALYSIS AN OVERVIEW1  

Microsoft Academic Search

Photocatalysis process, as an environmental application is a relatively novel subject with tremendous potential in the near future. This paper describes the basics of heterogeneous photocatalysis, mainly on TiO2 and the application of photocatalytic processes to water purification and treatment. The paper also reviews more than 50 references covering the wide scale of heterogeneous water phase applications. Finally, a short

Radwan A. Al-Rasheed

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

Disinfection byproduct formation resulting from settled, filtered, and finished water treated by titanium dioxide photocatalysis.  

PubMed

This study evaluated strategies targeting disinfection byproduct (DBP) mitigation using TiO2 photocatalysis with varying influent water quality. A Purifics Photo-CAT Lab reactor was used to assess total trihalomethane (TTHM) and haloacetic acid (HAA) formation as a function of photocatalytic treatment using water from a conventional coagulation/flocculation/sedimentation process, granular activated carbon filtration, and a DBP hot spot in the water distribution system. Regardless of influent water quality, photocatalysis reduced DBP precursors; however, low-energy limited photocatalysis (<5 kW h m(-3)), exacerbated the production of TTHMs and HAA5s beyond initial levels. Accordingly, limited photocatalysis is not a suitable option when TTHMs and HAA5s are a concern, regardless of the level of pretreatment. Limited photocatalysis yields incomplete oxidation, wherein larger, more aromatic, humic organic compounds are broken into smaller molecular weight, less aromatic, and less humic moieties, which have considerable potential to produce DBPs. More complete mineralization of DBP precursors is obtained using extended photocatalysis (80-160 kW h m(-3)), which substantially decreases DBP precursors as well as TTHM and HAA5 concentrations. In order to balance DBP mitigation, energy, and chemical usage, targeted use of TiO2 photocatalysis is necessary in a water treatment train (e.g., extended photocatalysis at a distribution system hot spot, where the volumetrically high energy requirements may be justifiable). PMID:24972073

Mayer, Brooke K; Daugherty, Erin; Abbaszadegan, Morteza

2014-12-01

4

Developments in solar photocatalysis for water purification.  

PubMed

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, gamma-lindane and EPTC have been tested at laboratory scale and in the field to determine the feasibility of the photocatalytic oxidation of organic contaminants in water. Our preliminary results at laboratory scale with these chemicals have provided a better understanding of the photocatalytic process which seems to be efficient and not selective. The application of these processes in removal of gamma-lindane from water operating in a parabolic trough concentrator has demonstrated to be effective, being possible to reduce 99.9% of gamma-lindane levels in water in acceptable times. PMID:9570109

Vidal, A

1998-05-01

5

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

6

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 ...

7

New Photocatalysis for Effective Degradation of Organic Pollutants in Water  

NASA Astrophysics Data System (ADS)

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 water treatment processes, have limitations of their own and none is cost effective. Advanced oxidation processes have been proposed as an alternative for the treatment of this kind of wastewater. Heterogeneous photocatalysis has recently emerged as an efficient method for purifying water. TiO2 has generally been demonstrated to be the most active semiconductor material for decontamination water. One significant factor is the cost of separation TiO2, which is generally a powder having a very small particle size from the water after treatment by either sedimentation or ultrafiltration. The new photocatalyst, HTiNbO5, has been tested to determine whether its photocatalytic efficiency is good enough for use in photocatalytic water purification since it has high surface area and relatively large particle size. The larger particle sizes of the porous materials facilitate catalyst removal from a solution, after purification has taken place. It can be separated from water easily than TiO2, a significant technical improvement that might eliminate the tedious final filtration necessary with a slurry. These materials are characterized and tested as water decontamination photocatalysts. The new catalyst exhibited excellent catalytic activity, but with a strong pH dependence on the photo efficiency. These results suggest that elimination of the ion exchange character of the catalyst may greatly improve its performance at various pHs. This new research proposes to study the effects of a topotactic dehydration reaction on these new porous material catalysts.

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

2009-12-01

8

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 (IrO(x)) 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 (Na2S2O8) to form Ru(3+) species. The Ru(3+) species extracts an electron from IrO(x) 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

9

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

10

Water oxidation electrocatalysis by a zeolitic imidazolate framework  

NASA Astrophysics Data System (ADS)

The search for efficient water oxidation catalysts (WOCs) is of paramount importance in energy and environmental fields, but there exists no good non-noble catalyst that works under acidic and alkaline conditions. Intensive investigations have recently focused on cobalt based complex/solid catalysts. Here, we have introduced a new type of cobalt-based WOC made of metal-organic frameworks where the redox function of cobalt centres was modified by imidazolate linkers for facilitating the proton transfer process. This cobalt-containing zeolitic imidazolate framework (Co-ZIF-9) has been demonstrated for the first time to electrocatalyze the oxygen evolution reaction in a wide pH range. The catalyst was found by theoretical calculation to be capable of activating the water molecule via binding the OH-group to the metal sites with low activation barriers, while the eliminated proton was accepted by the nearby benzimidazolate motifs. This allows Co-ZIF-9 to work effectively for the electrochemical oxygen-evolution reaction.The search for efficient water oxidation catalysts (WOCs) is of paramount importance in energy and environmental fields, but there exists no good non-noble catalyst that works under acidic and alkaline conditions. Intensive investigations have recently focused on cobalt based complex/solid catalysts. Here, we have introduced a new type of cobalt-based WOC made of metal-organic frameworks where the redox function of cobalt centres was modified by imidazolate linkers for facilitating the proton transfer process. This cobalt-containing zeolitic imidazolate framework (Co-ZIF-9) has been demonstrated for the first time to electrocatalyze the oxygen evolution reaction in a wide pH range. The catalyst was found by theoretical calculation to be capable of activating the water molecule via binding the OH-group to the metal sites with low activation barriers, while the eliminated proton was accepted by the nearby benzimidazolate motifs. This allows Co-ZIF-9 to work effectively for the electrochemical oxygen-evolution reaction. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr02399d

Wang, Sibo; Hou, Yidong; Lin, Sen; Wang, Xinchen

2014-08-01

11

Heterogeneous photocatalysis of moxifloxacin in water: chemical transformation and ecotoxicity.  

PubMed

This work provides new insights on the impact of TiO2/UV catalyzed chemical transformation of moxifloxacin on ecotoxicity effects towards the green alga Pseudokirchneriella subcapitata. The moxifloxacin median effect concentration (EC-50=0.78 [0.56, 1.09] mg L(-1)), determined in accordance to the OECD 72-h growth inhibition test guideline, was 7 times lower than that of the older and widely used fluoroquinolone ciprofloxacin (EC-50=5.57 [4.86, 6.38] mg L(-1)). Applying heterogeneous photocatalysis as an advanced oxidation technique to degrade moxifloxacin in aqueous solution decreased the average growth inhibition from 72% to 14% after 150 min of treatment. No significant carbon mineralization was observed and liquid chromatography mass spectrometry analysis revealed the formation of 13 degradation products for which a chemical structure could be proposed based on accurate mass determination. Combined chemical and ecotoxicological analysis showed that as long as moxifloxacin is present in the reaction solution, it is the main compound affecting algal growth inhibition. However, also the contribution of the degradation products to the observed ecotoxicity cannot be neglected. Photocatalytically induced modifications of moxifloxacin mainly occur at the diazobicyclo-substituent as ring opening, oxidation into carbonyl groups, and hydroxylation. This results into the formation of more hydrophilic compounds with a decreased biological activity compared with moxifloxacin. The change in lipophilicity, and possibly a modified acid-base speciation, most probably also affect the cell membrane permeation of the degradation products, which might be another factor explaining the observed lower residual ecotoxicity of the photocatalytically treated reaction solutions. PMID:24735961

Van Doorslaer, Xander; Haylamicheal, Israel Deneke; Dewulf, Jo; Van Langenhove, Herman; Janssen, Colin R; Demeestere, Kristof

2015-01-01

12

Solar photocatalysis—a possible step in drinking water treatment  

Microsoft Academic Search

Possibility of the use of solar radiation for reduction of Natural Organic Matter (NOM) content in natural lake water, as a source for drinking water preparation, was the topic of this research. Solar radiation alone does not have enough energy for sufficient degradation of NOM, but in combination with heterogeneous photocatalyst-titanium dioxide (TiO2), with or without other chemicals, the degradation

Davor Ljubas

2005-01-01

13

Electrocatalysis of water oxidation by H2O-capped iridium-oxide nanoparticles electrodeposited on spectroscopic graphite.  

PubMed

Electrocatalysis of water oxidation by 1.54 nm IrOx nanoparticles (NPs) immobilized on spectroscopic graphite electrodes was demonstrated to proceed with a higher efficiency than on all other, hitherto reported, electrode supports. IrOx NPs were electrodeposited on the graphite surface, and their electrocatalytic activity for water oxidation was correlated with the surface concentrations of different redox states of IrOx as a function of the deposition time and potential. Under optimal conditions, the overpotential of the reaction was reduced to 0.21 V and the electrocatalytic current density was 43 mA cm(-2) at 1 V versus Ag/AgCl (3 M KCl) and pH 7. These results beneficially compete with previously reported electrocatalytic oxidations of water by IrOx NPs electrodeposited onto glassy carbon and indium tin oxide electrodes and provide the basis for the further development of efficient IrOx NP-based electrocatalysts immobilized on high-surface-area carbon electrode materials. PMID:25044749

Mirbagheri, Naghmehalsadat; Chevallier, Jacques; Kibsgaard, Jakob; Besenbacher, Flemming; Ferapontova, Elena E

2014-09-15

14

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

15

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

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

Dimethylformamide-mediated synthesis of water-soluble platinum nanodendrites for ethanol oxidation electrocatalysis  

NASA Astrophysics Data System (ADS)

Herein we describe the synthesis of water-soluble platinum nanodendrites in dimethylformamide (DMF), in the presence of polyethyleneimine (PEI) as a stabilizing agent. The average size of the dendrites is in the range of 20-25 nm while their porosity can be tuned by modifying the concentration of the metal precursor. Electron tomography revealed different crystalline orientations of nanocrystallites in the nanodendrites and allowed a better understanding of their peculiar branching and porosity. The high surface area of the dendrites (up to 22 m2 g-1) was confirmed by BET measurements, while X-ray diffraction confirmed the abundance of high-index facets in the face-centered-cubic crystal structure of Pt. The prepared nanodendrites exhibit excellent performance in the electrocatalytic oxidation of ethanol in alkaline solution. Sensing, selectivity, cycleability and great tolerance toward poisoning were demonstrated by cyclic voltammetry measurements.Herein we describe the synthesis of water-soluble platinum nanodendrites in dimethylformamide (DMF), in the presence of polyethyleneimine (PEI) as a stabilizing agent. The average size of the dendrites is in the range of 20-25 nm while their porosity can be tuned by modifying the concentration of the metal precursor. Electron tomography revealed different crystalline orientations of nanocrystallites in the nanodendrites and allowed a better understanding of their peculiar branching and porosity. The high surface area of the dendrites (up to 22 m2 g-1) was confirmed by BET measurements, while X-ray diffraction confirmed the abundance of high-index facets in the face-centered-cubic crystal structure of Pt. The prepared nanodendrites exhibit excellent performance in the electrocatalytic oxidation of ethanol in alkaline solution. Sensing, selectivity, cycleability and great tolerance toward poisoning were demonstrated by cyclic voltammetry measurements. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00924f

Mourdikoudis, Stefanos; Chirea, Mariana; Altantzis, Thomas; Pastoriza-Santos, Isabel; Pérez-Juste, Jorge; Silva, Fernando; Bals, Sara; Liz-Marzán, Luis M.

2013-05-01

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

Application of immobilized TiO2 photocatalysis to improve the inactivation of Heterosigma akashiwo in ballast water by intense pulsed light.  

PubMed

Ballast water exotic discharge has been identified as a leading vector for marine species invasion. Here immobilized TiO2 photocatalysis is introduced to improve the performance of intense pulsed light. For intense pulsed light/TiO2 photocatalysis, a typical inactivation of 99.89±0.46% can be achieved under treatment condition of 1.78Lmin(-1) flow rate, 300V pulse peak voltage, 15Hz pulse frequency and 5ms pulse width. Moreover, within tested 220-260V peak voltage, 18.37-40.51% elevation in inactivation is observed in comparison with intense pulsed light treatment alone. The rough energy consumption of the tested intense pulsed light/TiO2 treatment system is about 1.51-2.51 times higher than that of the typical commercial UV ballast water treatment system. The stability of the photocatalytic reactivity and intactness of loaded TiO2 film is proved within 20-d's test, while local erosion on stainless steel support is observed after 30-d's test. The results indicate that intense pulsed light/TiO2 photocatalysis is likely to be a competitive ballast water treatment technique, while further measures is needed to reduce the energy consumption and ensure the performance of TiO2 film in a long run. PMID:25522854

Feng, Daolun; Xu, Shihong; Liu, Gang

2015-04-01

20

Solar photocatalysis for treatment of Acid Yellow-17 (AY-17) dye contaminated water using Ag@TiO2 core-shell structured nanoparticles.  

PubMed

Wastewater released from textile industries causes water pollution, and it needs to be treated before discharge to the environment by cost effective technologies. Solar photocatalysis is a promising technology for the treatment of dye wastewater. The Ag@TiO2 nanoparticles comprising of Ag core and TiO2 shell (Ag@TiO2) have unique photocatalytic property of inhibition of electron-hole recombination and visible light absorption, which makes it a promising photocatalyst for use in solar photocatalysis and with higher photocatalytic rate. Therefore, in the present work, the Ag@TiO2 nanoparticles synthesized by one pot method with postcalcination step has been used for the degradation of Acid Yellow-17 (AY-17) dye under solar light irradiation. The Ag@TiO2 nanoparticles were characterized using thermogravimetric-differential thermal analysis, X-ray diffraction, transmission electron microscopy, selected area electron diffraction, and energy dispersive X-ray analysis. The catalyst has been found to be very effective in solar photocatalysis of AY-17, as compared to other catalysts. The effects of pH, catalyst loading, initial dye concentration, and oxidants on photocatalysis were also studied. The optimized parameters for degradation of AY-17 using Ag@TiO2 were found to be pH?3, dye/catalyst ratio of 1:10 (g/g), and 2 g/L of (NH4)2S2O8 as oxidant. Efficient decolorization and mineralization of AY-17 was achieved. The kinetics of color, total organic carbon, and chemical oxygen demand removal followed the Langmuir-Hinshelwood model. Ag@TiO2 catalyst can be reused thrice without much decline in efficiency. The catalyst exhibited its potential as economic photocatalyst for treatment of dye wastewater. PMID:23463278

Khanna, Ankita; Shetty K, Vidya

2013-08-01

21

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

22

TREATMENT OF METHYL TERT-BUTYL ETHER CONTAMINATED WATER USING PHOTOCATALYSIS  

EPA Science Inventory

The feasibility of photo-oxidation treatment of methyl tert-butyl ether (MTBE) in water was investigated in three ways, 1) using a slurry falling film photo-reactor, 2) a batch solar reactor system, and 3) a combination of air-stripping and gas phase photooxidation system. MTBE-c...

23

Enhanced removal of dichloroacetonitrile from drinking water by the combination of solar-photocatalysis and ozonation.  

PubMed

In this study, the photocatalytic ozonation process using either UV lamps with a wavelength close to a solar wavelength (UVsolar) or natural solar light was established to study the effects of the major operating parameters on the removal of a toxic disinfection by-product (DBP), dichloroacetonitrile (DCAN), from drinking water. Based on the test results of a bench system, the UVsolar/TiO2/O3 process had the highest DCAN-removal rate among the advanced oxidation processes (AOPs). The optimal TiO2 and ozone doses were 1gL(-1) and 1.13gL(-1)h(-1), respectively, while room temperature (20°C) produced the highest rate constant in the kinetic tests. The kinetic rate constants linearly increased when the UVsolar intensity increased in the range 4.6-25Wm(-2); however, it increased less at intensities higher than 25Wm(-2). The test results of the outdoor system showed that the solar/TiO2/O3 process provided complete removal of DCAN that was two times faster and had about 4.6 times higher energy efficiency than with solar/TiO2. As a green oxidation technique, solar photocatalytic ozonation could be a good alternative for treating recalcitrant and toxic organic pollutants, because it has high oxidation potential and low energy consumption compared to conventional AOPs. PMID:24125715

Shin, Donghoon; Jang, Min; Cui, Mingcan; Na, Seungmin; Khim, Jeehyeong

2013-11-01

24

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

25

Studies of the pathways open to copper water oxidation catalysts containing proximal hydroxy groups during basic electrocatalysis.  

PubMed

Water oxidation can lead to a sustainable source of energy, but for water oxidation catalysts to be economical they must use earth abundant metals. We report here 2:1 6,6'-dihydroxybipyridine (6,6'-dhbp)/copper complexes that are capable of electrocatalytic water oxidation in aqueous base (pH = 10-14). Two crystal structures of the complex that contains 6,6'-dhbp and copper(II) in a ratio of 2:1 (complex 1) are presented at different protonation states. The thermodynamic acid dissociation constants were measured for complex 1, and these show that the complex is fully deprotonated above pH = 8.3 (i.e., under water oxidation conditions). CW-EPR, ENDOR, and HYSCORE spectroscopy confirmed that the 6,6'-dhbp ligand is bound to the copper ion over a wide pH range which shows how pH influences precatalyst structure. Additional copper(II) complexes were synthesized from the ligands 4,4'-dhbp (complex 2) and 6,6'-dimethoxybipyridine (complexes 3 and 4). A zinc complex of 6,6'-dhbp was also synthesized (complex 5). Crystal structures are reported for 1 (in two protonation states), 3, 4, and 5. Water oxidation studies using several of the above compounds (1, 2, 4, and 5) at pH = 12.6 have illustrated that both copper and proximal OH groups are necessary for water oxidation at a low overpotential. Our most active catalyst 1 was found to have an overpotential of 477 mV for water oxidation at a moderate rate of kcat = 0.356 s(-1) with a competing irreversible oxidation event at a rate of 1.082 s(-1). Furthermore, our combined work supports previous observations in which OH/O(-) groups on the bipyridine rings can hydrogen bond with metal bound substrate, support unusual binding modes, and potentially facilitate proton coupled electron transfer. PMID:25427106

Gerlach, Deidra L; Bhagan, Salome; Cruce, Alex A; Burks, Dalton B; Nieto, Ismael; Truong, Hai T; Kelley, Steven P; Herbst-Gervasoni, Corey J; Jernigan, Katherine L; Bowman, Michael K; Pan, Shanlin; Zeller, Matthias; Papish, Elizabeth T

2014-12-15

26

Efficient noble metal-free (electro)catalysis of water and alcohol oxidations by zinc-cobalt layered double hydroxide.  

PubMed

Replacing rare and expensive noble metal catalysts with inexpensive and earth-abundant ones for various renewable energy-related chemical processes as well as for production of high value chemicals is one of the major goals of sustainable chemistry. Herein we show that a bimetallic Zn-Co layered double hydroxide (Zn-Co-LDH) can serve as an efficient electrocatalyst and catalyst for water and alcohol oxidation, respectively. In the electrochemical water oxidation, the material exhibits a lower overpotential, by ~100 mV, than monometallic Co-based solid-state materials (e.g., Co(OH)2 and Co3O4)-catalytic systems that were recently reported to be effective for this reaction. Moreover, the material's turnover frequency (TOF) per Co atoms is >10 times as high as those of the latter at the same applied potentials. The Zn-Co-LDH also catalyzes oxidation of alcohols to the corresponding aldehydes or ketones at relatively low temperature, with moderate to high conversion and excellent selectivity. PMID:24116900

Zou, Xiaoxin; Goswami, Anandarup; Asefa, Tewodros

2013-11-20

27

Single-crystal-like NiO colloidal nanocrystal-aggregated microspheres with mesoporous structure: Synthesis and enhanced electrochemistry, photocatalysis and water treatment properties  

SciTech Connect

A new microwave-assisted hydrothermal synthetic route based on the self-assembly and subsequently controlled thermal decomposition process is proposed to fabricate nickel oxide colloidal nanocrystal aggregated microspheres (CNAMs) with mesoporous structure. XRD, EDS, SEM, TEM. FTIR, and N{sub 2} adsorption and desorption isotherm techniques are employed for morphology and structure characterizations. The as-prepared nickel oxide CNAMs, which has a high surface area (234 m{sup 2}/g) with narrow pore distribution at around 3.25 nm, are composed of numerous hexagonal mesoporous nanocrystals of approximately 50–60 nm in size, and present a single-crystal-like characteristic. The experimental results also demonstrated that the CNAMs showed outstanding performance in electrochemistry, photocatalysis and waste water treatment due to their special hierarchical and mesoporous structure, presenting the promising candidate for catalysis and catalysis support materials. - Graphical abstract: CNAMs with mesoporous structure synthesized via a simple microwave-assisted hydrothermal method was applied in electrochemistry and catalysis and exhibited enhanced performance. Display Omitted - Highlights: • CNAMs with mesoporous structure are achieved via a simple microwave-assisted hydrothermal method. • Morphology, structure and pore distribution of sample particles is specifically controlled. • The samples show enhanced properties in electrochemistry and catalysis due to hierarchical structure.

Suo, Zhirong [Analytical and Testing Center, Southwest University of Science and Technology, Mianyang 621010 (China); Dong, Xiaonan [School of Materials Science and Engineering, Shaanxi University of Science and Technology, Xi’an 710021 (China); Liu, Hui, E-mail: liuhui@sust.edu.cn [School of Materials Science and Engineering, Shaanxi University of Science and Technology, Xi’an 710021 (China)

2013-10-15

28

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

29

Plasmon-enhanced UV photocatalysis  

SciTech Connect

We report plasmonic nanoparticle enhanced photocatalysis on titanium dioxide (TiO{sub 2}) in the deep-UV range. Aluminum (Al) nanoparticles fabricated on TiO{sub 2} film increases the reaction rate of photocatalysis by factors as high as 14 under UV irradiation in the range of 260–340?nm. The reaction efficiency has been determined by measuring the decolorization rate of methylene blue applied on the TiO{sub 2} substrate. The enhancement of photocatalysis shows particle size and excitation wavelength dependence, which can be explained by the surface plasmon resonance of Al nanoparticles.

Honda, Mitsuhiro; Saito, Yuika, E-mail: yuika@ap.eng.osaka-u.ac.jp; Kawata, Satoshi [Department of Applied Physics, Osaka University, Suita, Osaka 565-0871 (Japan); Kumamoto, Yasuaki [Nanophotonics Laboratory, RIKEN, Wako, Saitama 351-0198 (Japan); Taguchi, Atsushi [Nanophotonics Laboratory, RIKEN, Wako, Saitama 351-0198 (Japan); Department of Mechanical Systems Engineering, School of Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588 (Japan)

2014-02-10

30

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. PMID:22733728

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

2012-01-01

31

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

32

Degradation of imidacloprid in water by photo-Fenton and TiO2 photocatalysis at a solar pilot plant: a comparative study.  

PubMed

The technical feasibility, mechanisms, and performance of degradation of aqueous imidacloprid have been studied at pilot scale in two well-defined photocatalytic systems of special interest because natural UV light can be used: heterogeneous photocatalysis with titanium dioxide and homogeneous photocatalysis by photo-Fenton. Equivalent pilot-scale and field conditions used for both allowed adequate comparison of the degree of mineralization and toxicity achieved as well as the transformation products generated in route to mineralization by both systems. Ninety-five percent of mineralization (<2.0 mg/L) was reached after 250 min of photocatalytic treatment with Fenton and 450 min with TiO2, meaning that TOC disappears 2.4 times faster with photo-Fenton photocatalytic treatment than with TiO2. The Daphnia Magna test for final residual TOC does not reveal anytoxic behavior. Transformation products evaluated by GC-MS/AED after two SPE procedures and LC-IC were the same in both cases. The main differences between the two processes are in the amount of transformation products (TPs) generated, not in the TPs detected which were always the same. At the end of both processes low concentration (<0.1 mg/L) of 2 pyrrolidinone (transformation product) remains in the dissolution and around 1 mg/L of formate in the case of photo-Fenton. PMID:11718357

Malato, S; Caceres, J; Agüera, A; Mezcua, M; Hernando, D; Vial, J; Fernández-Alba, A R

2001-11-01

33

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

34

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

2014-08-21

35

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.

36

First principles simulations of materials and processes in photo- and electro-catalysis  

NASA Astrophysics Data System (ADS)

I shall discuss applications of electronic structure calculations and molecular dynamics simulations to understand materials properties and reaction mechanisms in photo- and electro-catalysis. Examples will include studies of the interface between water and titanium dioxide (TiO2), a widely used photocatalyst capable of splitting water in O2 + H2, and the cycle of H2 production from water by the active site of an enzyme of hydrogen-producing bacteria, the di-iron hydrogenase, linked to a pyrite electrode.

Selloni, Annabella

2011-03-01

37

Quasi-equilibrium and non-equilibrium adsorption in heterogeneous photocatalysis  

Microsoft Academic Search

Heterogeneous photocatalysis is a promising alternative for the removal of organic and inorganic pollutants in water. Some chemical species display a strong and slow surface adsorption kinetics reacting under non-equilibrium while others adsorb quickly and moderately with adsorption taking place under quasi-equilibrium. In the specific case of a given pollutant once the intrinsic kinetic constants are evaluated, one can establish

Benito Serrano; Miguel Salaices; Aaron Ortiz; Hugo I. de Lasa

2007-01-01

38

HETEROGENOUS PHOTOCATALYSIS ON AEROSOL PROCESSED NANOSTRUCTURED TITANIA PARTICLES: ROLE OF PARTICLE SIZE  

EPA Science Inventory

Heterogenous photocatalysis with TiO2 has been extensively investigated as a method to oxidize organic pollutants in water and air, including phenols, chlorinated hydrocarbons, and other hydrocarbons. In addition, the use of titanium dioxide as a photocatalyst has also been demon...

39

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...

40

The destruction of 2-methylisoborneol and geosmin using titanium dioxide photocatalysis  

Microsoft Academic Search

Geosmin (GSM) and 2-methylisoborneol (MIB) are semi-volatile compounds produced by cyanobacteria in surface waters. These compounds present problems to the drinking water industry and in aquaculture because they can taint water and fish producing an earthy-musty flavour. This paper presents an initial study on the use of TiO2 photocatalysis for the destruction of these compounds in water. The process proved

Linda A. Lawton; Peter K. J. Robertson; Russell F. Robertson; Fiona G. Bruce

2003-01-01

41

Photocatalysis: Electrostatically Assembled CdS-Co3 O4 Nanostructures for Photo-assisted Water Oxidation and Photocatalytic Reduction of Dye Molecules (Small 6/2015).  

PubMed

Electrostatic assembly is used by O. Yehezkeli, D. R. B. de Oliveira, and J. N. Cha to couple CdS nanorods with Co3 O4 nanoparticles into photocatalytic systems that simultaneously oxidize water and mediate electron transfer. On page 668, layered films of CdS nanorods and Co3 O4 nanoparticles are first used to generate high photocurrents electrochemically as opposed to CdS or Co3 O4 alone. Dispersed clusters of CdS nanorods conjugated with Co3 O4 nanoparticles are next shown to efficiently oxidize water and reduce methylene blue in solution. PMID:25656146

Yehezkeli, Omer; de Oliveira, Débora R B; Cha, Jennifer N

2015-02-01

42

Titania carbon nanotube composites for enhanced photocatalysis  

NASA Astrophysics Data System (ADS)

Photocatalytic composites have been used for the past few decades in a wide range of applications. The most common application is the purification of air and water by removing toxic compounds. There is limited use however towards biocidal applications. Despite their high efficiency, photocatalytic materials are not comparable to the effectiveness of conventional biocidal compounds such as chlorine and alcoholic disinfectants. On the other hand, nearly a decade ago with the discovery of the carbon nanotubes a new vibrant scientific field emerged. Nanotubes are unique structures of carbon that posse amazing electrical, mechanical and thermal properties. In this research carbon nanotubes are used as photocatalytic enhancers. They were coated with anatase titania to form a composite material. Two different types of nanotubes (metallic versus non-metallic) were used and the photocatalytic activity was measured. The metallic tubes demonstrated exceptional photocatalytic properties, while non-metallic tubes had low photocatalytic efficiency. The reason for that difference was investigated and was the major focus of this research. The research concluded that the reasons for the high efficiency of the carbon nanotubes were (i) the metallic nature of the tubes and (ii) the possible bond between the titania coating and the underlying graphite layers (C-O-Ti). Since both composites had the same indications regarding the C-O-Ti bond, the metallic nature of the carbon nanotubes is believed to be the most dominant factor contributing to the enhancement of the photocatalysis. The composite material may have other potential applications such as for sensing and photovoltaic uses.

Pyrgiotakis, Georgios

43

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

44

Combination of ozonation and photocatalysis for purification of aqueous effluents containing formic acid as probe pollutant and bromide ion.  

PubMed

The treatment by advanced oxidation processes (AOPs) of waters contaminated by organic pollutants and containing also innocuous bromide ions may generate bromate ions as a co-product. In the present work heterogeneous photocatalysis and ozonation have individually been applied and in combination (integrated process) to degrade the organic compounds in water containing also bromide anions. The results show that: i) the sole photocatalysis does not produce bromate ions and in the case of its presence, it is able to reduce bromate to innocuous bromide ions; ii) the integration of photocatalysis and ozonation synergistically enhances the oxidation capabilities; and iii) in the integrated process bromate ions are not produced as long as some oxidizable organics are present. PMID:24374130

Parrino, F; Camera-Roda, G; Loddo, V; Palmisano, G; Augugliaro, V

2014-03-01

45

Removal of gas-phase ammonia and hydrogen sulfide using photocatalysis, nonthermal plasma, and combined plasma and photocatalysis at pilot scale.  

PubMed

This study focuses on the removal of gas-phase ammonia (NH3) and hydrogen sulfide (H2S) in a continuous reactor. Photocatalysis and surface dielectric barrier discharge (SDBD) plasma are studied separately and combined. Though the removal of volatile organic compounds by coupling plasma and photocatalysis has been reported on a number of studies in laboratory scale, this is as far as we know the first time that it is used to remove inorganic malodorous pollutants. While each separate process is able to degrade ammonia and hydrogen sulfide, a synergetic effect appears when they are combined at a pilot scale, leading to removal capacity higher than the sum of each separate process. The removal capacity is higher when the gas circulates at a higher flow rate and when pollutant concentration is higher. The presence of water vapor in the gas is detrimental to the efficiency of the process. Operating conditions also influence the production of nitrogen oxides and ozone. PMID:24996941

Maxime, Guillerm; Amine, Assadi Aymen; Abdelkrim, Bouzaza; Dominique, Wolbert

2014-11-01

46

Environmental green chemistry as defined by photocatalysis  

Microsoft Academic Search

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

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

2007-01-01

47

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

48

Electrocatalysis Breakout Session ANODE (H2//O2/Air)  

E-print Network

­ Discussion of role of local mobility of OH- in the anode double layer ­ Role of active site in non crossover and its eventual reduction). ­ Role of oxygen crossover in the context of anode Electrocatalysis. Durability ­ Role of oxygen crossover and ionomer/membrane stability at the anode interface. ­ Other

49

Dr. Piotr Zelenay's Professional Bio Dr. Zelenay's expertise is in polymer electrolyte fuel cells, electrocatalysis, surface  

E-print Network

Dr. Piotr Zelenay's Professional Bio Dr. Zelenay's expertise is in polymer electrolyte fuel cells of polymer electrolyte fuel cell science and technology, electrocatalysis, and electrode kinetics. Piotr

50

Conversion of Steel Mill's Surface Waste into Zero Valent Iron (ZVI) Nanoparticles for Hydrogen Generation for PEMFCs  

E-print Network

, photocatalysis and high temperature electrocatalysis of water and, sulfur-iodine cycle in a nuclear reactor by CO/CO2 emission. Recently, a novel, solution-based room temperature technique using an aqueous

Azad, Abdul-Majeed

51

Electrocatalysis: A direct alcohol fuel cell and surface science perspective  

SciTech Connect

In this report, we discuss some of the advances in surface science and theory that have ena bled a more detailed understanding of the mechanisms that govern the electrocatalysis.More specifically, we examine in detail the electrooxidation ofC1 and Cz alcohol molecules in both acidic and basic media. A combination of detailed in situ spectroscopic measurements along with density functional theory calculations have helped to establish the mechanisms that control the reaction paths and the innuence of acidic and alkaline media. We discuss some of the synergies and differences between electrocatalysis and aqueous phase heterogeneous catalysis.Such analyses begin to establish a common language and framework by which to compare as well as advance both fields.

Braunchweig, B [University of Illinois, Urbana-Champaign; Neurock, Matthew [University of Virginia; Wieckowski, A. [University of Illinois, Urbana-Champaign; Hibbitts, David D [ORNL

2012-01-01

52

Electrocatalysis: A Direct Alcohol Fuel Cell and Surface Science Perspective  

SciTech Connect

In this report, we discuss some of the advances in surface science and theory that have enabled a more detailed understanding of the mechanisms that govern the electrocatalysis. More specifically, we examine in detail the electrooxidation of C-1 and C-2 alcohol molecules in both acidic and basic media. A combination of detailed in situ spectroscopic measurements along with density functional theory calculations have helped to establish the mechanisms that control the reaction paths and the influence of acidic and alkaline media. We discuss some of the synergies and differences between electrocatalysis and aqueous phase heterogeneous catalysis. Such analyses begin to establish a common language and framework by which to compare as well as advance both fields. (C) 2012 Elsevier B.V. All rights reserved.

Braunchweig, B [University of Illinois, Urbana-Champaign; Hibbitts, David D [ORNL; Neurock, Matthew [University of Virginia; Wieckowski, A. [University of Illinois, Urbana-Champaign

2013-01-01

53

An overview of photocatalysis phenomena applied to NOx abatement.  

PubMed

This review provides a short introduction to photocatalysis technology in terms of the present environmental remediation paradigm and, in particular, NOx photoabatement. The fundamentals of photoelectrochemical devices and the photocatalysis phenomena are reviewed, highlighting the main reaction mechanisms. The critical historical developments on heterogeneous photocatalysis are briefly discussed, giving particular emphasis to the pioneer works in this field. The third part of this work focus mainly on NOx removal technology considering topics such as: TiO2 photochemistry; effect of the operating conditions on the photocatalysis process; Langmuir-Hinshelwood modeling; TiO2 photocatalytic immobilization approaches; and their applications. The last section of the paper presents the main conclusions and perspectives on the opportunities related to this technology. PMID:24018117

Ângelo, Joana; Andrade, Luísa; Madeira, Luís M; Mendes, Adélio

2013-11-15

54

Recyclable enzyme mimic of cubic Fe3O4 nanoparticles loaded on graphene oxide-dispersed carbon nanotubes with enhanced peroxidase-like catalysis and electrocatalysis  

SciTech Connect

Fe3O4 nanoparticles as nanocatalysts may present peroxidase-like catalysis activities and high electrocatalysis if loaded on conductive carbon nanotube (CNT) supports; however, their catalysis performances in an aqueous system might still be challenged by the poor aqueous dispersion of hydrophobic carbon supports and/or low stability of loaded iron catalysts. In this work, amphiphilic graphene oxide nanosheets were employed as “surfactant” to disperse CNTs to create stable graphene oxide-dispersed CNT (GCNT) supports in water for covalently loading cubic Fe3O4 nanoparticles with improved distribution and binding efficiency. Compared with original Fe3O4 nanos and CNT-loaded Fe3O4 nanocomplex, the prepared GCNT–Fe3O4 nanocomposite could achieve higher aqueous stability and, especially, much stronger peroxidase-like catalysis and electrocatalysis to H2O2, presumably resulting from the synergetic effects of two conductive carbon supports and cubic Fe3O4 nanocatalysts effectively loaded. Colorimetric and direct electrochemical detections of H2O2 and glucose using the GCNT–Fe3O4 nanocomposite were conducted with high detection sensitivities, demonstrating the feasibility of practical sensing applications. Such a magnetically recyclable “enzyme mimic” may circumvent some disadvantages of natural protein enzymes and common inorganic catalysts, featuring the multi-functions of high peroxidase-like catalysis, strong electrocatalysis, magnetic separation/recyclability, environmental stability, and direct H2O2 electrochemistry.

Wang, Hua; Li, Shuai; Si, Yanmei; Sun, Zhongzhao; Li, Shuying; Lin, Yuehe

2014-01-01

55

Effect of inorganic ions in heterogeneous photocatalysis of TCE  

SciTech Connect

The influence of 12 ionic compounds (Na{sub 2}SO{sub 4}, NaHCO{sub 3}, Na{sub 2}HPO{sub 4}, NaNO{sub 3}, NaCl, MnCl{sub 2}, NiCl{sub 2}, CaCl{sub 2}, MgCl{sub 2}, AlCl{sub 3}, FeCl{sub 3}, and MgSO{sub 4}) on performance of a fixed-bed photocatalytic reactor is examined. The fixed-bed photocatalyst was developed at Michigan Technological University and comprises 1% Pt-TiO{sub 2} on a silica-based support. The degradation of trichloroethylene (TCE) in Milli-Q water is used to monitor catalyst performance. All compounds are found to inhibit photocatalysis at some or all of the concentrations tested, although only MnCl{sub 2} seems to suppress it altogether. Fouling appears to be a least partially reversible. Electron microprobe analysis is employed to investigate how selected fouling agents interact with the catalyst and support.

Burns, R.A.; Crittenden, J.C.; Hand, D.W.; Selzer, V.H.; Sutter, L.L. [Michigan Technological Univ., Houghton, MI (United States). Dept. of Civil and Environmental Engineering] [Michigan Technological Univ., Houghton, MI (United States). Dept. of Civil and Environmental Engineering; Salman, S.R. [Yarmouk Univ., Irbid (Jordan). Dept. of Chemistry] [Yarmouk Univ., Irbid (Jordan). Dept. of Chemistry

1999-01-01

56

Laser Raman Spectroscopy in studies of corrosion and electrocatalysis  

SciTech Connect

Laser Raman Spectroscopy (LRS) has become an important tool for the in-situ structural study of electrochemical systems and processes in recent years. Following a brief introduction of the experimental techniques involved in applying LRS to electrochemical systems, we survey the literature for examples of studies in the inhibition of electrode reactions by surface films (e.g., corrosion and passivation phenomena) as well as the acceleration of reactions by electro-sorbates (electrocatalysis). We deal mostly with both normal and resonance Raman effects on fairly thick surface films in contrast to surface-enhanced Raman investigations of monolayer adsorbates, which is covered in another lecture. Laser Raman spectroelectrochemical studies of corrosion and film formation on such metals as Pb, Ag, Fe, Ni, Co, Cr, Au, stainless steel, etc. in various solution conditions are discussed. Further extension of the technique to studies in high-temperature and high-pressure aqueous environments is demonstrated. Results of studies of the structure of corrosion inhibitors are also presented. As applications of the LRS technique in the area of electrocatalysis, we cite studies of the structure of transition metal macrocyclic compounds, i.e., phthalocyanines and porphyrins, used for catalysis of the oxygen reduction reaction. 104 refs., 20 figs.

Melendres, C.A.

1988-01-01

57

A multiscale study of atomic interactions in the electrochemical double layer applied to electrocatalysis  

E-print Network

This work is an integrated study of chemical and electrostatic interactions in the electrochemical double layer, and their significance for accurate prediction of reaction kinetics in electrocatalysis. First, a kinetic ...

Bonnet, Nicéphore

2011-01-01

58

Enhanced photocatalysis in a pilot laminar falling film slurry reactor  

SciTech Connect

Laminar falling film slurry (LFFS) photocatalytic reactors are one of the most efficient reactor configurations for conducting heterogeneous photocatalytic reactions, particularly for wastewater treatment. This paper presents a study on the oxidation of an aqueous salicylic acid waste in a pilot continuous flow LFFS photocatalytic reactor which has an optimum design for light absorption. In conducting the oxidation reaction, heterogeneous photocatalysis was supplemented with other photon-assisted processes. The effect of light intensity, radiation wavelength, oxidizing-enhancing agents, substrate and photocatalyst concentration, and exposure time were studied. A comparison of six different photon-based processes showed that higher oxidation rates of salicylic acid were obtained when there was concomitant photocatalysis, photolysis, and UV peroxidation. The oxidation rates of salicylic acid with this combined process were at least 1 order of magnitude higher in comparison with those for UVA photocatalysis and 3-fold higher in comparison with homogeneous UVC photolysis/UVC peroxidation.

Puma, G.L.; Yue, P.L. [Hong Kong Univ. of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

1999-09-01

59

Heterogeneous electrocatalysis in porous cathodes of solid oxide fuel cells  

E-print Network

A general physics-based model is developed for heterogeneous electrocatalysis in porous electrodes and used to predict and interpret the impedance of solid oxide fuel cells. This model describes the coupled processes of oxygen gas dissociative adsorption and surface diffusion of the oxygen intermediate to the triple phase boundary, where charge transfer occurs. The model accurately captures the Gerischer-like frequency dependence and the oxygen partial pressure dependence of the impedance of symmetric cathode cells. Digital image analysis of the microstructure of the cathode functional layer in four different cells directly confirms the predicted connection between geometrical properties and the impedance response. As in classical catalysis, the electrocatalytic activity is controlled by an effective Thiele modulus, which is the ratio of the surface diffusion length (mean distance from an adsorption site to the triple phase boundary) to the surface boundary layer length (square root of surface diffusivity div...

Fu, Y; Bertei, A; Qi, C; Mohanram, A; Pietras, J D; Bazant, M Z

2014-01-01

60

Photocatalytic water treatment: solar energy applications  

Microsoft Academic Search

During the past 20 years research and development in the area of photocatalysis have been tremendous. One of the major applications of this technology is the degradation of organic pollutants in water and air streams which is considered as one of the so-called advanced oxidation processes. This overview briefly describes the basic principles of photocatalysis, focusing in particular on important

Detlef Bahnemann

2004-01-01

61

Graphene thickness-controlled photocatalysis and surface enhanced Raman scattering  

NASA Astrophysics Data System (ADS)

Exceptional photocatalytic enhancement of graphene-semiconductor composites has been widely reported, but our understanding of the role that graphene plays in this enhancement remains limited, which arises from the difficulty of precisely controlling graphene hybridization. Here we present a general platform of a graphene-semiconductor hybrid panel (GHP) system wherein a precise number of layers of graphene are hybridized with photoactive semiconductors (e.g. TiO2, ZnO) to study systematically how graphene affects the photocatalysis. The results show that the graphene enhancement of the photocatalysis depends on the number of graphene layers, with the maximum performance observed at 3 layers. Photodeposited indicators of gold particles further reveal that graphene thickness governs the density of photocatalytic sites and charge transfer efficiency at the graphene-semiconductor interfaces. We suggest that quantized energy levels caused by different numbers of stacked graphene sheets along the vector normal to the graphene basal plane affect the charge transfer routes and lead to the graphene thickness-controlled photocatalysis. GHP substrates deposited with gold particles are promising, uniform substrates for surface enhanced Raman scattering (SERS) applications with the enhancement factor as high as ~108 on 3-layer graphene.Exceptional photocatalytic enhancement of graphene-semiconductor composites has been widely reported, but our understanding of the role that graphene plays in this enhancement remains limited, which arises from the difficulty of precisely controlling graphene hybridization. Here we present a general platform of a graphene-semiconductor hybrid panel (GHP) system wherein a precise number of layers of graphene are hybridized with photoactive semiconductors (e.g. TiO2, ZnO) to study systematically how graphene affects the photocatalysis. The results show that the graphene enhancement of the photocatalysis depends on the number of graphene layers, with the maximum performance observed at 3 layers. Photodeposited indicators of gold particles further reveal that graphene thickness governs the density of photocatalytic sites and charge transfer efficiency at the graphene-semiconductor interfaces. We suggest that quantized energy levels caused by different numbers of stacked graphene sheets along the vector normal to the graphene basal plane affect the charge transfer routes and lead to the graphene thickness-controlled photocatalysis. GHP substrates deposited with gold particles are promising, uniform substrates for surface enhanced Raman scattering (SERS) applications with the enhancement factor as high as ~108 on 3-layer graphene. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03877k

Kuo, Cheng-Chi; Chen, Chun-Hu

2014-10-01

62

Hollow micro/nanomaterials as nanoreactors for photocatalysis  

NASA Astrophysics Data System (ADS)

Learning from nature, one of the most prominent goals of photocatalysis is to assemble multifunctional photocatalytic units in an integrated, high performance device that is capable of using solar energy to produce "solar hydrogen" from aqueous media. By analogy with natural systems it is clear that scaffolds with multi-scale structural architectures are necessary. In this perspective, recent progress related to the use of hollow micro/nanomaterials as nanoreactors for photocatalysis is discussed. Organised, multi-scale assemblies of photocatalytic units on hollow scaffolds is an emerging area that shows much promise for the synthesis of high performance photocatalysts. Not only do improved transport and diffusion characteristics play an import role, but increased electron/hole separation lifetimes as well as improved light harvesting characteristics by the hollow structures also do so and are touched upon in this short perspective.

Li, Xiaobo; Liu, Jian; Masters, Anthony F.; Pareek, Vishnu K.; Maschmeyer, Thomas

2013-10-01

63

Morphologies of zinc oxide particles and their effects on photocatalysis.  

PubMed

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 for the same original ZnO powders prepared by equal conditions other than the difference in calcination temperature. However, no direct relationship between photocatalytic activity and crystallinity or surface area was found for the differently original ZnO powders prepared by different methods, or the same method with different conditions. Instead, we find that the particle morphology significantly affects its photocatalysis. PMID:12586145

Li, Di; Haneda, Hajime

2003-04-01

64

Dendritic assembly of gold nanoparticles during fuel-forming electrocatalysis.  

PubMed

We observe the dendritic assembly of alkanethiol-capped gold nanoparticles on a glassy carbon support during electrochemical reduction of protons and CO2. We find that the primary mechanism by which surfactant-ligated gold nanoparticles lose surface area is by taking a random walk along the support, colliding with their neighbors, and fusing to form dendrites, a type of fractal aggregate. A random walk model reproduces the fractal dimensionality of the dendrites observed experimentally. The rate at which the dendrites form is strongly dependent on the solubility of the surfactant in the electrochemical double layer under the conditions of electrolysis. Since alkanethiolate surfactants reductively desorb at potentials close to the onset of CO2 reduction, they do not poison the catalytic activity of the gold nanoparticles. Although catalyst mobility is typically thought to be limited for room-temperature electrochemistry, our results demonstrate that nanoparticle mobility is significant under conditions at which they electrochemically catalyze gas evolution, even in the presence of a high surface area carbon and binder. A careful understanding of the electrolyte- and polarization-dependent nanoparticle aggregation kinetics informs strategies for maintaining catalyst dispersion during fuel-forming electrocatalysis. PMID:24766431

Manthiram, Karthish; Surendranath, Yogesh; Alivisatos, A Paul

2014-05-21

65

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

66

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

67

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

Microsoft Academic Search

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

Jianer Bao

2007-01-01

68

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

69

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

70

SOME RECENT STUDIES IN RUGHENIUM ELECTROCHEMISTRY AND ELECTROCATALYSIS.  

SciTech Connect

Ruthenium is a metal of a considerable importance in electrochemical science and technology. It is a catalyst or co-catalyst material in Pt-Ru alloys for methanol- and reformate hydrogen-oxidation in fuel cells, while ruthenium oxide, a component in chlorine-evolution catalysts, represents an attractive material for electrochemical supercapacitors. Its facile surface oxidation generates an oxygen-containing species that provides active oxygen in some reactions. Ru sites in Pt-Ru catalysts increase the ''CO tolerance'' of Pt in the catalytic oxidation-reaction in direct methanol fuel cells (DMFC) and in reformate hydrogen-oxidation in proton exchange membrane fuel cells (PEMFC). The mechanism of Ru action is not completely understood, although current consensus revolves around the so-called ''bifunctional mechanism'' wherein Ru provides oxygenated species to oxidize CO that blocks Pt sites, and has an electronic effect on Pt-CO interaction. While various studies of polycrystalline Ru go back several decades those involving single crystal surfaces and the structural sensitivity of reactions on Ru surfaces emerged only recently. Using well-ordered single crystalline surfaces brings useful information as the processes on realistic catalysts are far too complex to allow identification of the microscopic reaction steps. In this article, we focus on progress in model systems and conditions, such as electrochemistry and electrocatalysis on bare and Pt-modified well-ordered Ru(0001) and Ru(10{bar 1}0) single-crystal surfaces. We also review current understanding of the mechanistic principles of Pt-Ru systems and a new development of a Pt submonolayer on Ru support electrocatalyst. Ruthenium crystallizes in a hexagonal close-packed structure, (hcp). Figure 1.1 shows the two single crystal surfaces of Ru. The Ru(0001) surface possesses the densest, i.e. hexagonal arrangement of atoms, Fig. 1.1a. The other plane, Ru(10{bar 1}0), can have one of the two terminations of the surface atoms, Fig. 1.1b. One termination can be described as a stepped surface with a trigonal arrangement of atoms in two-atom-long terraces with a step of the same orientation; the other termination is a square-symmetrical arrangement of atoms in two-atom-long terraces with the same orientation of atoms in steps. In the faced-centered cubic (fcc) system, these three structures are uniquely defined and labeled as (111), (110), and (210), respectively.

MARINKOVIC, N.S.; VUKMIROVIC, M.B.; ADZIC, R.R.

2006-08-01

71

Study the Toxicity to Microcystis aeruginosa Induced by TiO2 Nanoparticles Photocatalysis Under UV Light.  

PubMed

In the present study, the biological effect of TiO2 nanoparticles on cyanobacteria cells was studied using Microcystis aeruginosa (M. aeruginosa) as a model. Nano-TiO2 as a photo-catalysts agent used for water treatment may pose a risk to ecosystems, especially for the water organisms such as cyanobacteria. Scanning electron microscope (SEM) images provided that with the increasing of photocatalytic time, slime layer on the cell surface was damaged and sunk. Attenuated total reflectance fourier transform infrared (ATR-FTIR) spectroscopy revealed that the vibration peaks of C-C, C-H, C=O, P=O weakened within 12 h. According to the dynamic analysis of the infrared peaks, the damage on the cell groups under nano-TiO2 photocatalysis with different time periods was analyzed. The concentrations of K(+), Ca(2+), Mg(2+) released from the cells were measured, which indicated that nano-TiO2 photocatalysis have changed the cell membrane permeability and fluidity of M. aeruginosa. PMID:25701241

Lu, Ruirui; Liu, Peng; Chen, Xiaojuan

2015-04-01

72

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

73

Tungsten oxide - fly ash oxide composites in adsorption and photocatalysis.  

PubMed

A novel composite based on tungsten oxide and fly ash was hydrothermally synthetized to be used as substrate in the advanced treatment of wastewaters with complex load resulted from the textile industry. The proposed treatment consists of one single step process combining photocatalysis and adsorption. The composite's crystalline structure was investigated by X-ray diffraction and FTIR, while atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to analyze the morphology. The adsorption capacity and photocatalytic properties of the material were tested on mono- and multi-pollutants systems containing two dyes (Bemacid Blau - BB and Bemacid Rot - BR) and one heavy metal ion-Cu(2+), and the optimized process conditions were identified. The results indicate better removal efficiencies using the novel composite material in the combined adsorption and photocatalysis, as compared to the separated processes. Dyes removal was significantly enhanced in the photocatalytic process by adding hydrogen peroxide and the mechanism was presented and discussed. The pseudo second order kinetics model best fitted the experimental data, both in the adsorption and in the combined processes. The kinetic parameters were calculated and correlated with the properties of the composite substrate. PMID:25733398

Visa, Maria; Bogatu, Cristina; Duta, Anca

2015-05-30

74

Direct bio-electrocatalysis of O2 reduction by Streptomyces coelicolor laccase orientated at promoter-modified graphite electrodes.  

PubMed

Bacterial laccase from Streptomyces coelicolor (SLAC) has been immobilised and orientated at promoter (pyrene and neocuproine)-modified electrodes productively both for direct electron transfer (ET) between the electrode and the T1 Cu site of SLAC and direct (unmediated) bio-electrocatalysis of dioxygen reduction. Its T1 Cu potential ranges between 471 and 318 mV versus the normal hydrogen electrode, at pH 5.5 and 8, respectively; this value is dependent both on the solution pH and electrode modification. In the presence of O2, Cu of the T2/T3 trinuclear centre is distinguished electrochemically at 748-623 mV. Depending on the promoter nature, different orientations of SLAC at pyrene- and neocuproine-modified electrodes can be followed from the kinetic analysis of the ET rates. Bio-electrocatalytic reduction of oxygen starts from the T1 Cu potentials of SLAC, and is most efficient at the promoter-modified electrodes, thereby demonstrating good performance both in neutral and basic media and in solutions with a high NaCl content, such as sea water. The obtained results allow consideration of a broader bioenergetic application of laccases as biocathodes operating directly in such environmental media as sea water and physiological fluids. PMID:23589501

Lörcher, Samuel; Lopes, Paula; Kartashov, Andrey; Ferapontova, Elena E

2013-07-22

75

Electrocatalysis of borohydride oxidation: a review of density functional theory approach combined with experimental validation  

NASA Astrophysics Data System (ADS)

The electrocatalysis of borohydride oxidation is a complex, up-to-eight-electron transfer process, which is essential for development of efficient direct borohydride fuel cells. Here we review the progress achieved by density functional theory (DFT) calculations in explaining the adsorption of BH4- on various catalyst surfaces, with implications for electrocatalyst screening and selection. Wherever possible, we correlate the theoretical predictions with experimental findings, in order to validate the proposed models and to identify potential directions for further advancements.

Sison Escaño, Mary Clare; Lacdao Arevalo, Ryan; Gyenge, Elod; Kasai, Hideaki

2014-09-01

76

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

2014-07-21

77

Experiment on TiO2/AC Photocatalysis Technique to Eliminate Toluene in Air Conditioning Systems  

E-print Network

at present, the article proposes that new-type purification technique and hopes to promote the upgrading of the product about purification. 2. INTRODUTION ON THE STRURE AND STUFF OF ACTIVE CARBON AND NANO- TITANIUM DIOXIDE PHOTOCATALYSIS PURIFICATION... WEB What is called active carbon and nano-titanium dioxide photocatalysis technique is to utilize the method of compounding active carbon and nanometer photocatalyst to firstly form absorption layer on supporting body surface by gluing, which...

Hu, Y.; Feng, G.; Yuan, Q.

2006-01-01

78

Evaluation of the after-effects of cyanobacterial cell removal and lysis by photocatalysis using Ag/AgBr/TiO2.  

PubMed

This study aimed to evaluate the after-effects of cyanobacterial cell removal and lysis by photocatalysis in water. A low concentration of 50 mg/L Ag/AgBr/TiO2 was applied to inactivate Microcystis aeruginosa under visible light irradiation. Most of the M. aeruginosa was killed within 5 h while microcystins-LR (MC-LR) was released into water and accumulated to a high concentration of 100 ?g/L. Organic constituents released from cell damage led to 70 mg/L of total organic carbon (TOC) in water. The release of MC-LR and TOC would affect the biostability in the receiving water. Further, mineralization of cell lysis after photocatalysis over a long time resulted in the release of nutrients in water which would be a risk to cause cyanobacterial blooming again. Therefore, these after-effects should not be ignored when photochemical catalysis is applied to mitigate cyanobacterial blooming. Perhaps the best treatment is to remove intact cyanobacterial cells from water and then treat them off-site, for example by anaerobic digestion. PMID:25225929

Shen, Nan; Zhang, Fang; Zhang, Feng; Zeng, Raymond J

2014-01-01

79

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

80

High efficiency photocatalysis for pollutant degradation with MoS2/C3N4 heterostructures.  

PubMed

Porous graphitic carbon nitride was synthesized by controllable thermal polymerization of urea in air. Their textural, electrical, and optical properties were tuned by varying the heating rate. The presence of proper residual oxygen in carbon nitride matrix had enhanced light absorption and inhibited the recombination of charge carriers. Furthermore, the MoS2 nanosheets were coupled into the carbon nitride to form MoS2/C3N4 heterostructures via a facile ultrasonic chemical method. The optimized MoS2/C3N4 heterostructure with 0.05 wt % MoS2 showed a reaction rate constant as high as 0.301 min(-1), which was 3.6 times that of bare carbon nitride. As analyzed by SEM, TEM, UV-vis absorption, PL and photoelectrochemical measurements, intimate contact interface, extended light response range, enhanced separation speed of charge carriers, and high photocurrent density upon MoS2 coupling led to the photocatalytic promotion of the MoS2/C3N4 heterostructures. In this architecture, MoS2 served as electron trapper to extend the lifetime of separated electron-hole pairs. Meanwhile, the accumulated holes on the surface of carbon nitride oxidized the organic dye directly, which was a predominant process in the photodegradation of organic pollutants in water treatment. The promotional mechanisms and principles reported here would have great significance in heterogeneous photocatalysis. PMID:25017627

Li, Qian; Zhang, Ning; Yang, Yong; Wang, Guozhong; Ng, Dickon H L

2014-07-29

81

Carbon nanotubes, phthalocyanines and porphyrins: attractive hybrid materials for electrocatalysis and electroanalysis.  

PubMed

The manuscript discusses different ways of forming hybrid materials between single (SWCNT) or multi (MWCNT) walled carbon nanotubes and biomimetic compounds such as metalloporphyrins, metallophthalocyanines and other MN4 complexes. The hybrid materials are employed for electrocatalysis of reactions such as oxygen and hydrogen peroxide reduction, nitric oxide oxidation, oxidation of thiols and other pollutants. Methods of characterizing the hybrid materials such as cyclic voltammetry (CV), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and scanning electrochemical microscopy (SECM) are discussed. PMID:19437959

Zagal, José H; Griveau, Sophie; Ozoemena, Kenneth I; Nyokong, Tebello; Bedioui, Fethi

2009-04-01

82

Degradation mechanism and the toxicity assessment in TiO2 photocatalysis and photolysis of parathion.  

PubMed

The photocatalytic degradation of methyl parathion was carried out using a circulating TiO2/UV reactor. The experimental results showed that parathion was more effectively degraded in the photocatalytic condition than the photolysis and TiO2-only condition. With photocatalysis, 10mg/l parathion was completely degraded within 60 min with a TOC decrease exceeding 90% after 150 min. The main ionic byproducts during photocatalysis were measured. The nitrogen from parathion was recovered mainly as NO3-, NO2- and NH4+, 80% of the sulfur as SO4(2-), and less than 5% of the phosphorus as PO4(3-). The organic intermediates 4-nitrophenol and paraoxon were also identified, and these were further degraded. Two different bioassays (Vibrio fischeri and Daphnia magna) were used to test the acute toxicity of solutions treated by photocatalysis and photolysis. A Microtox test using V. fischeri showed that the toxicity, expressed as the relative toxicity (%), was reduced almost completely after 90 min under photocatalysis, whereas only an 83% reduction was achieved with photolysis alone. Another toxicity test using D. magna also showed that the relative toxicity disappeared after 90 min under photocatalysis, whereas there was a 65% reduction in relative toxicity with photolysis alone. The pattern of toxicity reduction parallels the decrease in parathion and TOC concentrations. PMID:16051312

Kim, Tak-Soo; Kim, Jung-Kon; Choi, Kyungho; Stenstrom, Michael K; Zoh, Kyung-Duk

2006-02-01

83

CO2 SEQUESTRATION AND RECYCLE BY PHOTOCATALYSIS WITH VISIBLE LIGHT  

SciTech Connect

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 research tasks accomplished during first six months include setting up a photo-catalytic reactor, optical bench, calibration of gas chromatograph, catalyst preparation, and catalyst screening study. Addition of Pt and Cu on TiO{sub 2} was found to increase the activity of TiO{sub 2} catalysts for the synthesis of methanol and methane. The most active catalysts obtained from this study will be used for mechanistic study. 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

1999-12-31

84

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

85

Fuel cell applied research: electrocatalysis and materials. Quarterly report, July 1-September 30, 1979  

SciTech Connect

The effect of underpotential deposited metal layers on the electrocatalysis of fuel cell reactions was studied. It was found that Bi, Ag and Pb form underpotential deposited metal adatom layers on gold in 85% H/sub 3/PO/sub 4/. Underpotential deposited Bi enhances oxygen reduction on gold with the formation of peroxide. Underpotential deposited Ag on the other hand inhibits oxygen reduction. Results indicate the potential for developing organic compound/air fuel cells using underpotential deposited Pb adatoms to enhance the electrocatalysis of the fuel electrode. The effects of adsorbed layers of Pb, Tl and Bi on formic acid and methanol oxidation on platinum in 85% H/sub 3/PO/sub 4/ were investigated. The effect of crystal orientation on formic acid oxidation on platinum in 1 M CHlO/sub 2/ 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. Platinum point contact electrodes were also used in the preliminary studies of the fuel electrode reaction. dc, ac and potential sweep methods were used in this study. Results are reported. Progress on a survey of status studies of phosphoric acid and molten carbonate fuel cells is reported. (WHK)

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

1980-03-01

86

Plasmonic hot electron enhanced MoS2 photocatalysis in hydrogen evolution.  

PubMed

With plasmonic hot electron doping, the molybdenum disulfide (MoS2) monolayer with deposited Au@Ag nanorattles effectively enhanced the hydrogen evolution reaction (HER) efficiency. The maximum photocatalysis is achieved under plasmon resonance excitation, and is actively controlled by the incident laser wavelength and power intensity. The localized phase transition of MoS2 is achieved and characterized to explicate this plasmon-enhanced hydrogen evolution. The proposed MoS2-nanoparticle composite combines surface plasmons and planar 2D materials, and pioneers a frontier field of plasmonic MoS2 photocatalysis. PMID:25682885

Kang, Yimin; Gong, Yongji; Hu, Zhijian; Li, Ziwei; Qiu, Ziwei; Zhu, Xing; Ajayan, Pulickel M; Fang, Zheyu

2015-02-26

87

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

88

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

89

Removal of Indoor Air ppb Level Volatile Organic Compounds (VOCs) and NOx by Heterogeneous Photocatalysis  

Microsoft Academic Search

VOCs and NOx are the major pollutants in Hong Kong indoor environment. Traditional air purification method such as adsorption by activated carbon is not reliable and get saturated easily. Adsorption merely transfers pollutants from gaseous phase to solid phase and poses the disposal problem. Using photocatalysis, however, strong oxidant such as hydroxyl radical is generated and actually oxidized the pollutant

Chio Hang Ao; Shun Cheng Lee

2002-01-01

90

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. PMID:19931554

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

2012-01-01

91

Silica-Metal Core-Shells and Metal Shells Synthesized by Porphyrin-Assisted Photocatalysis  

E-print Network

Silica-Metal Core-Shells and Metal Shells Synthesized by Porphyrin-Assisted Photocatalysis Haorong acid. Magnetic silica-platinum core-shell spheres can also be prepared starting from silica spheres overlayer.11,12 Using uniform core templates such as Sto¨ber silica spheres,19 core-shell metal spheres can

Shelnutt, John A.

92

UV and solar TiO(2) photocatalysis of brevetoxins (PbTxs).  

PubMed

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. TiO(2) photocatalysis under 350 nm and solar irradiation leads to significant degradation of PbTxs via first order kinetics. ELISA results demonstrate TiO(2) 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 TiO(2) photocatalysis of PbTxs. Our results indicate TiO(2) photocatalysis may be applicable for the degradation of PbTxs. PMID:19931554

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

2010-05-01

93

Degradation of pesticides chlorpyrifos, cypermethrin and chlorothalonil in aqueous solution by TiO2 photocatalysis.  

PubMed

Degradation of pesticides chlorpyrifos, cypermethrin and chlorothalonil in aqueous solution by TiO2 photocatalysis under UVA (365 nm) irradiation was examined. Enhancement of degradation and improvement in biodegradability index (BOD5/COD ratio) by H2O2 addition were also evaluated. UVA irradiation per se produced insignificant degradation of the pesticides. In UV/TiO2 photocatalysis (TiO2 1.5 g L(-1), pH 6 and 300 min irradiation), COD and TOC removal were 25.95 and 8.45%, respectively. In UV/TiO2/H2O2 photocatalysis (TiO2 1.5 g L(-1), H2O2 100 mg L(-1), pH 6 and 300 min irradiation), COD and TOC removal were 53.62 and 21.54%, respectively and biodegradability index improved to 0.26. Ammonia-nitrogen (NH3-N) decreased from 22 to 7.8 mg L(-1) and nitrate-nitrogen (NO3(-)-N) increased from 0.7 to 13.8 mg L(-1) in 300 min, indicating mineralization. Photocatalytic degradation followed pseudo-first order kinetics with rate constant (k) of 0.0025 and 0.0008 min(-1) for COD and TOC removal, respectively. FTIR spectra indicated degradation of the organic bonds of the pesticides. UV/TiO2/H2O2 photocatalysis is effective in degradation of pesticides chlorpyrifos, cypermethrin and chlorothalonil in aqueous solution. UV/TiO2/H2O2 photocatalysis may be applied as pretreatment of a chlorpyrifos, cypermethrin and chlorothalonil pesticide wastewater at pH 6, for biological treatment. PMID:24076516

Affam, Augustine Chioma; Chaudhuri, Malay

2013-11-30

94

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

95

Lanthanide-doped upconversion materials: emerging applications for photovoltaics and photocatalysis.  

PubMed

Photovoltaics and photocatalysis are two significant applications of clean and sustainable solar energy, albeit constrained by their inability to harvest the infrared spectrum of solar radiation. Lanthanide-doped materials are particularly promising in this regard, with tunable absorption in the infrared region and the ability to convert the long-wavelength excitation into shorter-wavelength light output through an upconversion process. In this review, we highlight the emerging applications of lanthanide-doped upconversion materials in the areas of photovoltaics and photocatalysis. We attempt to elucidate the fundamental physical principles that govern the energy conversion by the upconversion materials. In addition, we intend to draw attention to recent technologies in upconversion nanomaterials integrated with photovoltaic and photocatalytic devices. This review also provides a useful guide to materials synthesis and optoelectronic device fabrication based on lanthanide-doped upconversion materials. PMID:25397916

Yang, Weifeng; Li, Xiyan; Chi, Dongzhi; Zhang, Hongjie; Liu, Xiaogang

2014-12-01

96

Lanthanide-doped upconversion materials: emerging applications for photovoltaics and photocatalysis  

NASA Astrophysics Data System (ADS)

Photovoltaics and photocatalysis are two significant applications of clean and sustainable solar energy, albeit constrained by their inability to harvest the infrared spectrum of solar radiation. Lanthanide-doped materials are particularly promising in this regard, with tunable absorption in the infrared region and the ability to convert the long-wavelength excitation into shorter-wavelength light output through an upconversion process. In this review, we highlight the emerging applications of lanthanide-doped upconversion materials in the areas of photovoltaics and photocatalysis. We attempt to elucidate the fundamental physical principles that govern the energy conversion by the upconversion materials. In addition, we intend to draw attention to recent technologies in upconversion nanomaterials integrated with photovoltaic and photocatalytic devices. This review also provides a useful guide to materials synthesis and optoelectronic device fabrication based on lanthanide-doped upconversion materials.

Yang, Weifeng; Li, Xiyan; Chi, Dongzhi; Zhang, Hongjie; Liu, Xiaogang

2014-12-01

97

Controlling algal growth in photo-dependent decolorant sludge by photocatalysis.  

PubMed

In the treatment of synthetic dye wastewater by photosynthetic bacteria under optical irradiation, excessive algal growth and adhesion on the walls of the reactor are serious problems. The adverse effects of excessive algal growth on photosynthetic bacterial activity are significantly greater than those of the decreased optical irradiation of the solution. In this report, we investigated the effects of photocatalysis on the growth of algae (Chroococcus sp.) and photosynthetic bacteria. The different sensitivities of Chroococcus sp. and photosynthetic bacteria to photocatalysis were observed by an ATP assay. Moreover, from microscopy findings, some algae were damaged by TiO2 with UV. We suggested that some algae suffered from membrane damage and consequently cell substances were released, resulting in the increase of dissolved material following treatment using TiO2 with UV. PMID:16233836

Hong, Jinglan; Ma, Hua; Otaki, Masahiro

2005-06-01

98

Plasmonic hot electron enhanced MoS2 photocatalysis in hydrogen evolution  

NASA Astrophysics Data System (ADS)

With plasmonic hot electron doping, the molybdenum disulfide (MoS2) monolayer with deposited Au@Ag nanorattles effectively enhanced the hydrogen evolution reaction (HER) efficiency. The maximum photocatalysis is achieved under plasmon resonance excitation, and is actively controlled by the incident laser wavelength and power intensity. The localized phase transition of MoS2 is achieved and characterized to explicate this plasmon-enhanced hydrogen evolution. The proposed MoS2-nanoparticle composite combines surface plasmons and planar 2D materials, and pioneers a frontier field of plasmonic MoS2 photocatalysis.With plasmonic hot electron doping, the molybdenum disulfide (MoS2) monolayer with deposited Au@Ag nanorattles effectively enhanced the hydrogen evolution reaction (HER) efficiency. The maximum photocatalysis is achieved under plasmon resonance excitation, and is actively controlled by the incident laser wavelength and power intensity. The localized phase transition of MoS2 is achieved and characterized to explicate this plasmon-enhanced hydrogen evolution. The proposed MoS2-nanoparticle composite combines surface plasmons and planar 2D materials, and pioneers a frontier field of plasmonic MoS2 photocatalysis. Electronic supplementary information (ESI) available: SEM images of the as-grown 2H-MoS2 on a Si substrate and Ag@Au nanorattles; extinction spectrum of Ag@Au nanorattles; HER polarization curves under 690 nm laser illumination for Si and MoS2, respectively; calculated near-field optical intensity map of Ag@Ag nanorattles; HER polarization curves under 690 nm laser illumination for the MoS2 monolayer with Ag@Au nanorattles. See DOI: 10.1039/c4nr07303g

Kang, Yimin; Gong, Yongji; Hu, Zhijian; Li, Ziwei; Qiu, Ziwei; Zhu, Xing; Ajayan, Pulickel M.; Fang, Zheyu

2015-02-01

99

Experimental Study of Nanometer TiO2 Photocatalysis Material in Air Purification  

Microsoft Academic Search

With the enhancement of environmental awareness, controlling oil mist in machinery processing workshop has become more and more important. Nanometer titanium dioxide (TiO2) photocatalysis material can treat with manifold pollutants, which is widely applied with its merits of decomposing products sufficiently and no secondary pollution. The nanometer TiO2 photocatalyst was prepared by using the sol-gel method on the optimum formulation

Wang Nan; Wu Zhijiang; Zhu Gongsheng

2009-01-01

100

Imitation of phase I oxidative metabolism of anabolic steroids by titanium dioxide photocatalysis.  

PubMed

The aim of this study was to investigate the feasibility of titanium dioxide (TiO2) photocatalysis for oxidation of anabolic steroids and for imitation of their phase I metabolism. The photocatalytic reaction products of five anabolic steroids were compared to their phase I in vitro metabolites produced by human liver microsomes (HLM). The same main reaction types - hydroxylation, dehydrogenation and combination of these two - were observed both in TiO2 photocatalysis and in microsomal incubations. Several isomers of each product type were formed in both systems. Based on the same mass, retention time and similarity of the product ion spectra, many of the products observed in HLM reactions were also formed in TiO2 photocatalytic reactions. However, products characteristic to only either one of the systems were also formed. In conclusion, TiO2 photocatalysis is a rapid, simple and inexpensive method for imitation of phase I metabolism of anabolic steroids and production of metabolite standards. PMID:25220585

Ruokolainen, Miina; Valkonen, Minna; Sikanen, Tiina; Kotiaho, Tapio; Kostiainen, Risto

2014-12-18

101

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

102

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. PMID:24778974

Samhaber, Wolfgang M

2014-01-01

103

Triplet-triplet annihilation upconversion in CdS-decorated SiO2 nanocapsules for sub-bandgap photocatalysis.  

PubMed

This study reports the first successful nanoscale encapsulation of triplet-triplet annihilation upconversion (TTA-UC) medium within a rigid silica shell using a self-assembly microemulsion process. These newly synthesized nanocapsules present a few critical advances that could be instrumental for a wide range of aqueous-based photonics applications, including photocatalysis, artificial photosynthesis, and bioimaging. The nanocapsules form a homogeneous suspension that can produce intense, diffuse UC emission in water without deoxygenation, closely resembling conventional TTA-UC processes that have been performed in deoxygenated organic solvents. The silica shell provides sites for further surface modification, which allows, when combined with its nanoscale dimension and structural rigidity, this TTA-UC system to acquire various useful functionalities. A benchmark TTA-UC pair, palladium(II) tetraphenyltetrabenzoporphyrin as a sensitizer and perylene as an acceptor, was used to demonstrate efficient red-to-blue (635 nm, 1.95 eV ? 470 nm, 2.6 eV) upconversion in the oxygen-rich aqueous phase. The nanocapsule surface was further functionalized with cadmium sulfide nanoparticles (Eg = 2.4 eV) to demonstrate sub-bandgap sensitization and subsequent aqueous-phase catalytic oxidation. PMID:25522373

Kwon, Oh Seok; Kim, Jae-Hyuk; Cho, Jin Ku; Kim, Jae-Hong

2015-01-14

104

Ligand-exchange assisted formation of Au/TiO2 Schottky contact for visible-light photocatalysis.  

PubMed

Plasmonic noble metal nanoparticles have emerged as a promising material in sensitizing wide-bandgap semiconductors for visible-light photocatalysis. Conventional methods in constructing such heterocatalysts suffer from either poor control over the size of the metal nanoparticles or inefficient charge transfer through the metal/semiconductor interface, which limit their photocatalytic activity. To solve this problem, in this work we construct Au/TiO2 photocatalysts by depositing presynthesized colloidal Au nanoparticles with well-controlled sizes to TiO2 nanocrystals and then removing capping ligands on the Au surface through a delicately designed ligand-exchange method, which leads to close Au/TiO2 Schottky contact after a mild annealing process. Benefiting from this unique synthesis strategy, the obtained photocatalysts show superior activity to conventionally prepared photocatalysts in dye decomposition and water-reduction hydrogen production under visible-light illumination. This study not only opens up new opportunities in designing photoactive materials with high stability and enhanced performance for solar energy conversion but also provides a potential solution for the well-recognized challenge in cleaning capping ligands from the surface of colloidal catalyst nanoparticles. PMID:25329925

Ding, Dawei; Liu, Kai; He, Shengnan; Gao, Chuanbo; Yin, Yadong

2014-11-12

105

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

106

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

107

Photocatalytic treatment of water-soluble pesticides by photo-Fenton and TiO 2 using solar energy  

Microsoft Academic Search

The technical feasibility and performance of photocatalytic degradation of four water-soluble pesticides (diuron, imidacloprid, formetanate and methomyl) have been studied at pilot scale in two well-defined systems of special interest because natural-solar UV light can be used: heterogeneous photocatalysis with titanium dioxide and homogeneous photocatalysis by photo-Fenton. The pilot plant is made up of compound parabolic collectors (CPCs) specially designed

S Malato; J Blanco; J Cáceres; A. R Fernández-Alba; A Agüera; A Rodr??guez

2002-01-01

108

From single crystal surfaces to single atoms: investigating active sites in electrocatalysis  

NASA Astrophysics Data System (ADS)

Electrocatalytic processes will undoubtedly be at the heart of energising future transportation and technology with the added importance of being able to create the necessary fuels required to do so in an environmentally friendly and cost effective manner. For this to be successful two almost mutually exclusive surface properties need to be reconciled, namely producing highly active/reactive surface sites that exhibit long term stability. This article reviews the various approaches which have been undertaken to study the elusive nature of these active sites on metal surfaces which are considered as adatoms or clusters of adatoms with low coordination number. This includes the pioneering studies at extended well defined stepped single crystal surfaces using cyclic voltammetry up to the highly sophisticated in situ electrochemical imaging techniques used to study chemically synthesised nanomaterials. By combining the information attained from single crystal surfaces, individual nanoparticles of defined size and shape, density functional theory calculations and new concepts such as mesoporous multimetallic thin films and single atom electrocatalysts new insights into the design and fabrication of materials with highly active but stable active sites can be achieved. The area of electrocatalysis is therefore not only a fascinating and exciting field in terms of realistic technological and economical benefits but also from the fundamental understanding that can be acquired by studying such an array of interesting materials.

O'Mullane, Anthony P.

2014-03-01

109

Fuel cell applied research: electrocatalysis and materials. Quarterly report, October 1-December 31, 1979  

SciTech Connect

Research on electrocatalysis of phosphoric acid fuel cell reactions is reported. Five types of carbon obtained from Cabot Laboratories (Cabot designation of carbons - Monarch 1300, CSX 98, Mogul L, Vulcan XC-72R and Regan 660R) were compared as supports for platinum electrocatalysts. Experiments were conducted to determine the wetting characteristics of the carbons on the electrocatalytic activity of supported platinum for oxygen reduction. The latter was investigated by a cyclic voltammetry technique. The changes in the electrochemically active surface areas on increasing the temperature from 25/sup 0/ to 135/sup 0/C and after carrying out oxygen reduction were measured from the hydrogen desorption charge in the cyclic voltammograms. Also, research on electrode kinetics in high-temperature solid electrolyte fuel cells is described. The influence of electrode material on oxygen reduction kinetics and the reaction mechanism on platinum at interfaces with solid electrolytes were investigated. Direct current and alternating current impedance techniques were used. Studies on the oxidation of H/sub 2/ on platinum and gold interfaces with the zirconia electrolyte interface were begun. Experiments on single contact ball electrodes of platinum were used. Slow potential sweep techniques (scan rate 5 mV/sec) were used. Results are presented and discussed. (WHK)

Srinivasan, S.; Isaacs, H.S.; McBreen, J.; O'Grady, W.E.; Olender, H.; Olmer, L.J.; Schouler, E.J.L.; Kordesch, K.V.

1980-05-01

110

Electrocatalysis of formic acid on palladium and platinum surfaces: from fundamental mechanisms to fuel cell applications.  

PubMed

Formic acid as a natural biomass and a CO2 reduction product has attracted considerable interest in renewable energy exploitation, serving as both a promising candidate for chemical hydrogen storage material and a direct fuel for low temperature liquid fed fuel cells. In addition to its chemical dehydrogenation, formic acid oxidation (FAO) is a model reaction in the study of electrocatalysis of C1 molecules and the anode reaction in direct formic acid fuel cells (DFAFCs). Thanks to a deeper mechanistic understanding of FAO on Pt and Pd surfaces brought about by recent advances in the fundamental investigations, the "synthesis-by-design" concept has become a mainstream idea to attain high-performance Pt- and Pd-based nanocatalysts. As a result, a large number of efficient nanocatalysts have been obtained through different synthesis strategies by tailoring geometric and electronic structures of the two primary catalytic metals. In this paper, we provide a brief overview of recent progress in the mechanistic studies of FAO, the synthesis of novel Pd- and Pt-based nanocatalysts as well as their practical applications in DFAFCs with a focus on discussing studies significantly contributing to these areas in the past five years. PMID:25144896

Jiang, Kun; Zhang, Han-Xuan; Zou, Shouzhong; Cai, Wen-Bin

2014-10-14

111

Synergistic effect of titanium dioxide nanocrystal/reduced graphene oxide hybrid on enhancement of microbial electrocatalysis  

NASA Astrophysics Data System (ADS)

A small sized TiO2 nanocrystal (?10 nm)/reduced graphene oxide (TiO2/rGO) hybrid is synthesized through a sol-gel process for hybrid TiO2/GO followed by solvothermal reduction of GO to rGO and is further used as a microbial fuel cell (MFC) anode. The strong synergistic effect from a large surface area produced by uniformly deposited TiO2 nanocrystals, good hydrophilicity of TiO2 nanocrystals and superior conductivity of rGO leads to significantly improved electrocatalysis. In particular, a direct electrochemistry is realized by generating endogenous flavins from a large amount of microbes grown on the highly biocompatible TiO2 nanocrystals to mediate fast electron transfer between microbes and conductive rGO for a high performance anode. The TiO2/rGO hybrid anode delivers a maximum power density of 3169 mW m-2 in Shewanella putrefaciens CN32 MFC, which is much large than that of the conventional carbon cloth anode and reported TiO2/carbon hybrid anode, thus offering great potential for practical applications of MFC. This work is for the first time to report that the synergistic effect from tailoring the physical structure to achieve small sized TiO2 nanocrystals while rationally designing chemistry to introduce highly conductive rGO and superior biocompatible TiO2 is able to significantly boost the MFC performance.

Zou, Long; Qiao, Yan; Wu, Xiao-Shuai; Ma, Cai-Xia; Li, Xin; Li, Chang Ming

2015-02-01

112

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

113

Differences in elimination efficiencies of Escherichia coli in freshwater and seawater as a result of TiO2 photocatalysis.  

PubMed

The effects of UV irradiation on the respiration and survival of Escherichia coli in various concentrations of aqueous NaCl were investigated in the presence of a photocatalyst. In this study, we anticipated that the photocatalysis of residual chlorine generated in a solution containing Cl(-) would result in bacterial elimination. Our results indicated a gradual reduction in the E. coli survival ratio in freshwater; however, no decrease in total abundance was observed during 8 h of photocatalysis with UV irradiation. Conversely, the survival ratio of E. coli in the artificial seawater decreased drastically as a consequence of photocatalysis, with a concomitant decrease in total abundance. These results revealed that the chlorinated active species that formed on the photocatalyst surface influenced the observed inactivation. PMID:23523173

Yamada, Namiha; Suzumura, Masahiro; Koiwa, Fumiko; Negishi, Nobuaki

2013-05-15

114

Electrochemical enhancement of solar photocatalysis: degradation of endocrine disruptor bisphenol-A on Ti/TiO2 films.  

PubMed

The photoelectrocatalytic oxidation over immobilized Ti/TiO(2) films in the presence of simulated solar light was investigated for the degradation of bisphenol-A (BPA) in water. The catalyst, consisting of 75:25 anatase:rutile, was prepared by a sol-gel method and characterized by cyclic voltammetry, X-ray diffraction and scanning electron microscopy. Experiments were conducted to assess the effect of applied current (0.02-0.32 mA/cm(2)), TiO(2) loading (1.3-9.2 mg), BPA concentration (120-820 ?g/L), initial solution pH (1 and 7.5) and the aqueous matrix (pure water and treated effluent) on BPA photoelectrocatalytic degradation which was monitored by high performance liquid chromatography equipped with a fluorescence detector. The reaction was favored at anodic currents up to 0.04 mA/cm(2) and lower substrate concentrations, but it was hindered by the presence of residual organic matter and radical scavengers (e.g. bicarbonates) in treated effluents. Moreover, a pseudo-first order kinetic model could fit the experimental data well with the apparent reaction constant taking values between 2.9 and 32.4 10(-3)/min. The degradation of BPA by pure photocatalysis or electrochemical oxidation alone was also studied leading to partial substrate removal. In all cases, the contribution of applied potential to photocatalytic degradation was synergistic with the photocatalytic efficiency increasing between 24% and 97% possibly due to a more efficient separation and utilization of the photogenerated charge carriers. The effect of photoelectrocatalysis on the ecotoxic and estrogenic properties of BPA was also evaluated measuring the bioluminescence inhibition of Vibrio fischeri and performing the yeast estrogen screening assay, respectively. PMID:21458019

Frontistis, Zacharias; Daskalaki, Vasileia M; Katsaounis, Alexandros; Poulios, Ioannis; Mantzavinos, Dionissios

2011-04-01

115

Identification of Plant Growth-Promoting Bacteria Using Titanium Dioxide Photocatalysis-Assisted Photoacoustic Technique  

NASA Astrophysics Data System (ADS)

The effect of titanium dioxide photocatalysis against bacteria that are dangerous for human health has been investigated in the past, suggesting the possibility of using a specific behavior for each microorganism during this process for its discrimination. In this study, the behavior of some plants’ growth promoting bacteria ( Burkholderia unamae (Strain MTI 641), Acetobacter diazotrophicus (Strain PAl 5T), A. diazotrophicus (Strain CFN-Cf 52), and B. unamae (Strain TATl-371)) interacting with light and bactericidal titanium dioxide films have been analyzed using the photoacoustic technique. The monitoring of these interactions shows particular characteristics that could serve for identifying these species.

Gordillo-Delgado, F.; Marín, E.; Calderón, A.

2013-09-01

116

Oxalic acid destruction at high concentrations by combined heterogeneous photocatalysis and photo-Fenton processes  

Microsoft Academic Search

Heterogeneous photocatalysis (HP) using UV\\/TiO2, photo-Fenton (PF) reaction using UV\\/Fe\\/H2O2 and the combination UV\\/TiO2\\/Fe\\/H2O2 (HP–PF) were tested as processes to degrade oxalic acid (Ox) at relatively high concentrations (0.032M). PF reactions were generally more efficient than HP including the reaction in the absence of H2O2. Oppositely to previous results (e.g., with EDTA), HP–PF combinations did not result, in the case

Natalia Quici; María E. Morgada; Gabriela Piperata; Paola Babay; Raquel T. Gettar; Marta I. Litter

2005-01-01

117

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

2014-06-21

118

Production of Hydrogen by Electrocatalysis: Making the H-H Bond by Combining Protons and Hydrides  

SciTech Connect

Generation of hydrogen by reduction of two protons by two electrons can be catalysed by molecular electrocatalysts. Determination of the thermodynamic driving force for elimination of H2 from molecular complexes is important for the rational design of molecular electrocatalysts, and allows the design of metal complexes of abundant, inexpensive metals rather than precious metals (“Cheap Metals for Noble Tasks”). The rate of H2 evolution can be dramatically accelerated by incorporating pendant amines into diphosphine ligands. These pendant amines in the second coordination sphere function as protons relays, accelerating intramolecular and intermolecular proton transfer reactions. The thermodynamics of hydride transfer from metal hydrides and the acidity of protonated pendant amines (pKa of N-H) contribute to the thermodynamics of elimination of H2; both of the hydricity and acidity can be systematically varied by changing the substituents on the ligands. A series of Ni(II) electrocatalysts with pendant amines have been developed. In addition to the thermochemical considerations, the catalytic rate is strongly influenced by the ability to deliver protons to the correct location of the pendant amine. Protonation of the amine endo to the metal leads to the N-H being positioned appropriately to favor rapid heterocoupling with the M-H. Designing ligands that include proton relays that are properly positioned and thermodynamically tuned is a key principle for molecular electrocatalysts for H2 production as well as for other multi-proton, multi-electron reactions important for energy conversions. The research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for DOE.

Bullock, R. Morris; Appel, Aaron M.; Helm, Monte L.

2014-03-25

119

UV-absorption--the primary process in photocatalysis and some practical consequences.  

PubMed

TiO2 photochemistry studies generally address reactions of photogenerated charge-carriers at the oxide surface or the recombination reactions which control the proportion of charge carriers that reach the surface. By contrast, this review focuses on UV absorption, the first photochemical step in semiconductor photocatalysis. The influence of particle size on absorption and scattering of light by small TiO2 particles is summarized and the importance of considering, the particle size in the application, not the BET or X-ray line broadening size, is emphasized. Three different consequences of UV absorption are then considered. First, two commercially important systems, pigmented polymer films and paints, are used to show that TiO2 can protect from direct photochemical degradation. Then the effect of UV absorption on the measured photocatalytic degradation of aqueous solutions of organics is considered for two separate cases. Firstly, the consequences of UV absorption by TiO2 on the generation of hydroxyl radicals from H2O2 are considered in the context of the claimed synergy between H2O2 and TiO2. Secondly, the effect of altered UV absorption, caused by changed effective particle size of the catalyst, is demonstrated for photocatalysis of propan-2-ol oxidation and salicylic acid degradation. PMID:25383755

Egerton, Terry A

2014-01-01

120

Engaging in Curriculum Reform of Chinese Chemistry Graduate Education: An Example from a Photocatalysis--Principles and Applications Course  

ERIC Educational Resources Information Center

As worldwide energy shortages and environmental degradation increase, along with steady increases in population, current science and technology are confronted with many challenges to successfully sustain our society. Among the existing promising choices, photocatalysis has been widely considered as a potential solution to energy and environment…

Ma, Jiahai; Guo, Rongrong

2014-01-01

121

A new metal-free carbon hybrid for enhanced photocatalysis.  

PubMed

Carbon nitride (C3N4) is a layered, stable, and polymeric metal-free material that has been discovered as a visible-light-response photocatalyst. Owing to C3N4 having a higher conduction band position, most previous studies have been focused on its reduction capability for solar fuel production, such as hydrogen generation from water splitting or hydrocarbon production from CO2. However, photooxidation ability of g-C3N4 is weak and has been less explored, especially for decomposition of chemically stable phenolics. Carbon spheres prepared by a hydrothermal carbonization of glucose have been widely applied as a support material or template due to their interesting physicochemical properties and the functional groups on the reactive surface. This study demonstrated that growth of carbon nanospheres onto g-C3N4 (CN-CS) can significantly increase the photooxidation ability (to about 4.79 times higher than that of pristine g-C3N4) in phenol degradation under artificial sunlight irradiations. The crystal structure, optical property, morphology, surface groups, recombination rate of electron/hole pairs, and thermal stability of CN-CS were investigated by a variety of characterization techniques. This study contributes to the further promising applications of carbon nitride in metal-free catalysis. PMID:25212502

Sun, Hongqi; Zhou, Guanliang; Wang, Yuxian; Suvorova, Alexandra; Wang, Shaobin

2014-10-01

122

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

123

Proton-Coupled Electron Transfer in Molecular Electrocatalysis: Theoretical Methods and Design Principles  

SciTech Connect

Molecular electrocatalysts play an essential role in a wide range of energy conversion processes. The objective of electrocatalyst design is to maximize the turnover frequency and minimize the overpotential for the overall catalytic cycle. Typically the catalytic cycle is dominated by key proton-coupled electron transfer (PCET) processes comprised of sequential or concerted electron transfer and proton transfer steps. A variety of theoretical methods have been developed to investigate the mechanisms, thermodynamics, and kinetics of PCET processes in electrocatalytic cycles. Electronic structure methods can be used to calculate the reduction potentials and pKa’s and to generate thermodynamic schemes, free energy reaction pathways, and Pourbaix diagrams, which indicate the most stable species at each pH and potential. These types of calculations have assisted in identifying the thermodynamically favorable mechanisms under specified experimental conditions, such as acid strength and overpotential. Such calculations have also revealed linear correlations among the thermodynamic properties, which can be used to predict the impact of modifying the ligand, substituents, or metal center. The role of non-innocent ligands, namely ligand protonation or reduction, has also been examined theoretically. In addition, the rate constants for electron and proton transfer reactions, as well as concerted PCET reactions, have been calculated to investigate the kinetics of molecular electrocatalysts. The concerted PCET mechanism is thought to lower the overpotential required for catalysis by avoiding high-energy intermediates. Rate constant calculations have revealed that the concerted mechanism involving intramolecular proton transfer will be favored by designing more flexible ligands that facilitate the proton donor-acceptor motion while also maintaining a sufficiently short equilibrium proton donor-acceptor distance. Overall, theoretical methods have assisted in the interpretation of experimental data and the design of more effective molecular electrocatalysts. The research on the Ni(P2N2)2 catalysts was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

Solis, Brian H.; Hammes-Schiffer, Sharon

2014-07-07

124

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

125

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. PMID:24991507

Chen, Hongjun

2014-01-01

126

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

127

PHOTOCATALYTIC OXIDATION OF METHYL-TERT-BUTYL ETHER FOR DRINKING WATER TREATMENT  

EPA Science Inventory

The photo-oxidation of methyl tert-butyl ether (MTBE) in water was investigated to determine the feasibility of using photocatalysis for the treatment of MTBE-contaminated drinking water. The feasibility assessment was conducted using slurries of titanium dioxide in both a photo-...

128

Application of oxidative removal of NOM to drinking water and formation of disinfection by-products  

Microsoft Academic Search

Water samples of different origins (Buyukcekmece and Omerli, Istanbul, Turkey, and Alento, Salerno, Italy) were treated by coagulation, ozonation, and coagulation followed by ozonation and photocatalysis. Disinfection by-products (DBPs) formation potential of raw and treated water samples was compared in relation to removal efficiencies by the respective treatment methods. The major DBPs, namely trihalomethanes (THMs) and haloacetic acids (HAAs), and

M. Bekbolet; C. S. Uyguner; H. Selcuk; L. Rizzo; A. D. Nikolaou; S. Meriç; V. Belgiorno

2005-01-01

129

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

130

Microfluidic reactors for photocatalytic water purification.  

PubMed

Photocatalytic water purification utilizes light to degrade the contaminants in water and may enjoy many merits of microfluidics technology such as fine flow control, large surface-area-to-volume ratio and self-refreshing of reaction surface. Although a number of microfluidic reactors have been reported for photocatalysis, there is still a lack of a comprehensive review. This article aims to identify the physical mechanisms that underpin the synergy of microfluidics and photocatalysis, and, based on which, to review the reported microfluidic photocatalytic reactors. These microreactors help overcome different problems in bulk reactors such as photon transfer limitation, mass transfer limitation, oxygen deficiency, and lack of reaction pathway control. They may be scaled up for large-throughput industrial applications of water processing and may also find niche applications in rapid screening and standardized tests of photocatalysts. PMID:24481005

Wang, Ning; Zhang, Xuming; Wang, Yu; Yu, Weixing; Chan, Helen L W

2014-03-21

131

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

132

Kinetic study of the heterogeneous photocatalysis of porous nanocrystalline TiO? assemblies using a continuous random walk simulation.  

PubMed

The continuous time random walk (CTRW) simulation was used to study the photocatalytic kinetics of nanocrystalline (nc)-TiO2 assemblies in this research. nc-TiO2 assemblies, such as nc-TiO2 porous films and nc-TiO2 hierarchical structures, are now widely used in photocatalysis. The nc-TiO2 assemblies have quasi-disordered networks consisting of many tiny nanoparticles, so the charge transport within them can be studied by CTRW simulation. We considered the experimental facts that the holes can be quickly trapped and transferred to organic species just after photogeneration, and the electrons transfer to O2 slowly and accumulate in the conduction band of TiO2, which is believed to be the rate-limiting process of the photocatalysis under low light intensity and low organic concentration. Due to the existence of numerous traps, the electron transport within the nc-TiO2 assemblies follows a multi-trapping (MT) mechanism, which significantly limits the electron diffusion speed. The electrons need to undergo several steps of MT transport before transferring to oxygen, so it is highly important that the electron transport in nc-TiO2 networks is determined for standard photocatalytic reactions. Based on the MT transport model, the transient decays of photocurrents during the photocatalytic oxidation of formic acid were studied by CTRW simulation, and are in good accordance with experiments. The steady state photocatalysis was also simulated. The effects of organic concentration, light intensity, temperature, and nc-TiO2 crystallinity on the photocatalytic kinetics were investigated, and were also consistent with the experimental results. Due to the agreement between the simulation and the experiments for both the transient and the steady state photocatalysis, the MT charge transport should be an important mechanism that controls the kinetics of recombination and photocatalysis in nc-TiO2 assemblies. Also, our research provides a new methodology to study the photocatalytic dynamics from the random event viewpoint, which can be revised to investigate the kinetic processes of other kinds of material. PMID:25224752

Liu, Baoshun; Zhao, Xiujian

2014-10-28

133

Effect of Morphology of Co3O4 for Oxygen Evolution Reaction in Alkaline Water Electrolysis  

PubMed Central

In this paper, three different morphological Co3O4 electrodes for oxygen evolution reaction (OER) have been synthesized. By comparing the three morphologies of Co3O4, the electrocatalytic properties show that the urchin-like spheres of Co3O4 electrode has relative low overpotential and good electrocatalysis stability, indicating that the structure of urchin-like Co3O4 spheres exhibit an easy OER for water splitting. PMID:25525423

Xu, Qi-Zhi; Xu, Qi-Zhi; Su, Yu-Zhi; Wu, Hao; Cheng, Hui; Hui, Yun-Ping; Li, Nan; Liu, Zhao-Qing

2014-01-01

134

Theory and experiments for voltammetric and SECM investigations and application to ORR electrocatalysis at nanoelectrode ensembles of ultramicroelectrode dimensions.  

PubMed

Theoretical and experimental approaches to characterizing nanoelectrode (NE) ensembles of ultramicroelectrode dimensions (UME-NEEs) as a function of fraction of active area and random NE distribution are described. UME-NEEs were fabricated by addressing microregions of a gold-filled polycarbonate membrane through the UMEs of an underlying microfabricated addressable array. Results of Comsol Multiphysics 3D simulations based on randomly spaced NEs of 15 nm radius on a UME disk geometry of radii up to 5 ?m are shown for steady-state voltammetry (SSV) and scanning electrochemical microscopy (SECM) experiments. Analytical equations were developed to describe the diffusion-limited steady-state current and steady-state voltammogram at an UME-NEE. These equations are shown to be in good agreement with the simulations and enabled evaluation of experimental SSVs. Comparison of experimental and simulated SECM approach curves, images, and tip voltammograms enabled the fraction of active area and distribution of NEs to be visualized and determined for individual UME-NEEs. Gold UME-NEEs are shown to be unique platforms for electrodeposition in forming nanoparticle electrodes (UME-NPEs). Electrocatalysis results for the oxygen reduction reaction (ORR) on Pt UME-NPEs in 0.1 M H2SO4 are also shown. PMID:25495486

Fernández, José L; Wijesinghe, Manjula; Zoski, Cynthia G

2015-01-20

135

Effect of Component Distribution and Nanoporosity in CuPt Nanotubes on Electrocatalysis of the Oxygen Reduction Reaction.  

PubMed

Pt-based bimetallic electrocatalysts hold great potential in the oxygen reduction reaction (ORR) in current fuel-cell prototypes. However, they also face challenges from drastic dealloying of less-noble metals and coalescence of small nanoparticles. Porous and structure-ordered nanotubes may hold the potential to improve the stability of bimetallic electrocatalysts. Herein, we report a method to prepare CuPt nanotubes and porous Cu3 Pt intermetallic nanorods through a controlled galvanic replacement reaction and heat treatment process. The effect of the geometric features and compositional segregation on the electrocatalysis of the ORR was clarified. The outstanding performance of the Cu3 Pt/C-700 catalyst in the ORR relative to that of CuPt/C-RT was mainly attributed to the nanoporosity of the catalyst, whereas the enhanced specific activity on CuPt/C-RT after potential cycling was attributed to the interaction between the CuPt alloyed core and the Pt shell in the tube wall. PMID:25505002

Guo, Huizhang; Liu, Xiang; Bai, Chengdong; Chen, Yuanzhi; Wang, Laisen; Zheng, Mingsen; Dong, Quanfeng; Peng, Dong-Liang

2015-02-01

136

Optimized electrospinning synthesis of iron-nitrogen-carbon nanofibers for high electrocatalysis of oxygen reduction in alkaline medium.  

PubMed

To achieve iron-nitrogen-carbon (Fe-N-C) nanofibers with excellent electrocatalysis for replacing high-cost Pt-based catalysts in the cathodes of fuel cells and metal-air batteries, we have investigated and evaluated the effects of polyacrylonitrile (PAN) concentration and the proportion of iron to PAN, along with voltage and flow rate during the electrospinning process, and thus proposed three criteria to optimize these parameters for ideal nanofiber catalysts. The best half-wave potential of an optimized catalysts is 0.82 V versus reversible hydrogen electrode in an alkaline medium, which reaches the best range of the non-precious-metal catalysts reported and is very close to that of commercial Pt/C catalysts. Furthermore, the electron-transfer number of our catalysts is superior to that of the Pt/C, indicating the catalysts undergo a four-electron process. The durability of the optimized Fe-N-C nanofibers is also better than that of the Pt/C, which is attributed to the homogeneous distribution of the active sites in our catalysts. PMID:25815586

Yan, Xingxu; Liu, Kexi; Wang, Xiangqing; Wang, Tuo; Luo, Jun; Zhu, Jing

2015-04-24

137

Electrocatalysis and simultaneous determination of catechol and quinol by poly(malachite green) coated multiwalled carbon nanotube film.  

PubMed

Electrochemically active composite film that contains multiwalled carbon nanotubes (MWCNTs), Nafion (NF), and poly(malachite green) (PMG) has been synthesized on glassy carbon electrode (GCE), gold, and indium tin oxide (ITO) electrodes by potentiodynamic method. The presence of MWCNTs in the composite film (MWCNT-NF-PMG) enhances the surface coverage concentration (?) of PMG by fivefold. Similarly, an electrochemical quartz crystal microbalance study revealed enhancement in the deposition of PMG at MWCNT-NF film when compared with bare and only NF modified electrodes. The surface morphology of the composite film was studied using atomic force microscopy, which revealed that the PMG incorporated on MWCNT-NF film. The composite film exhibited enhanced electrocatalytic activity toward the mixture of biochemical compounds catechol and quinol. The electrocatalytic responses of analytes at MWCNT-NF-PMG composite film were measured using both cyclic voltammetry (CV) and differential pulse voltammetry (DPV). From electrocatalysis studies, well-separated voltammetric peaks were obtained at the composite film for catechol and quinol with a peak separation of 147mV. The sensitivity values of the composite film toward catechol and quinol by the DPV technique were 0.4 and 3.2mAmM(-1)cm(-2), respectively, which are higher than the values obtained by the CV technique. Similarly, the above-mentioned values are better than the previously reported electroanalytical values for the same analytes. PMID:21138725

Umasankar, Yogeswaran; Periasamy, Arun Prakash; Chen, Shen-Ming

2011-04-01

138

Lignin depolymerization and upgrading via fast pyrolysis and electrocatalysis for the production of liquid fuels and value-added products  

NASA Astrophysics Data System (ADS)

The production of liquid hydrocarbon fuels from biomass is needed to replace fossil fuels, which are decreasing in supply at an unsustainable rate. Renewable fuels also address the rising levels of greenhouse gases, an issue for which the Intergovernmental Panel on Climate Change implicated humanity in 2013. In response, the Energy Independence and Security Act (EISA) mandates the production of 21 billion gallons of advanced biofuels by 2022. Biomass fast pyrolysis (BFP) uses heat (400-600 °C) without oxygen to convert biomass to liquids fuel precursors offering an alternative to fossil fuels and a means to meet the EISA mandate. The major product, bio-oil, can be further upgraded to liquid hydrocarbon fuels, while biochar can serve as a solid fuel or soil amendment. The combustible gas co-product is typically burned for process heat. Though the most valuable of the pyrolysis products, the liquid bio-oil is highly oxygenated, corrosive, low in energy content and unstable during storage. As a means of improving bio-oil properties, electrocatalytic hydrogenation (ECH) is employed to reduce and deoxygenate reactive compounds. This work specifically focuses on lignin as a feed material for BFP. As lignin comprises up to 30% of the mass and 40% of the energy stored in biomass, it offers great potential for the production of liquid fuels and value-added products by utilizing fast pyrolysis as a conversion method coupled with electrocatalysis as an upgrading method.

Garedew, Mahlet

139

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 ...

140

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

141

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

142

Electrochemical reactions at the electrode\\/solution interface: Theory and applications to water electrolysis and oxygen reduction  

Microsoft Academic Search

Theoretical simulations on complex electrochemical processes have been developed on the basis of the understanding in electrochemistry,\\u000a which has benefited from quantum mechanics calculations. This article reviews the recent progress on the theory and applications\\u000a in electrocatalysis. Two representative reactions, namely water electrolysis and oxygen reduction, are selected to illustrate\\u000a how the theoretical methods are applied to electrocatalytic reactions. The

YaHui Fang; ZhiPan Liu

2010-01-01

143

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

144

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

145

Assessment of solar driven TiO2-assisted photocatalysis efficiency on amoxicillin degradation.  

PubMed

The objective of this work was to evaluate the efficiency of a solar TiO2-assisted photocatalytic process on amoxicillin (AMX) degradation, an antibiotic widely used in human and veterinary medicine. Firstly, solar photolysis of AMX was compared with solar photocatalysis in a compound parabolic collectors pilot scale photoreactor to assess the amount of accumulated UV energy in the system (Q UV) necessary to remove 20 mg L(-1) AMX from aqueous solution and mineralize the intermediary by-products. Another experiment was also carried out to accurately follow the antibacterial activity against Escherichia coli DSM 1103 and Staphylococcus aureus DSM 1104 and mineralization of AMX by tracing the contents of dissolved organic carbon (DOC), low molecular weight carboxylate anions, and inorganic anions. Finally, the influence of individual inorganic ions on AMX photocatalytic degradation efficiency and the involvement of some reactive oxygen species were also assessed. Photolysis was shown to be completely ineffective, while only 3.1 kJUV?L(-1) was sufficient to fully degrade 20 mg L(-1) AMX and remove 61% of initial DOC content in the presence of the photocatalyst and sunlight. In the experiment with an initial AMX concentration of 40 mg L(-1), antibacterial activity of the solution was considerably reduced after elimination of AMX to levels below the respective detection limit. After 11.7 kJUV?L(-1), DOC decreased by 71%; 30% of the AMX nitrogen was converted into ammonium and all sulfur compounds were converted into sulfate. A large percentage of the remaining DOC was in the form of low molecular weight carboxylic acids. Presence of phosphate ions promoted the removal of AMX from solution, while no sizeable effects on the kinetics were found for other inorganic ions. Although the AMX degradation was mainly attributed to hydroxyl radicals, singlet oxygen also plays an important role in AMX self-photosensitization under UV/visible solar light. PMID:23900954

Pereira, João H O S; Reis, Ana C; Nunes, Olga C; Borges, Maria T; Vilar, Vítor J P; Boaventura, Rui A R

2014-01-01

146

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

PubMed

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. PMID:24056871

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

2013-11-01

147

Influence of azo dye-TiO2 interactions on the filtration performance in a hybrid photocatalysis/ultrafiltration process.  

PubMed

Filtration performances of hollow fiber ultrafiltration membrane were investigated in a photocatalysis/ultrafiltration process used for dyeing wastewater treatment. Special attentions were focused on the dye-TiO(2) interactions and their effect on membrane flux and dye rejection. Solution pH was proved to be the predominant force that controlled the interactions by changing the surface charge characteristics of TiO(2) and altering the size and fractal dimension of TiO(2) aggregates which determined the property and structure of deposit layer. Dye-TiO(2) interaction had pronounced effect on membrane flux in adsorptive regions, but this effect became insignificant in non-adsorptive regions. The rejection of dye in the presence of TiO(2) was found to decrease markedly due to the deposition of TiO(2) particles on membrane interface. Bridging effect of TiO(2) between membrane interface and dyes produced by electronic interaction, coordination, and hydrogen bonding was responsible for the decrease in dye rejection. In view of the results presented in this paper, the interactions between pollutant and photocatalysts and their effect on the performance of membrane in hybrid photocatalysis/membrane process should be taken into consideration in the future practice. PMID:23062964

Zhang, Jiwei; Wang, Ling; Zhang, Guoliang; Wang, Zhiyang; Xu, Lusheng; Fan, Zheng

2013-01-01

148

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

149

Selective reduction of Cr(VI) in chromium, copper and arsenic (CCA) mixed waste streams using UV/TiO2 photocatalysis.  

PubMed

The highly toxic Cr(VI) is a critical component in the Chromated Copper Arsenate (CCA) formulations extensively employed as wood preservatives. Remediation of CCA mixed waste and discarded treated wood products is a significant challenge. We demonstrate that UV/TiO2 photocatalysis effectively reduces Cr(VI) to less toxic Cr(III) in the presence of arsenate, As(V), and copper, Cu(II). The rapid conversion of Cr(VI) to Cr(III) during UV/TiO2 photocatalysis occurs over a range of concentrations, solution pH and at different Cr:As:Cu ratios. The reduction follows pseudo-first order kinetics and increases with decreasing solution pH. Saturation of the reaction solution with argon during UV/TiO2 photocatalysis had no significant effect on the Cr(VI) reduction demonstrating the reduction of Cr(VI) is independent of dissolved oxygen. Reduction of Cu(II) and As(V) does not occur under the photocatalytic conditions employed herein and the presence of these two in the tertiary mixtures had a minimal effect on Cr(VI) reduction. The Cr(VI) reduction was however, significantly enhanced by the addition of formic acid, which can act as a hole scavenger and enhance the reduction processes initiated by the conduction band electron. Our results demonstrate UV/TiO2 photocatalysis effectively reduces Cr(VI) in mixed waste streams under a variety of conditions. PMID:25654531

Zheng, Shan; Jiang, Wenjun; Rashid, Mamun; Cai, Yong; Dionysiou, Dionysios D; O'Shea, Kevin E

2015-01-01

150

Fabrication of Transparent-Conducting-Oxide-Coated Inverse Opals as Mesostructured Architectures for Electrocatalysis Applications: A  

E-print Network

Fabrication of Transparent-Conducting-Oxide-Coated Inverse Opals as Mesostructured Architectures: Highly ordered, and conductive inverse opal arrays were made with silica and subsequently coated with tin of efficiently electrochemically evolving oxygen from water. These modular, crack-free, transparent, high surface

151

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 ...

152

Nanoscale nickel oxide/nickel heterostructures for active hydrogen evolution electrocatalysis  

NASA Astrophysics Data System (ADS)

Active, stable and cost-effective electrocatalysts are a key to water splitting for hydrogen production through electrolysis or photoelectrochemistry. Here we report nanoscale nickel oxide/nickel heterostructures formed on carbon nanotube sidewalls as highly effective electrocatalysts for hydrogen evolution reaction with activity similar to platinum. Partially reduced nickel interfaced with nickel oxide results from thermal decomposition of nickel hydroxide precursors bonded to carbon nanotube sidewalls. The metal ion-carbon nanotube interactions impede complete reduction and Ostwald ripening of nickel species into the less hydrogen evolution reaction active pure nickel phase. A water electrolyzer that achieves ~20?mA?cm-2 at a voltage of 1.5?V, and which may be operated by a single-cell alkaline battery, is fabricated using cheap, non-precious metal-based electrocatalysts.

Gong, Ming; Zhou, Wu; Tsai, Mon-Che; Zhou, Jigang; Guan, Mingyun; Lin, Meng-Chang; Zhang, Bo; Hu, Yongfeng; Wang, Di-Yan; Yang, Jiang; Pennycook, Stephen J.; Hwang, Bing-Joe; Dai, Hongjie

2014-08-01

153

Nanoscale nickel oxide/nickel heterostructures for active hydrogen evolution electrocatalysis.  

PubMed

Active, stable and cost-effective electrocatalysts are a key to water splitting for hydrogen production through electrolysis or photoelectrochemistry. Here we report nanoscale nickel oxide/nickel heterostructures formed on carbon nanotube sidewalls as highly effective electrocatalysts for hydrogen evolution reaction with activity similar to platinum. Partially reduced nickel interfaced with nickel oxide results from thermal decomposition of nickel hydroxide precursors bonded to carbon nanotube sidewalls. The metal ion-carbon nanotube interactions impede complete reduction and Ostwald ripening of nickel species into the less hydrogen evolution reaction active pure nickel phase. A water electrolyzer that achieves ~20?mA?cm(-2) at a voltage of 1.5?V, and which may be operated by a single-cell alkaline battery, is fabricated using cheap, non-precious metal-based electrocatalysts. PMID:25146255

Gong, Ming; Zhou, Wu; Tsai, Mon-Che; Zhou, Jigang; Guan, Mingyun; Lin, Meng-Chang; Zhang, Bo; Hu, Yongfeng; Wang, Di-Yan; Yang, Jiang; Pennycook, Stephen J; Hwang, Bing-Joe; Dai, Hongjie

2014-01-01

154

Development of Novel Electrode Materials for the Electrocatalysis of Oxygen-Transfer and Hydrogen-Transfer Reactions  

SciTech Connect

Throughout this thesis, the fundamental aspects involved in the electrocatalysis of anodic O-transfer reactions and cathodic H-transfer reactions have been studied. The investigation into anodic O-transfer reactions at undoped and Fe(III)[doped MnO{sub 2} films] revealed that MnO{sub 2} film electrodes prepared by a cycling voltammetry deposition show improved response for DMSO oxidation at the film electrodes vs. the Au substrate. Doping of the MnO{sub 2} films with Fe(III) further enhanced electrode activity. Reasons for this increase are believed to involve the adsorption of DMSO by the Fe(III) sites. The investigation into anodic O-transfer reactions at undoped and Fe(III)-doped RuO{sub 2} films showed that the Fe(III)-doped RuO{sub 2}-film electrodes are applicable for anodic detection of sulfur compounds. The Fe(III) sites in the Fe-RuO{sub 2} films are speculated to act as adsorption sites for the sulfur species while the Ru(IV) sites function for anodic discharge of H{sub 2}O to generate the adsorbed OH species. The investigation into cathodic H-transfer reactions, specifically nitrate reduction, at various pure metals and their alloys demonstrated that the incorporation of metals into alloy materials can create a material that exhibits bifunctional properties for the various steps involved in the overall nitrate reduction reaction. The Sb{sub 10}Sn{sub 20}Ti{sub 70}, Cu{sub 63}Ni{sub 37} and Cu{sub 25}Ni{sub 75} alloy electrodes exhibited improved activity for nitrate reduction as compared to their pure component metals. The Cu{sub 63}Ni{sub 37} alloy displayed the highest activity for nitrate reduction. The final investigation was a detailed study of the electrocatalytic activity of cathodic H-transfer reactions (nitrate reduction) at various compositions of Cu-Ni alloy electrodes. Voltammetric response for NO{sub 3}{sup -} at the Cu-Ni alloy electrode is superior to the response at the pure Cu and Ni electrodes. This is explained on the basis of the synergism of the two different metal sites at these binary alloy electrodes acting within the proposed response mechanism. Accordingly, adsorbed H-atoms are generated by cathodic discharge of H{sup +} at the Ni-sites whereas adsorption of NO{sub 3}{sup -} occurs at the Cu-sites.

Brett Kimball Simpson

2002-08-27

155

Palladium nanotubes formed by lipid tubule templating and their application in ethanol electrocatalysis.  

PubMed

Palladium nanotubes were fabricated by using lipid tubules as templates for the first time in a controlled manner. The positively charged lipid 1,2-dioleoyl-3-trimethylammoniumpropane (DOTAP) was doped into lipid tubules to adsorb PdCl4 (2-) on the tubule surfaces for further reduction. The lipid tubule formation was optimized by studying the growing dynamics and ethanol/water ratio. The DOTAP-doped tubules showed pH stability from 0 to 14, which makes them ideal templates for metal plating. The Pd nanotubes are open-ended with a tunable wall thickness. They exhibited good electrocatalytic performance in ethanol. Their electrochemically active surface areas were 6.5, 10.6, and 83.2?m(2) ?g(-1) for Pd nanotubes with 77, 101, and 150?nm wall thickness, respectively. These Pd nanotubes have great potential in fuel cells. The method demonstrated also opens up a way to synthesize hollow metal nanotubes. PMID:25766748

Wang, Yinan; Ma, Shenghua; Su, Yingchun; Han, Xiaojun

2015-04-13

156

One-step synthesis of graphene/polyallylamine-Au nanocomposites and their electrocatalysis toward oxygen reduction.  

PubMed

A simple, inexpensive, one-step synthesis of graphene/PAA-Au nanocomposites was achieved by using polyallylamine (PAA) as a reducing and stabilizing agent. The synthetic process was carried out only in aqueous solution, which is versatile and environmentally friendly. The resulting nanocomposites could be dispersed into water stably without any additional protection by polymeric or surfactant stabilizers. The products were further characterized by UV-visible absorption spectroscopy, transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR) and photoelectron spectroscopy (XPS). The results indicate that graphene sheets played an important role as a support material to increase the active area of Au nanoparticles (AuNPs). And the resulting graphene/PAA-Au nanocomposites film exhibited good electrocatalytical activity towards reduction of both H(2)O(2) and O(2), which showed potential application in electrochemical sensors. PMID:22284507

Zhang, Qixian; Ren, Qiaoqiao; Miao, Yuqing; Yuan, Junhua; Wang, Kaikai; Li, Fenghua; Han, Dongxue; Niu, Li

2012-01-30

157

In situ precipitation preparation of ZnO hollow spheres and their photocatalysis and gas-sensing properties  

NASA Astrophysics Data System (ADS)

ZnO hollow spheres were synthesized by in situ precipitation method in the presence of surfactant polyvinylpyrrolidone combined with subsequent calcination. The prepared ZnO was characterized using scanning electron microscopy, X-ray diffraction, high-resolution transmission electron microscopy. The results indicated that the prepared ZnO hollow spheres were well crystalline with wurtzite hexagonal phase. The formation mechanism of ZnO hollow spheres was discussed. Furthermore, the gas-sensing properties for detection of organic gas and photocatalytic activities for the degradation of rhodamine B (RhB) of the prepared ZnO hollow spheres were investigated. The results indicated that the prepared ZnO hollow spheres exhibited superior photocatalysis properties on decomposition of RhB and high gas-sensing properties for detection of acetone gas.

Jia, Xiaohua; Tian, Minggang; Liu, Yingying; Wu, Xiangyang; Song, Haojie

2015-03-01

158

Solar-Chemical Treatment of Groundwater Contaminated with Petroleum at Gas Station Sites: Ex Situ Remediation Using Solar\\/TiO2 Photocatalysis and Solar Photo-Fenton  

Microsoft Academic Search

Groundwater samples contaminated by BTEX (benzene, toluene, ethylbenzene, xylene isomers and TPHs (total petroleum hydrocarbons) were treated with advanced oxidation processes (AOPs), such as TiO2 photocatalysis and Fe\\/H2O2 exposed to solar light (37°N and 128°E) with an average intensity of 1.7 mW\\/cm at 365 nm. These AOP processes showed feasibility in the treatment of groundwater contaminated with BTEX, TPH and

II-HYOUNG CHO; YOUNG-GYU KIM; JAE-KYU YANG; Nae-Hyun Lee; Seung-Mok Lee

2006-01-01

159

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

160

Water  

NSDL National Science Digital Library

Water is an environmental chemistry Flash video designed to give students and educators an informative look into Water Treatment and Waste Water Treatment. It covers a variety of water and waste water treatment plants and processes including: Watersheds, Ozonation, Chlorination, Flocculation, Sand Filtration, Trickling Filters, Activated Sludge, and more. This program includes both live video and animations.~~~~

Dr. Frank Dunnivant

2008-02-20

161

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 ...

162

Computational Catalysis and Electrocatalysis  

E-print Network

Reactions are too slow to be useful... Catalyst-Reactants Catalysts speed up a chemical reaction without. Balbuena, Nanotechnology, 2009 #12;Predictions and challenges Graphene growth parallel to the (100) plane

163

Bifunctional AgCl/Ag composites for SERS monitoring and low temperature visible light photocatalysis degradation of pollutant  

NASA Astrophysics Data System (ADS)

With the assistance of Polyvinylpyrrolidone (PVP), AgCl/Ag composites were fabricated in N, N-Dimethylformamide (DMF) solvent via a photoactivated route. The size of AgCl particles was in the range of 500 nm to 1 ?m and the Ag particle's diameter was about 10-20 nm. Different from those core-shell structures reported before, the Ag nanoparticles were dispersed uniformly both on the surface and in the body of AgCl particles. The generation of such kind of composites was resulted from the reducing ability of DMF and light irradiation during the formation of AgCl particles. The as-obtained AgCl/Ag composites presented great activity for both surface-enhanced Raman scattering (SERS) detection and visible light photocatalytic degradation of organic dyes. Additionally, the AgCl/Ag composites could maintain high photocatalytic activity even though the ambient temperature was as low as 15 °C and recycle photocatalysis experiments indicated that the photocatalyst exhibited higher stability. Such kind of AgCl/Ag composites holds great potential for environmental monitoring devices and pollutant treatments.

Dong, Lihong; Zhu, Junyi; Xia, Guangqing

2014-12-01

164

Solar photo-Fenton using peroxymonosulfate for organic micropollutants removal from domestic wastewater: comparison with heterogeneous TiO? photocatalysis.  

PubMed

This work aims at decontaminating biologically treated domestic wastewater effluents from organic micropollutants by sulfate radical based (SO4(-)) homogeneous photo-Fenton involving peroxymonosulfate as an oxidant, ferrous iron (Fe(II)) as a catalyst and simulated solar irradiation as a light source. This oxidative system was evaluated by using several probe compounds belonging to pesticides (bifenthrin, mesotrione and clothianidin) and pharmaceuticals (diclofenac, sulfamethoxazole and carbamazepine) classes and its kinetic efficiency was compared to that to the well known UV-Vis/TiO2 heterogeneous photocatalysis. Except for carbamazepine, apparent kinetic rate constants were always 10 times higher in PMS/Fe(II)/UV-Vis than in TiO2/UV-Vis system and more than 70% of total organic carbon abatement was reached in less than one hour treatment. Hydroxyl radical (OH) and SO4(-) reactivity was investigated using mesotrione as a probe compound through by-products identification by liquid chromatography-high resolution-mass spectrometry and transformation pathways elucidation. In addition to two OH based transformation pathways, a specific SO4(-) transformation pathway which first involved degradation through one electron transfer oxidation processes followed by decarboxylation were probably responsible for mesotrione degradation kinetic improvement upon UV-Vis/PMS/Fe(II) system in comparison to UVVis/TiO2 system. PMID:25108605

Ahmed, Moussa Mahdi; Brienza, Monica; Goetz, Vincent; Chiron, Serge

2014-12-01

165

The highly efficient photocatalysts of Co/TiO2: Photogenerated charge-transfer properties and their applications in photocatalysis  

NASA Astrophysics Data System (ADS)

A convenient and simple sol-gel method has been developed for the synthesis of anatase TiO2 and Co-doped TiO2 nanoparticles. The samples were characterized by XRD, XPS, UV-vis DRS and it was found that the dopant ions replaced some of the crystal lattice titanium ions, existing in the form of Co2+. UV-vis DRS confirm that the obtained Co/TiO2 samples have an extended light absorption range compared with pure TiO2. Photocatalytic activities of the catalysts were assessed based on the degradation of single rhodamine B (RhB) and mixed dyes in aqueous solution in the present of visible light (? > 420 nm). With an optimal molar ratio of 1% (Co/Ti), the sample shows the highest rate photodegradation efficiency under the same experimental conditions. SPV was used to investigate photophysical mechanism of the visible light photocatalytic activity and revealed that there is an electronic interaction between the Co and TiO2, which plays a significant effect in improving the efficiency of photocatalysis.

Yue, Xinzheng; Jiang, Shang; Ni, Ling; Wang, Runwei; Qiu, Shilun; Zhang, Zongtao

2014-11-01

166

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

167

A new dielectric ta-C film coating of Ag-nanoparticle hybrids to enhance TiO2 photocatalysis  

NASA Astrophysics Data System (ADS)

We have demonstrated a novel method to enhance TiO2 photocatalysis by adopting a new ultrathin tetrahedral-amorphous-carbon (ta-C) film coating on Ag nanoparticles to create strong plasmonic near-field enhancement. The result shows that the decomposition rate of methylene blue on the Ag/10 Å ta-C/TiO2 composite photocatalyst is ten times faster than that on a TiO2 photocatalyst and three times faster than that on a Ag/TiO2 photocatalyst. This can be ascribed to the simultaneous realization of two competitive processes: one that excites the surface plasmons (SPs) of the ta-C-film/Ag-nanoparticle hybrid and provides a higher electric field near the ta-C/TiO2 interface compared to Ag nanoparticles alone, while the other takes advantage of the dense diamond-like ta-C layer to help reduce the transfer of photogenerated electrons from the conduction band of TiO2 to the metallic surface, since any electron transfer will suppress the excitation of SP modes in the metal nanoparticles.

Liu, Fanxin; Tang, Chaojun; Wang, Zhenlin; Sui, Chenghua; Ma, Hongtao

2014-03-01

168

Fabrication of Au/Graphene-Wrapped ZnO-Nanoparticle-Assembled Hollow Spheres with Effective Photoinduced Charge Transfer for Photocatalysis.  

PubMed

Heterostructures of gold-nanoparticle-decorated reduced-graphene-oxide (rGO)-wrapped ZnO hollow spheres (Au/rGO/ZnO) are synthesized using tetra-n-butylammonium bromide as a mediating agent. The structure of amorphous ZnO hollow spheres is found to be transformed from nanosheet- to nanoparticle-assembled hollow spheres (nPAHS) upon annealing at 500 °C. The ZnO nPAHS hybrids with Au/rGO are characterized using various techniques, including photoluminescence, steady-state absorbance, time-resolved photoluminescence, and photocatalysis. The charge-transfer time of ZnO nPAHS is found to be 87 ps, which is much shorter than that of a nanorod (128 ps), nanoparticle (150 ps), and nanowall (990 ps) due to its unique structure. The Au/rGO/ZnO hybrid shows a higher charge-transfer efficiency of 68.0% in comparison with rGO/ZnO (40.3%) and previously reported ZnO hybrids. The photocatalytic activities of the samples are evaluated by photodegrading methylene blue under black-light irradiation. The Au/rGO/ZnO exhibits excellent photocatalytic efficiency due to reduced electron-hole recombination, fast electron-transfer rate, and high charge-transfer efficiency. PMID:25629618

Khoa, Nguyen Tri; Kim, Soon Wook; Yoo, Dae-Hwang; Cho, Shinuk; Kim, Eui Jung; Hahn, Sung Hong

2015-02-18

169

THIN NANOPOROUS TITANIA FILMS ON THE ELECTRODELESS DISCHARGE LAMPS FOR PHOTOCATALYSIS  

E-print Network

. The photocatalytic activity of titania films was followed by decomposition of Rhodamine B in water, Electrodeless discharge lamp, Mono-chloroacetic acid, Rhodamine B, Nanoporous titania thin film, Transition

Cirkva, Vladimir

170

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

171

DOE Laboratory Catalysis Research Symposium - Abstracts  

SciTech Connect

The conference consisted of two sessions with the following subtopics: (1) Heterogeneous Session: Novel Catalytic Materials; Photocatalysis; Novel Processing Conditions; Metals and Sulfides; Nuclear Magnetic Resonance; Metal Oxides and Partial Oxidation; Electrocatalysis; and Automotive Catalysis. (2) Homogeneous Catalysis: H-Transfer and Alkane Functionalization; Biocatalysis; Oxidation and Photocatalysis; and Novel Medical, Methods, and Catalyzed Reactions.

Dunham, T.

1999-02-01

172

Water  

NSDL National Science Digital Library

Perhaps the single most critical element of the Earth system is water, the carrier and bearer of life that is inextricably woven into the fabric of the Earth system. Only on Earth does water occur in equilibrium ...

173

Pt@TiO2- Au nanoCORRUGATed STUCTURE for visible-light active photocatalysis  

NASA Astrophysics Data System (ADS)

In this paper, we design and fabricate a NanoFinger Plasmonic Structure (NFPS) utilized in water splitting for hydrogrn production by visible light irradiation. This structure can generate numerous hot electrons from localized surface plasmon resonance (LSPR) during visible light irradiation. Through this hot electrons transferred via titanium dioxide to platinum nanoparticles, hydrogen ions in water can be efficiently reducing into hydrogen, while hot holes left in gold oxidizing into oxygen. Experimental results demonstrated the photoelectrochemical signal can be enhanced by 1.96~2.09-fold in on-off test under visible light, indicating the possibility for high efficient hydrogen generation.

Peng, Yu-Hsuan; Chen, Chun-Sheng; Lin, Chun-ting; Tseng, Fan-Gang

2014-11-01

174

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

175

Water  

NSDL National Science Digital Library

This tutorial examines the importance of water to Earth's ecosystems. Topics include the sources and distribution of water, the water cycle, and how snow and rain occur. There is a discussion of the phases in which it can exist (solid, liquid, or vapor), and a description of how animals adapt to cold snowy environments in the winter. Examples include burrowing, hibernation, migration, and thick fur. A quiz and glossary are included.

176

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

177

Bio-inspired synthesis of Y2O3: Eu(3+) red nanophosphor for eco-friendly photocatalysis.  

PubMed

We report the synthesis of Y2O3: Eu(3+) (1-11mol%) nanoparticles (NPs) with different morphologies via eco-friendly, inexpensive and simple low temperature solution combustion method using Aloe Vera gel as fuel. The formation of different morphologies of Y2O3: Eu(3+) NPs were characterized by PXRD, SEM, TEM, HRTEM, UV-Visible and PL techniques. The PXRD data and Rietveld analysis confirms the formation of single phase Y2O3 with cubic crystal structure. The influence of Eu(3+) ion concentration on the morphology, UV-Visible absorption, PL emission and photocatalytic activity of Y2O3: Eu(3+) nanostructures were investigated. Y2O3: Eu(3+) NPs exhibit intense red emission with CIE chromaticity coordinates (0.50, 0.47) and correlated color temperature values at different excitation ranges from 1868 to 2600K. The control of Eu(3+) ion on Y2O3 matrix influences the photocatalytic decolorization of methylene blue (MB) as a model compound was evaluated under UVA light. Enhanced photocatalytic activity of conical shaped Y2O3: Eu(3+) (1mol%) was attributed to dopant concentration, crystallite size, textural properties and capability of reducing the electron-hole pair recombination. The trend of inhibitory effect in the presence of different radical scavengers followed the order SO4(2-)>Cl(-)>C2H5OH>HCO3(-)>CO3(2-). These findings show great promise of Y2O3: Eu(3+) NPs as a red phosphor in warm white LEDs as well as eco-friendly heterogeneous photocatalysis. PMID:25668696

Prasanna Kumar, J B; Ramgopal, G; Vidya, Y S; Anantharaju, K S; Daruka Prasad, B; Sharma, S C; Prashantha, S C; Premkumar, H B; Nagabhushana, H

2015-04-15

178

Water  

NSDL National Science Digital Library

This video segment from IdahoPTV's D4K shows us from where we get water, how it's stored and how powerful it can be. We learn how important it is to conserve the .3% of usable fresh water available on earth.

Idaho PTV

2011-10-06

179

Water  

NSDL National Science Digital Library

The same water that has existed on Earth for millions of years travels through a series of steps in a cycle from mountains to the sea, flows in and out of the cells in your body, and comprises 95% of the mass of a jellyfish. In short, water is the connect

J. Adam Frederick

2010-02-01

180

Water  

MedlinePLUS

... authorities have websites that include data on drinking water quality, including results of lead testing. Links to such data can be found on the EPA website: http://www.epa.gov/safewater/dwinfo.htm . ... with Elevated Lead in Tap Water---District of Columbia, 2004 . MMWR. April 2, 2004; ...

181

Photocatalysis on (CdS) x (ZnTe)1 - x solid solutions  

NASA Astrophysics Data System (ADS)

Photocatalytic properties of the surface of binary compounds (CdS, ZnTe) and solid solutions (CdS) x (ZnTe)1 - x formed on their basis are studied by means of potentiometry and chromatography. The values of forbidden gap ? E are calculated from the resulting UV spectra, according to which the components of the CdS-ZnTe system can display photocatalytic activity in the wavelength range of 364 to 670 nm. A scheme of a model setup for producing hydrogen from water is proposed using the authors' method.

Karpova, E. O.; Nagibina, I. Yu.; Makarova, A. S.

2015-01-01

182

On the role of localized surface plasmon resonance in UV-Vis light irradiated Au/TiO? photocatalysis systems: pros and cons.  

PubMed

The role of localized surface plasmon resonance (LSPR) in UV-Vis light irradiated Au/TiO2 photocatalysis systems has been investigated, and it is demonstrated experimentally for the first time that both pros and cons of LSPR exist simultaneously for this photocatalytic reaction. We have proved that when operating under mixed UV and green light irradiation, the LSPR injected hot electrons (from the Au nanoparticles to TiO2 under green light irradiation) may surmount the Schottky barrier (SB) formed between the Au nanoparticles and TiO2, and flow back into the TiO2. As a result, these electrons may compensate for and even surpass those transferred from TiO2 to the Au nanoparticles, thus accelerating the recombination of UV excited electron-hole pairs in TiO2. This is the negative effect of LSPR. On the other hand, more hot electrons existing on the surface of the Au nanoparticles due to LSPR would favor the photocatalytic reaction, which accompanied by the negative effect dominates the overall photocatalytic performance. The presented results reveal the multi-faceted essence of LSPR in Au/TiO2 structures, and is instructive for the application of metal-semiconductor composites in photocatalysis. Moreover, it is confirmed that the extent to which the above pros and cons of LSPR dominate the overall photocatalytic reaction depends on the intensity ratio of visible to UV light. PMID:25665512

Lin, Zhongjin; Wang, Xiaohong; Liu, Jun; Tian, Zunyi; Dai, Loucheng; He, Beibei; Han, Chao; Wu, Yigui; Zeng, Zhigang; Hu, Zhiyu

2015-03-01

183

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

184

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

185

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

186

Degradation, mineralization and antibiotic inactivation of amoxicillin by UV-A/TiO? photocatalysis.  

PubMed

The UV-A/TiO(2) photocatalytic decomposition of amoxicillin (AMX) in aqueous suspensions was investigated. Experiments were performed at antibiotic concentrations between 2.5 and 30 mg/L, eight commercially available TiO(2) catalysts at loadings between 100 and 750 mg/L, acidic or near-neutral conditions (pH 5 or 7.5) and two different matrices (ultrapure water and secondary treated effluent) at a photon flux of 8 × 10(-4) E/(L min). Of the various catalysts tested, Degussa P25 was highly active, i.e. complete AMX degradation and 93% mineralization could be achieved after 25 and 90 min of reaction, respectively at 10 mg/L AMX and 250 mg/L titania. In general, mineralization was slower than degradation due to the formation of stable transformation by-products. For the range of concentrations studied, initial degradation rates can be approached by a Langmuir-Hinshelwood kinetic model, while the reaction order with respect to AMX shifts from first to zeroth as initial concentration increases from 2.5 to 5 mg/L to higher values. Degradation in treated effluent was partly impeded compared to pure water due to the inherent presence of organic and inorganic constituents that compete for hydroxyl radicals. Although increasing solution pH from 5 to 7.5 had no effect on degradation, it retarded mineralization. The antibiotic activity of AMX prior to and after photocatalytic degradation was tested to three reference bacterial strains, namely Escherichia coli (ATCC 23716), Klebsiella pneumoniae (NCTC 5056) and Enterococcus faecalis (ATCC 14506). The first two were found to be highly resistant at AMX concentrations up to 25 mg/L, while the latter could partly be inactivated at lower AMX concentrations (i.e. 10 mg/L) and/or in the presence of photocatalytic by-products. PMID:22277347

Dimitrakopoulou, Despina; Rethemiotaki, Irene; Frontistis, Zacharias; Xekoukoulotakis, Nikolaos P; Venieri, Danae; Mantzavinos, Dionissios

2012-05-15

187

Remediation of 17-?-ethinylestradiol aqueous solution by photocatalysis and electrochemically-assisted photocatalysis using TiO2 and TiO2/WO3 electrodes irradiated by a solar simulator.  

PubMed

TiO2 and TiO2/WO3 electrodes, irradiated by a solar simulator in configurations for heterogeneous photocatalysis (HP) and electrochemically-assisted HP (EHP), were used to remediate aqueous solutions containing 10 mg L(-1) (34 ?mol L(-1)) of 17-?-ethinylestradiol (EE2), active component of most oral contraceptives. The photocatalysts consisted of 4.5 ?m thick porous films of TiO2 and TiO2/WO3 (molar ratio W/Ti of 12%) deposited on transparent electrodes from aqueous suspensions of TiO2 particles and WO3 precursors, followed by thermal treatment at 450 (°)C. First, an energy diagram was organized with photoelectrochemical and UV-Vis absorption spectroscopy data and revealed that EE2 could be directly oxidized by the photogenerated holes at the semiconductor surfaces, considering the relative HOMO level for EE2 and the semiconductor valence band edges. Also, for the irradiated hybrid photocatalyst, electrons in TiO2 should be transferred to WO3 conduction band, while holes move toward TiO2 valence band, improving charge separation. The remediated EE2 solutions were analyzed by fluorescence, HPLC and total organic carbon measurements. As expected from the energy diagram, both photocatalysts promoted the EE2 oxidation in HP configuration; after 4 h, the EE2 concentration decayed to 6.2 mg L(-1) (35% of EE2 removal) with irradiated TiO2 while TiO2/WO3 electrode resulted in 45% EE2 removal. A higher performance was achieved in EHP systems, when a Pt wire was introduced as a counter-electrode and the photoelectrodes were biased at +0.7 V; then, the EE2 removal corresponded to 48 and 54% for the TiO2 and TiO2/WO3, respectively. The hybrid TiO2/WO3, when compared to TiO2 electrode, exhibited enhanced sunlight harvesting and improved separation of photogenerated charge carriers, resulting in higher performance for removing this contaminant of emerging concern from aqueous solution. PMID:25238917

Oliveira, Haroldo G; Ferreira, Leticia H; Bertazzoli, Rodnei; Longo, Claudia

2015-04-01

188

Controlled synthesis and facets-dependent photocatalysis of TiO2 nanocrystals  

NASA Astrophysics Data System (ADS)

Titanium dioxide (TiO2) is a wide band gap semiconductor that has been extensively used in several environmental applications including degradation of organic hazardous chemicals, water splitting to generate hydrogen, dye sensitized solar cells, self cleaning agents, and pigments. Herein we demonstrate the synthesis of TiO2 nanocrystals (NCs) with the shapes of ellipsoids, rods, cuboids, and sheets with different exposed facets using a noncorrosive and nontoxic chemical (i.e. diethanolamine) as the shape controlling agent, unlike hydrofluoric acid commonly used. The TiO2 NCs of diverse shapes with different exposed facets were tested for photocatalytic hydroxyl radical (OH•) formation, which determines their photocatalytic behavior and the results were compared with the standard P-25 Degussa. The formation rate of OH• per specific surface area was found to be >6 fold higher for rod-shaped TiO2 NCs than that of commercial Degussa P25 catalyst. The highest photocatalytic activity of rod-shaped TiO2 NCs is ascribed to the unique chemical environment of {010} exposed facets which facilitates the electron/hole separation in presence of {101} facets.

Roy, Nitish; Park, Yohan; Sohn, Youngku; Pradhan, Debabrata

2015-04-01

189

Fe ion-implanted TiO2 thin film for efficient visible-light photocatalysis  

NASA Astrophysics Data System (ADS)

This work shows the application of metal ion-implantation to realize an efficient second-generation TiO2 photocatalyst. High fluence Fe+ ions were implanted into thin TiO2 films and subsequently annealed up to 550 °C. The ion-implantation process modified the TiO2 pure film, locally lowering its band-gap energy from 3.2 eV to 1.6-1.9 eV, making the material sensitive to visible light. The measured optical band-gap of 1.6-1.9 eV was associated with the presence of effective energy levels in the energy band structure of the titanium dioxide, due to implantation-induced defects. An accurate structural characterization was performed by Rutherford backscattering spectrometry, transmission electron microscopy, Raman spectroscopy, X-ray diffraction, and UV/VIS spectroscopy. The synthesized materials revealed a remarkable photocatalytic efficiency in the degradation of organic compounds in water under visible light irradiation, without the help of any thermal treatments. The photocatalytic activity has been correlated with the amount of defects induced by the ion-implantation process, clarifying the operative physical mechanism. These results can be fruitfully applied for environmental applications of TiO2.

Impellizzeri, G.; Scuderi, V.; Romano, L.; Sberna, P. M.; Arcadipane, E.; Sanz, R.; Scuderi, M.; Nicotra, G.; Bayle, M.; Carles, R.; Simone, F.; Privitera, V.

2014-11-01

190

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

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

191

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

192

On the role of localized surface plasmon resonance in UV-Vis light irradiated Au/TiO2 photocatalysis systems: pros and cons  

NASA Astrophysics Data System (ADS)

The role of localized surface plasmon resonance (LSPR) in UV-Vis light irradiated Au/TiO2 photocatalysis systems has been investigated, and it is demonstrated experimentally for the first time that both pros and cons of LSPR exist simultaneously for this photocatalytic reaction. We have proved that when operating under mixed UV and green light irradiation, the LSPR injected hot electrons (from the Au nanoparticles to TiO2 under green light irradiation) may surmount the Schottky barrier (SB) formed between the Au nanoparticles and TiO2, and flow back into the TiO2. As a result, these electrons may compensate for and even surpass those transferred from TiO2 to the Au nanoparticles, thus accelerating the recombination of UV excited electron-hole pairs in TiO2. This is the negative effect of LSPR. On the other hand, more hot electrons existing on the surface of the Au nanoparticles due to LSPR would favor the photocatalytic reaction, which accompanied by the negative effect dominates the overall photocatalytic performance. The presented results reveal the multi-faceted essence of LSPR in Au/TiO2 structures, and is instructive for the application of metal-semiconductor composites in photocatalysis. Moreover, it is confirmed that the extent to which the above pros and cons of LSPR dominate the overall photocatalytic reaction depends on the intensity ratio of visible to UV light.The role of localized surface plasmon resonance (LSPR) in UV-Vis light irradiated Au/TiO2 photocatalysis systems has been investigated, and it is demonstrated experimentally for the first time that both pros and cons of LSPR exist simultaneously for this photocatalytic reaction. We have proved that when operating under mixed UV and green light irradiation, the LSPR injected hot electrons (from the Au nanoparticles to TiO2 under green light irradiation) may surmount the Schottky barrier (SB) formed between the Au nanoparticles and TiO2, and flow back into the TiO2. As a result, these electrons may compensate for and even surpass those transferred from TiO2 to the Au nanoparticles, thus accelerating the recombination of UV excited electron-hole pairs in TiO2. This is the negative effect of LSPR. On the other hand, more hot electrons existing on the surface of the Au nanoparticles due to LSPR would favor the photocatalytic reaction, which accompanied by the negative effect dominates the overall photocatalytic performance. The presented results reveal the multi-faceted essence of LSPR in Au/TiO2 structures, and is instructive for the application of metal-semiconductor composites in photocatalysis. Moreover, it is confirmed that the extent to which the above pros and cons of LSPR dominate the overall photocatalytic reaction depends on the intensity ratio of visible to UV light. Electronic supplementary information (ESI) available: Detailed description of the calculation parameters. Additional I-V characteristics of bare TiO2 and the tip of CAFM probe. See DOI: 10.1039/c4nr06929c

Lin, Zhongjin; Wang, Xiaohong; Liu, Jun; Tian, Zunyi; Dai, Loucheng; He, Beibei; Han, Chao; Wu, Yigui; Zeng, Zhigang; Hu, Zhiyu

2015-02-01

193

A perfectly aligned 63 helical tubular cuprous bromide single crystal for selective photo-catalysis, luminescence and sensing of nitro-explosives.  

PubMed

A perfectly aligned 63 helical tubular cuprous bromide single crystal has been synthesized and characterized, which can selectively decompose negatively charged dyes of Methyl Orange (MO) and Kermes Red (KR), and the photocatalytic efficiency is higher than that of nanosized (?25 nm) TiO2 and ZnO. The direction and magnitude of the dipole moments as well as the band structure were calculated to reveal high photocatalytic efficiency. Moreover, luminescence studies indicate that the CuBr tube materials show very strong yellowish green emissions in the solid state and emulsion even at room temperature, and exhibit extremely high detection sensitivity towards nitro-explosives via fluorescence quenching. Detectable luminescence responses were observed at a very low concentration of 20 ppm with a high quenching efficiency of 94.90%. The results suggest that they may be promising multifunctional materials for photo-catalysis, luminescence and sensing of nitro-explosives. PMID:25601196

Yao, Ru-Xin; Hailili, Reshalaiti; Cui, Xin; Wang, Li; Zhang, Xian-Ming

2015-02-01

194

Electrochemical surface science twenty years later: Expeditions into the electrocatalysis of reactions at the core of artificial photosynthesis  

NASA Astrophysics Data System (ADS)

Surface science research fixated on phenomena and processes that transpire at the electrode-electrolyte interface has been pursued in the past. A considerable proportion of the earlier work was on materials and reactions pertinent to the operation of small-molecule fuel cells. The experimental approach integrated a handful of surface-sensitive physical-analytical methods with traditional electrochemical techniques, all harbored in a single environment-controlled electrochemistry-surface science apparatus (EC-SSA); the catalyst samples were typically precious noble metals constituted of well-defined single-crystal surfaces. More recently, attention has been diverted from fuel-to-energy generation to its converse, (solar) energy-to-fuel transformation; e.g., instead of water synthesis (from hydrogen and oxygen) in fuel cells, water decomposition (to hydrogen and oxygen) in artificial photosynthesis. The rigorous surface-science protocols remain unchanged but the experimental capabilities have been expanded by the addition of several characterization techniques, either as EC-SSA components or as stand-alone instruments. The present manuscript describes results selected from on-going studies of earth-abundant electrocatalysts for the reactions that underpin artificial photosynthesis: nickel-molybdenum alloys for the hydrogen evolution reaction, calcium birnessite as a heterogeneous analogue for the oxygen-evolving complex in natural photosynthesis, and single-crystalline copper in relation to the carbon dioxide reduction reaction.

Soriaga, Manuel P.; Baricuatro, Jack H.; Cummins, Kyle D.; Kim, Youn-Geun; Saadi, Fadl H.; Sun, Guofeng; McCrory, Charles C. L.; McKone, James R.; Velazquez, Jesus M.; Ferrer, Ivonne M.; Carim, Azhar I.; Javier, Alnald; Chmielowiec, Brian; Lacy, David C.; Gregoire, John M.; Sanabria-Chinchilla, Jean; Amashukeli, Xenia; Royea, William J.; Brunschwig, Bruce S.; Hemminger, John C.; Lewis, Nathan S.; Stickney, John L.

2015-01-01

195

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

196

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

197

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

198

Enhanced photocatalytic-electrolytic degradation of Reactive Brilliant Red X-3B in the presence of water jet cavitation.  

PubMed

Photocatalysis, electrolysis, water jet cavitation (WJC), alone and in combinations were applied to degrade an azo dye, Reactive Brilliant Red X-3B (X-3B). Experiments were conducted in a 4.0 L aqueous solution with different initial dye concentrations, TiO? dose, and solution pH. WJC substantially increased the photocatalytic, electrolytic and photocatalytic-electrolytic rates of the dye removal. The observed first-order rate of X-3B decolorization in the process of combined photocatalysis and electrolysis coupled with WJC was 1.6-2.9 times of that in the process of combined photocatalysis and electrolysis coupled with mechanical stirring. The rate enhancements may be attributed primarily to the reduced diffusion layer thickness on the electrodes and the deagglomeration of photocatalyst particles due to the chemical and physical effects of WJC. Under the conditions of 80 mg/L X-3B solution, 100 mg/L TiO? dose and solution pH 6.3, 97% and 71% of color and chemical oxygen demand (CODCr) were removed, respectively, within 90-min photocatalytic-electrolytic treatment coupled with WJC. During this process, azo groups and naphthalene, benzene and triazine structures of the dye can be destroyed. Industrial textile effluent was also investigated, and a positive synergistic effect between photocatalytic-electrolytic system and WJC was observed considering color removal. PMID:25453209

Wang, Xiaoning; Jia, Jinping; Wang, Yalin

2015-03-01

199

The nature of photocatalytic "water splitting" on silicon nanowires.  

PubMed

Silicon should be an ideal semiconductor material if it can be proven usable for photocatalytic water splitting, given its high natural abundance. Thus it is imperative to explore the possibility of water splitting by running photocatalysis on a silicon surface and to decode the mechanism behind it. It is reported that hydrogen gas can indeed be produced from Si nanowires when illuminated in water, but the reactions are not a real water-splitting process. Instead, the production of hydrogen gas on the Si nanowires occurs through the cleavage of Si?H bonds and the formation of Si?OH bonds, resulting in the low probability of generating oxygen. On the other hand, these two types of surface dangling bonds both extract photoexcited electrons, whose competition greatly impacts on carrier lifetime and reaction efficiency. Thus surface chemistry holds the key to achieving high efficiency in such a photocatalytic system. PMID:25565663

Liu, Dong; Li, Leilei; Gao, Yang; Wang, Chengming; Jiang, Jun; Xiong, Yujie

2015-03-01

200

Field performance test of an air-cleaner with photocatalysis-plasma synergistic reactors for practical and long-term use.  

PubMed

A practical and long-term usable air-cleaner based on the synergy of photocatalysis and plasma treatments has been developed. A field test of the air-cleaner was carried out in an office smoking room. The results were compared to previously reported laboratory test results. Even after a treatment of 12,000 cigarettes-worth of tobacco smoke, the air-cleaner maintained high-level air-purification activity (98.9% ± 0.1% and 88% ± 1% removal of the total suspended particulate (TSP) and total volatile organic compound (TVOC) concentrations, respectively) at single-pass conditions. Although the removal ratio of TSP concentrations was 98.6% ± 0.2%, the ratio of TVOC concentrations was 43.8% after a treatment of 21,900 cigarettes-worth of tobacco smoke in the field test. These results indicate the importance of suitable maintenance of the reactors in the air-cleaner during field use. PMID:25356565

Ochiai, Tsuyoshi; Ichihashi, Erina; Nishida, Naoki; Machida, Tadashi; Uchida, Yoshitsugu; Hayashi, Yuji; Morito, Yuko; Fujishima, Akira

2014-01-01

201

TiO2 incorporated in magnetic mesoporous SBA-15 by a facile inner-pore hydrolysis process toward enhanced adsorption-photocatalysis performances for As(III).  

PubMed

A facile inner-pore hydrolysis combining solvent evaporation method was used to decorate mesoporous silica, in which ?-Fe2O3 nanoparticles was preloaded onto mesoporous SBA-15 followed by decoration of TiO2 nanoparticles. This decoration process exploited the homogeneous dispersivity of ?-Fe2O3 and TiO2 nanoparticles in/on SBA-15 and inhibit aggregation of ?-Fe2O3 and TiO2 nanoparticles, which in turn leaded to a synergistic photocatalytic oxidation and adsorption of As(III). It was found that the prepared nanocomposites had mesoporous structure, large specific surface area, high pore volume and superparamagetism according to SEM/TEM, N2 adsorption-desorption isotherms, XRD and VSM analysis. Experimental results show that SBA-15/?-Fe2O3-TiO2 can oxidize As(III) to As(V) efficiently in the photocatalysis reaction. At the same time, As(V) is effectively removed through adsorption by the composites. In addition, with the treatment of alkali solution, As(V) can be easily desorbed from SBA-15/?-Fe2O3-TiO2. After reusage for 5 times, the composites still retain comparable catalysis and adsorption performance compared with that of first use, revealing the excellent stability of the composites. PMID:25792475

Yu, Lian; Yang, Xiaofang; Wang, Dongsheng

2015-06-15

202

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

PubMed

In the present study the degradation kinetics and mineralization of diclofenac (DCF) by the TiO(2) 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 (0.2-1.6gTiO(2)L(-1)) in a batch reactor system. A set of bioassays (Daphnia magna, Pseudokirchneriella subcapitata and Artemia salina) was performed to evaluate the potential detoxification of DCF. A pseudo-first-order kinetic model was found to fit well most of the experimental data, while at high initial DCF concentrations (40 and 80mgL(-1)) and at 1.6gTiO(2)L(-1) photocatalyst loading a second-order kinetic model was found to fit the data better. The toxicity of the treated DCF samples on D. magna and P. subcapitata varied during the oxidation, probably due to the formation of some intermediate products more toxic than DCF. Unicellular freshwater algae was found to be very sensitive to the treated samples as well as the results from D. magna test were consistent to those of algae tests. A. salina was not found to be sensitive under the investigated conditions. Finally, UV absorbance analysis were found to be an useful tool for a fast and easy to perform measurement to get preliminary information on the organic intermediates that are formed during oxidation and also on their disappearance rate. PMID:19081596

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

2009-03-01

203

Solutions Network Formulation Report. NASA's Potential Contributions for Using Solar Ultraviolet Radiation in Conjunction with Photocatalysis for Urban Air Pollution Mitigation and Increasing Air Quality  

NASA Technical Reports Server (NTRS)

This Candidate Solution is based on using NASA Earth science research on atmospheric ozone and aerosols data as a means to predict and evaluate the effectiveness of photocatalytically created surfaces (building materials like glass, tile and cement) for air pollution mitigation purposes. When these surfaces are exposed to near UV light, organic molecules, like air pollutants and smog precursors, will degrade into environmentally friendly compounds. U.S. EPA (Environmental Protection Agency) is responsible for forecasting daily air quality by using the Air Quality Index (AQI) that is provided by AIRNow. EPA is partnered with AIRNow and is responsible for calculating the AQI for five major air pollutants that are regulated by the Clean Air Act. In this Solution, UV irradiance data acquired from the satellite mission Aura and the OMI Surface UV algorithm will be used to help understand both the efficacy and efficiency of the photocatalytic decomposition process these surfaces facilitate, and their ability to reduce air pollutants. Prediction models that estimate photocatalytic function do not exist. NASA UV irradiance data will enable this capability, so that air quality agencies that are run by state and local officials can develop and implement programs that utilize photocatalysis for urban air pollution control and, enable them to make effective decisions about air pollution protection programs.

Underwood, Lauren; Ryan, Robert E.

2007-01-01

204

TiO2 nanotube arrays grown in ionic liquids: high-efficiency in photocatalysis and pore-widening  

SciTech Connect

Debris-free, long, well-separated TiO2 nanotube arrays were obtained using an ionic liquid (IL) as electrolyte. The high conductivity of IL resulted in fast pore widening and few contaminants from electrolyte decomposition leading to high photocatalytic efficiency in water splitting.

Li, Huaqing [ORNL; Qu, Jun [ORNL; Cui, Qingzhou [ORNL; Xu, Hanbing [ORNL; Luo, Huimin [ORNL; Chi, Miaofang [ORNL; Meisner, Roberta Ann [ORNL; Wang, Wei [ORNL; Dai, Sheng [ORNL

2011-01-01

205

Disinfection of urban wastewater by solar driven and UV lamp - TiO? photocatalysis: effect on a multi drug resistant Escherichia coli strain.  

PubMed

The effect of TiO? photocatalysis on the inactivation of an antibiotic resistant Escherichia coli strain selected from an urban wastewater treatment plant (UWWTP) effluent was investigated. Different light sources including a 250 W wide spectrum lamp, a 125 W UV-A lamp and solar radiation, as well as, photocatalysts loadings (TiO? Degussa P25) in the range from 0.05 to 2.00 g TiO? L(-1) were evaluated. The higher efficiency (total bacterial inactivation after 10 min of irradiation) was observed in the absence of TiO? when the wastewater was irradiated using the 250 W lamp. In the presence of TiO? a decreasing inactivation trend was observed (99.76% and 72.22% inactivation after 10 min irradiation at 0.10 and 2.00 g TiO? L(-1) respectively). Under solar simulated conditions the highest inactivation efficiency (93.17%) after 10 min of irradiation was achieved at the lower photocatalyst loading (0.05 g TiO? L(-1)). The concept of "reactor optical thickness" was introduced to explain the rates of disinfection observed. The optimum photocatalyst loading estimated by radiation absorption-scattering modeling was found to be 0.1 g TiO? L(-1) for all lamps. The difference between experimental tests and modeling may be due to TiO? particles aggregation. Comparative kinetic tests between solar and solar simulated photocatalytic (SSP) processes using 0.05 g TiO? L(-1) in suspension showed a quite similar inactivation behavior up to 30 min of irradiation, but only the SSP process resulted in a total inactivation of bacteria after 60 min of exposure. Antibiotic resistant test (Kirby-Bauer) on survived colonies showed that the SSP and SP processes affected in different ways the resistance of E. coli strain to the target antibiotics. PMID:24525064

Rizzo, L; Della Sala, A; Fiorentino, A; Li Puma, G

2014-04-15

206

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

207

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

208

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

209

Visible-Light Responsive Catalysts Using Quantum Dot-Modified TiO2 for Air and Water Purification  

NASA Technical Reports Server (NTRS)

Photocatalysis, the oxidation or reduction of contaminants by light-activated catalysts, utilizing titanium dioxide (TiO2) as the catalytic substrate has been widely studied for trace contaminant control in both air and water applications. The interest in this process is due primarily to its low energy consumption and capacity for catalyst regeneration. Titanium dioxide requires ultraviolet light for activation due to its relatively large band gap energy of 3.2 eV. Traditionally, Hg-vapor fluorescent light sources are used in PCO reactors; however, the use of mercury precludes the use of this PCO technology in a spaceflight environment due to concerns over crew Hg exposure.

Coutts, Janelle L.; Hintze, Paul E.; Clausen, Christian A.; Richards, Jeffrey T.

2014-01-01

210

Large-Scale, Three–Dimensional, Free–Standing, and Mesoporous Metal Oxide Networks for High–Performance Photocatalysis  

PubMed Central

Mesoporous nanostructures represent a unique class of photocatalysts with many applications, including splitting of water, degradation of organic contaminants, and reduction of carbon dioxide. In this work, we report a general Lewis acid catalytic template route for the high–yield producing single– and multi–component large–scale three–dimensional (3D) mesoporous metal oxide networks. The large-scale 3D mesoporous metal oxide networks possess large macroscopic scale (millimeter–sized) and mesoporous nanostructure with huge pore volume and large surface exposure area. This method also can be used for the synthesis of large–scale 3D macro/mesoporous hierarchical porous materials and noble metal nanoparticles loaded 3D mesoporous networks. Photocatalytic degradation of Azo dyes demonstrated that the large–scale 3D mesoporous metal oxide networks enable high photocatalytic activity. The present synthetic method can serve as the new design concept for functional 3D mesoporous nanomaterials. PMID:23857595

Bai, Hua; Li, Xinshi; Hu, Chao; Zhang, Xuan; Li, Junfang; Yan, Yan; Xi, Guangcheng

2013-01-01

211

Daylight photocatalysis performance of biomorphic CeO{sub 2} hollow fibers prepared with lens cleaning paper as biotemplate  

SciTech Connect

Highlights: ? A novel, simple and eco-friendly approach for hierarchical, biomorphic CeO{sub 2} hollow fibers with mesoporous tube walls is presented by using paper as template. ? The biomorphic CeO{sub 2} fibers was composed of nanosheets with bimodal pore-size mesoporous distribution and exhibited high light-harvesting under sunlight irradiation. ? The CeO{sub 2} microfibers biomimicking the natural plant structures have promising application for photodegradation of organic pollutants in water. -- Abstract: Hierarchical, biomorphic CeO{sub 2} hollow fibers with mesoporous tube walls have been fabricated using lens cleaning paper as biotemplates. After sintered at 550 °C in air, the cellulosic fibers of paper were converted into micro-tubes composing of CeO{sub 2} crystallites with grain size about 8 nm. The photocatalytic activity of the CeO{sub 2} fibers was evaluated by photodegradation efficiency of methylene blue in aqueous solution under daylight irradiation. The characterized results show that the CeO{sub 2} fibers faithfully replicated micro-fibrous structure derived from original template and possessed dramatic enhanced photocatalytic activity compared with bulk CeO{sub 2}. This simple biotemplate method provides a cost-effective and eco-friendly route to obtain high performance photocatalysts.

Qian, Junchao; Chen, Feng [Department of Material Science and Engineering, Jiangsu University, 212013 Zhenjiang (China)] [Department of Material Science and Engineering, Jiangsu University, 212013 Zhenjiang (China); Wang, Fang; Zhao, Xiaobing [Department of Materials Science and Engineering, Changzhou University, 213164 Changzhou (China)] [Department of Materials Science and Engineering, Changzhou University, 213164 Changzhou (China); Chen, Zhigang, E-mail: ziyou1900@gmail.com [Department of Material Science and Engineering, Jiangsu University, 212013 Zhenjiang (China) [Department of Material Science and Engineering, Jiangsu University, 212013 Zhenjiang (China); Jiangsu Key Laboratory for Environment Functional Materials, 215009 Suzhou University of Science and Technology, Suzhou (China); State Key laboratory of Crystal Material, Shandong University, 250100 Jinan (China)

2012-08-15

212

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

213

The design, synthesis and fabrication of electrospun titanium dioxide nanomaterials for use in greener chemical transformations and photocatalysis  

NASA Astrophysics Data System (ADS)

Electrospun TiO2 nanofibers present a unique class of active materials with optimized photoactivity and cost efficiency due to ease of synthesis and fabrication in bulk. The high aspect ratios for these nanostructured materials shorten the transportation length of electrons and holes from the crystal interface to the surface, thus accelerating their migration to the surface active sites. Additionally, the increased surface areas and high porosity ensures maximum adsorption of the reaction intermediates on the TiO2 surface, and high diffusion co-efficient within the material. The primary goal of this dissertation is to develop TiO2 nanofibers as an efficient and cost-effective catalyst for practical and multi-purpose application in greener chemical transformations and environmental remediation from organic pollutants in waste-waters. To achieve this, the surface, crystal and electronic structures of electrospun TiO2 will be optimized to allow for visible light-enhanced photodegradation processes. Pd nanoparticles of between 2-5 nm were successfully stabilized on the surface of electrospun nanofibers which had diameters between 150 ± 50 nm. The new catalyst was found to have increased surface area and improved catalytic functions compared to commercially available materials or other Pd-TiO2 catalysts produced by different modes of synthesis. The activity and selectivity of 0.05 mol% Pd-TiO2 catalyst in the Heck reaction has been investigated with a careful look into the nature of starting materials and products under varying conditions of temperature, solvent and base. The catalyst was found to be highly active under air atmosphere with reaction temperatures of up to 160°C. Optimized reaction conditions resulted in a 98% yield of trans-stilbene for the iodobenzene-styrene system with a TOF value of 7.85 min-1. The surface properties of TiO2 nanofibers were explored for the in-situ and ex-situ nucleation and growth of group VIII metal nanoparticles. The nanoparticles were effectively anchored on the numerous pores on the TiO2 surface that acted as seeding grounds for the control of nanoparticle growth. The semiconductor nature of these TiO2-based catalysts enabled UV/visible light enhanced generation of reactive O2 species for the degradation of rhodamine B. The photodegradation followed first order kinetics with a rate constant of 0.0158 min-1.

Obuya, Emilly Akinyi

214

Development of solar-driven electrochemical and photocatalytic water treatment system using a boron-doped diamond electrode and TiO2 photocatalyst.  

PubMed

A high-performance, environmentally friendly water treatment system was developed. The system consists mainly of an electrochemical and a photocatalytic oxidation unit, with a boron-doped diamond (BDD) electrode and TiO(2) photocatalyst, respectively. All electric power for the mechanical systems and the electrolysis was able to be provided by photovoltaic cells. Thus, this system is totally driven by solar energy. The treatment ability of the electrolysis and photocatalysis units was investigated by phenol degradation kinetics. An observed rate constant of 5.1 x 10(-3)dm(3)cm(-2)h(-1) was calculated by pseudo-first-order kinetic analysis for the electrolysis, and a Langmuir-Hinshelwood rate constant of 5.6 microM(-1)min(-1) was calculated by kinetic analysis of the photocatalysis. According to previous reports, these values are sufficient for the mineralization of phenol. In a treatment test of river water samples, large amounts of chemical and biological contaminants were totally wet-incinerated by the system. This system could provide 12L/day of drinking water from the Tama River using only solar energy. Therefore, this system may be useful for supplying drinking water during a disaster. PMID:19863989

Ochiai, Tsuyoshi; Nakata, Kazuya; Murakami, Taketoshi; Fujishima, Akira; Yao, Yanyan; Tryk, Donald A; Kubota, Yoshinobu

2010-02-01

215

Ga4B2O9: An Efficient Borate Photocatalyst for Overall Water Splitting without Cocatalyst.  

PubMed

Borates are well-known candidates for optical materials, but their potentials in photocatalysis are rarely studied. Ga(3+)-containing oxides or sulfides are good candidates for photocatalysis applications because the unoccupied 4s orbitals of Ga usually contribute to the bottom of the conducting band. It is therefore anticipated that Ga4B2O9 might be a promising photocatalyst because of its high Ga/B ratio and three-dimensional network. Various synthetic methods, including hydrothermal (HY), sol-gel (SG), and high-temperature solid-state reaction (HTSSR), were employed to prepare crystalline Ga4B2O9. The so-obtained HY-Ga4B2O9 are micrometer single crystals but do not show any UV-light activity unless modified by Pt loading. The problem is the fast recombination of photoexcitons. Interestingly, the samples obtained by SG and HTSSR methods both possess a fine micromorphology composed of well-crystalline nanometer strips. Therefore, the excited e(-) and h(+) can move to the surface easily. Both samples exhibit excellent intrinsic UV-light activities for pure water splitting without the assistance of any cocatalyst (47 and 118 ?mol/h/g for H2 evolution and 22 and 58 ?mol/h/g for O2 evolution, respectively), while there is no detectable activity for P25 (nanoparticles of TiO2 with a specific surface area of 69 m(2)/g) under the same conditions. PMID:25714488

Wang, Guangjia; Jing, Yan; Ju, Jing; Yang, Dingfeng; Yang, Jia; Gao, Wenliang; Cong, Rihong; Yang, Tao

2015-03-16

216

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

217

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

218

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

219

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

220

Enhanced Reduced Nicotinamide Adenine Dinucleotide electrocatalysis onto multi-walled carbon nanotubes-decorated gold nanoparticles and their use in hybrid biofuel cell  

NASA Astrophysics Data System (ADS)

We report the preparation of Au nanoparticles synthetized by different protocols and supported on the surface of multi-walled carbon nanotubes containing different functional groups, focusing on their electrochemical performance towards NADH oxidation, ethanol bioelectrocatalysis, and ethanol/O2 biofuel cell. We describe four different synthesis protocols: microwave-assisted heating, water-in-oil, and dendrimer-encapsulated nanoparticles using acid or thiol species in the extraction step. The physical characterization of the metallic nanoparticles indicated that both the synthetic protocol as well as the type of functional groups on the carbon nanotubes affect the final particle size (varying from 13.4 to 2.4 nm) and their distribution onto the carbon surface. Moreover, the electrochemical data indicated that these two factors also influence their performance toward the electrooxidation of NADH. We observed that the samples containing Au nanoparticles with smaller size leads to higher catalytic currents and also shifts the oxidation potential of the targeted reaction, which varied from 0.13 to -0.06 V vs Ag/AgCl. Ethanol/O2 biofuel cell tests indicated that the hybrid bioelectrodes containing smaller and better distributed Au nanoparticles on the surface of carbon nanotubes generates higher power output, confirming that the electrochemical regeneration of NAD+ plays an important role in the overall biofuel cell performance.

Aquino Neto, S.; Almeida, T. S.; Belnap, D. M.; Minteer, S. D.; De Andrade, A. R.

2015-01-01

221

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

222

Ru dye functionalized Au-SiO2@TiO2 and Au/Pt-SiO2@TiO2 nanoassemblies for surface-plasmon-induced visible light photocatalysis.  

PubMed

The most commonly used material in photocatalysis is TiO2. Since TiO2 absorbs only UV-light, photosensitizers are used to extend these catalysts' absorption properties into the Vis/NIR spectral range. In this work we merge the commonly used approach of dye sensitization with the only recently developed approach of functionalizing the catalyst with plasmonically active metal nanoparticles in order to achieve synergistic effects between these two types of visible light sensitization. To this end SiO2@TiO2 nanostructures are functionalized with gold nanoparticles or a combination of gold/platinum nanoparticles loaded with Ru dyes and thoroughly characterized by means of transmission electron microscopy (TEM) and scanning electron microscopy (SEM) imaging as well as energy dispersive X-ray spectroscopy (EDX), UV/VIS and surface enhanced resonance Raman scattering (SERRS) spectroscopy. The photocatalytic performance is tested by applying the benchmark experiment of methylene blue degradation. Spectroscopic investigations and electron microscopy proof the successful synthesis of the envisioned structure. The photocatalytic activity of the nanostructures shows up to 52% higher first order rate constants compared to the corresponding nanostructures without further dye functionalization. PMID:24594039

Theil, Frank; Dellith, Andrea; Dellith, Jan; Undisz, Andreas; Csáki, Andrea; Fritzsche, Wolfgang; Popp, Jürgen; Rettenmayr, Markus; Dietzek, Benjamin

2014-05-01

223

Effect of water composition on TiO2 photocatalytic removal of endocrine disrupting compounds (EDCs) and estrogenic activity from secondary effluent.  

PubMed

The effect of inorganic ions and dissolved organic matter (DOM) on the TiO(2) photocatalytic removal of estrogenic activity from secondary effluents of municipal wastewater treatment plants was investigated. The presence of HPO(4)(2-), NH(4)(+), and HCO(3)(-) resulted in a significantly negative impact on the photocatalytic removal of estrogenic activity from synthetic water due to their strong adsorption on the surface of TiO(2). However, only a weak impact was noted during photocatalytic removal of estrogenic activity from secondary effluent with these ions added, since the presence of DOM in real wastewater played a more important role in inhibiting photocatalytic removal of estrogenic activity than inorganic ions. By investigating the effect of different DOM fractions on photocatalytic removal of estrogenic activity, polar compounds (PC) were found to cause a temporary increase in estrogenic activity during TiO(2) photocatalysis. Fluorescence spectroscopy and molecular weight (MW) analysis on secondary effluent spiked with PC during TiO(2) photocatalysis suggest that large MW organic matter (>4.5kDa) in secondary effluent, such as humic/fulvic acid, not only could play an important role in inhibiting photocatalytic removal of estrogenic activity but also is responsible for the temporary increase in estrogenic activity during the same process. PMID:22436342

Zhang, Wenlong; Li, Yi; Su, Yaling; Mao, Kai; Wang, Qing

2012-05-15

224

Achieving solar overall water splitting with hybrid photosystems of photosystem II and artificial photocatalysts.  

PubMed

Solar overall water splitting is a promising sustainable approach for solar-to-chemical energy conversion, which harnesses solar irradiation to oxidize water to oxygen and reduce the protons to hydrogen. The water oxidation step is vital but difficult to achieve through inorganic photocatalysis. However, nature offers an efficient light-driven water-oxidizing enzyme, photosystem II (PSII). Here we report an overall water splitting natural-artificial hybrid system, in which the plant PSII and inorganic photocatalysts (for example, Ru/SrTiO3:Rh), coupled with an inorganic electron shuttle [Fe(CN)6(3-)/Fe(CN)6(4-)], are integrated and dispersed in aqueous solutions. The activity of this hybrid photosystem reaches to around 2,489 mol H2 (mol PSII)(-1) h(-1) under visible light irradiation, and solar overall water splitting is also achieved under solar irradiation outdoors. The optical imaging shows that the hybrid photosystems are constructed through the self-assembly of PSII adhered onto the inorganic photocatalyst surface. Our work may provide a prototype of natural-artificial hybrids for developing autonomous solar water splitting system. PMID:25115942

Wang, Wangyin; Chen, Jun; Li, Can; Tian, Wenming

2014-01-01

225

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

226

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

227

Functionalization and electrocatalysis on carbon nanofibers  

NASA Astrophysics Data System (ADS)

Nanoscale hybrid materials such as metal nanoparticles dispersed on nanostructured carbons are promising for use as electrocatalysts due to their chemical and physical properties. Vertically aligned carbon nanofibers (VACNFs) have a unique structure that exposes large amounts of graphitic edge-plane along the sidewalls, suggesting that hybrid VACNF-nanoparticle structures may have particularly good electrochemical response for electrocatalytic reactions. As with other carbon materials, the surface of VACNFs is not highly selective, but the high reactivity of the graphitic edge-plane sites allows for chemical modification with functional organic monolayers, avoiding the need for harsh oxidation techniques. The use of molecular functionalization to interface VACNFs with catalytic metal particles was investigated using two different growth techniques: electroless deposition and pulsed electrochemical deposition. Deposited particles are demonstrated to be catalytically active, despite the presence of the molecular layer. The presence of graphitic edge-plane is found to be important for electrochemical nucleation. Evaluation of the catalytic behavior of this hybrid system using the methanol oxidation reaction as a model system reveals differences in initial catalytic activity and long-term stability of nanoparticles produced by the two growth methods. Development of the electrochemical deposition method demonstrates that nucleation and growth can be controlled by the use of multiple-pulse sequences. This work provides insights into the use of molecular systems for chemical selectivity and the importance of edge-plane sites in catalytic activity of carbon-based hybrid nanostructures.

Hogendoorn, Stephanie Ruth

228

Electrocatalysis in proteins, nucleic acids and carbohydrates.  

PubMed

The ability of proteins to catalyze hydrogen evolution has been known for more than 80 years, but the poorly developed d.c. polarographic "pre-sodium wave" was of little analytical use. Recently, we have shown that by using constant current chronopotentiometric stripping analysis, proteins produce a well-developed peak H at hanging mercury drop and solid amalgam electrodes. Peak H sensitively reflects changes in protein structures due to protein denaturation, single amino acid exchange, etc. at the picomole level. Unmodified DNA and RNA do not yield such a peak, but they produce electrocatalytic voltammetric signals after modification with osmium tetroxide complexes with nitrogen ligands [Os(VIII)L], binding covalently to pyrimidine bases in nucleic acids. Recently, it has been shown that six-valent [Os(VI)L] complexes bind to 1,2-diols in polysaccharides and oligosaccharides, producing voltammetric responses similar to those of DNA-Os(VIII)L adducts. Electrocatalytic peaks produced by Os-modified nucleic acids, proteins (reaction with tryptophan residues) and carbohydrates are due to the catalytic hydrogen evolution, allowing determination of oligomers at the picomolar level. PMID:22287069

Pale?ek, Emil; Bartošík, Martin; Ostatná, Veronika; Trefulka, Mojmír

2012-02-01

229

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

230

Water Resources Water Quality and Water Treatment  

E-print Network

Water Resources TD 603 Lecture 1: Water Quality and Water Treatment CTARA Indian Institute of Technology, Bombay 2nd November, 2011 #12;OVERVIEW Water Quality WATER TREATMENT PLANTS WATER TREATMENT PLANTS WATER TREATMENT PLANTS WATER TRE OVERVIEW OF THE LECTURE 1. Water Distribution Schemes Hand Pump

Sohoni, Milind

231

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)...

232

Turbid water Clear water  

E-print Network

Turbid water Clear water pixel position cameraresponsecameraresponse pixel position ABSTRACT: A new the backscatter component resulting in enhanced performance in turbid waters. The system is expected to provide-submerged mines in turbid coastal waters. To extract high resolution bathymetric information optically from turbid

Jaffe, Jules

233

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.

2012-06-26

234

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

235

Evaluation of the Role of Water in the H2 Bond Formation by Ni(II)-based Electrocatalysts  

SciTech Connect

We investigate the role of water in the H-H bond formation by a family of nickel molecular catalysts that exhibit high rates for H2 production in acetonitrile solvent. A key feature leading to the high reactivity is the Lewis acidity of the Ni(II) center and pendant amines in the diphosphine ligand that function as Lewis bases, facilitating H-H bond formation or cleavage. Significant increases in the rate of H2 production have been reported in the presence of added water. Our calculations show that molecular water can displace an acetonitrile solvent molecule in the first solvation shell of the metal. One or two water molecules can also participate in shuttling a proton that can combine with a metal hydride to form the H-H bond. However the participation of the water molecules does not lower the barrier to H-H bond formation. Thus these calculations suggest that the rate increase due to water in these electrocatalysts is not associated with the elementary step of H-H bond formation or cleavage, but rather with the proton delivery steps. We attribute the higher barrier in the H-H bond formation in the presence of water to a decrease in direct interaction between the protic and hydridic hydrogen atoms forced by the water molecules. 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, Office of Basic Energy Sciences. Computational resources were provided at W. R. Wiley Environmental Molecular Science Laboratory - Pacific Northwest National Laboratory, the National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory, and the Jaguar supercomputer at Oak Ridge National Laboratory.

Ho, Ming-Hsun; Raugei, Simone; Rousseau, Roger J.; Dupuis, Michel; Bullock, R. Morris

2013-07-17

236

Heterogeneous photocatalysis: enhanced H/sub 2/ production in TiO/sub 2/ dispersions under irradiation. The effect of Mg promoter at the semiconductor interface  

SciTech Connect

Promoter action in semiconductors was studied by using Mg/sup 2 +/ doping of TiO/sub 2/ powders as a model system. This paper describes a novel series of Pt-Mg/sup 2 +/-TiO/sub 2/ catalysts. The catalytic properties of these novel catalysts were determined in relation to their efficiency in water-splitting processes under UV irradiation. The most efficient catalysts range up to 4 times in activity over the catalysts without Mg/sup 2 +/. A proportionality is observed for the activity of the catalyst with magnesium loading reaching a plateau at 1-2%. 20 references, 7 figures, 1 table.

Kiwi, J.; Graetzel, M.

1986-02-13

237

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.

Regina Bale

2012-07-17

238

Preparation and Photocatalysis of Schlumbergera bridgesii-Like CdS Modified One-Dimensional TiO2 Nanowires on Zeolite  

NASA Astrophysics Data System (ADS)

In recent years, composite semiconductor photocatalytic materials have received significant attention as a novel type of materials and technical means. So in this work, CdS-modified TiO2 nanowires are fabricated on natural zeolite by simple sol-gel and hydrothermal synthesis method. This novel composite semiconductor photocatalytic material has almost solved the shortcomings of pure TiO2, such as easy cohesion, low utilization rate, and exceedingly weak photocatalytic activities under visible light. The degradation efficiency of methylene blue dye in water is near to 90% with CdS-modified TiO2 nanowires/zeolite composite materials after 60 min under visible light, which indicated its huge potential application in wastewater treatment.

Liu, Zhichao; Liu, Zhifeng; Cui, Ting; Zhang, Jing; Zhao, Yufeng; Han, Jianhua; Guo, Keying; Domenico, Caputo

2015-02-01

239

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

240

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

241

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

242

Water oxidation by electrodeposited cobalt oxides--role of anions and redox-inert cations in structure and function of the amorphous catalyst.  

PubMed

For the production of nonfossil fuels, water oxidation by inexpensive cobalt-based catalysts is of high interest. Films for the electrocatalysis of water oxidation were obtained by oxidative self-assembly (electrodeposition) from aqueous solutions containing, apart from Co, either K, Li or Ca with either a phosphate, acetate or chloride anion. X-ray absorption spectroscopy (XAS) at the Co K-edge revealed clusters of edge-sharing CoO(6) octahedra in all films, but the size or structural disorder of the Co-oxido clusters differed. Whereas potassium binding is largely unspecific, CaCo(3) O(4) cubanes, which resemble the CaMn(3) O(4) cubane of the biological catalyst in oxygenic photosynthesis, may form, as suggested by XAS at the Ca K-edge. Cyclic voltammograms in a potassium phosphate buffer at pH?7 revealed that no specific combination of anions and redox-inactive cations is required for catalytic water oxidation. However, the anion type modulates not only the size (or order) of the Co-oxido clusters, but also electrodeposition rates, redox potentials, the capacity for oxidative charging, and catalytic currents. On these grounds, structure-activity relations are discussed. PMID:22323319

Risch, Marcel; Klingan, Katharina; Ringleb, Franziska; Chernev, Petko; Zaharieva, Ivelina; Fischer, Anna; Dau, Holger

2012-03-12

243

Inactivation of Amphidinium sp. in ballast waters using UV/Ag-TiO2+O3 advanced oxidation treatment.  

PubMed

Ballast water poses a biological threat to the world's waterways by transferring aquatic species from one body of water to another. This study investigates the use of combined ultraviolet (UV)/Ag-TiO(2)+ozone (O(3)) processes for treating ballast water using Amphidinium sp. as an indicator microorganism. Sufficient Amphidinium sp. cells in ballast waters can be inactivated using O(3) alone, UV irradiation alone (with or without an Ag-TiO(2) coating), and combined treatments. For the low inactivation ratio (<40%) regime, the effects of ozonation and photocatalysis were observed to be cumulative. The combined UV/Ag-TiO(2)+O(3) treatment produced excess hydroxyl radicals and total residual oxidants (TROs), and readily damaged cell membranes to release intracellular substances. The comparison tests revealed that the combined treatments synergistically inactivate Escherichia coli in ballast waters. However, the combined process did not synergistically inactivate Amphidinium sp. cells. Inactivating different aqua species in ballast waters needs distinct treatment methods and dosages. PMID:21890347

Wu, Donghai; You, Hong; Zhang, Ran; Chen, Chuan; Lee, Duu-Jong

2011-11-01

244

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

245

UNL WATER CENTER WATER CURRENT  

E-print Network

INSIDE UNL WATER CENTER WATER CURRENT PROTECTING NEBRASKA'S WATER RESOURCES THROUGH RESEARCH.....................Meet the Faculty 4.....................GuestColumn 5.....................WaterSupplySecurity 7...................Nebraska Depletions Plan 10 ..................Water News Briefs 11 ..................Calendar 12

Nebraska-Lincoln, University of

246

UNL WATER CENTER WATER CURRENT  

E-print Network

INSIDE UNL WATER CENTER WATER CURRENT PROTECTING NEBRASKA'S WATER RESOURCES THROUGH RESEARCH................ Guest Column 10..............Water News Briefs 11..............Calendar 12..............Free Lectures Continue Summer Water/Natural Resources Tour Examines Republican River Issues by Steve Ress This summer

Nebraska-Lincoln, University of

247

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

248

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

249

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

250

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

251

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 ...

252

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

253

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.

254

Potable water from waste water  

Microsoft Academic Search

The idea of obtaining potable water from waste water is a psychologically difficult one for many people to accept. The tendency is to think that waste water is dirty and cannot be converted to clean water. This book describes significant advances in waste water treatment technology which make possible the control and\\/or removal of conventional pollutants, thus making potable water

Gillies

1981-01-01

255

UNL WATER CENTER WATER CURRENT  

E-print Network

INSIDE UNL WATER CENTER WATER CURRENT PROTECTING NEBRASKA'S WATER RESOURCES THROUGH RESEARCHGroundwaterRecharge 6-7 ............ NebraskaWaterMarketingPolicyChoices 10 .............Water News Briefs 11 sites visited on July's water and natural resources tour (photo: Kyle Hoagland). (continued on page 9

Nebraska-Lincoln, University of

256

water intake Water sampling site  

E-print Network

x Drinking water intake WWTP discharge WWTP Water sampling site Reference MICROPOLLUTANT PLUME at WWTP discharge · Conductivity may be used to predict concentrations of waste water derived MPs downstream, a drinking water plant pumps lake water (ca. 100'000 m3 /day) for potable water (sand filter

257

UNL WATER CENTER WATER CURRENT  

E-print Network

INSIDE UNL WATER CENTER WATER CURRENT PROTECTING NEBRASKAíS WATER RESOURCES THROUGH RESEARCH the Faculty 4................ Guest Column 5................ Clean Water Act 6................ Water News in Empty Hog Barns by Steve Ress, UNL Water Center Jim Rosowski sees potential for a freshwater farming

Nebraska-Lincoln, University of

258

Special Topics in Water Science (Water Pollution)  

MedlinePLUS

... Basics Water Properties Water Cycle Surface Water Groundwater Water Quality Water Use Activities Photos Q&A Teachers Contact ... explore other water-science topic areas, such as water quality, urbanization and water, saline water, watersheds, runoff, and ...

259

Selectivity in photocatalysis by particulate semiconductors  

Microsoft Academic Search

TiO2, Fe2O3, CuO, ZnO, ZnS, Nb2O5, MoO3, CdO, CdS, Sb2O3, CeO2, HgO, Pb2O3, PbO2 and Bi2O3 microparticles exhibit band gap excitation with UV-A light but they are selective to photodegrade phenols. While TiO2 anatase and ZnO photocatalyze the degradation of phenol, o-aminophenol, m-aminophenol, p-aminophenol, o-chlorophenol, m-chlorophenol,\\u000a p-chlorophenol, o-nitrophenol, p-nitrophenol, o-cresol, m-cresol, p-cresol, catechol, resorcinol and quinol, MoO3 does not photodegrade

Chockalingam Karunakaran; Ramamoorthy Dhanalakshmi

2009-01-01

260

The viability of photocatalysis for air purification.  

PubMed

Photocatalytic oxidation (PCO) air purification technology is reviewed based on the decades of research conducted by the United Technologies Research Center (UTRC) and their external colleagues. UTRC conducted basic research on the reaction rates of various volatile organic compounds (VOCs). The knowledge gained allowed validation of 1D and 3D prototype reactor models that guided further purifier development. Colleagues worldwide validated purifier prototypes in simulated realistic indoor environments. Prototype products were deployed in office environments both in the United States and France. As a result of these validation studies, it was discovered that both catalyst lifetime and byproduct formation are barriers to implementing this technology. Research is ongoing at the University of Connecticut that is applicable to extending catalyst lifetime, increasing catalyst efficiency and extending activation wavelength from the ultraviolet to the visible wavelengths. It is critical that catalyst lifetime is extended to realize cost effective implementation of PCO air purification. PMID:25594345

Hay, Stephen O; Obee, Timothy; Luo, Zhu; Jiang, Ting; Meng, Yongtao; He, Junkai; Murphy, Steven C; Suib, Steven

2015-01-01

261

Drinking Water  

NSDL National Science Digital Library

This tutorial introduces students to the importance of water to living organisms, including humans. The discussion points out that all organisms contain water, and decribes how water is accumulated and stored. There is also an examination of the water supplies of Winnipeg, Ontario, and Vancouver, British Columbia, and a discussion of the importance of purifying driking water supplies to remove harmful bacteria and microbes.

262

Water Conditioner  

NASA Technical Reports Server (NTRS)

A home use water treatment incorporates technology developed to purify water aboard Space Shuttle Orbiters. The General Ionics Model IQ Bacteriostatic Water Softener softens water and inhibits bacteria growth in the filtering unit. Ionics used NASA silver ion technology as a basis for development of a silver carbon dense enough to remain on top of the water softening resin bed.

1991-01-01

263

Earth's Water  

NSDL National Science Digital Library

This resource provides an overview of the distribution and occurence of water on Earth. Topics include where and how much water there is, the water cycle, and how water is measured. There is also discussion of characteristics and distribution of surface water, groundwater, glaciers, and icecaps.

264

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

265

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

266

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

267

Healthy Water  

MedlinePLUS

... 5 Causes - Drinking Water Outbreaks Giardia Legionella Shigella Norovirus Campylobacter Top 5 Causes - Recreational Water Outbreaks Cryptosporidium Pseudomonas Shigella Legionella Norovirus For a complete listing of water-related surveillance ...

268

Drinking Water  

MedlinePLUS

... safest water supplies in the world, but drinking water quality can vary from place to place. It depends on the condition of the source water and the treatment it receives. Treatment may include ...

269

Water Treatment  

NSDL National Science Digital Library

Water treatment on a large scale enables the supply of clean drinking water to communities. In this activity, learners develop methods to clean a polluted water sample, describe components of a water treatment process, and learn how humans impact Earth's freshwater supply. The activity simulates methods used in real water treatment including aeration, coagulation, sedimentation, filtration and disinfection. This activity would be an excellent adjunct to a guided tour of a local water treatment plant.

New Jersey

2006-01-01

270

Drinking Water  

NSDL National Science Digital Library

This publication, authored by Thodore B. Shelton of Rutgers University, summarizes the information necessary for interpreting drinking water quality analyses performed by water testing laboratories. It focuses on testing results obtained from drinking water supplies from public water systems and non-public water systems (home wells). It is intended primarily for homeowners, but environmental organizations, health departments, and commercial water testing laboratories and others should find this material of interest and value.

Shelton, Thodore B.

271

UNL WATER CENTER WATER CURRENT  

E-print Network

INSIDE UNL WATER CENTER WATER CURRENT PROTECTING NEBRASKA'S WATER RESOURCES THROUGH RESEARCH................ Sidney Area Deals with Drought 6................ Water and Electricity Are Inseparable 10's School of Natural Resource Sciences,Conservation and Survey Division and Water Center into the School

Nebraska-Lincoln, University of

272

UNL WATER CENTER WATER CURRENT  

E-print Network

INSIDE UNL WATER CENTER WATER CURRENT PROTECTING NEBRASKA'S WATER RESOURCES THROUGH RESEARCH Researchers Honing Methods to Sample Field Run-off Water by Steve Ress The effectiveness of riparian buffer is important since many fertilizers and pesticides are designed to adhere to soil molecules. So if water

Nebraska-Lincoln, University of

273

Water, Water Everywhere  

NSDL National Science Digital Library

Students learn about floods, discovering that different types of floods occur from different water sources, but primarily from heavy rainfall. While floods occur naturally and have benefits such as creating fertile farmland, students learn that with the increase in human population in flood-prone areas, floods are become increasingly problematic. Both natural and manmade factors contribute to floods. Students learn what makes floods dangerous and what engineers design to predict, control and survive floods.

2014-09-18

274

Remediation of Water Contaminated with an Azo Dye: An Undergraduate Laboratory Experiment Utilizing an Inexpensive Photocatalytic Reactor  

NASA Astrophysics Data System (ADS)

The construction and use of an inexpensive photocatalytic reactor that utilizes titanium dioxide as the photocatalyst for wastewater treatment is described. In these experiments and in supplementary material, students are made aware that a variety of techniques have been developed to treat wastewaters, including those generated by the chemical industry. Water contaminated with the azo dye Congo Red was selected as an example of how one might treat contaminated water from a textile manufacturing facility. These experiments emphasize that, in addition to product development, chemists must also be concerned with waste treatment. A summary of the theory of titanium dioxide-mediated photocatalysis is provided. The phenomenon of photosensitization is also discussed. The usefulness of Congo Red is summarized and a brief history of this dye is given. In addition to being inexpensive, the photocatalytic reactor described is easy to construct and uses a readily available low-wattage fluorescent light. An important feature of this reactor is that the heat generated by the light source is readily dissipated by the water undergoing treatment. Thus no special cooling apparatus is required. One of the most important aspects of this work is that it provides a wide variety of continuing research suggestions that would be suitable and readily accomplished in undergraduate departments and high school laboratories; even those where budgetary priorities are a major concern. Use of this reactor would also enable students to design systems to treat "real-world" wastes, including some that are generated in instructional laboratories.

Bumpus, John A.; Tricker, Jennifer; Andrzejewski, Ken; Rhoads, Heather; Tatarko, Matthew

1999-12-01

275

WATER QUALITY  

EPA Science Inventory

Water quality is important not only because of its linkage to the availability of water for various uses and its impact on public health, but also because water quality has an intrinsic value. he quality of life is often judged on the availability of pristine water. ontamination ...

276

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 ...

Mr. Hughes

2006-02-11

277

Stacking Water  

NSDL National Science Digital Library

In this lesson, students become familiar with how ocean water forms density-stratified layers in many places. They design and carry out a series of tests to show how water masses of four different densities interact, using clear straws to stack colored water of different salinities. Temperature is varied to increase the differences in density of each water sample.

278

Water Cycle  

NSDL National Science Digital Library

4th Grade Science - Water Cycle Water Cycle two day interactive lesson plan. DAY 1: Welcome to the Water Cycle! Today we are going to be exploring and finding out more about the wonderful Water Cycle! For starters we are going to start with a movie, click the following link and watch the video and ...

Mrs. Staley

2009-11-09

279

Parasites: Water  

MedlinePLUS

... water, they can spread the parasite into the water and continue the cycle of contamination and infection. Schistosomiasis can be spread when people swim in or have contact with freshwater lakes that are contaminated ... drinking water or recreational water. Individuals spending time in the ...

280

Ground Water  

NSDL National Science Digital Library

This United States Geological Survey (USGS) general interest publication presents a description of ground water in the U.S. This includes what ground water is, how it occurs, aquifers and wells, ground water quality and what affects it, and the state of U.S. ground water resources.

281

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

282

Disappearing Water  

NSDL National Science Digital Library

In this outdoor water activity, learners explore evaporation by painting with water and tracing puddles. Learners will discover that wet things become dry as the water evaporates. This activity is part of the curriculum Explore Water, related to Peep and the Big Wide World, a preschool science series on public television. The activity starts on page 36 of the PDF.

WGBH Educational Foundation

2005-01-01

283

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 ...

284

Water Conservation  

NSDL National Science Digital Library

In this lesson, students study the availability of water on Earth and discuss methods that can be used to purify and conserve this critical resource. Using multimedia interactives, video, and classroom activities, they will identify sources of fresh water available for consumption, understand the need for water conservation, and compare the benefits and drawbacks of different water management techniques. They will also assess how much water they and their families typically use, and think about ways to reduce their water usage. Finally, students explore different techniques being employed for water management around the world, including the use of dams to create reservoirs.

2005-01-01

285

Nanostructured manganese oxides as highly active water oxidation catalysts: a boost from manganese precursor chemistry.  

PubMed

We present a facile synthesis of bioinspired manganese oxides for chemical and photocatalytic water oxidation, starting from a reliable and versatile manganese(II) oxalate single-source precursor (SSP) accessible through an inverse micellar molecular approach. Strikingly, thermal decomposition of the latter precursor in various environments (air, nitrogen, and vacuum) led to the three different mineral phases of bixbyite (Mn2 O3 ), hausmannite (Mn3 O4 ), and manganosite (MnO). Initial chemical water oxidation experiments using ceric ammonium nitrate (CAN) gave the maximum catalytic activity for Mn2 O3 and MnO whereas Mn3 O4 had a limited activity. The substantial increase in the catalytic activity of MnO in chemical water oxidation was demonstrated by the fact that a phase transformation occurs at the surface from nanocrystalline MnO into an amorphous MnOx (1water oxidation in the presence of [Ru(bpy)3 ](2+) (bpy=2,2'-bipyridine) as a sensitizer and peroxodisulfate as an electron acceptor was carried out for all three manganese oxides including the newly formed amorphous MnOx . Both Mn2 O3 and the amorphous MnOx exhibit tremendous enhancement in oxygen evolution during photocatalysis and are much higher in comparison to so far known bioinspired manganese oxides and calcium-manganese oxides. Also, for the first time, a new approach for the representation of activities of water oxidation catalysts has been proposed by determining the amount of accessible manganese centers. PMID:25044528

Menezes, Prashanth W; Indra, Arindam; Littlewood, Patrick; Schwarze, Michael; Göbel, Caren; Schomäcker, Reinhard; Driess, Matthias

2014-08-01

286

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

287

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

288

Low overpotential in vacancy-rich ultrathin CoSe2 nanosheets for water oxidation.  

PubMed

According to Yang Shao-Horn's principle, CoSe2 is a promising candidate as an efficient, affordable, and sustainable alternative electrocatalyst for the oxygen evolution reaction, owing to its well-suited electronic configuration of Co ions. However, the catalytic efficiency of pure CoSe2 is still far below what is expected, because of its poor active site exposure yield. Herein, we successfully overcome the disadvantage of insufficient active sites in bulk CoSe2 by reducing its thickness into the atomic scale rather than any additional modification (such as doping or hybridizing with graphene or noble metals). The positron annihilation spectrometry and XAFS spectra provide clear evidence that a large number of VCo? vacancies formed in the ultrathin nanosheets. The first-principles calculations reveal that these VCo? vacancies can serve as active sites to efficiently catalyze the oxygen evolution reaction, manifesting an OER overpotential as low as 0.32 V at 10 mA cm(-2) in pH 13 medium, which is superior to the values for its bulk counterparts as well as those for the most reported Co-based electrocatalysts. Considering the outstanding performance of the simple, unmodified ultrathin CoSe2 nanosheets as the only catalyst, further improvement of the catalytic activity is expected when various strategies of doping or hybridizing are used. These results not only demonstrate the potential of a notable, affordable, and earth-abundant water oxidation electrocatalyst based on ultrathin CoSe2 nanosheets but also open up a promising avenue into the exploration of excellent active and durable catalysts toward replacing noble metals for oxygen electrocatalysis. PMID:25310506

Liu, Youwen; Cheng, Hao; Lyu, Mengjie; Fan, Shaojuan; Liu, Qinghua; Zhang, Wenshuai; Zhi, Yuduo; Wang, Chengming; Xiao, Chong; Wei, Shiqiang; Ye, Bangjiao; Xie, Yi

2014-11-01

289

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.

290

Marketing water  

E-print Network

and Texas AgriLife Extension Service, gives ?earth friendly? gardening solutions to reduce water pollution. Austin is also tailoring a water conserva- tion program, developed for the Texas Water Development Board, to the city?s needs. The campaign... ] Many cities are promoting landscape management and water conservation practices with their citizens. This garden demonstrates the EARTH- KIND principles of environmentally tolerant, low water use ornamentals. tx H2O | pg. 18 and no adverse runoff...

Wythe, Kathy

2008-01-01

291

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.

292

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.

293

Water tight.  

PubMed

Many cities worldwide have gone beyond the limits of their water supply. Growing urban populations increase their demand for water, thereby straining local water supplies and requiring engineers to seek our even more distant water sources. It is costly to build and maintain reservoirs, canals, pumping stations, pipes, sewers, and treatment plants. Water supply activities require much energy and chemicals, thereby contributing to environmental pollution. Many cities are beginning to manage the water supply rather than trying to keep up with demand. Pumping ground water for Mexico City's 18 million residents (500,000 people added/year) surpasses natural replenishment by 50% to 80%, resulting in falling water tables and compressed aquifers. Mexico City now ambitiously promotes replacement of conventional toilets with 1.6 gallon toilets (by late 1991, this had saved almost 7.4 billion gallons of water/year). Continued high rural-urban migration and high birth rates could negate any savings, however. Waterloo, Ontario, has also used conservation efforts to manage water demand. These efforts include retrofit kits to make plumbing fixtures more efficient, efficiency standards for plumbing fixtures, and reduction of water use outdoors. San Jose, California, has distributed water savings devices to about 220,000 households with a 90% cooperation rate. Boston, Massachusetts, not only promoted water saving devices but also repaired leaks and had an information campaign. Increasing water rates to actually reflect true costs also leads to water conservation, but not all cities in developing countries use water meters. All households in Edmonton, Alberta, are metered and its water use is 1/2 of that of Calgary, where only some households are metered. Tucson, Arizona, reduced per capita water use 16% by raising water rates and curbing water use on hot days. Bogor, Indonesia, reduced water use almost 30% by increasing water rates. In the US, more and more states are mandating use of water-efficient plumbing fixtures. Multilateral development agencies have identified some developing country cities as demonstrated sites for urban water conservation. PMID:12286138

Postel, S

1993-01-01

294

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

295

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

296

Earth-Abundant Metal Pyrites (FeS2, CoS2, NiS2, and Their Alloys) for Highly Efficient Hydrogen Evolution and Polysulfide Reduction Electrocatalysis.  

PubMed

Many materials have been explored as potential hydrogen evolution reaction (HER) electrocatalysts to generate clean hydrogen fuel via water electrolysis, but none so far compete with the highly efficient and stable (but cost prohibitive) noble metals. Similarly, noble metals often excel as electrocatalytic counter electrode materials in regenerative liquid-junction photoelectrochemical solar cells, such as quantum dot-sensitized solar cells (QDSSCs) that employ the sulfide/polysulfide redox electrolyte as the hole mediator. Here, we systematically investigate thin films of the earth-abundant pyrite-phase transition metal disulfides (FeS2, CoS2, NiS2, and their alloys) as promising alternative electrocatalysts for both the HER and polysulfide reduction. Their electrocatalytic activity toward the HER is correlated to their composition and morphology. The emergent trends in their performance suggest that cobalt plays an important role in facilitating the HER, with CoS2 exhibiting highest overall performance. Additionally, we demonstrate the high activity of the transition metal pyrites toward polysulfide reduction and highlight the particularly high intrinsic activity of NiS2, which could enable improved QDSSC performance. Furthermore, structural disorder introduced by alloying different transition metal pyrites could increase their areal density of active sites for catalysis, leading to enhanced performance. PMID:25247028

Faber, Matthew S; Lukowski, Mark A; Ding, Qi; Kaiser, Nicholas S; Jin, Song

2014-09-18

297

Wasted waters.  

PubMed

This article presents the increasing mismanagement of water as a result of increasing delivery of water volume, water pollution, and water wasting. One example of water mismanagement is irrigation, through which 67% of water is withdrawn from the hydrological cycle. In addition, reports from European communities reveal that pesticides from agriculture worsen the existing underground pollution. Furthermore, a 25% drop in land productivity was observed in Africa due to erosion, salinization, water logging, and desertification. Also, 23% of withdrawn water goes to industries, which are the major polluters. Since 1900 about 250,000 tons of cadmium have been produced worldwide, which eventually enter and harm the aquatic and terrestrial ecosystems. Moreover, high mercury levels were observed in Malaysia's Kelang River in the late 1980s, and river pollution in Thailand and Malaysia is recorded to be 30-100 times higher than accepted levels. Aside from that, the human race must also understand that there is a connection between water scarcity and water quality. When there is water pollution, it is expected that many people will suffer diarrheal diseases and intestinal parasite infections, which will further increase the mortality rate to 3.3 million per year. Realizing the severity of the problem, it is suggested that the human race must learn to recycle water like stormwater to prevent scarcity with drinking water. PMID:12295784

Niemczynowicz, J

1996-11-01

298

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. PMID:24742528

Dolnicar, Sara; Hurlimann, Anna; Grün, Bettina

2014-01-01

299

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

300

Water Pollution  

ERIC Educational Resources Information Center

Deals with water pollution in the following categories: a global view, self purification, local pollution, difficulties in chemical analysis, and remedies for water pollution. Emphasizes the extent to which man's activities have modified the cycles of certain elements. (GS)

Bowen, H. J. M.

1975-01-01

301

Water Distribution  

NSDL National Science Digital Library

Grade 6-10 geography lesson plan evaluating population growth and water availability in the United States and in other countries. Students will learn how to draw bar graphs and develop plans of action for water scarcity problems.

302

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 ...

303

Microbiology: water  

SciTech Connect

Topics discussed in this literature review with 173 references dealing with the microbiology of aquatic ecosystems include microbial indicators of water pollution, and the microbial ecology of water. Solar radiation and naturally occurring microbial predators are important forces in the natural self-purification of polluted surface waters. The relationship between water quality and microbiology of river systems and natural lakes is discussed.(KRM)

Geldrich, E.E.

1982-06-01

304

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

305

Water Walk  

NSDL National Science Digital Library

Learners take a field trip along a local body of water and conduct a visual survey to discover information about local land use and water quality. Learners document their findings by mapping and profiling the water body. They can upload their measurements via the internet to a GLOBE scientist. Learners also use this initial investigation to raise questions about local land use and/or water quality issues that may require further study.

Beth Isaacs

2009-01-01

306

Falling Water  

NSDL National Science Digital Library

Students drop water from different heights to demonstrate the conversion of water's potential energy to kinetic energy. They see how varying the height from which water is dropped affects the splash size. They follow good experiment protocol, take measurements, calculate averages and graph results. In seeing how falling water can be used to do work, they also learn how this energy transformation figures into the engineering design and construction of hydroelectric power plants, dams and reservoirs.

2014-09-18

307

Surface Water  

NSDL National Science Digital Library

This is the USGS Water Science for School's page and the topic is surface water. Explained are surface water use, importance, rivers and streams. Also answers the questions of what is runoff, how is the flow of a stream measured, how does stream height relate to flow and much, much more.

308

Water Cycle  

NSDL National Science Digital Library

Water Cycle fun From water cycle Web Quest Links Introduction Task Process Evaluation Conclusion Resources Teacher Guide Introduction Luke Warm, a weather man, and you will help two baseball players understand why the big game might be rained out. You will explore the Water cycle and ...

Mrs. Terry

2009-04-03

309

Water electrolysis  

Microsoft Academic Search

The electrolysis of water is evaluated as a potentially efficient, low cost means of hydrogen production. The theoretical energy and voltage, current, and energy efficiencies of water electrolysis are considered. The present status of water electrolysis is reviewed, with attention given to caustic potash of soda electrolytes, electrode materials, diaphragms inserted between the electrodes, and the design of unipolar and

T. Takahashi

1979-01-01

310

Water Resources  

NASA Technical Reports Server (NTRS)

Uses of ERTS-1 imagery and data for water resources surveys and management are summarized. Areas discussed are: (1) land use and geology; (2) flood plain and flood inundation mapping; (3) snow cover mapping; (4) glacier observations; (5) data collection systems; (6) surface waters; (7) wetlands mapping; (8) water quality; (9) soil mapping; (10) phreatophyte and riparian vegetation mapping; and (11) evapotranspiration.

Salomonson, V. V.

1973-01-01

311

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. PMID:23194331

2012-01-01

312

Water Treatment  

NSDL National Science Digital Library

This web site showcases Lenntech's Complete Water treatment and Air filtration solutions. This company designs, manufactures and installs complete air and water treatment system solutions. Lenntech proclaims, "Our wide range of technologies and extended know-how in all water-related sectors will guarantee you a cost-efficient solution meeting your water quality requirements." Whether or not you're looking to purchase one of these fine water treatment systems, the site will still provide beneficial resources about how said systems operate.

313

Water Conservation  

NSDL National Science Digital Library

This activity was developed to get students thinking about the many ways that people use freshwater and how we can conserve this precious and fundamental natural resource. Students will watch a short documentary describing issues related to clean water availability, analyze water-use data and start to think about how they consume and can conserve water. This background knowledge will lead to students collecting data about their own water use and finding areas in their lives to conserve water. This activity uses the 5E instructional model and is part of the "Survivor Earth" series of one-hour lessons.

314

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

315

EXTENSION WATER SUMMIT PRIORITY: WATER CONSERVATION  

E-print Network

EXTENSION WATER SUMMIT PRIORITY: WATER CONSERVATION Leadership Team Subcommittee: Joan Bradshaw Michael Dukes Pierce Jones Kati Migliaccio #12;Water Conservation - Situation · Florida water supplies;Water Conservation Initiative 2: Enhancing and protecting water quality, quantity, and supply Priority 1

Kane, Andrew S.

316

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 ...

317

Ground Water Ground Sky Sky Water Vegetation Ground Vegetation Water  

E-print Network

Bear Snow Vegetation RhinoWater Vegetation Ground Water Ground Sky Sky Rhino Water Vegetation Ground Vegetation Water Rhino Water Vegetation Ground Rhino Water Rhino Water Ground Ground Vegetation Water Rhino Vegetation Rhino Vegetation Ground Rhino Vegetation Ground Sky Rhino Vegetation Ground Sky

Chen, Tsuhan

318

An overview on the advanced oxidation processes applied for the treatment of water pollutants defined in the recently launched Directive 2013/39/EU.  

PubMed

Environmental pollution is a recognized issue of major concern since a wide range of contaminants has been found in aquatic environment at ngL(-1) to ?gL(-1) levels. In the year 2000, a strategy was defined to identify the priority substances concerning aquatic ecosystems, followed by the definition of environmental quality standards (EQS) in 2008. Recently it was launched the Directive 2013/39/EU that updates the water framework policy highlighting the need to develop new water treatment technologies to deal with such problem. This review summarizes the data published in the last decade regarding the application of advanced oxidation processes (AOPs) to treat priority compounds and certain other pollutants defined in this Directive, excluding the inorganic species (cadmium, lead, mercury, nickel and their derivatives). The Directive 2013/39/EU includes several pesticides (aldrin, dichlorodiphenyltrichloroethane, dicofol, dieldrin, endrin, endosulfan, isodrin, heptachlor, lindane, pentachlorophenol, chlorpyrifos, chlorfenvinphos, dichlorvos, atrazine, simazine, terbutryn, diuron, isoproturon, trifluralin, cypermethrin, alachlor), solvents (dichloromethane, dichloroethane, trichloromethane and carbon tetrachloride), perfluorooctane sulfonic acid and its derivatives (PFOS), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), nonylphenol and octylphenol, as well as the three compounds included in the recommendation for the first watch list of substances (diclofenac, 17-alpha-ethinylestradiol (EE2) and 17-beta-estradiol (E2)). Some particular pesticides (aclonifen, bifenox, cybutryne, quinoxyfen), organotin compounds (tributyltin), dioxins and dioxin-like compounds, brominated diphenylethers, hexabromocyclododecanes and di(2-ethylhexyl)phthalate are also defined in this Directive, but studies dealing with AOPs are missing. AOPs are recognized tools to destroy recalcitrant compounds or, at least, to transform them into biodegradable species. Diuron (a phenylurea herbicide) and atrazine (from the triazine chemical class) are the most studied pesticides from Directive 2013/39/EU. Fenton-based processes are the most frequently applied to treat priority compounds in water and their efficiency typically increases with the operating temperature as well as under UV or solar light. Heterogeneous photocatalysis is the second most used treatment to destroy pollutants defined in the Directive. Ozone alone promotes the partial oxidation of pollutants, and an increase in the effluent biodegradability, but complete mineralization of pollutants is difficult. To overcome this drawback, ozonation has been combined with heterogeneous catalysts, addition of H2O2, other AOPs (such as photocatalysis) or membrane technologies. PMID:25461413

Ribeiro, Ana R; Nunes, Olga C; Pereira, Manuel F R; Silva, Adrián M T

2015-02-01

319

Water Filter  

NASA Technical Reports Server (NTRS)

A compact, lightweight electrolytic water sterilizer available through Ambassador Marketing, generates silver ions in concentrations of 50 to 100 parts per billion in water flow system. The silver ions serve as an effective bactericide/deodorizer. Tap water passes through filtering element of silver that has been chemically plated onto activated carbon. The silver inhibits bacterial growth and the activated carbon removes objectionable tastes and odors caused by addition of chlorine and other chemicals in municipal water supply. The three models available are a kitchen unit, a "Tourister" unit for portable use while traveling and a refrigerator unit that attaches to the ice cube water line. A filter will treat 5,000 to 10,000 gallons of water.

1982-01-01

320

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).

National Park Service

2011-08-20

321

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

322

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 ...

Lori Peterson

2009-09-28

323

Water Jetting  

NASA Technical Reports Server (NTRS)

Hi-Tech Inc., a company which manufactures water jetting equipment, needed a high pressure rotating swivel, but found that available hardware for the system was unsatisfactory. They were assisted by Marshall, which had developed water jetting technology to clean the Space Shuttles. The result was a completely automatic water jetting system which cuts rock and granite and removes concrete. Labor costs have been reduced; dust is suppressed and production has been increased.

1985-01-01

324

Computerized Waters  

E-print Network

Microsoft Windows,Dr. Ralph Wurbs has designed a computer mod- eling system that has changed the way Texas manages its rivers, streams and reservoirs. The modeling system called Water Rights Availability Package, or WRAP for short, is a set of computer... water use and assesses the impacts on all the other water uses in the river basin. #2; Dr. Ralph Wurbs, professor of civil engineering, examines the Texas river basin maps with Richard Hoffpauir, graduate student. These maps were developed, using...

Wythe, Kathy

2006-01-01

325

Treatment of Well Water  

MedlinePLUS

... CDC–INFO Drinking Water Home Public Water Systems Water Quality & Testing Consumer Confidence Reports Regulations Water Sources Water Treatment Disinfection with Chlorine & Chloramine Disinfection ...

326

Water Harvesting  

NSDL National Science Digital Library

This manual has been written with the intention of providing technicians and extension workers with practical guidelines on the implementation of water harvesting schemes. However it will also be of interest to a wider audience, such as rural development specialists and planners. The focus of the manual is on simple, field scale systems for improved production of crops, trees and rangeland species in drought prone areas. Water harvesting systems for water supply such as haffirs, ponds and rooftop tanks are not covered in this manual, nor are large-scale water spreading systems (spate irrigation).

Critchley, Will

327

Water Exploration  

NSDL National Science Digital Library

Water Exploration uses a project-based learning approach, permitting students to conduct research and build an understanding about water science and critical water-related issues. All learning activities and resources are packaged into three modules, or Legacy Cycles, in a way that enhances student learning by making use of the Internet and computer technology to promote inquiry learning. The Earth Science Literacy Principles provide the organizing framework for the lessons and activities in each Water Exploration Legacy Cycle. The curriculum is applicable to high school science courses such as Earth and Space Science, Advanced Placement Environmental Science, Biology, Chemistry, and Aquatic Science.

Kathy Kelly Ellins

2012-01-01

328

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 ( ...

329

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

330

Mixing Water  

NSDL National Science Digital Library

The purpose of this assessment probe is to elicit students' ideas about temperature and energy transfer. The probe is designed to find out whether students recognize that a transfer of energy from the warm water to the cool water occurs until they reach the same temperature. Additionally, students' explanations reveal whether they use an addition, subtraction, or averaging strategy to determine the resulting temperature.

Francis Eberle

2007-01-01

331

Water snails  

NSDL National Science Digital Library

Water snails have a shell for protection. They have two tentacles, a foot, and a head and a tail region. Water snails have eyes at the base of their sensory stalks. The stalks are used to smell and feel around the snail's environment.

Scott Bauer (USDA; ARS)

2005-08-03

332

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.

WGBH Boston

2002-01-01

333

Drinking Water  

EPA Science Inventory

This encyclopedic entry deals with various aspects of microbiology as it relates to drinking water treatment. The use of microbial indicators for assessing fecal contamination is discussed as well as current national drinking water regulations (U.S. EPA) and guidelines proposed ...

334

WATER EROSION  

Technology Transfer Automated Retrieval System (TEKTRAN)

Water erosion is caused by the detachment and transport of soil by runoff, melting snow or ice, and irrigation. Excessive erosion could threaten the production of agricultural and forest products. Erosion may also impact water conveyance and storage structures, and contribute to pollution from land ...

335

Ground Water And Drinking Water  

NSDL National Science Digital Library

This is the official website for the Office of Groundwater and Safe Drinking Water (OGWDW) at the Environmental Protection Aagency (EPA). The OGWDW works to ensure safe drinking water and to protect the quality of our nation's drinking water supply. This mission is accomplished using five guiding principles: prevention, risk-based priority setting for new and existing regulations, public and private partnerships, flexibility and effectiveness in implementation while maintaining a national public health baseline, accountability of all parties through public participation and accessible information, and clear documentation and presentation of results. This site is a major clearinghouse for safe water guidelines, programs, data, publications, and news relevant to the OGWDW's operations.

336

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

337

Photocatalytic degradation of methyl orange dye in water solutions in the presence of MWCNT/TiO{sub 2} composites  

SciTech Connect

Highlights: ? MWCNTs/TiO{sub 2} composites were obtained to degrade organic dyes in water. ? MWCNT/TiO{sub 2} composites were analyzed by photocatalysis and structural characterization. ? The photocatalytic shows efficient method for the degradation of dyes from aqueous effluents. - Abstract: The textile and dyestuff industries are the primary sources of the release of synthetic dyes into the environment and usually there are major pollutants in dye wastewaters. Because of their toxicity and slow degradation, these dyes are categorized as environmentally hazardous materials. In this context, carbon nanotubes/TiO{sub 2} (CNTs/TiO{sub 2}) composites were prepared using multi-walled CNTs (MWCNTs), titanium (IV) propoxide and commercial TiO{sub 2} (P25{sup ®}) as titanium oxide sources, to degrade the methyl orange dye in solution through photocatalyst activity using UV irradiation. The composites were prepared by solution processing followed by thermal treatment at 400, 500 and 600 °C. The heterojunction between nanotubes and TiO{sub 2} was confirmed by XRD, specific surface area. The coating morphology was observed with SEM and TEM.

Da Dalt, S., E-mail: silvana.da.dalt@ufrgs.br [Department of Material, Federal University of Rio Grande do Sul, Av. Osvaldo Aranha 99, Laboratory 705C, ZIP 90035-190, Porto Alegre, RS (Brazil); Alves, A.K.; Bergmann, C.P. [Department of Material, Federal University of Rio Grande do Sul, Av. Osvaldo Aranha 99, Laboratory 705C, ZIP 90035-190, Porto Alegre, RS (Brazil)

2013-05-15

338

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

339

Water Pressure. Water in Africa.  

ERIC Educational Resources Information Center

The Water in Africa Project was realized over a 2-year period by a team of Peace Corps volunteers. As part of an expanded, detailed design, resources were collected from over 90 volunteers serving in African countries, photos and stories were prepared, and standards-based learning units were created for K-12 students. This unit, "Water Pressure,"…

Garrett, Carly Sporer

340

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

341

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

342

Fuel cells: spectroscopic studies in the electrocatalysis of alcohol oxidation  

Microsoft Academic Search

Métodos spectroscópicos modernos são úteis na elucidação de mecanismos eletroquímicos complexos, como os que ocorrem durante a oxidação de pequenas moléculas orgânicas (CH 3 OH, HCOH, HCOOH). Neste trabalho apresentamos o uso de métodos espectroscópicos para o estudo da oxidação de álcoois em eletrodos de platina ou bin ários principalmente constituídospor Pt. Estas reações são importantes para o desenvolvimento de

Teresa Iwasita

2002-01-01

343

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

344

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. PMID:24991521

Quaino, Paola; Juarez, Fernanda; Santos, Elizabeth

2014-01-01

345

Trends in electrocatalysis : from extended to nanoscale surfaces.  

SciTech Connect

One of the key objectives in fuel-cell technology is to improve and reduce Pt loading as the oxygen-reduction catalyst. Here, we show a fundamental relationship in electrocatalytic trends on Pt{sub 3}M (M=Ni, Co, Fe, Ti, V) surfaces between the experimentally determined surface electronic structure (the d-band centre) and activity for the oxygen-reduction reaction. This relationship exhibits 'volcano-type' behavior, where the maximum catalytic activity is governed by a balance between adsorption energies of reactive intermediates and surface coverage by spectator (blocking) species. The electrocatalytic trends established for extended surfaces are used to explain the activity pattern of Pt{sub 3}M nanocatalysts as well as to provide a fundamental basis for the catalytic enhancement of cathode catalysts. By combining simulations with experiments in the quest for surfaces with desired activity, an advanced concept in nanoscale catalyst engineering has been developed.

Stamenkovic, V. R.; Mun, B. S.; Arenz, M.; Mayrhofer, K. J. J.; Lucas, C. A.; Wang, G.; Ross, P. N.; Markovic, N. M.; Materials Science Division; Lawrence Berkeley Nat. Lab.; Technical Univ. Munich; Univ. of Liverpool; Univ. of South Carolina

2007-01-01

346

Trends in electrocatalysis: from extended to nanoscale surfaces.  

SciTech Connect

One of the key objectives in fuel-cell technology is to improve and reduce Pt loading as the oxygen-reduction catalyst. Here, we show a fundamental relationship in electrocatalytic trends on Pt{sub 3}M (M=Ni, Co, Fe, Ti, V) surfaces between the experimentally determined surface electronic structure (the d-band centre) and activity for the oxygen-reduction reaction. This relationship exhibits 'volcano-type' behavior, where the maximum catalytic activity is governed by a balance between adsorption energies of reactive intermediates and surface coverage by spectator (blocking) species. The electrocatalytic trends established for extended surfaces are used to explain the activity pattern of Pt{sub 3}M nanocatalysts as well as to provide a fundamental basis for the catalytic enhancement of cathode catalysts. By combining simulations with experiments in the quest for surfaces with desired activity, an advanced concept in nanoscale catalyst engineering has been developed.

Stamenkovic, V. R.; Mun, B. S.; Arenz, M.; Lucas, C. A.; Wang, G.; Ross, P. N.; Markovic, N. M.; Materials Science Division; Univ. of California at Berkeley; Technical Univ.; Univ. of Liverpool; Univ. of South Carolina

2007-01-01

347

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

348

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

349

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. PMID:24487242

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

2014-01-01

350

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

351

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. 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.

1983-01-01

352

Characterizing nano-scale electrocatalysis during partial oxidation of methane  

NASA Astrophysics Data System (ADS)

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

2014-02-01

353

Zirconium alkoxide interfaces for adhesion enhancement and electrocatalysis  

NASA Astrophysics Data System (ADS)

Tetra(tert-butoxy)zirconium was chemisorbed onto the native oxide layers of aluminum, iron, copper, and porous silicon, forming surface bound di- or tri-alkoxy zirconium species. Poly(ethylene- co-acrylic acid) was subsequently reacted with the surface forming chemically bound copolymer through carboxyzirconium linkages. Copolymer bound through the zirconium complex adhered to the metal oxide surfaces better than without the zirconium alkoxide intermediate, as determined by FTIR spectroscopy. Copper substrates were subjected to a variety of stability tests, including exposure to ambient conditions, base washing, and chronocoulometry. The copper-zirconium-copolymer ensemble was shown to be very stable in all of these tests. Indium tin oxide (ITO) powder was titrated to determine surface hydroxyl content per unit area. ITO-coated glass slides were reacted with tetra( tert-butoxy)zirconium, and subsequently with both carboxylic acid and phenol derivatives. Ferrocene-carboxyzirconium-coated ITO was characterized electrochemically, and the surface loading of ferrocene was found to be approximately one monolayer. Phenoxyzirconium-coated ITO was also characterized electrochemically and tested for electrocatalytic properties for the oxidation of several compounds in solution. Phenoxyzirconium-coated ITO was found to improve the oxidation kinetics for ferrocene and tetramethylphenylenediamine in acetonitrile.

Vanderkam, Susan Killian

354

Nickel surface anodic oxidation and electrocatalysis of oxygen evolution  

Microsoft Academic Search

The processes of nickel surface anodic oxidation taking place within the range of potentials preceding oxygen evolution reaction\\u000a (OER) in the solutions of 1 M KOH, 0.5 M K2SO4, and 0.5 M H2SO4 have been analyzed in the present paper. Metallic nickel, thermally oxidized nickel, and black nickel coating were used as\\u000a Ni electrodes. The methods of cyclic voltammetry and X-ray photoelectron spectroscopy

K. Juodkazis; J. Juodkazyt?; R. Vilkauskait?; V. Jasulaitien?

2008-01-01

355

Sinking Water  

NSDL National Science Digital Library

In this experiment, learners float colored ice cubes in hot and cold water. They compare the behavior of the melting ice cubes to understand how temperature is related to ocean currents and how temperature changes water density. The printable eight-page handout includes a series of inquiry-based questions to get learners thinking about how and why water temperature changes along with depth. Illustrated experiment directions and a worksheet help learners use the experiment results to gain a deeper understanding of buoyancy and density.

2012-08-01

356

Fragile Waters  

NSDL National Science Digital Library

In this activity (on pages 18-29) learners explore the impact of the March 24, 1989 oil spill in Alaska caused by the Exxon Valdez tanker. First they use a map to track the movement of the spill over 56 days. Learners then explore how oil behaves in water by examining the relative weight of water vs. oil, and the properties of oil. They test how oil damages various natural materials such as bird feathers, fur fabric, plants, shells, and rocks, and then try water and detergent to see which cleaning methods work best.

2014-01-28

357

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.

358

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.

359

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

360

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

361

Water Safety  

MedlinePLUS

... by a lifeguard. No one can anticipate changing ocean currents, rip currents, sudden storms, or other hidden ... body of water (like a river, lake, or ocean) is different from swimming in a pool. You ...

362

Fertilized water  

NASA Astrophysics Data System (ADS)

Following the most extensive study of nutrients in the nation's water resources, the U.S. Geological Survey finds that the drinking water standard for nitrate, a nutrient commonly derived from fertilizer, was exceeded in 21% of shallow wells in agricultural areas. The standard was exceeded in only 1% of public supply wells and in very few streams.The study indicates that nitrate levels in ground and surface waters are higher in agricultural areas, indicating patterns of contamination related to land use. The highest concentrations of nitrate were in shallow ground water, less than 100 feet below the surface. Concentrations were higher in parts of the Northeast, Midwest, and on the West Coast, with generally lower concentrations in the Southeast.

363

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.

Jason Voss

364

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.

2014-05-22

365

Grabbing Water  

E-print Network

We introduce a novel technique for grabbing water with a flexible solid. This new passive pipetting mechanism was inspired by floating flowers and relies purely on the coupling of the elasticity of thin plates and the ...

Reis, Pedro Miguel

366

Water Privatisation   

E-print Network

This dissertation deals with the policy issues of large-scale, urban water privatisation projects in the face of uncertainty and variability. The main objective is to evaluate whether a single policy approach, namely privatisation associated...

Zölls, Elisa

2011-08-17

367

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...

368

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.

369

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...

370

Drinking Water FAQ  

MedlinePLUS

... or ground water. Surface water collects in streams, rivers, lakes, and reservoirs. Ground water is water located ... protect drinking water and its sources, which include rivers, lakes, reservoirs, springs, and ground water wells. Top ...

371

Filtering Water  

NSDL National Science Digital Library

The first site related to water filtration is from the US Environmental Agency entitled EPA Environmental Education: Water Filtration (1 ). The two-page document explains the need for water filtration and the steps water treatment plants take to purify water. To further understand the process, a demonstration project is provided that illustrates these purification steps, which include coagulation, sedimentation, filtration, and disinfection. The second site is an interesting Flash animation called Filtration: How Does it Work (2 ) provided by Canada's Prairie Farm Rehabilitation Administration. Visitors will learn various types of filtration procedures and systems and the materials that are used such as carbon and sand. Next, from the National Science Foundation is a learning activity called Get Out the Gunk (3 ). Using just a few simple items from around the house, kids will be able to answer questions like "Does a filter work better with a lot of water rushing through, or a small trickle?" and "Does it make the water cleaner if you pour it through a filter twice?" The fourth Web site, Rapid Sand Filtration (4 ), is provided by Dottie Schmitt and Christie Shinault of Virginia Tech. The authors describe the process, which involves the flow of water through a bed of granular media, normally following settling basins in conventional water treatment trains to remove any particulate matter left over after flocculation and settling. Along with its thorough description, readers can view illustrations and photographs that further explain the process. The Vegetative Buffer Strips for Improved Surface Water Quality (5) Web site is provided by the Iowa State University Extension office. The document explains what vegetative buffer strips are, how they filter contaminants and sediment from surface water, how effective they are, and more. The sixth offering is a file called Infiltration Basins and Trenches (6) that is offered by the University of Wisconsin Extension. These structures are intended to collect water, have it infiltrate into the ground, and have it purified along the way. This document explains how effective they are at removing pollutants, how to install them, design guidelines, maintenance, and more. Next, from a site called Wilderness Survial.net is the Water Filtration Devices (7) page. Visitors read how to make a filtering system out of cloth, sand, crushed rock, charcoal, or a hollow log, although as is stated, the water still has to be purified. The last site, from the US Geological Survey, is called A Visit to a Wastewater-Treatment Plant: Primary Treatment of Wastewater (8). Although geared towards children, the site does a good job of explaining what happens at each stage of the treatment process and how pollutants are removed to help keep water clean. Everything from screening, pumping, aerating, sludge and scum removal, killing bacteria, and what is done with wastewater residuals is covered.

Brieske, Joel A.

2003-01-01

372

Arnold Schwarzenegger WATER HEATERS AND HOT WATER  

E-print Network

Arnold Schwarzenegger Governor WATER HEATERS AND HOT WATER DISTRIBUTION SYSTEMS;#12;Appendices Appendix A. Multifamily Water Heating Construction Practices, Pricing and Availability Survey Report Appendix B. Multifamily Water Heating Controls Performance Field Report Appendix C. Pipe

373

Water Walk  

NSDL National Science Digital Library

In this field activity, students conduct a visual survey of a hydrology study site, and collect information about land cover and water quality. These observations are used to stimulate research-able questions about land cover and water chemistry that can be the focus of future investigations. The use of archival evidence in an investigation is discussed. This is a learning activity associated with the GLOBE hydrology investigations and is supported by the Hydrology chapter of the GLOBE Teacher's Guide. GLOBE (Global Learning and Observation to Benefit the Environment) is a worldwide, hands-on, K-12 school-based science education program.

374

Water watch  

SciTech Connect

This issue of [open quotes]Water Watch[close quotes] focuses on soil moisture and fall streamflow, particularly in the Western US. The information is based on reports and data provided by the National Weather Service Office of Hydrology, the US Dept. of Agriculture, the Bureau of Reclamation, the Soil Conservation Service, the California Dept. of Water Resources, and the US Geological Survey. Ninety-day outlooks are through October 1992. For purposes of reporting, the US is divided into six regions. The data can be used to observe how weather conditions affected hydro generation in July.

Not Available

1992-10-01

375

Water Watch  

SciTech Connect

This issue of [open quotes]Water Watch,[close quotes] focusing on streamflow, is based on reports and data provided by the National Weather Service Office of hydrology and River Forecast Centers, US Department of Agriculture, the Bureau of Reclamation, Soil Conservation Service, California Department of Water Resources, and the US Geological Survey. Ninety-day outlooks are through August. 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 May.

Gruber, N.

1993-08-01

376

Regional Water Management: Adapting to Uncertain Water  

E-print Network

Regional Water Management: Adapting to Uncertain Water Supply and Demand Jim Schneider, Ph · How Nebraska manages water · Dealing with uncertain water supplies: adaptive management #12;Regional · Identify the basin goals and concerns · Assess the water supply and water demands · Develop

Nebraska-Lincoln, University of

377

WATER MARKETS AND DECENTRALIZED WATER RESOURCES MANAGEMENT  

Microsoft Academic Search

Because of its importance and the perceived inability of private sector sources to meet water demands, many countries have depended on the public sector to provide water services for their populations. Yet this has resulted in many inefficient public water projects and in inadequate supplies of good quality and reliable water. Decentralization of water management, including the use of water

K. William Easter; Robert R. Hearne

1994-01-01

378

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.

2012-08-03

379

Blue Water  

USGS Multimedia Gallery

The Canadian Coast Guard Ship Louis S. St-Laurent has a mechanical system that creates bubbles that rise to the surface and push ice away from the ship's hull. It also happens to churn the water into an amazing shade of blue....

380

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...

381

Water Hyacinth  

Technology Transfer Automated Retrieval System (TEKTRAN)

An important new reference book entitled the “Encyclopedia of Invasive Introduced Species” is being published by the University of California Press. We were invited to provide a chapter on water hyacinth, which is the world’s worst aquatic weed. In this chapter, we provide information on the origi...

382

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

383

Grabbing water  

E-print Network

We introduce a novel technique for grabbing water with a flexible solid. This new passive pipetting mechanism was inspired by floating flowers and relies purely on the coupling of the elasticity of thin plates and the hydrodynamic forces at the liquid interface. Developing a theoretical model has enabled us to design petal-shaped objects with maximum grabbing capacity.

P. M. Reis; J. Hure; S. Jung; J. W. M. Bush; C. Clanet

2012-07-16

384

Investigating Water  

E-print Network

substances. It covers most of the earth?s surface, sometimes to a depth of more than a mile. It exists as a colorless gas in the atmosphere. It caps the poles with ice and occurs in the snows of winter. Liquid water fills brooks, streams, rivers, lakes, ponds...

Howard Jr., Ronald A.

2002-01-02

385

Weightless Water  

NSDL National Science Digital Library

In this physics activity (page 5 of the PDF), learners will witness the effects of free fall by observing falling water, and will gain a better understanding of the concept of weightlessness. Although this activity was created as a post-visit for a workshop about astronomy, it also makes an excellent stand alone activity!

2012-06-26

386

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

387

Water Filtration  

ERIC Educational Resources Information Center

A water filtration column is devised by students using a two-liter plastic bottle containing gravel, sand, and activated charcoal, to test the filtration potential of the column. Results indicate that the filtration column eliminates many of the contaminating materials, but does not kill bacteria.

Jacobsen, Erica K.

2004-01-01

388

The Water Cycle  

NSDL National Science Digital Library

4th Grade Science Learn all about the Water Cycle! The Water Cycle: Water Storage Learn about Evaporation, Condensation, Precipitation, and Collection! The Water Cycle Here are some activites to learn about the water cycle. Hydrologic Cycle ...

Ms. Andrus

2007-10-12

389

UNL WATER CENTER WATER CURRENT  

E-print Network

........SPECIAL BUREAU OF RECLAMATION CENTENNIAL COVERAGE 14..............Water News Briefs 15 Keyes, Commissioner of Reclamation, U.S. Bureau of Reclamation. Several con- vention topics will focus in the teens or 1920's. Exact date unknown U.S. Bureau of Reclamation projects to "reclaim" the arid western

Nebraska-Lincoln, University of

390

UNL WATER CENTER WATER CURRENT  

E-print Network

at drought condi- tions in the North Platte River watershed from head- waters in Colorado to Lake Mc in the North Platte River watershed, and with the current drought conditions in those areas, the tour should.....................Managing the Missouri River System 5.....................Nebraska's Wetlands 6.....................Risk

Nebraska-Lincoln, University of

391

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

392

Minimization of methabenzthiazuron residues in leaching water using amended soils and photocatalytic treatment with TiO2 and ZnO.  

PubMed

In the present work, potential groundwater pollution by methabenzthiazuron (MTBU) and the effect of three different amendments (composted sheep manure, composted pine bark and spent coffee grounds) on its mobility were investigated under laboratory conditions. The efficiency of ZnO and TiO2 suspensions in the photocatalytic degradation of MTBU in leaching water was also investigated. The relative and cumulative breakthrough curves were obtained from disturbed soil columns. The presence and/or addition of organic matter drastically reduced the movement of the herbicide. On other hand, photocatalytic experiments showed that the addition of ZnO and TiO2 strongly enhances the degradation rate of this herbicide compared with the results of photolytic experiments under artificial light. ZnO appeared to be more effective in MTBU oxidation than TiO2. The results obtained point to the interest of using organic wastes and heterogeneous photocatalysis for reducing the pollution of groundwater by pesticide drainage. PMID:25079405

Fenoll, José; Flores, Pilar; Hellín, Pilar; Hernández, Joaquín; Navarro, Simon

2014-04-01

393

Water Striders  

NSDL National Science Digital Library

In this outdoor activity/field trip, learners catch and observe water striders to explore their movement and feeding behaviors. To observe strider locomotion, learners look closely at caught water striders' body structure, then mark the striders' bodies with a dot of thick tempera or acrylic paint and release the insects back to different areas of the pond habitat. The paint markings make it easier for learners to watch each insect's movement. To observe strider feeding, learners catch other small insects from the pond habitat and offer them to caught striders. After the activity, all organisms should be released into the pond habitat. If possible, learners can return to the strider habitat a few weeks after the activity, to check how far the marked striders have moved from where they were released.

Lawrence Hall of Science

1981-01-01

394

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.

John Farmer

395

Water Pollution  

NSDL National Science Digital Library

This set of activities is designed to help students understand water pollution and its potential effects on human and wildlife habitats. They will understand that pollutants can be divided into three groups: chemical, thermal, and biological. Learning objectives include identification of two or more pollutants in a bog, marsh, stream or other wetland area, using words and art to relate a message about pollution, and understanding that some pollutants cannot be seen.

396

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.

397

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

398

Water Resources Data, Louisiana, Water Year 2000  

USGS Publications Warehouse

Water resources data for the 2000 water year for Louisiana consists 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 66 gaging stations; stage only for 70 gaging stations and 7 lakes; water quality for 45 surface-water stations (including 25 gaging stations) and 108 wells; and water levels for 221 observation wells. Also included are data for 204 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.

Goree, B.B.; Lovelace, W.M.; Montgomery, P.A.; Resweber, J.C.; Sasser, D.C., Jr.; Walters, David J.

2001-01-01

399

Water Resources Data, Louisiana, Water Year 2001  

USGS Publications Warehouse

Water resources data for the 2001 water year for Louisiana consists 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 71 gaging stations; stage only for 73 gaging stations and 7 lakes; water quality for 66 surface-water stations (including 39 gaging stations) and 92 wells; and water levels for 205 observation wells. Also included are data for 166 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.

Goree, B.B.; Lovelace, W.M.; Montgomery, P.A.; Resweber, J.C.; Sasser, D.C., Jr.; Walters, David J.

2002-01-01

400

Water resources data, Louisiana, water year 2003  

USGS Publications Warehouse

Water resources data for the 2003 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 76 gaging stations; stage only for 86 gaging stations and 7 lakes; water quality for 56 surface-water stations (including 44 gaging stations) and 142 wells; and water levels for 313 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 Federal and State agencies in Louisiana.

Baumann, Todd; Goree, B.B.; Lovelace, W.M.; Montgomery, P.A.; Resweber, J.C.; Ross, Garron B.; Sasser, D.C., Jr.; Walters, D.J.

2004-01-01

401

Water Resources Data, Louisiana, Water Year 2002  

USGS Publications Warehouse

Water resources data for the 2002 water year for Louisiana consists 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 85 gaging stations; stage only for 79 gaging stations and 7 lakes; water quality for 52 surface-water stations (including 40 gaging stations) and 104 wells; and water levels for 300 observation wells. Also included are data for 143 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.

Goree, B.B.; Lovelace, W.M.; Montgomery, P.A.; Resweber, J.C.; Labbe, Charles K.; Walters, David J.

2003-01-01

402

Campus Water Uses and Potential Water Efficiencies  

Microsoft Academic Search

With recent increases in the price of water, saving water has become one of the main focuses for sustainability. The California Institute of Technology used 200,000,000 gallons of water in the year 2008; however the institute has never tracked this water to its destination within the campus. Using data collected from water meters on campus and from the utility company

Calvin Kuo; Melany Hunt; John Onderdonk; Matthew Berbee

2008-01-01

403

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.

404

Cleaner, Safer Water through Water Safety Plans  

E-print Network

and a local university, the WSP process resulted in improvements at the drinking water treatment plantCS232615A Cleaner, Safer Water through Water Safety Plans National Center for Environmental Health (NCEH) Global Water, Sanitation, and Hygiene Team's Water Safety Plan Assistance 1.5 million deaths

405

WATER RESOURCES NEBRASKA WATER RESOURCES RESEARCH INSTITUTE  

E-print Network

WATER RESOURCES NEBRASKA WATER RESOURCES RESEARCH INSTITUTE 212 AGRICULTURAL ENGINEERING BUILDING Committee on Natioha1 Water Resources report in 1961 and the formation of the Committee on Water Resources in emphasis"and values regarding water resources' research. Interest has shifted from}J4ter supply

Nebraska-Lincoln, University of

406

WATER RESOURCES NEBRASKA WATER RESOURCES RESEARCH INSTITUTE  

E-print Network

WATER RESOURCES NEBRASKA WATER RESOURCES RESEARCH INSTITUTE 212 AGRICULTURAL ENGINEERING BUILDING.ROGRAM FOR THE 1972, I~TERDISCIPL1NARY SEMINAR ON WATER RESOURCES1 The Interdisciplinary Water Resources Seminar upper classmen,graduate stUdents, ~rofessiona1 persons, faculty, nd others interested 1n water topics

Nebraska-Lincoln, University of

407

Water Sustainability Program Challenges to Sustainable Water  

E-print Network

Water Sustainability Program Forum Challenges to Sustainable Water Management in Arizona Sharon B. Megdal Director, WSP & Water Resources Research Center November 22, 2010 smegdal@cals.arizona.edu #12;· The Water Sustainability Program endeavors to ensure that we have safe and reliable water supplies

Cushing, Jim. M.

408

WATER RESOURCES NEBRASKA WATER RESOURCES RESEARCH INSTITUTE  

E-print Network

WATER RESOURCES NEBRASKA WATER RESOURCES RESEARCH INSTITUTE 212 AGRICULTURAL ENGINEERING BUILDING of the National Environmental Policy Act of 1969, water resources professionals squarely faced the fact that water has changed and improved the entire planning process so that it will ultimately serve water and other

Nebraska-Lincoln, University of

409

Water, Water Everywhere! [Narrator] Water, Water Everywhere Water is all around us, and its importance to nearly every process  

E-print Network

Water, Water Everywhere! [Narrator] Water, Water Everywhere Water is all around us, and its naturally as a liquid, gas, and solid. The process by which water moves around the Earth, from the ocean to the atmosphere to the land, and back to the ocean, is called the water cycle. Water regulates climate, storing

Waliser, Duane E.

410

XENOWAC 2009 International Conference on Xenobiotics in the Urban Water Cycle  

E-print Network

studied using immobilized titanium dioxide as catalyst. T he processes of degradation and reduction words: Tylosin; photocatalysis; titanium dioxide; immobilization; 1 Introduction The pollution of ground hydrogen peroxide or ozone are more efficient but may be costly. An alternative cheaper AOP

Boyer, Edmond

411

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.

412

Water, Ohio's Remarkable Resource.  

ERIC Educational Resources Information Center

Information on water and water resources in Ohio is presented in seven sections. Water from Ohio streams, water storage, lakes in Ohio, and ground water are discussed in the first section ("Water, A Part of the Earth"). A brief discussion on the ecosystem is provided in the second section ("Water and Life"). Topics discussed in the third section…

Groves, Carrie J.

413

Discovering the Water Cycle!  

NSDL National Science Digital Library

We will be learning about what the water cycle is and how it works. Resources! The Hydrologic Cycle: Water's journey through time The Water Cycle Thirstin's Water Cycle Activity Water evaporates from the surface Water Wonders These are a collection of websites that are going to help us in our journey of discovering what the water cycle is. ...

Miss Mortensen

2009-10-09

414

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.

415

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

416

Water Resources of Alaska  

NSDL National Science Digital Library

The Water Resources of Alaska homepage is provided by the US Geological Survey. The goal of this project is to study and understand Alaska's hydrology (surface water, ground water, and water quality) for use and management of the nation's water resources. The site features a list of published reports and information about current projects as well as a vast amount of hydrologic data such as surface water, ground water, water quality, glaciers, water use, and hydrologic data reports.

Geological Survey (U.S.). Water Resources Division. Alaska District.

1999-01-01

417

California's Water Energy Relationship  

E-print Network

?........................................................6 THE WATER USE CYCLE .........................................................................................................................7 THE ENERGY INTENSITY OF THE WATER USE CYCLE ................................................................................................................................................16 Energy Recovery from the Water Use Cycle...............................................................................................

418

Water Wonders  

NSDL National Science Digital Library

Students will be introduced to different species of macroinvertebrates. They will hypothesize why each insect looks the way it does. Then students will make observations of macroinvertebrates in an aquarium in their classroom. For an optional extension, teachers can take students to a local stream or pond to conduct field observations. Materials needed include sand, water, aquatics plants and insects; estimated materials cost does not include aquarium. This is the 3rd of 3 sets of learning activities that are companion activities to the Elementary GLOBE children's book, Discoveries at Willow Creek. Includes a teacher implementation guide.

2012-08-03

419

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

420

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

421

Water watch  

SciTech Connect

This issue of [open quotes]Water Watch[close quotes] focuses on spring flood potential based on reports and data provided by the National Weather Service Office of Hydrology, the US Department of Agriculture, the Bureau of Reclamation, the Soil Conservation Service, and the US Geological Survey. Ninety-day outlooks are through June 1992. For purposes of reporting, the US is divided into six regions. The data presented in the Hydropower Generation Report can be used to observe how weather conditions affected hydro generation in March.

Not Available

1992-06-01

422

Water watch  

SciTech Connect

This issue of [open quotes]Water Watch[close quotes] focuses on soil moisture conditions across the country as of the first of April. In addition, the department describes streamflow conditions across the US forecast for April through July. The information presented is based on data from the US Geological Survey, the National Weather Service, and the Soil Conservation Service. For purposes of providing this information, the US is divided into six regions. The Hydropower Generation Report can be used to observe how weather conditions affected hydro generation in March.

Not Available

1991-06-01

423

Environment Canada: Water  

NSDL National Science Digital Library

This comprehensive site contains facts, figures, references, teacher's aides, news, events, and much more on subjects pertaining to water. Some of the subjects touched on include aquatic ecosystems, groundwater, lakes, permafrost, properties of water, rivers, sediment, snow and ice, water and climate, and Wetlands. Water policy and legislation is also discussed and includes information on federal-provincial cooperation, international, legislation and regulation, provincial/territorial, and water policy in Canada. There is also a section on the management of water including bulk water removal and water export, Flood Damage Reduction Program, floods, water efficiency/conservation, water modeling, water pollution, water quality, water resource economics, and water use. The section on water and culture discusses Aboriginal issues, water and art, and water and Canadian identity. The site is available in English and French.

424

Water Resources Outreach Program - Water Education Posters  

NSDL National Science Digital Library

This site contains a series of six posters all relating to water education: wetlands, water use, waste water, navigation, ground water, and water quality. Each poster includes information about the topic as well as related classroom activities. The objective of the water-resources education program is to stimulate interest in and provide a basic knowledge of water resources for students in grades K-12. This United States Geological Survey (USGS) website is part of the Water Resources Education Initiative (WREI), a program developed by the USGS in 1991.

425

Improved water does not mean safe water  

NASA Astrophysics Data System (ADS)

This work presents a model for estimating global access to drinking water that meets World Health Organization (WHO) water quality guidelines. The currently accepted international estimate of global access to safe water, the WHO and United Nations Children's Fund's (UNICEF) Joint Monitoring Program (JMP) report, estimates the population with access to water service infrastructure that is classified as improved and unimproved. The JMP report uses access to improved water sources as a proxy for access to safe water, but improved water sources do not always meet drinking water quality guidelines. Therefore, this report likely overestimates the number of people with access to safe water. Based on the JMP estimate, the United Nations has recently announced that the world has reached the Millennium Development Goal (MDG) target for access to safe water. Our new framework employs a statistical model that incorporates source water quality, water supply interruptions, water storage practices, and point of use water treatment to estimate access to safe water, resulting in a figure that is lower than the JMP estimate of global access to safe water. We estimate that at least 28% of the world does not have access to safe water today, as compared to the JMP estimate of 12%. These findings indicate that much more work is needed on the international scale to meet the MDG target for access to safe water.

MacDonald, L. H.; Guo, Y.; Schwab, K. J.

2012-12-01

426

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.

Hitch, D. E., (compiler); Soensken, P.J.; Sebree, S.K.; Wilson, K.E.; Walczyk, V.C.; Drudik, R.A.; Miller, J.D.; Hull, S.H.

2005-01-01

427

Frontispiece: Enhancing Electrochemical Water-Splitting Kinetics by Polarization-Driven Formation of Near-Surface Iron(0): An In?Situ XPS Study on Perovskite-Type Electrodes.  

PubMed

Electrocatalysis In their Communication on page?2628?ff., A.?K. Opitz et?al. show that a large increase in H2 production rate is connected with the exsolution of metallic iron particles from a perovskite-type electrode. PMID:25689478

Opitz, Alexander K; Nenning, Andreas; Rameshan, Christoph; Rameshan, Raffael; Blume, Raoul; Hävecker, Michael; Knop-Gericke, Axel; Rupprechter, Günther; Fleig, Jürgen; Klötzer, Bernhard

2015-02-23

428

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.

429

Sodium in Drinking Water  

MedlinePLUS

... To reduce my sodium intake, should I buy bottled water instead of using tap water? For more information. ... To reduce my sodium intake, should I buy bottled water instead of using tap water? It is not ...

430

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, ...

431

Bottled Water and Fluoride  

MedlinePLUS

... Water Fluoridation Journal Articles for Community Water Fluoridation Community Water Fluoridation Recommend on Facebook Tweet Share Compartir ... What's this? Submit Button Related Links Overview for Community Water Fluoridation Guidelines & Recommendations for Fluoride Fact Sheets ...

432

Learn about Water  

MedlinePLUS

... Learn about Water When the water in our rivers, lakes, and oceans becomes polluted, the effects can ... resources . Water Bodies Oceans, Coasts, Estuaries and Beaches Rivers and Streams Wetlands More Water Bodies resources Drinking ...

433

Drinking Water Standards  

E-print Network

This publication explains the federal safety standards for drinking water provided by public water supply systems. It discusses the legal requirements for public water supplies, the maximum level allowed for contaminants in the water...

Dozier, Monty; McFarland, Mark L.

2006-04-26

434

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 ...

435

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, ...

436

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, ...

437

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 ...

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

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 ...

440

Autoionization of water  

NSDL National Science Digital Library

This site provides an animation showing the three normal vibrational modes of the water molecule as well as proton transfer in the following three situations: (1) hydronium ion/water, (2) hydroxide ion/water, and (3)two water molecules.

Craig Merlic

441

Water Structure and Behavior  

NSDL National Science Digital Library

In this site, Martin Chaplin has brought together a selection of ideas concerning the complex behavior of water in hopes of encouraging both the understanding of water and further work. Some of the many ideas presented are: the structure of water, water anomalies, hydrogen bonding, the phase diagram of water, and water hydration.

Martin Chaplin

442

MODELING WATER QUALITY  

Technology Transfer Automated Retrieval System (TEKTRAN)

Water quality models are based on some representation of hydrology and may include movement of surface water, ground water, and mixing of water in lakes and water bodies. Water quality models simulate some combination of sediment, nutrients, heavy metals, xenobiotics, and aquatic biology. Althoug...

443

WRAMS, sustainable water recycling  

Microsoft Academic Search

The Water Reclamation and Management Scheme (WRAMS) at Sydney Olympic Park was built as part of the Olympic Games in 2000. The Scheme was designed to treat raw domestic sewage into recycled water which is then sold back to consumers. The main elements of WRAMS are a water reclamation plant, a water treatment plant, storm water collection, clean water storage

H. Chapman

2006-01-01

444

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 ...

Miss Amanda

2011-02-14

445

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

446

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

447

EPANET water quality model  

Microsoft Academic Search

EPANET represents a third generation of water quality modeling software developed by the U.S. EPA's Drinking Water Research Division, offering significant advances in the state of the art for network water quality analysis. EPANET performs extended period simulation of hydraulic and water quality behavior within water distribution systems. In addition to substance concentration, water age and source tracing can also

Rossman

1993-01-01

448

Waters of the Earth  

NSDL National Science Digital Library

In this lesson, students make a visual display showing the distribution of water on earth. Using separate bottles, students illustrate the amount of water in oceans, fresh water locked up as ice, underground fresh water, surface fresh water, and water in air and soil.

449

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

450

Water Resources Policy & Economics  

E-print Network

Water Resources Policy & Economics FOR 4984 Selected Course Topics · Appropriative and riparian water institutions · Incentives for conservation · Water rights for in-stream environmental use · Surface water-groundwater management · Water quality regulations · Water markets · Economic and policy

Buehrer, R. Michael

451

SOIL WATER SENSING FOR PLANT WATER UPTAKE  

Technology Transfer Automated Retrieval System (TEKTRAN)

Of the many ways to deduce plant water uptake, the soil water balance is the most frequently used, with plant water uptake determined as the residual of other terms in the equation. Extensive work with weighing lysimeters and soil water sensing methods allows us to contrast the effectiveness of and ...

452

Household Water Quality Home Water Quality Problems  

E-print Network

Household Water Quality Home Water Quality Problems­ Causes and Treatments Blake Ross, Extension cause health problems, damage equipment or plumbing, or make the water undesirable due to taste, odor, appearance or staining. Waterrelated problems will be found primarily in homes serviced by a private water

Liskiewicz, Maciej

453

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

454

Water Withdrawals and Water Use in Michigan  

E-print Network

Page 1 Water Withdrawals and Water Use in Michigan Michigan State University · New · February 2011 information about the amount of water used in Michigan and the purposes of its use is important for effective River Basin Water Resources Compact (the Compact). As part of implementing the Compact and facilitating

455

Water 3: Accounting For Our Water Needs  

NSDL National Science Digital Library

How do we account for water use? What is the difference between water consumed and water withdrawn? What is the water footprint tool? This video examines these questions. This video is part of the Sustainability Learning Suites, made possible in part by a grant from the National Science Foundation. See 'Learn more about this resource' for Learning Objectives and Activities.

2012-12-19

456

WATER RESOURCES NEBRASKA WATER RESOURCES RESEARCH INSTITUTE  

E-print Network

WATER RESOURCES NEBRASKA WATER RESOURCES RESEARCH INSTITUTE 212 AGRICULTURAL ENGINEERING BUILDING OF THE DIRECTOR . . · Once again during the spring 1973 semester the Nebraska Water Resources Research Institute will sponsor an Interdisciplinary Water Resources Seminar. These seminars have been held for the past five

Nebraska-Lincoln, University of

457

WATER RESOURCES NEBRASKA WATER RESOURCES RESEARCH INSTITUTE  

E-print Network

WATER RESOURCES NEBRASKA WATER RESOURCES RESEARCH INSTITUTE 212 AGRICULTURAL ENGINEERING BUILDING ALLOTMENT PROJECT DEADLINE The Nebraska Water Resources Research Institute is now prepared to receive basicIe. LB-334, enacted by the 1969 Legislature, authorized the Nebraska Soil a~d Water Conservation

Nebraska-Lincoln, University of

458

WATER RESOURCES NEBRASKA WATER RESOURCES RESEARCH INSTITUTE  

E-print Network

WATER RESOURCES NEBRASKA WATER RESOURCES RESEARCH INSTITUTE 212 AGRICULTURAL ENGINEERING BUILDING,000,000 for the Sec. 101 matching grant program, and $2,000,000 for the Title II program. INTERDISCIPLINARY WATER RESOURCE SEMINAR An Interdisciplinary Water Resource Seminar will be offered during the 1970 Semeste

Nebraska-Lincoln, University of

459

WATER RESOURCES NEBRASKA WATER RESOURCES RESEARCH INSTITUTE  

E-print Network

WATER RESOURCES NEBRASKA WATER RESOURCES RESEARCH INSTITUTE 212 AGRICULTURAL ENGINEERING BUILDING LABLE FRm1 ~.~, VI I RI RI I · The Nebraska Water Resources Research Institute has recently issued a new. This publi- cation may be obtained by writing: Dr. Warren Viessman, Jr., Director, Nebraska Water Resources

Nebraska-Lincoln, University of

460

WATER RESOURCES NEBRASKA WATER RESOURCES RESEARCH INSTITUTE  

E-print Network

WATER RESOURCES NEBRASKA WATER RESOURCES RESEARCH INSTITUTE 212 AGRICULTURAL ENGINEERING BUILDING Research application is an educational activity. Its aim is to pro- duce a change in the water resource environment by producing a change in people who manage water resources. #12;-2- 6. Provide Readable Reports

Nebraska-Lincoln, University of

461

WATER RESOURCES NEBRASKA WATER RESOURCES RESEARCH INSTITUTE  

E-print Network

WATER RESOURCES NEBRASKA WATER RESOURCES RESEARCH INSTITUTE 212 AGRICULTURAL ENGINEERING BUILDING~ November 1973 Opportunities for cost effective research related to energy-water issues are abundant. Many. It would be impossible to list all fruitful avenues for energy-water research, but some important issues

Nebraska-Lincoln, University of

462

WATER RESOURCES NEBRASKA WATER RESOURCES RESEARCH INSTITUTE  

E-print Network

WATER RESOURCES NEBRASKA WATER RESOURCES RESEARCH INSTITUTE 212 AGRICULTURAL ENGINEERING BUILDING during precipitation-free periods and constitutes the principal source of fresh water for many arid local- ities. About 70-80 percent of the water used in Nebraska is from groundwater sources, while the national

Nebraska-Lincoln, University of

463

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

464

DISINFECTION OF WATER: DRINKING WATER, RECREATIONAL WATER, AND WASTEWATER  

EPA Science Inventory

This chapter describes and categorizes the methodology used for disinfection of drinking water, recreational water and wastewater including wastewater sludges. It largely is a literature summary and references articles covering the years of 1939 through 1999, with a few reference...

465

The Water Cycle  

NSDL National Science Digital Library

Students will learn the process of the water cycle. Alabama Course of Study: Science. Second Grade: Standard 9: Describe evaporation, condensation, and precipitation in the water cycle. What is the water cycle? On the worksheet provided, list the 4 parts of the water cycle. Between the parts draw a small picture to represent what is happening during this cycle. The Water Cycle See how we use the water in the water cycle. Thirstins Water Cycle Name 3 ways water changes form. This is an animated diagram of the Water Cycle Here is a ...

Mrs. Lopez

2009-07-09

466

THE WATER CYCLE/ CLOUDS  

NSDL National Science Digital Library

Students will learn about the water cycle and how it works. You will explore many resources to find out many new factors about the water cycle. What is the water cycle? National water cycle Name the 4 water parts of the water cycle? Weather wonders Where are 3 places that the water cycle exists- What happens after condensation? animated water cycle Name 4 types of clouds? What is the highest level cloud called? Which cloud is associated with powerful thunderstorms? Cloud Types What do clouds have to do with the water cycle? National water cycle What is ...

Ms.Brown

2009-04-06

467

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.

468

Smart Water: Energy-Water Optimization in Drinking Water Systems  

EPA Science Inventory

This project aims to develop and commercialize a Smart Water Platform ? Sensor-based Data-driven Energy-Water Optimization technology in drinking water systems. The key technological advances rely on cross-platform data acquisition and management system, model-based real-time sys...

469

Water, Water Everywhere: Phase Diagrams of Ordinary Water Substance  

ERIC Educational Resources Information Center

The full phase diagram of water in the form of a graphical representation of the three-dimensional (3D) PVT diagram using authentic data is presented. An interesting controversy regarding the phase behavior of water was the much-touted proposal of a solid phase of water, polywater, supposedly stable under atmospheric conditions.

Glasser, L.

2004-01-01

470

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

471

A Proton Channel Allows a Hydrogen Oxidation Catalyst to Operate at a Moderate Overpotential with Water Acting as a Base  

SciTech Connect

Proton channels facilitate the movement of protons over large distances and are critical in many reactions, from controlling proton delivery in metalloenzymes[1] to moving protons through PEM fuel cells.[2] Hydrogenases are enzymes that use proton channels to deliver protons to or from the enzyme active site to achieve high rates of hydrogen production and oxidation at low overpotentials.[3] The [Ni(PR2NR’2)2]2+ series of complexes, which are functional mimics of the [FeFe]-hydrogenase active site, utilize pendant amines to move the proton to or from the Ni, resulting in some of the fastest synthetic catalysts for hydrogen production and oxidation reported.[4] While intramolecular proton movement has been shown to be facile,[5] deprotonation of hydrogen oxidation catalysts can be a slow step for catalysis.[6] Additionally, a stable H2 adduct (endo-endo) is formed which, if bypassed, could contribute to an overall enhanced rate (Figure 1). A proton channel may aid in addressing these outstanding issues, and the well-studied nature of these catalysts allows them to serve as a platform to investigate the role of a proton channel in solving these problems. To this end we added a second proton relay to this complex, which we demonstrate serves two purposes: we show that the second proton relay facilitates rapid proton transfer, altering the kinetic products formed following H2 addition, and avoiding the low energy endo-endo intermediate. It also aids in lowering the overpotential at which the catalyst operates using water as a base, demonstrating the multi-functional role of a proton channel in molecular catalysts, and possibly in enzymes. This work was supported by the US Department of Energy, Early Career Research Program, Basic Energy Sciences, Chemical Sciences, Geosciences & Biosciences Division and by the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

Lense, Sheri J.; Dutta, Arnab; Roberts, John A.; Shaw, Wendy J.

2014-01-25

472

Interfacial fabrication of functional supramolecular polymeric networks for photocatalysis.  

PubMed

Supramolecular polymeric networks based on host-enhanced ?-? interaction have been obtained at a liquid-solid interface through the layer-by-layer (LbL) assembly of porphyrin bearing four naphthalene groups and cucurbit[8]uril. The fabricating progress of supramolecular networks at interface can be efficiently controlled, simply by adjusting the layer-pair number of LbL films. Moreover, upon irradiation of visible light, these supramolecular networks exhibit good catalytic features for the oxidation of various phenols. It is anticipated that this strategy of fabricating supramolecular polymeric networks at the interface has potential applications in the fields of sewage disposal and biocatalysis, just to name a few. PMID:25479195

Yuan, Bin; Yang, Hui; Wang, Zhiqiang; Zhang, Xi

2014-12-30

473

Photocatalysis of fenoxycarb over silver-modified zeolites.  

PubMed

Two samples of silver doped into zeolite Y were prepared and characterized. ICP and SEM-EDS analysis indicate that the AgY1 sample contains twice the amount of silver compared to the AgY2 sample. Solid state luminescence spectroscopy shows variations in the emission modes of the site-selective luminescence where various luminophores might be excited upon selecting the proper excitation energy. The selected material effectively decomposed the pesticide fenoxycarb in aqueous solution. The photodecomposition of fenoxycarb reached 80 % upon irradiation for 60 min in the presence of the AgY1 catalyst. 2-(4-Phenoxy-phenoxy)ethyl] carbamic acid (1) and 1-amine-2-(phenoxy-4-ol) ethane (2) were identified as products for both uncatalyzed solution and the catalyzed fenoxycarb with AgY2 catalyst. Whereas, compound (2) was the only product identified in the catalyzed reaction with AgY1. PMID:24562452

Ahern, John; Kanan, Sofian; Sara, Ziad; Job, Thomas; Alnaizy, Raafat; Abu Farha, Nedal; Patterson, Howard

2015-03-01

474

Visible photocatalysis and photostability of Ag3PO4 photocatalyst  

NASA Astrophysics Data System (ADS)

Ag3PO4 photocatalyst was prepared by precipitation method and characterized by SEM, XRD and diffusive reflectance UV-vis (DRUV-vis) absorption spectra. The gas-phase photodegradation of volatile organic compounds (VOCs) such as benzene and acetone, and the liquid-phase photodegradation of the cationic and anionic dyes on Ag3PO4 were systematically investigated. Both benzene and acetone could not be photodegraded on the Ag3PO4 photocatalyst under the visible irradiation. The Ag3PO4 photocatalyst is efficient for the photodegradation of the aqueous dye solutions, but could not completely photomineralize the dyes to CO2 and H2O. The reason is discussed by comparing the oxidation potential of organic pollutants and the potential of photogenerated holes in Ag3PO4, and measuring the absorption of organic pollutants on Ag3PO4. The photostability of the Ag3PO4 photocatalyst for the photo-degradation of the dyes was tested. The Ag3PO4 photocatalyst itself is photostable in the absence of the scavenger of the photogenerated holes, but is photocatalytically instable in the liquid-phase photodegradation of dyes due to the photoreduction of Ag+ in Ag3PO4 to Ag.

Luo, Lin; Li, Yuanzhi; Hou, Jingtao; Yang, Yi

2014-11-01

475

CLEANER SYNTHESIS OF ORGANIC COMPOUNDS USING SEMICONDUCTER PHOTOCATALYSIS  

EPA Science Inventory

The chemical industry is a significant component of the domestic economy, generating well over $250 billion in sales and a trade surplus exceeding $15 billion in each of the last 5 years. The industry is also a major source of industrial waste and is the dominant source of hazard...

476

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 com