Special Issue "Nanomaterials for Environmental Purification and Energy Conversion"

A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Metal Catalysis".

Deadline for manuscript submissions: closed (15 May 2018)

Special Issue Editors

Guest Editor
Prof. Ewa Kowalska

Institute for Catalysis, Hokkaido University, N21, W10, 001-0026 Sapporo, Japan
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Interests: heterogeneous photocatalysis; advanced oxidation processes (AOPs); environmental purification; plasmonic nanoparticles; antimicrobial properties; visible-light-responsive materials
Guest Editor
Dr. Marcin Janczarek

Department of Chemical Technology, Gdansk University of Technology, Narutowicza 11/12, 80-233 Gdansk, Poland
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Interests: heterogeneous photocatalysis; photoresponsive nanomaterials; environmental purification; photocatalytic reactors
Guest Editor
Prof. Agata Markowska-Szczupak

Department of Biotechnology, West Pomeranian University of Technology, Szczecin, Pulaskiego 10, 70-322 Szczecin, Poland
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Interests: biotechnology; microbiology; drug delivery; nanomedicine; nanotechnology; cell biology; bionanoscience; nanomaterials

Special Issue Information

Dear Colleagues,

The Symposium on Nanomaterials for Environmental Purification and Energy Conversion (SNEPEC) will be held in "snowy" city of Sapporo, at Hokkaido University, from 20 to 21 February, 2018.

The Symposium is organized (and sponsored) by the Institute for Catalysis, Hokkaido University, to share the knowledge and the development of catalysis science.

SPEPEC will have an exciting scientific program lead by renowned international experts, which will focus on the central role of catalysis in solving environmental and energy problems of modern societies at the interface of material, chemistry and environmental sciences.

The list of confirmed speakers includes, Michael R. Hoffmann (Caltech, USA; http://hoffmann.caltech.edu/), Detlef Bahnemann (Leibniz University of Hannover, Germany; https://www.lnqe.uni-hannover.de/bahnemann.html?&L=1), Bunsho Ohtani (Hokkaido University, http://pcat.cat.hokudai.ac.jp/pcat/), Teruhisa Ohno (Kyushu Institute of Technology, Japan; https://research02.jimu.kyutech.ac.jp/html/98_en.html), Ryu Abe (Kyoto University, Japan; http://www.ehcc.kyoto-u.ac.jp/eh41/home/abe/en/profile/), Michael Wark (University Oldenburg, Germany; https://www.uni-oldenburg.de/tc-wark/).

The SNEPEC welcomes participants from industry, government, as well as academia, which are cordially invited to contribute original research papers or reviews to this Special Issue of Catalysts. The contributions from those who would like, but could not attend to the SNEPEC, are also welcome.

For more details, please visit http://www.cat.hokudai.ac.jp/icat-nepec/.

Prof. Ewa Kowalska
Dr. Marcin Janczarek
Prof. Agata Markowska-Szczupak
Guest Editors

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Catalysts is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1300 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Heterogeneous photocatalysis

  • Nanomaterials fabrication

  • Environmental purification

  • Energy conversion

  • Water splitting

  • New techniques of nanomaterials characterization

  • Morphology-governed activity

  • Removal of microbiological pollutants

  • Water/wastewater treatment

  • Air treatment

  • Self-cleaning surfaces

  • Mechanism of pollutants’ decomposition

Published Papers (16 papers)

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Research

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Open AccessArticle Highly Active TiO2 Microspheres Formation in the Presence of Ethylammonium Nitrate Ionic Liquid
Catalysts 2018, 8(7), 279; https://doi.org/10.3390/catal8070279
Received: 14 May 2018 / Revised: 13 June 2018 / Accepted: 13 June 2018 / Published: 11 July 2018
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Abstract
Spherical microparticles of TiO2 were synthesized by the ionic liquid-assisted solvothermal method at different reaction times (3, 6, 12, and 24 h). The properties of the prepared photocatalysts were investigated by means of UV-VIS diffuse-reflectance spectroscopy (DRS), Brunauer–Emmett–Teller (BET) surface area measurements,
[...] Read more.
Spherical microparticles of TiO2 were synthesized by the ionic liquid-assisted solvothermal method at different reaction times (3, 6, 12, and 24 h). The properties of the prepared photocatalysts were investigated by means of UV-VIS diffuse-reflectance spectroscopy (DRS), Brunauer–Emmett–Teller (BET) surface area measurements, scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). The results indicated that the efficiency of the phenol degradation was related to the time of the solvothermal synthesis, as determined for the TiO2_EAN(1:1)_24h sample. The microparticles of TiO2_EAN(1:1)_3h that formed during only 3 h of the synthesis time revealed a really high photoactivity under visible irradiation (75%). This value increased to 80% and 82% after 12 h and 24 h, respectively. The photoactivity increase was accompanied by the increase of the specific surface area, thus the poresize as well as the ability to absorb UV-VIS irradiation. The high efficiency of the phenol degradation of the ionic liquid (IL)–TiO2 photocatalysts was ascribed to the interaction between the surface of the TiO2 and ionic liquid components (carbon and nitrogen). Full article
(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)
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Open AccessFeature PaperArticle Synergistic Effect of Cu2O and Urea as Modifiers of TiO2 for Enhanced Visible Light Activity
Catalysts 2018, 8(6), 240; https://doi.org/10.3390/catal8060240
Received: 14 March 2018 / Revised: 1 June 2018 / Accepted: 1 June 2018 / Published: 6 June 2018
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Abstract
Low cost compounds, i.e., Cu2O and urea, were used as TiO2 modifiers to introduce visible light activity. Simple and cheap methods were applied to synthesize an efficient and stable nanocomposite photocatalytic material. First, the core-shell structure TiO2–polytriazine derivatives
[...] Read more.
Low cost compounds, i.e., Cu2O and urea, were used as TiO2 modifiers to introduce visible light activity. Simple and cheap methods were applied to synthesize an efficient and stable nanocomposite photocatalytic material. First, the core-shell structure TiO2–polytriazine derivatives were prepared. Thereafter, Cu2O was added as the second semiconductor to form a dual heterojunction system. Enhanced visible light activity was found for the above-mentioned nanocomposite, confirming a synergistic effect of Cu2O and urea (via polytriazine derivatives on titania surface). Two possible mechanisms of visible light activity of the considered material were proposed regarding the type II heterojunction and Z-scheme through the essential improvement of the charge separation effect. Full article
(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)
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Open AccessArticle Electrochemically Obtained TiO2/CuxOy Nanotube Arrays Presenting a Photocatalytic Response in Processes of Pollutants Degradation and Bacteria Inactivation in Aqueous Phase
Catalysts 2018, 8(6), 237; https://doi.org/10.3390/catal8060237
Received: 15 May 2018 / Revised: 1 June 2018 / Accepted: 2 June 2018 / Published: 5 June 2018
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Abstract
TiO2/CuxOy nanotube (NT) arrays were synthesized using the anodization method in the presence of ethylene glycol and different parameters applied. The presence, morphology, and chemical character of the obtained structures was characterized using a variety of methods—SEM (scanning
[...] Read more.
TiO2/CuxOy nanotube (NT) arrays were synthesized using the anodization method in the presence of ethylene glycol and different parameters applied. The presence, morphology, and chemical character of the obtained structures was characterized using a variety of methods—SEM (scanning electron microscopy), XPS (X-ray photoelectron spectroscopy), XRD (X-ray crystallography), PL (photoluminescence), and EDX (energy-dispersive X-ray spectroscopy). A p-n mixed oxide heterojunction of Ti-Cu was created with a proved response to the visible light range and the stable form that were in contact with Ti. TiO2/CuxOy NTs presented the appearance of both Cu2O (mainly) and CuO components influencing the dimensions of the NTs (1.1–1.3 µm). Additionally, changes in voltage have been proven to affect the NTs’ length, which reached a value of 3.5 µm for Ti90Cu10_50V. Degradation of phenol in the aqueous phase was observed in 16% of Ti85Cu15_30V after 1 h of visible light irradiation (λ > 420 nm). Scavenger tests for phenol degradation process in presence of NT samples exposed the responsibility of superoxide radicals for degradation of organic compounds in Vis light region. Inactivation of bacteria strains Escherichia coli (E. coli), Bacillus subtilis (B. subtilis), and Clostridium sp. in presence of obtained TiO2/CuxOy NT photocatalysts, and Vis light has been studied showing a great improvement in inactivation efficiency with a response rate of 97% inactivation for E. coli and 98% for Clostridium sp. in 60 min. Evidently, TEM (transmission electron microscopy) images confirmed the bacteria cells’ damage. Full article
(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)
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Open AccessArticle The Pros and Cons of Polydopamine-Sensitized Titanium Oxide for the Photoreduction of CO2
Catalysts 2018, 8(5), 215; https://doi.org/10.3390/catal8050215
Received: 17 April 2018 / Revised: 11 May 2018 / Accepted: 15 May 2018 / Published: 17 May 2018
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Abstract
Photocatalytic reduction of CO2 into fuels is a promising route to reduce greenhouse gas emission, and it demands high-performance photocatalysts that can use visible light in the solar spectrum. Due to its broadband light adsorption, polydopamine (PDA) is considered as a promising
[...] Read more.
Photocatalytic reduction of CO2 into fuels is a promising route to reduce greenhouse gas emission, and it demands high-performance photocatalysts that can use visible light in the solar spectrum. Due to its broadband light adsorption, polydopamine (PDA) is considered as a promising photo-sensitization material for semiconductor photocatalysts. In this work, titanium oxides have been coated with PDA through an in-situ oxidation polymerization method to pursue CO2 reduction under visible light. We have shown that the surface coated PDA with a thickness of around 1 nm can enhance the photocatalytic performance of anatase under visible light to reduce CO2 into CO. Assisted with additional UV-vis adsorption and photoluminescence characterizations, we confirmed the sensitization effect of PDA on anatase. Furthermore, our study shows that thicker PDA coating might not be favorable, as PDA could decompose under both visible and UV-vis light irradiations. 13C solid-state nuclear magnetic resonance showed structural differences between thin and thick PDA coatings and revealed compositional changes of PDA after light irradiation. Full article
(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)
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Open AccessArticle Synthesis, Characterization of Nanosized ZnCr2O4 and Its Photocatalytic Performance in the Degradation of Humic Acid from Drinking Water
Catalysts 2018, 8(5), 210; https://doi.org/10.3390/catal8050210
Received: 31 March 2018 / Revised: 10 May 2018 / Accepted: 12 May 2018 / Published: 15 May 2018
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Abstract
Zinc chromite (ZnCr2O4) has been synthesized by the thermolysis of a new Zn(II)-Cr(III) oxalate coordination compound, namely [Cr2Zn(C2O4)4(OH2)6]·4H2O. The coordination compound has been characterized by
[...] Read more.
Zinc chromite (ZnCr2O4) has been synthesized by the thermolysis of a new Zn(II)-Cr(III) oxalate coordination compound, namely [Cr2Zn(C2O4)4(OH2)6]·4H2O. The coordination compound has been characterized by chemical analysis, infrared spectroscopy (IR), and thermal analysis. The zinc chromite obtained after a heating treatment of the coordination compound at 450 °C for 1 h has been investigated by XRD, FE-SEM, TEM/HR-TEM coupled with selected area electron diffraction (SAED) measurements. The photocatalytic performance of nanosized zinc chromite was assessed for the degradation and mineralization of humic acid (HA) from a drinking water source, envisaging the development of the advanced oxidation process for drinking water treatment technology. A mineralization efficiency of 60% was achieved after 180 min of 50 mg L−1 HA photocatalysis using zinc chromite under UV irradiation, in comparison with 7% efficiency reached by photolysis. Full article
(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)
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Open AccessArticle A Demonstration of Pt L3-Edge EXAFS Free from Au L3-Edge Using Log–Spiral Bent Crystal Laue Analyzers
Catalysts 2018, 8(5), 204; https://doi.org/10.3390/catal8050204
Received: 30 March 2018 / Revised: 30 April 2018 / Accepted: 8 May 2018 / Published: 13 May 2018
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Abstract
Pt-Au nanostructures are important and well-studied fuel cell catalysts for their promising catalytic performance. However, a detailed quantitative local structure analysis, using extended X-ray absorption fine structure (EXAFS) spectroscopy, have been inhibited by interference between Pt and Au L3-edges. In this
[...] Read more.
Pt-Au nanostructures are important and well-studied fuel cell catalysts for their promising catalytic performance. However, a detailed quantitative local structure analysis, using extended X-ray absorption fine structure (EXAFS) spectroscopy, have been inhibited by interference between Pt and Au L3-edges. In this paper, Pt L3-edge XAFS analysis, free of Au L3 edge, is demonstrated for a Pt-Au reference sample using a low-cost log–spiral bent crystal Laue analyzer (BCLA). This method facilitates the EXAFS structural analysis of Pt-Au catalysts, which are important to improve fuel cell catalysts. Full article
(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)
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Open AccessArticle Surface Reduced CeO2 Nanowires for Direct Conversion of CO2 and Methanol to Dimethyl Carbonate: Catalytic Performance and Role of Oxygen Vacancy
Catalysts 2018, 8(4), 164; https://doi.org/10.3390/catal8040164
Received: 14 March 2018 / Revised: 4 April 2018 / Accepted: 4 April 2018 / Published: 19 April 2018
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Abstract
Ultralong 1D CeO2 nanowires were synthesized via an advanced solvothermal method, surface reduced under H2 atmosphere, and first applied in direct synthesis of dimethyl carbonate (DMC) from CO2 and CH3OH. The micro morphologies, physical parameters of nanowires were
[...] Read more.
Ultralong 1D CeO2 nanowires were synthesized via an advanced solvothermal method, surface reduced under H2 atmosphere, and first applied in direct synthesis of dimethyl carbonate (DMC) from CO2 and CH3OH. The micro morphologies, physical parameters of nanowires were fully investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), N2 adsorption, X-ray photoelectron spectrum (XPS), and temperature-programmed desorption of ammonia/carbon dioxide (NH3-TPD/CO2-TPD). The effects of surface oxygen vacancy and acidic/alkaline sites on the catalytic activity was explored. After reduction, the acidic/alkaline sites of CeO2 nanowires can be dramatically improved and evidently raised the catalytic performance. CeO2 nanowires reduced at 500 °C (CeO2_NW_500) exhibited notably superior activity with DMC yield of 16.85 mmol gcat−1. Furthermore, kinetic insights of initial rate were carried out and the apparent activation energy barrier of CeO2_NW_500 catalyst was found to be 41.9 kJ/mol, much tiny than that of CeO2_NW catalyst (74.7 KJ/mol). Full article
(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)
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Open AccessArticle Synthesis of Rectorite/Fe3O4/ZnO Composites and Their Application for the Removal of Methylene Blue Dye
Catalysts 2018, 8(3), 107; https://doi.org/10.3390/catal8030107
Received: 10 February 2018 / Revised: 2 March 2018 / Accepted: 6 March 2018 / Published: 9 March 2018
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Abstract
A novel series of rectorite-based magnetic zinc oxide (ZnO) photocatalysts (REC/Fe3O4/ZnO) was synthesized and characterized in the present work. The fabricated REC/Fe3O4/ZnO composite possessed a high specific surface area and high capacity of adsorption and
[...] Read more.
A novel series of rectorite-based magnetic zinc oxide (ZnO) photocatalysts (REC/Fe3O4/ZnO) was synthesized and characterized in the present work. The fabricated REC/Fe3O4/ZnO composite possessed a high specific surface area and high capacity of adsorption and photocatalysis toward methylene blue (MB) dye. The adsorption isotherm of the dye on the composite fitted well to the Langmuir model, with a maximum adsorption of 35.1 mg/g. The high adsorption capacity increased the interactions between the dye and the REC/Fe3O4/ZnO, which enabled efficient decomposition of the dye under simulated solar radiation using REC/Fe3O4/ZnO as the photocatalyst. The degradation kinetics of MB dye followed the Langmuir–Hinshelwood model. More importantly, the degradation of MB dye and the mass loss of REC/Fe3O4/ZnO after three repetitive experiments were quite small. This suggests that the magnetic composite has great potential as an effective, stable, and easily recovered catalyst. Four major intermediates were detected during the degradation of MB dye and the degradation pathway was proposed. Full article
(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)
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Open AccessArticle Photocatalytic Reduction of CO2 from Simulated Flue Gas with Colored Anatase
Catalysts 2018, 8(2), 78; https://doi.org/10.3390/catal8020078
Received: 29 December 2017 / Revised: 6 February 2018 / Accepted: 9 February 2018 / Published: 13 February 2018
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Abstract
Photocatalytic reduction with sunlight is an economical and promising advanced approach for reducing the excessive emissions of CO2 from the combustion of fossil fuels. Aimed at practical applications, a type of inexpensive colored anatase material was used to evaluate CO2 photoreduction
[...] Read more.
Photocatalytic reduction with sunlight is an economical and promising advanced approach for reducing the excessive emissions of CO2 from the combustion of fossil fuels. Aimed at practical applications, a type of inexpensive colored anatase material was used to evaluate CO2 photoreduction performance on a platform with a continuous flow of gas mixtures (10 vol % CO2, 90% N2), which resembles realistic flue gas conditions. The results showed an enhanced photocatalytic activity compared with standard P25 and significant improvement over pristine anatase. Based on a series of characterization techniques, we propose that the oxygen vacancies and surface hydroxyl groups on colored anatase can reduce the bandgap and assist the binding of CO2 molecules. Our results showed that photoreduction of CO2 is feasible under practical conditions, and the efficiency could be improved through modification of catalysts. Full article
(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)
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Open AccessArticle Inhibiting Fe–Al Spinel Formation on a Narrowed Mesopore-Sized MgAl2O4 Support as a Novel Catalyst for H2 Production in Chemical Looping Technology
Catalysts 2018, 8(1), 27; https://doi.org/10.3390/catal8010027
Received: 13 October 2017 / Revised: 20 December 2017 / Accepted: 29 December 2017 / Published: 15 January 2018
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Abstract
In this paper, the structure of Al2O3 is modified with magnesium to synthesize MgAl2O4 as an oxygen carrier (OC) support. The surface properties and structural stability of the modified support are improved by the incorporation of magnesium
[...] Read more.
In this paper, the structure of Al2O3 is modified with magnesium to synthesize MgAl2O4 as an oxygen carrier (OC) support. The surface properties and structural stability of the modified support are improved by the incorporation of magnesium in the structure of the support and additionally by narrowing the pore size distribution (about 2.3 nm). Then, iron oxide is impregnated on both an Al2O3 support and a MgAl2O4 support as the oxygen transfer active site. The XRD results showed the formation of solely Fe2O3 on the MgAl2O4 support, while both Fe2O3 and Fe3O4 are detected in the synthesized Fe2O3-Al2O3 structure. The synthesized samples are investigated in chemical looping cycles, including CO reduction (as one of the most important side reactions of chemical looping reforming), at different temperatures (300–500 °C) and oxidation with steam at 700 °C for hydrogen production. The obtained results showed the inhibition of Fe–Al spinel formation in the structure of the Fe2O3-MgAl2O4 OC. In addition, H2 with a purity higher than 98% is achievable in oxidation of the OC with steam. In addition, the activity and crystalline change of the Fe2O3-MgAl2O4 OC is investigated after 20 reduction-oxidation cycles. Full article
(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)
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Open AccessArticle Cu Nanoparticles/Fluorine-Doped Tin Oxide (FTO) Nanocomposites for Photocatalytic H2 Evolution under Visible Light Irradiation
Catalysts 2017, 7(12), 385; https://doi.org/10.3390/catal7120385
Received: 12 August 2017 / Revised: 29 September 2017 / Accepted: 29 September 2017 / Published: 12 December 2017
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Abstract
Copper nanoparticles/fluorine-doped tin oxide (FTO) nanocomposites were successfully prepared by a simple hydrothermal method. The synthesized nanocomposites were characterized by X-ray diffraction (XRD), UV-visible diffuse-reflectance spectrum (UV-VIS DRS), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), Raman spectra, and X-ray photoelectron spectroscopy (XPS).
[...] Read more.
Copper nanoparticles/fluorine-doped tin oxide (FTO) nanocomposites were successfully prepared by a simple hydrothermal method. The synthesized nanocomposites were characterized by X-ray diffraction (XRD), UV-visible diffuse-reflectance spectrum (UV-VIS DRS), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), Raman spectra, and X-ray photoelectron spectroscopy (XPS). The obtained Cu/FTO nanocomposites exhibit high photocatalytic activity for H2 evolution under visible light (λ > 420 nm) irradiation. When the content of Cu is 19.2 wt % for FTO, the Cu/FTO photocatalyst shows the highest photocatalytic activity and the photocatalytic H2 evolution rate is up to 11.22 μmol·h−1. Meanwhile, the photocatalyst exhibits excellent stability and repeatability. It is revealed that the transfer efficiency of the photogenerated electrons is improved greatly because of the intense interaction between Cu NPs and FTO. Furthermore, a possible mechanism is proposed for enhanced photocatalytic H2 evolution of Cu/FTO photocatalysts under visible light irradiation. Full article
(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)
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Open AccessArticle Promoting the Synthesis of Ethanol and Butanol by Salicylic Acid
Catalysts 2017, 7(10), 295; https://doi.org/10.3390/catal7100295
Received: 3 September 2017 / Revised: 21 September 2017 / Accepted: 22 September 2017 / Published: 1 October 2017
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Abstract
Multiwalled carbon nanotubes (MWCNTs) were functionalized with salicylic acid (SA). The copper-cobalt catalyst was impregnated on the SA functionalized MWCNTs (SA-MWCNTs). The catalyst copper-cobalt/SA-MWCNTs was used to catalyze the synthesis of alcohols from synthesis gas. Salicylic acid can promote the synthesis of ethanol
[...] Read more.
Multiwalled carbon nanotubes (MWCNTs) were functionalized with salicylic acid (SA). The copper-cobalt catalyst was impregnated on the SA functionalized MWCNTs (SA-MWCNTs). The catalyst copper-cobalt/SA-MWCNTs was used to catalyze the synthesis of alcohols from synthesis gas. Salicylic acid can promote the synthesis of ethanol and butanol from synthesis gas, thus reducing the synthesis of methanol. This work demonstrated that salicylic acid not only can be used to functionalize carbon nanotubes, but also can enhance the production of ethanol and butanol from synthesis gas. On the other hand, the copper-cobalt catalyst supported on MWCNTs of 30 nm in diameter can synthesize more ethanol and butanol than supported on MWCNTs of 15 and 50 nm in diameter, indicating that the diameter of MWCNTs also has an effect on the synthesis of alcohols. Full article
(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)
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Open AccessArticle Conductive Cotton Filters for Affordable and Efficient Water Purification
Catalysts 2017, 7(10), 291; https://doi.org/10.3390/catal7100291
Received: 12 September 2017 / Revised: 26 September 2017 / Accepted: 26 September 2017 / Published: 29 September 2017
Cited by 1 | PDF Full-text (3211 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
It is highly desirable to develop affordable, energy-saving, and highly-effective technologies to alleviate the current water crisis. In this work, we reported a low-cost electrochemical filtration device composing of a conductive cotton filter anode and a Ti foil cathode. The device was operated
[...] Read more.
It is highly desirable to develop affordable, energy-saving, and highly-effective technologies to alleviate the current water crisis. In this work, we reported a low-cost electrochemical filtration device composing of a conductive cotton filter anode and a Ti foil cathode. The device was operated by gravity feed. The conductive cotton filter anodes were fabricated by a facile dying method to incorporate carbon nanotubes (CNTs) as fillers. The CNTs could serve as adsorbents for pollutants adsorption, as electrocatalysts for pollutants electrooxidation, and as conductive additives to render the cotton filters highly conductive. Cellulose-based cotton could serve as low-cost support to ‘host’ these CNTs. Upon application of external potential, the developed filtration device could not only achieve physically adsorption of organic compounds, but also chemically oxide these compounds on site. Three model organic compounds were employed to evaluate the oxidative capability of the device, i.e., ferrocyanide (a model single-electron-transfer electron donor), methyl orange (MO, a common recalcitrant azo-dye found in aqueous environments), and antibiotic tetracycline (TC, a common antibiotic released from the wastewater treatment plants). The devices exhibited a maximum electrooxidation flux of 0.37 mol/h/m2 for 5.0 mmol/L ferrocyanide, of 0.26 mol/h/m2 for 0.06 mmol/L MO, and of 0.9 mol/h/m2 for 0.2 mmol/L TC under given experimental conditions. The effects of several key operational parameters (e.g., total cell potential, CNT amount, and compound concentration) on the device performance were also studied. This study could shed some light on the good design of effective and affordable water purification devices for point-of-use applications. Full article
(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)
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Open AccessArticle Hydrogen Production from Cyclic Chemical Looping Steam Methane Reforming over Yttrium Promoted Ni/SBA-16 Oxygen Carrier
Catalysts 2017, 7(10), 286; https://doi.org/10.3390/catal7100286
Received: 3 September 2017 / Revised: 21 September 2017 / Accepted: 22 September 2017 / Published: 25 September 2017
Cited by 4 | PDF Full-text (4067 KB) | HTML Full-text | XML Full-text
Abstract
In this work, the modification of Ni/SBA-16 oxygen carrier (OC) with yttrium promoter is investigated. The yttrium promoted Ni-based oxygen carrier was synthesized via co-impregnation method and applied in chemical looping steam methane reforming (CL-SMR) process, which is used for the production of
[...] Read more.
In this work, the modification of Ni/SBA-16 oxygen carrier (OC) with yttrium promoter is investigated. The yttrium promoted Ni-based oxygen carrier was synthesized via co-impregnation method and applied in chemical looping steam methane reforming (CL-SMR) process, which is used for the production of clean energy carrier. The reaction temperature (500–750 °C), Y loading (2.5–7.4 wt. %), steam/carbon molar ratio (1–5), Ni loading (10–30 wt. %) and life time of OCs over 16 cycles at 650 °C were studied to investigate and optimize the structure of OC and process temperature with maximizing average methane conversion and hydrogen production yield. The synthesized OCs were characterized by multiples techniques. The results of X-ray powder diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) of reacted OCs showed that the presence of Y particles on the surface of OCs reduces the coke formation. The smaller NiO species were found for the yttrium promoted OC and therefore the distribution of Ni particles was improved. The reduction-oxidation (redox) results revealed that 25Ni-2.5Y/SBA-16 OC has the highest catalytic activity of about 99.83% average CH4 conversion and 85.34% H2 production yield at reduction temperature of 650 °C with the steam to carbon molar ratio of 2. Full article
(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)
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Open AccessArticle Synthesis of NaOH-Modified TiOF2 and Its Enhanced Visible Light Photocatalytic Performance on RhB
Catalysts 2017, 7(8), 243; https://doi.org/10.3390/catal7080243
Received: 16 July 2017 / Revised: 7 August 2017 / Accepted: 16 August 2017 / Published: 22 August 2017
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Abstract
NaOH-modified TiOF2 was successfully prepared using a modified low-temperature hydrothermal method. Scanning electron microscopy shows that NaOH-modified TiOF2 displayed a complex network shape with network units of about 100 nm. The structures of NaOH-modified TiOF2 have not been reported elsewhere.
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NaOH-modified TiOF2 was successfully prepared using a modified low-temperature hydrothermal method. Scanning electron microscopy shows that NaOH-modified TiOF2 displayed a complex network shape with network units of about 100 nm. The structures of NaOH-modified TiOF2 have not been reported elsewhere. The network shape permits the NaOH-modified TiOF2 a SBET of 36 m2∙g−1 and a pore diameter around 49 nm. X-ray diffraction characterization shows that TiOF2 and NaOH-modified TiOF2 are crystallized with a pure changed cubic phase which accords with the SEM results. Fourier transform infrared spectroscopy characterization shows that NaOH-modified TiOF2 has more O–H groups to supply more lone electron pairs to transfer from O of O–H to Ti and O of TiOF2. UV–vis diffuse reflectance spectroscopy (DRS) shows that the NaOH-modified TiOF2 sample has an adsorption plateau rising from 400 to 600 nm in comparison with TiOF2, and its band gap is 2.62 eV, lower than that of TiOF2. Due to the lower band gap, more O–H groups adsorption, network morphologies with larger surface area, and sensitization progress, the NaOH-modified TiOF2 exhibited much higher photocatalytic activity for Rhodamine B (RhB) degradation. In addition, considering the sensitization progress, O–H groups on TiOF2 not only accelerated the degradation rate of RhB, but also changed its degradation path. As a result, the NaOH-modified TiOF2 exhibited much higher photocatalytic activity for RhB degradation than the TiOF2 in references under visible light. This finding provides a new idea to enhance the photocatalytic performance by NaOH modification of the surface of TiOF2. Full article
(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)
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Review

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Open AccessFeature PaperReview Recent Advances in Graphene Based TiO2 Nanocomposites (GTiO2Ns) for Photocatalytic Degradation of Synthetic Dyes
Catalysts 2017, 7(10), 305; https://doi.org/10.3390/catal7100305
Received: 24 August 2017 / Revised: 3 October 2017 / Accepted: 10 October 2017 / Published: 16 October 2017
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Abstract
Synthetic dyes are widely used in textile, paper, food, cosmetic, and pharmaceutical industries. During industrial processes, some of these dyes are released into the wastewater and their successive release into rivers and lakes produces serious environmental problems. TiO2 is one of the
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Synthetic dyes are widely used in textile, paper, food, cosmetic, and pharmaceutical industries. During industrial processes, some of these dyes are released into the wastewater and their successive release into rivers and lakes produces serious environmental problems. TiO2 is one of the most widely studied and used photocatalysts for environmental remediation. However, it is mainly active under UV-light irradiation due to its band gap of 3.2 eV, while it shows low efficiency under the visible light spectrum. Regarding the exploration of TiO2 activation in the visible light region of the total solar spectrum, the incorporation of carbon nanomaterials, such as graphene, in order to form carbon-TiO2 composites is a promising area. Graphene, in fact, has a large surface area which makes it a good adsorbent for organic pollutants removal through the combination of electrostatic attraction and π-π interaction. Furthermore, it has a high electron mobility and therefore it reduces the electron-hole pair recombination, improving the photocatalytic activity of the semiconductor. In recent years, there was an increasing interest in the preparation of graphene-based TiO2 photocatalysts. The present short review describes the recent advances in TiO2 photocatalyst coupling with graphene materials with the aim of extending the light absorption of TiO2 from UV wavelengths into the visible region, focusing on recent progress in the design and applications in the photocatalytic degradation of synthetic dyes. Full article
(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)
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