Editorial

6 pages, 1408 KiB

Open AccessEditorial

Nanomaterials for Environmental Purification and Energy Conversion

by Ewa Kowalska, Agata Markowska-Szczupak and Marcin Janczarek

Catalysts 2019, 9(10), 855; https://doi.org/10.3390/catal9100855 - 14 Oct 2019

Cited by 2 | Viewed by 2128

Nanomaterials, engineered structures of which a single unit is sized (in at least one dimension) between 1 to 100 nm, are probably the fastest growing market in the world [...] Full article

(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)

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Research

Jump to: Editorial, Review

16 pages, 5740 KiB

Open AccessArticle

Photocatalytic Water Disinfection under Solar Irradiation by d-Glucose-Modified Titania

by Agata Markowska-Szczupak, Paulina Rokicka, Kunlei Wang, Maya Endo, Antoni Waldemar Morawski and Ewa Kowalska

Catalysts 2018, 8(8), 316; https://doi.org/10.3390/catal8080316 - 01 Aug 2018

Cited by 27 | Viewed by 4222

Abstract

Modified titania photocatalysts were synthesized by the pressure method using titanium(IV) oxide from Grupa Azoty Zakłady Chemiczne “Police” S.A., Police, Poland, and d-glucose solution. Characterization of obtained composites was performed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), elemental analysis, and measurements [...] Read more.

Modified titania photocatalysts were synthesized by the pressure method using titanium(IV) oxide from Grupa Azoty Zakłady Chemiczne “Police” S.A., Police, Poland, and d-glucose solution. Characterization of obtained composites was performed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), elemental analysis, and measurements of zeta potential and specific surface area (SSA). The possibility of using glucose-titania composites as photocatalysts for simulated solar-assisted disinfection against gram-negative Escherichia coli and gram-positive Stapchyloccocus epidermidis bacteria were examined in two reaction systems, i.e., for suspended and immobilized photocatalysts (on the concrete). It was found that an increase in the d-glucose concentration, i.e., higher carbon content, led to a decrease in antibacterial properties. The sample obtained from 1% of d-glucose solution at 100 °C (TiO₂-1%-G-100) showed superior photocatalytic activity under UV-Vis irradiation toward both bacteria species. Water disinfection was more efficient for suspended photocatalyst than that for supported one, where complete disinfection was reached during 55–70 min and 120 min of irradiation, respectively. For the first time, it has been shown that titania modified with monosaccharides can be efficiently used for water disinfection, and the immobilization of photocatalyst on the concrete might be a prospective method for public water supplies. Full article

(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)

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17 pages, 4206 KiB

Open AccessArticle

Highly Active TiO₂ Microspheres Formation in the Presence of Ethylammonium Nitrate Ionic Liquid

by Anna Gołąbiewska, Micaela Checa-Suárez, Marta Paszkiewicz-Gawron, Wojciech Lisowski, Edyta Raczuk, Tomasz Klimczuk, Żaneta Polkowska, Ewelina Grabowska, Adriana Zaleska-Medynska and Justyna Łuczak

Catalysts 2018, 8(7), 279; https://doi.org/10.3390/catal8070279 - 11 Jul 2018

Cited by 11 | Viewed by 3549

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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12 pages, 2111 KiB

Open AccessFeature PaperArticle

Synergistic Effect of Cu₂O and Urea as Modifiers of TiO₂ for Enhanced Visible Light Activity

by Marcin Janczarek, Kunlei Wang and Ewa Kowalska

Catalysts 2018, 8(6), 240; https://doi.org/10.3390/catal8060240 - 06 Jun 2018

Cited by 7 | Viewed by 4966

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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20 pages, 11578 KiB

Open AccessEditor’s ChoiceArticle

Electrochemically Obtained TiO₂/Cu_xO_y Nanotube Arrays Presenting a Photocatalytic Response in Processes of Pollutants Degradation and Bacteria Inactivation in Aqueous Phase

by Magda Kozak, Paweł Mazierski, Joanna Żebrowska, Marek Kobylański, Tomasz Klimczuk, Wojciech Lisowski, Grzegorz Trykowski, Grzegorz Nowaczyk and Adriana Zaleska-Medynska

Catalysts 2018, 8(6), 237; https://doi.org/10.3390/catal8060237 - 05 Jun 2018

Cited by 19 | Viewed by 4452

Abstract

TiO₂/Cu_xO_y 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/Cu_xO_y 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/Cu_xO_y 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/Cu_xO_y 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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10 pages, 2892 KiB

Open AccessArticle

The Pros and Cons of Polydopamine-Sensitized Titanium Oxide for the Photoreduction of CO₂

by Tongyao Wang, Ming Xia and Xueqian Kong

Catalysts 2018, 8(5), 215; https://doi.org/10.3390/catal8050215 - 17 May 2018

Cited by 17 | Viewed by 5141

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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15 pages, 27615 KiB

Open AccessArticle

Synthesis, Characterization of Nanosized ZnCr₂O₄ and Its Photocatalytic Performance in the Degradation of Humic Acid from Drinking Water

by Raluca Dumitru, Florica Manea, Cornelia Păcurariu, Lavinia Lupa, Aniela Pop, Adrian Cioablă, Adrian Surdu and Adelina Ianculescu

Catalysts 2018, 8(5), 210; https://doi.org/10.3390/catal8050210 - 15 May 2018

Cited by 22 | Viewed by 5162

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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6 pages, 1233 KiB

Open AccessArticle

A Demonstration of Pt L₃-Edge EXAFS Free from Au L₃-Edge Using Log–Spiral Bent Crystal Laue Analyzers

by Yuki Wakisaka, Daiki Kido, Hiromitsu Uehara, Qiuyi Yuan, Satoru Takakusagi, Yohei Uemura, Toshihiko Yokoyama, Takahiro Wada, Motohiro Uo, Tomohiro Sakata, Oki Sekizawa, Tomoya Uruga, Yasuhiro Iwasawa and Kiyotaka Asakura

Catalysts 2018, 8(5), 204; https://doi.org/10.3390/catal8050204 - 13 May 2018

Cited by 2 | Viewed by 4824

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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11 pages, 5008 KiB

Open AccessArticle

Surface Reduced CeO₂ Nanowires for Direct Conversion of CO₂ and Methanol to Dimethyl Carbonate: Catalytic Performance and Role of Oxygen Vacancy

by Zhongwei Fu, Yuehong Yu, Zhen Li, Dongmei Han, Shuanjin Wang, Min Xiao and Yuezhong Meng

Catalysts 2018, 8(4), 164; https://doi.org/10.3390/catal8040164 - 19 Apr 2018

Cited by 27 | Viewed by 5673

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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18 pages, 9762 KiB

Open AccessArticle

Synthesis of Rectorite/Fe₃O₄/ZnO Composites and Their Application for the Removal of Methylene Blue Dye

by Huanhuan Wang, Peijiang Zhou, Rui Guo, Yifei Wang, Hongju Zhan and Yunfei Yuan

Catalysts 2018, 8(3), 107; https://doi.org/10.3390/catal8030107 - 09 Mar 2018

Cited by 33 | Viewed by 4833

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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11 pages, 3418 KiB

Open AccessArticle

Photocatalytic Reduction of CO₂ from Simulated Flue Gas with Colored Anatase

by Yebin Guan, Ming Xia, Alessandro Marchetti, Xiaohong Wang, Weicheng Cao, Hanxi Guan and Xueqian Kong

Catalysts 2018, 8(2), 78; https://doi.org/10.3390/catal8020078 - 13 Feb 2018

Cited by 8 | Viewed by 4271

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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15 pages, 5356 KiB

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

by Ali Hafizi and Mohammad Reza Rahimpour

Catalysts 2018, 8(1), 27; https://doi.org/10.3390/catal8010027 - 15 Jan 2018

Cited by 17 | Viewed by 4536

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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4401 KiB

Open AccessArticle

Cu Nanoparticles/Fluorine-Doped Tin Oxide (FTO) Nanocomposites for Photocatalytic H₂ Evolution under Visible Light Irradiation

by Hui Liu, An Wang, Quan Sun, Tingting Wang and Heping Zeng

Catalysts 2017, 7(12), 385; https://doi.org/10.3390/catal7120385 - 12 Dec 2017

Cited by 32 | Viewed by 9160

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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3367 KiB

Open AccessArticle

Promoting the Synthesis of Ethanol and Butanol by Salicylic Acid

by Jinxin Zou, Lei Wang and Peijun Ji

Catalysts 2017, 7(10), 295; https://doi.org/10.3390/catal7100295 - 01 Oct 2017

Cited by 2 | Viewed by 4810

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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3211 KiB

Open AccessArticle

Conductive Cotton Filters for Affordable and Efficient Water Purification

by Fang Li, Qin Xia, Qianxun Cheng, Mingzhi Huang and Yanbiao Liu

Catalysts 2017, 7(10), 291; https://doi.org/10.3390/catal7100291 - 29 Sep 2017

Cited by 9 | Viewed by 7090

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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4067 KiB

Open AccessArticle

Hydrogen Production from Cyclic Chemical Looping Steam Methane Reforming over Yttrium Promoted Ni/SBA-16 Oxygen Carrier

by Sanaz Daneshmand-Jahromi, Mohammad Reza Rahimpour, Maryam Meshksar and Ali Hafizi

Catalysts 2017, 7(10), 286; https://doi.org/10.3390/catal7100286 - 25 Sep 2017

Cited by 45 | Viewed by 7015

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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5658 KiB

Open AccessArticle

Synthesis of NaOH-Modified TiOF₂ and Its Enhanced Visible Light Photocatalytic Performance on RhB

by Chentao Hou, Wenli Liu and Jiaming Zhu

Catalysts 2017, 7(8), 243; https://doi.org/10.3390/catal7080243 - 22 Aug 2017

Cited by 29 | Viewed by 4907

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. [...] Read more.

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 S_BET 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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Recent Advances in Graphene Based TiO₂Nanocomposites (GTiO₂Ns) for Photocatalytic Degradation of Synthetic Dyes

by Rita Giovannetti, Elena Rommozzi, Marco Zannotti and Chiara Anna D’Amato

Catalysts 2017, 7(10), 305; https://doi.org/10.3390/catal7100305 - 16 Oct 2017

Cited by 123 | Viewed by 10716

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 [...] Read more.

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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