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Special Issue "Photocatalytic Materials"

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A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (31 October 2014)

Special Issue Editor

Guest Editor
Prof. Dr. Klara Hernadi

Department of Applied and Environmental Chemistry, University of Szeged, H-6720 Szeged, Rerrich B. ter 1., Hungary
Phone: +36 62 544626
Fax: +36 62 544619
Interests: heterogeneous catalysis; carbon nanotubes; nanocomposite materials; immobilization of biologically active units; cell-to-biomaterials interactions

Special Issue Information

Dear Colleagues,

Photocatalysis is one of the most frequently investigated topic in the field of advanced oxidation processes. Researchers around the world aim at developing semiconductor materials that can be effectively utilized for decomposing potentially harmful compounds in gas, liquid and solid phase. These catalysts can also be suitable for converting the energy of sunlight to chemical energy by generating hydrogen from water-based solutions. This special issue is targeted to gather quality papers about the synthesis and application of photocatalytic materials.

The collected articles will emphasize the surface and structural properties of these micro- and nanoscaled materials and focus on the applicability of the catalysts in UV or visible light irradiation. Studies concerning synthesis methods and reaction mechanisms are also welcome.

I am pleased to invite you to submit manuscripts for this special issue on Photocatalytic Materials in the form of research papers, communications, letters and review articles. We look forward to your participation in this special issue of the journal Materials.

Klara Hernadi
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials 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 1400 CHF (Swiss Francs).


Keywords

  • photocatalytic materials
  • advanced oxidation processes
  • decomposing harmful compounds
  • converting of sunlight
  • generating hydrogen
  • uv or visible light irradiation

Published Papers (10 papers)

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Research

Open AccessArticle One-Step Formation of WO3-Loaded TiO2 Nanotubes Composite Film for High Photocatalytic Performance
Materials 2015, 8(5), 2139-2153; doi:10.3390/ma8052139
Received: 12 November 2014 / Revised: 19 March 2015 / Accepted: 20 March 2015 / Published: 27 April 2015
Cited by 2 | PDF Full-text (1248 KB) | HTML Full-text | XML Full-text
Abstract
High aspect ratio of WO3-loaded TiO2 nanotube arrays have been successfully synthesized using the electrochemical anodization method in an ethylene glycol electrolyte containing 0.5 wt% ammonium fluoride in a range of applied voltage of 10–40 V for 30 min. [...] Read more.
High aspect ratio of WO3-loaded TiO2 nanotube arrays have been successfully synthesized using the electrochemical anodization method in an ethylene glycol electrolyte containing 0.5 wt% ammonium fluoride in a range of applied voltage of 10–40 V for 30 min. The novelty of this research works in the one-step formation of WO3-loaded TiO2 nanotube arrays composite film by using tungsten as the cathode material instead of the conventionally used platinum electrode. As compared with platinum, tungsten metal has lower stability, forming dissolved ions (W6+) in the electrolyte. The W6+ ions then move towards the titanium foil and form a coherent deposit on titanium foil. By controlling the oxidation rate and chemical dissolution rate of TiO2 during the electrochemical anodization, the nanotubular structure of TiO2 film could be achieved. In the present study, nanotube arrays were characterized using FESEM, EDAX, XRD, as well as Raman spectroscopy. Based on the results obtained, nanotube arrays with average pore diameter of up to 74 nm and length of 1.6 µm were produced. EDAX confirmed the presence of tungsten element within the nanotube arrays which varied in content from 1.06 at% to 3.29 at%. The photocatalytic activity of the nanotube arrays was then investigated using methyl orange degradation under TUV 96W UV-B Germicidal light irradiation. The nanotube with the highest aspect ratio, geometric surface area factor and at% of tungsten exhibited the highest photocatalytic activity due to more photo-induced electron-hole pairs generated by the larger surface area and because WO3 improves charge separation, reduces charge carrier recombination and increases charge carrier lifetime via accumulation of electrons and holes in the two different metal oxide semiconductor components. Full article
(This article belongs to the Special Issue Photocatalytic Materials)
Open AccessArticle Photocatalytic, Morphological and Structural Properties of the TiO2-SiO2-Ag Porous Structures Based System
Materials 2015, 8(3), 1059-1073; doi:10.3390/ma8031059
Received: 18 December 2014 / Revised: 19 February 2015 / Accepted: 28 February 2015 / Published: 12 March 2015
Cited by 1 | PDF Full-text (900 KB) | HTML Full-text | XML Full-text
Abstract
TiO2-SiO2-based nanocomposites with highly porous structures are gaining ever increasing attention due to their specific properties and large variability of synthesis pathways together with wide information on the impact of the synthesis on the activity of the catalyst. [...] Read more.
TiO2-SiO2-based nanocomposites with highly porous structures are gaining ever increasing attention due to their specific properties and large variability of synthesis pathways together with wide information on the impact of the synthesis on the activity of the catalyst. This thereby offers an alternative approach to traditional/commercially available photocatalysts. In our work TiO2-SiO2 based aerogels were obtained and modified with various amount of Ag nanoparticles, using different synthesis pathways. In the first instance their photocatalytic activity was examined in detail, by observing major differences toward salicylic acid and correlating them with their morphological and structural properties (investigating their mesoporous character, band-gap values, crystallinity grade etc.). Applying different techniques such as diffuse reflectance spectroscopy (DRS), X-ray diffraction measurements (XRD), transmission electron microscopy (TEM), Raman- and X-ray photoelectron spectroscopy (XPS) the nanoparticles and their composite morphological and structural details were successfully evaluated. Major differences were observed in the activity towards salicylic acid. Full article
(This article belongs to the Special Issue Photocatalytic Materials)
Figures

Open AccessArticle TiO2-Mediated Photocatalytic Mineralization of a Non-Ionic Detergent: Comparison and Combination with Other Advanced Oxidation Procedures
Materials 2015, 8(1), 231-250; doi:10.3390/ma8010231
Received: 7 November 2014 / Accepted: 6 January 2015 / Published: 14 January 2015
Cited by 2 | PDF Full-text (768 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Triton X-100 is one of the most widely-applied man-made non-ionic surfactants. This detergent can hardly be degraded by biological treatment. Hence, a more efficient degradation method is indispensable for the total mineralization of this pollutant. Application of heterogeneous photocatalysis based on a [...] Read more.
Triton X-100 is one of the most widely-applied man-made non-ionic surfactants. This detergent can hardly be degraded by biological treatment. Hence, a more efficient degradation method is indispensable for the total mineralization of this pollutant. Application of heterogeneous photocatalysis based on a TiO2 suspension is a possible solution. Its efficiency may be improved by the addition of various reagents. We have thoroughly examined the photocatalytic degradation of Triton X-100 under various circumstances. For comparison, the efficiencies of ozonation and treatment with peroxydisulfate were also determined under the same conditions. Besides, the combination of these advanced oxidation procedures (AOPs) were also studied. The mineralization of this surfactant was monitored by following the TOC and pH values, as well as the absorption and emission spectra of the reaction mixture. An ultra-high-performance liquid chromatography (UHPLC) method was developed and optimized for monitoring the degradation of Triton X-100. Intermediates were also detected by GC-MS analysis and followed during the photocatalysis, contributing to the elucidation of the degradation mechanism. This non-ionic surfactant could be efficiently degraded by TiO2-mediated heterogeneous photocatalysis. However, surprisingly, its combination with the AOPs applied in this study did not enhance the rate of the mineralization. Moreover, the presence of persulfate hindered the photocatalytic degradation. Full article
(This article belongs to the Special Issue Photocatalytic Materials)
Open AccessArticle Differently Shaped Au Nanoparticles: A Case Study on the Enhancement of the Photocatalytic Activity of Commercial TiO2
Materials 2015, 8(1), 162-180; doi:10.3390/ma8010162
Received: 16 October 2014 / Accepted: 24 December 2014 / Published: 31 December 2014
PDF Full-text (3809 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In the present work, the influence of a gold nanoparticle’s shape was investigated on the commercially available Evonik Aeroxide P25. By the variation of specific synthesis parameters, three differently shaped Au nanoparticles were synthetized and deposited on the surface of the chosen [...] Read more.
In the present work, the influence of a gold nanoparticle’s shape was investigated on the commercially available Evonik Aeroxide P25. By the variation of specific synthesis parameters, three differently shaped Au nanoparticles were synthetized and deposited on the surface of the chosen commercial titania. The nanoparticles and their composites’ morphological and structural details were evaluated, applying different techniques such as Diffuse Reflectance Spectroscopy (DRS), X-ray Diffraction (XRD), and Transmission Electron Microscopy (TEM). The influence of the Au nanoparticles’ shape was discussed by evaluating their photocatalytic efficiency on phenol and oxalic acid degradation and by investigating the H2 production efficacy of the selected composites. Major differences in their photocatalytic performance depending on the shape of the deposited noble metal were evidenced. Full article
(This article belongs to the Special Issue Photocatalytic Materials)
Open AccessArticle Photocatalytic Water Splitting for Hydrogen Production with Gd2MSbO7 (M = Fe, In, Y) Photocatalysts under Visible Light Irradiation
Materials 2015, 8(1), 16-30; doi:10.3390/ma8010016
Received: 31 October 2014 / Accepted: 18 December 2014 / Published: 24 December 2014
Cited by 2 | PDF Full-text (558 KB) | HTML Full-text | XML Full-text
Abstract
Novel photocatalysts Gd2FeSbO7, Gd2InSbO7 and Gd2YSbO7 were synthesized by the solid state reaction method for the first time. A comparative study about the structural and photocatalytic properties of Gd2MSbO7 [...] Read more.
Novel photocatalysts Gd2FeSbO7, Gd2InSbO7 and Gd2YSbO7 were synthesized by the solid state reaction method for the first time. A comparative study about the structural and photocatalytic properties of Gd2MSbO7 (M = Fe, In, Y) was reported. The results showed that Gd2FeSbO7, Gd2InSbO7 and Gd2YSbO7 crystallized with the pyrochlore-type structure, cubic crystal system and space group Fd3m. The lattice parameter a for Gd2FeSbO7, Gd2InSbO7 or Gd2YSbO7 was 10.276026 Å, 10.449546 Å or 10.653651 Å. The band gap of Gd2FeSbO7, Gd2InSbO7 or Gd2YSbO7 was estimated to be 2.151 eV, 2.897 eV or 2.396 eV. For the photocatalytic water-splitting reaction, H2 or O2 evolution was observed from pure water with Gd2FeSbO7, Gd2InSbO7 or Gd2YSbO7 as catalyst under visible light irradiation (wavelength > 420 nm). Moreover, H2 or O2 also spilt by using Gd2FeSbO7, Gd2InSbO7 or Gd2YSbO7 as catalyst from CH3OH/H2O or AgNO3/H2O solutions under visible light irradiation (λ > 420 nm). Gd2FeSbO7 showed the highest activity compared with Gd2InSbO7 or Gd2YSbO7. At the same time, Gd2InSbO7 showed higher activity compared with Gd2YSbO7. The photocatalytic activities were further improved under visible light irradiation with Gd2FeSbO7, Gd2InSbO7 or Gd2YSbO7 being loaded by Pt, NiO or RuO2. The effect of Pt was better than that of NiO or RuO2 for improving the photocatalytic activity of Gd2FeSbO7, Gd2InSbO7 or Gd2YSbO7. Full article
(This article belongs to the Special Issue Photocatalytic Materials)
Figures

Open AccessArticle Enhanced Photocatalytic Efficiency of N–F-Co-Embedded Titania under Visible Light Exposure for Removal of Indoor-Level Pollutants
Materials 2015, 8(1), 31-41; doi:10.3390/ma8010031
Received: 13 September 2014 / Accepted: 1 December 2014 / Published: 24 December 2014
Cited by 1 | PDF Full-text (1260 KB) | HTML Full-text | XML Full-text
Abstract
N–F-co-embedded titania (N–F–TiO2) photocatalysts with varying N:F ratios were synthesized and tested for their ability to photocatalyze the degradation of pollutants present at indoor air levels using visible light. The synthesis was achieved using a solvothermal process with tetrabutyl titanate, [...] Read more.
N–F-co-embedded titania (N–F–TiO2) photocatalysts with varying N:F ratios were synthesized and tested for their ability to photocatalyze the degradation of pollutants present at indoor air levels using visible light. The synthesis was achieved using a solvothermal process with tetrabutyl titanate, urea and ammonium fluoride as sources of Ti, N and F, respectively. Three selected volatile organic compounds (toluene, ethyl benzene and o-xylene) were selected as the test pollutants. The prepared composites were characterized using X-ray diffraction, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and Ultra-violet (UV)-visible spectroscopy. The photocatalytic degradation efficiencies of N–F–TiO2 composites were higher than those obtained using pure TiO2 and N–TiO2. Moreover, these efficiencies increased as the N:F ratio decreased from sixteen to eight, then decreased as it dropped further to three, indicating the presence of an optimal N:F ratio. Meanwhile, as retention time decreased from 12.4 to 0.62 s, the average photocatalytic efficiencies decreased from 65.4% to 21.7%, 91.5% to 37.8% and 95.8% to 44.7% for toluene, ethyl benzene and o-xylene, respectively. In contrast, the photocatalytic reaction rates increased as retention time decreased. In consideration of all of these factors, under optimized operational conditions, the prepared N–F–TiO2 composites could be utilized for the degradation of target pollutants at indoor air levels using visible light. Full article
(This article belongs to the Special Issue Photocatalytic Materials)
Open AccessArticle Enhanced Photocatalytic Degradation of Methyl Orange Dye under the Daylight Irradiation over CN-TiO2 Modified with OMS-2
Materials 2014, 7(12), 8024-8036; doi:10.3390/ma7128024
Received: 22 October 2014 / Revised: 2 December 2014 / Accepted: 9 December 2014 / Published: 12 December 2014
Cited by 4 | PDF Full-text (590 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this study, CN-TiO2 was modified with cryptomelane octahedral molecular sieves (OMS-2) by the sol-gel method based on the self-assembly technique to enhance its photocatalytic activity under the daylight irradiation. The synthesized samples were characterized by X-ray diffraction (XRD), UV-vis spectroscopy, [...] Read more.
In this study, CN-TiO2 was modified with cryptomelane octahedral molecular sieves (OMS-2) by the sol-gel method based on the self-assembly technique to enhance its photocatalytic activity under the daylight irradiation. The synthesized samples were characterized by X-ray diffraction (XRD), UV-vis spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and porosimeter analysis. The results showed that the addition of OMS-2 in the sol lead to higher Brunauer-Emmett-Teller (BET) surface area, pore volume, porosity of particle after heat treatment and the specific surface area, porosity, crystallite size and pore size distribution could be controlled by adjusting the calcination temperature. Compared to the CN-TiO2-400 sample, CN-TiO2/OMS-2-400 exhibited greater red shift in absorption edge of samples in visible region due to the OMS-2 coated. The enhancement of photocatalytic activity of CN-TiO2/OMS-2 composite photocatalyst was subsequently evaluated for the degradation of the methyl orange dye under the daylight irradiation in water. The results showed that the methyl orange dye degradation rate reach to 37.8% for the CN-TiO2/OMS-2-400 sample under the daylight irradiation for 5 h, which was higher than that of reference sample. The enhancement in daylight photocatalytic activities of the CN-TiO2/OMS samples could be attributed to the synergistic effects of OMS-2 coated, larger surface area and red shift in adsorption edge of the prepared sample. Full article
(This article belongs to the Special Issue Photocatalytic Materials)
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Open AccessArticle Photocatalytic H2 Evolution Using Different Commercial TiO2 Catalysts Deposited with Finely Size-Tailored Au Nanoparticles: Critical Dependence on Au Particle Size
Materials 2014, 7(12), 7615-7633; doi:10.3390/ma7127615
Received: 4 August 2014 / Revised: 28 September 2014 / Accepted: 14 November 2014 / Published: 26 November 2014
Cited by 1 | PDF Full-text (1410 KB) | HTML Full-text | XML Full-text
Abstract
One weight percent of differently sized Au nanoparticles were deposited on two commercially available TiO2 photocatalysts: Aeroxide P25 and Kronos Vlp7000. The primary objective was to investigate the influence of the noble metal particle size and the deposition method on the [...] Read more.
One weight percent of differently sized Au nanoparticles were deposited on two commercially available TiO2 photocatalysts: Aeroxide P25 and Kronos Vlp7000. The primary objective was to investigate the influence of the noble metal particle size and the deposition method on the photocatalytic activity. The developed synthesis method involves a simple approach for the preparation of finely-tuned Au particles through variation of the concentration of the stabilizing agent. Au was deposited on the TiO2 surface by photo- or chemical reduction, using trisodium citrate as a size-tailoring agent. The Au-TiO2 composites were synthetized by in situ reduction or by mixing the titania suspension with a previously prepared gold sol. The H2 production activities of the samples were studied in aqueous TiO2 suspensions irradiated with near-UV light in the absence of dissolved O2, with oxalic acid or methanol as the sacrificial agent. The H2 evolution rates proved to be strongly dependent on Au particle size: the highest H2 production rate was achieved when the Au particles measured ~6 nm. Full article
(This article belongs to the Special Issue Photocatalytic Materials)
Open AccessArticle Photocatalytic H2 Production Using Pt-TiO2 in the Presence of Oxalic Acid: Influence of the Noble Metal Size and the Carrier Gas Flow Rate
Materials 2014, 7(10), 7022-7038; doi:10.3390/ma7107022
Received: 4 August 2014 / Revised: 11 September 2014 / Accepted: 10 October 2014 / Published: 17 October 2014
Cited by 4 | PDF Full-text (968 KB) | HTML Full-text | XML Full-text
Abstract
The primary objective of the experiments was to investigate the differences in the photocatalytic performance when commercially available Aeroxide P25 TiO2 photocatalyst was deposited with differently sized Pt nanoparticles with identical platinum content (1 wt%). The noble metal deposition onto the [...] Read more.
The primary objective of the experiments was to investigate the differences in the photocatalytic performance when commercially available Aeroxide P25 TiO2 photocatalyst was deposited with differently sized Pt nanoparticles with identical platinum content (1 wt%). The noble metal deposition onto the TiO2 surface was achieved by in situ chemical reduction (CRIS) or by mixing chemically reduced Pt nanoparticle containing sols to the aqueous suspensions of the photocatalysts (sol-impregnated samples, CRSIM). Fine and low-scale control of the size of resulting Pt nanoparticles was obtained through variation of the trisodium citrate concentration during the syntheses. The reducing reagent was NaBH4. Photocatalytic activity of the samples and the reaction mechanism were examined during UV irradiation (λmax = 365 nm) in the presence of oxalic acid (50 mM) as a sacrificial hole scavenger component. The H2 evolution rates proved to be strongly dependent on the Pt particle size, as well as the irradiation time. A significant change of H2 formation rate during the oxalic acid transformation was observed which is unusual. It is probably regulated both by the decomposition rate of accumulated oxalic acid and the H+/H2 redox potential on the surface of the catalyst. The later potential is influenced by the concentration of the dissolved H2 gas in the reaction mixture. Full article
(This article belongs to the Special Issue Photocatalytic Materials)
Open AccessArticle Benzylpyrazinium Salts as Photo-Initiators in the Polymerization of Epoxide Monomers
Materials 2014, 7(8), 5581-5590; doi:10.3390/ma7085581
Received: 4 July 2014 / Revised: 23 July 2014 / Accepted: 24 July 2014 / Published: 31 July 2014
PDF Full-text (813 KB) | HTML Full-text | XML Full-text
Abstract
In order to study the capability of pyrazinium salt derivatives to act as photo-initiators of epoxide monomers, benzyl pyrazinium hexafluoroantimonate (BPH), benzyl 3,5-dimethyl pyrazine hexafluoroantimonate (BDH) and benzyl quinoxalinium hexafluoroantimonate (BQH) were synthesized by the Menschutkin reaction of benzyl bromide with pyrazine, [...] Read more.
In order to study the capability of pyrazinium salt derivatives to act as photo-initiators of epoxide monomers, benzyl pyrazinium hexafluoroantimonate (BPH), benzyl 3,5-dimethyl pyrazine hexafluoroantimonate (BDH) and benzyl quinoxalinium hexafluoroantimonate (BQH) were synthesized by the Menschutkin reaction of benzyl bromide with pyrazine, 2,6-dimethyl pyrazine, and quinoxaline, followed by exchanging with hexafluoroantimonate (SbF6). BPH, BDH, and BQH exhibited characteristic ultraviolet (UV) absorbance as well as exothermic peaks as a function of irradiation time in a differential photo-calorimeter (DPC). In the absence of photo-irradiation, cyclohexene oxide (CHO) underwent slow polymerization at 25 °C using BPH derivatives, but quantitative conversion was achieved even after a 5-min photo-irradiation. In addition, photo-irradiation was required for the photo-polymerization of CHO and styrene oxide (STO), which was characterized by a short induction period followed by a very rapid and exothermic polymerization. While glycidyl methyl ether (GME) required long induction periods, glycidyl phenyl ether (GPE) underwent rather slow and/or no photo-polymerization. The reactivity order of the monomers was CHO > STO >> GME >>> GPE, and the reactivity order for the photo-polymerization of CHO was BPH > BQH > BDH. It was found that BPH, BDH, and BQH could serve as photo-latent initiators for CHO, STO and GME, respectively. Full article
(This article belongs to the Special Issue Photocatalytic Materials)

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