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Nanomaterials
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Synthesis and Applications of Nanomaterials for Photocatalysis and Electrocatalysis
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Synthesis and Applications of Nanomaterials for Photocatalysis and Electrocatalysis

A special issue of Nanomaterials (ISSN 2079-4991).

Deadline for manuscript submissions: closed (30 October 2018) | Viewed by 67963

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Prof. Dr. Giuseppe Cappelletti

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Dipartimento di Chimica, Università degli Studi di Milano, Via Golgi 19, 20133 Milan, Italy
Interests: surface modification and functionalization; wettability; nanomaterials; thin layer; cultural heritage protection; colloids and interfaces; photocatalysis and VOC sensing; advanced oxidation processes for environmental remediation; formulation technology
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Claudia Letizia Bianchi

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Guest Editor
Department of Chemistry, University of Milan, Via Golgi 19, 20133 Milano, Italy
Interests: process intensification; photocatalysis; ultrasound; advanced materials synthesis; gas and liquid phase reactors
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Heterogeneous catalysis, exploiting photo- and electro-chemical reactions, has expanded rapidly in the last few decades, having undergone various developments, especially from the energetic and the environmental points of view. Photocatalysis plays a pivotal role in applications, such as water splitting and air/water remediation. Electrocatalysis can be found in a large array of research fields, including the development of electroanalytical sensors, waste water treatment and energy conversion devices (e.g., batteries, fuel and solar cells, etc.). Therefore, the fine control of the synthetic procedures, together with extensive physico-chemical characterizations of the tailored-made catalytic nanomaterials, are of fundamental importance to reach desired results.

The present Special Issue of Nanomaterials will include recent enhancements in the oxide/metal nanoparticles for photocatalytic and electrocatalytic applications, especially in the fields of pollutants abatement and energy conversion.

Prof. Giuseppe Cappelletti
Prof. Claudia L. Bianchi
Guest Editors

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2900 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

  • water and air photocatalytic remediation
  • energy conversion (e.g., batteries, fuel cells and solar cells, photovoltaic devices)
  • synthesis of nanomaterials
  • bulk/surface characterizations

Published Papers (13 papers)

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12 pages, 2544 KiB  
Article
Nano-MnO2 Decoration of TiO2 Microparticles to Promote Gaseous Ethanol Visible Photoremoval
by Marta Stucchi, Daria C. Boffito, Eleonora Pargoletti, Giuseppina Cerrato, Claudia L. Bianchi and Giuseppe Cappelletti
Nanomaterials 2018, 8(9), 686; https://doi.org/10.3390/nano8090686 - 03 Sep 2018
Cited by 23 | Viewed by 3495
Abstract
TiO2-based photocatalysis under visible light is an attractive way to abate air pollutants. Moreover, developing photocatalytic materials on a large-scale requires safe and low-cost precursors. Both high-performance TiO2 nanopowders and visible-light active noble metals do not match these requirements. Here, [...] Read more.
TiO2-based photocatalysis under visible light is an attractive way to abate air pollutants. Moreover, developing photocatalytic materials on a large-scale requires safe and low-cost precursors. Both high-performance TiO2 nanopowders and visible-light active noble metals do not match these requirements. Here, we report the design of novel Mn-decorated micrometric TiO2 particles. Pigmentary TiO2 replaced unsafe nano-TiO2 and firmly supported MnOx particles. Mn replaced noble metals such as Au or Ag, opening the way for the development of lower cost catalysts. Varying Mn loading or pH during the impregnation affected the final activity, thus giving important information to optimize the synthesis. Photocatalytic activity screening occurred on the gas-phase degradation of ethanol as a reference molecule, both under ultraviolet (UV) (6 h) and Light Emitting Diode (LED) (24 h) irradiation. Mn-doped TiO2 reached a maximum ethanol degradation of 35% under visible light after 24 h for the sample containing 20% of Mn. Also, we found that an acidic pH increased both ethanol degradation and mineralization to CO2, while an alkaline pH drastically slowed down the reaction. A strict correlation between photocatalytic results and physico-chemical characterizations of the synthesized powders were drawn. Full article
(This article belongs to the Special Issue Synthesis and Applications of Nanomaterials for Photocatalysis and Electrocatalysis)
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14 pages, 3936 KiB  
Article
Synergistic Effects of Active Sites’ Nature and Hydrophilicity on the Oxygen Reduction Reaction Activity of Pt-Free Catalysts
by Mariangela Longhi, Camilla Cova, Eleonora Pargoletti, Mauro Coduri, Saveria Santangelo, Salvatore Patanè, Nicoletta Ditaranto, Nicola Cioffi, Anna Facibeni and Marco Scavini
Nanomaterials 2018, 8(9), 643; https://doi.org/10.3390/nano8090643 - 22 Aug 2018
Cited by 11 | Viewed by 3512
Abstract
This work highlights the importance of the hydrophilicity of a catalyst’s active sites on an oxygen reduction reaction (ORR) through an electrochemical and physico-chemical study on catalysts based on nitrogen-modified carbon doped with different metals (Fe, Cu, and a mixture of them). BET, [...] Read more.
This work highlights the importance of the hydrophilicity of a catalyst’s active sites on an oxygen reduction reaction (ORR) through an electrochemical and physico-chemical study on catalysts based on nitrogen-modified carbon doped with different metals (Fe, Cu, and a mixture of them). BET, X-ray Powder Diffraction (XRPD), micro-Raman, X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Scanning Transmission Electron Microscopy (STEM), and hydrophilicity measurements were performed. All synthesized catalysts are characterized not only by a porous structure, with the porosity distribution centered in the mesoporosity range, but also by the presence of carbon nanostructures. In iron-doped materials, these nanostructures are bamboo-like structures typical of nitrogen carbon nanotubes, which are better organized, in a larger amount, and longer than those in the copper-doped material. Electrochemical ORR results highlight that the presence of iron and nitrogen carbon nanotubes is beneficial to the electroactivity of these materials, but also that the hydrophilicity of the active site is an important parameter affecting electrocatalytic properties. The most active material contains a mixture of Fe and Cu. Full article
(This article belongs to the Special Issue Synthesis and Applications of Nanomaterials for Photocatalysis and Electrocatalysis)
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14 pages, 4480 KiB  
Article
Band Gap Implications on Nano-TiO2 Surface Modification with Ascorbic Acid for Visible Light-Active Polypropylene Coated Photocatalyst
by Chiara Anna D’Amato, Rita Giovannetti, Marco Zannotti, Elena Rommozzi, Marco Minicucci, Roberto Gunnella and Andrea Di Cicco
Nanomaterials 2018, 8(8), 599; https://doi.org/10.3390/nano8080599 - 07 Aug 2018
Cited by 46 | Viewed by 6084
Abstract
The effect of surface modification using ascorbic acid as a surface modifier of nano-TiO2 heterogeneous photocatalyst was studied. The preparation of supported photocatalyst was made by a specific paste containing ascorbic acid modified TiO2 nanoparticles used to cover Polypropylene as a [...] Read more.
The effect of surface modification using ascorbic acid as a surface modifier of nano-TiO2 heterogeneous photocatalyst was studied. The preparation of supported photocatalyst was made by a specific paste containing ascorbic acid modified TiO2 nanoparticles used to cover Polypropylene as a support material. The obtained heterogeneous photocatalyst was thoroughly characterized (scanning electron microscope (SEM), RAMAN, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and Diffuse Reflectance Spectra (DRS) and successfully applied in the visible light photodegradation of Alizarin Red S in water solutions. In particular, this new supported TiO2 photocatalyst showed a change in the adsorption mechanism of dye with respect to that of only TiO2 due to the surface properties. In addition, an improvement of photocatalytic performances in the visible light photodegration was obtained, showing a strict correlation between efficiency and energy band gap values, evidencing the favorable surface modification of TiO2 nanoparticles. Full article
(This article belongs to the Special Issue Synthesis and Applications of Nanomaterials for Photocatalysis and Electrocatalysis)
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16 pages, 2688 KiB  
Article
Morphology, Optical Properties and Photocatalytic Activity of Photo- and Plasma-Deposited Au and Au/Ag Core/Shell Nanoparticles on Titania Layers
by Alexander Müller, Sandra Peglow, Michael Karnahl, Angela Kruth, Henrik Junge, Volker Brüser and Christina Scheu
Nanomaterials 2018, 8(7), 502; https://doi.org/10.3390/nano8070502 - 06 Jul 2018
Cited by 13 | Viewed by 4498
Abstract
Titania is a promising material for numerous photocatalytic reactions such as water splitting and the degradation of organic compounds (e.g., methanol, phenol). Its catalytic performance can be significantly increased by the addition of co-catalysts. In this study, Au and Au/Ag nanoparticles were deposited [...] Read more.
Titania is a promising material for numerous photocatalytic reactions such as water splitting and the degradation of organic compounds (e.g., methanol, phenol). Its catalytic performance can be significantly increased by the addition of co-catalysts. In this study, Au and Au/Ag nanoparticles were deposited onto mesoporous titania thin films using photo-deposition (Au) and magnetron-sputtering (Au and Au/Ag). All samples underwent comprehensive structural characterization by grazing incidence X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Nanoparticle distributions and nanoparticle size distributions were correlated to the deposition methods. Light absorption measurements showed features related to diffuse scattering, the band gap of titania and the local surface plasmon resonance of the noble metal nanoparticles. Further, the photocatalytic activities were measured using methanol as a hole scavenger. All nanoparticle-decorated thin films showed significant performance increases in hydrogen evolution under UV illumination compared to pure titania, with an evolution rate of up to 372 μL H2 h−1 cm−2 representing a promising approximately 12-fold increase compared to pure titania. Full article
(This article belongs to the Special Issue Synthesis and Applications of Nanomaterials for Photocatalysis and Electrocatalysis)
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17 pages, 4612 KiB  
Article
Facile Synthesis of Novel CaIn2S4/ZnIn2S4 Composites with Efficient Performance for Photocatalytic Reduction of Cr(VI) under Simulated Sunlight Irradiation
by Siyu Xu, Jun Dai, Juan Yang, Jun You and Jingyi Hao
Nanomaterials 2018, 8(7), 472; https://doi.org/10.3390/nano8070472 - 27 Jun 2018
Cited by 29 | Viewed by 4707
Abstract
A series of novel and efficient heterostructured composites CaIn2S4/ZnIn2S4 have been synthesized using a facile hydrothermal method. XRD patterns indicate the as-prepared catalysts are two-phase composites of cubic phase CaIn2S4 and hexagonal phase [...] Read more.
A series of novel and efficient heterostructured composites CaIn2S4/ZnIn2S4 have been synthesized using a facile hydrothermal method. XRD patterns indicate the as-prepared catalysts are two-phase composites of cubic phase CaIn2S4 and hexagonal phase ZnIn2S4. FESEM (field emission scanning electron microscope) images display that the synthesized composites are composed of flower-like microspheres with wide diameter distribution. UV–Vis diffuse reflectance spectra (DRS) show that the optical absorption edges of the CaIn2S4/ZnIn2S4 composites shift toward longer wavelengths with the increase of the CaIn2S4 component. The photocatalytic activities of the as-synthesized composites are investigated by using the aqueous-phase Cr(VI) reduction under simulated sunlight irradiation. This is the first report on the application of the CaIn2S4/ZnIn2S4 composites as stable and efficient photocatalysts for the Cr(VI) reduction. The fabricated CaIn2S4/ZnIn2S4 composites possess higher photocatalytic performance in comparison with pristine CaIn2S4 or ZnIn2S4. The CaIn2S4/ZnIn2S4 composite with a CaIn2S4 molar content of 30% exhibits the optimum photocatalytic activity. The primary reason for the significantly enhanced photoreduction activity is proved to be the substantially improved separation efficiency of photogenerated electrons/holes caused by forming the CaIn2S4/ZnIn2S4 heterostructured composites. The efficient charge separation can be evidenced by steady-state photoluminescence spectra (PLs) and transient photocurrent response. Based on the charge transfer between CaIn2S4 and ZnIn2S4, an enhancement mechanism of photocatalytic activity and stability for the Cr(VI) reduction is proposed. Full article
(This article belongs to the Special Issue Synthesis and Applications of Nanomaterials for Photocatalysis and Electrocatalysis)
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13 pages, 3062 KiB  
Article
Construction of g-C3N4-mNb2O5 Composites with Enhanced Visible Light Photocatalytic Activity
by Meiyin Wang, Hui Wang, Yuanhang Ren, Cheng Wang, Zhewei Weng, Bin Yue and Heyong He
Nanomaterials 2018, 8(6), 427; https://doi.org/10.3390/nano8060427 - 12 Jun 2018
Cited by 15 | Viewed by 3822
Abstract
A series of composites consisting of g-C3N4 sheet and mesoporous Nb2O5 (mNb2O5) microsphere were fabricated by in situ hydrolysis deposition of NbCl5 onto g-C3N4 sheet followed by solvothermal treatment. [...] Read more.
A series of composites consisting of g-C3N4 sheet and mesoporous Nb2O5 (mNb2O5) microsphere were fabricated by in situ hydrolysis deposition of NbCl5 onto g-C3N4 sheet followed by solvothermal treatment. The samples were characterized using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), N2 adsorption-desorption, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy (PL). The photocatalytic activity of the composites was studied by degradation of rhodamine B (RhB) and tetracycline hydrochloride (TC-HCl) in aqueous solution under visible light irradiation (λ > 420 nm). Compared with g-C3N4 and mNb2O5, g-C3N4-mNb2O5 composites have higher photocatalytic activity due to synergistic effect between g-C3N4 and mNb2O5. Among these composites, 4% g-C3N4-mNb2O5 has the highest efficiency and good recyclability for degradation of both RhB and TC-HCl. Full article
(This article belongs to the Special Issue Synthesis and Applications of Nanomaterials for Photocatalysis and Electrocatalysis)
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14 pages, 4278 KiB  
Article
A Facile Approach for the Synthesis of Zn2SnO4/BiOBr Hybrid Nanocomposites with Improved Visible-Light Photocatalytic Performance
by Tiekun Jia, Ming Liu, Dongsheng Yu, Fei Long, Shuyi Mo, Zhao Deng and Weimin Wang
Nanomaterials 2018, 8(5), 313; https://doi.org/10.3390/nano8050313 - 09 May 2018
Cited by 26 | Viewed by 3771
Abstract
In this study, a novel Zn2SnO4/BiOBr hybrid photocatalyst was prepared via a mild hydrothermal synthesis combined with a chemical deposition method. The morphological structure, chemical composition, crystal structure, and optical properties were comprehensively characterized by a series of measurement [...] Read more.
In this study, a novel Zn2SnO4/BiOBr hybrid photocatalyst was prepared via a mild hydrothermal synthesis combined with a chemical deposition method. The morphological structure, chemical composition, crystal structure, and optical properties were comprehensively characterized by a series of measurement techniques. Morphological observation showed that fine Zn2SnO4 nanoparticles were anchored on the nanoplate surface of a flower-like BiOBr 3D hierarchical structure. The experimental results of UV-vis diffuse reflection spectroscopy revealed that the visible-light absorptive capacity of the Zn2SnO4/BiOBr hybrid photocatalyst was promoted, as compared to that of pure Zn2SnO4. Evidenced by electro-negativity theoretical calculation, Zn2SnO4 and BiOBr possessed matched band edges for accelerating photogenerated charge separation at the interface. The Zn2SnO4/BiOBr hybrid photocatalyst exhibited enhanced photocatalytic performance in the degradation of Rhodamine B (RhB) under visible light irradiation. According to the band energy structure and the experimental results, the enhanced photocatalytic performance was ascribed to the improved visible-light absorptive capacity and the contact interface between Zn2SnO4 nanoparticles and BiOBr nanoplates, being able to favor the prompt charge migration and suppress the recombination of photogenerated carriers in the hybrid system. Full article
(This article belongs to the Special Issue Synthesis and Applications of Nanomaterials for Photocatalysis and Electrocatalysis)
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11 pages, 3576 KiB  
Article
Enhanced Photocatalytic Activity of {110}-Faceted TiO2 Rutile Nanorods in the Photodegradation of Hazardous Pharmaceuticals
by Tran Thi Thuong Huyen, Tran Thi Kim Chi, Nguyen Duc Dung, Hendrik Kosslick and Nguyen Quang Liem
Nanomaterials 2018, 8(5), 276; https://doi.org/10.3390/nano8050276 - 25 Apr 2018
Cited by 30 | Viewed by 5286
Abstract
Rutile TiO2 with highly active facets has attracted much attention owing to its enhanced activity during the photocatalytic degradation of pollutants such as pharmaceuticals in wastewater. However, it is difficult to obtain by controlling the synthetic conditions. This paper reports a simple [...] Read more.
Rutile TiO2 with highly active facets has attracted much attention owing to its enhanced activity during the photocatalytic degradation of pollutants such as pharmaceuticals in wastewater. However, it is difficult to obtain by controlling the synthetic conditions. This paper reports a simple hydrothermal synthesis of rutile TiO2 nanorods with highly exposed {110} facets. The obtained rutile was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and Raman spectroscopy. The main contribution to the photocatalytic activity comes from rutile nanorods with highly dominant active {110} facets, which were studied in the photodegradation of reactive cinnamic acid and more recalcitrant ibuprofen. The contribution of active species was also investigated. The present work further confirmed the hydrothermal synthesis route for controlling the preparation of highly crystalline and active rutile nanocrystals. Full article
(This article belongs to the Special Issue Synthesis and Applications of Nanomaterials for Photocatalysis and Electrocatalysis)
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11 pages, 5436 KiB  
Article
Effect of Organic Substrates on the Photocatalytic Reduction of Cr(VI) by Porous Hollow Ga2O3 Nanoparticles
by Jin Liu, Huihui Gan, Hongzhang Wu, Xinlei Zhang, Jun Zhang, Lili Li and Zhenling Wang
Nanomaterials 2018, 8(4), 263; https://doi.org/10.3390/nano8040263 - 22 Apr 2018
Cited by 4 | Viewed by 4287
Abstract
Porous hollow Ga2O3 nanoparticles were successfully synthesized by a hydrolysis method followed by calcination. The prepared samples were characterized by field emission scanning electron microscope, transmission electron microscope, thermogravimetry and differential scanning calorimetry, UV-vis diffuse reflectance spectra and Raman spectrum. [...] Read more.
Porous hollow Ga2O3 nanoparticles were successfully synthesized by a hydrolysis method followed by calcination. The prepared samples were characterized by field emission scanning electron microscope, transmission electron microscope, thermogravimetry and differential scanning calorimetry, UV-vis diffuse reflectance spectra and Raman spectrum. The porous structure of Ga2O3 nanoparticles can enhance the light harvesting efficiency, and provide lots of channels for the diffusion of Cr(VI) and Cr(III). Photocatalytic reduction of Cr(VI), with different initial pH and degradation of several organic substrates by porous hollow Ga2O3 nanoparticles in single system and binary system, were investigated in detail. The reduction rate of Cr(VI) in the binary pollutant system is markedly faster than that in the single Cr(VI) system, because Cr(VI) mainly acts as photogenerated electron acceptor. In addition, the type and concentration of organic substrates have an important role in the photocatalytic reduction of Cr(VI). Full article
(This article belongs to the Special Issue Synthesis and Applications of Nanomaterials for Photocatalysis and Electrocatalysis)
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21 pages, 34606 KiB  
Article
A Facile Method for the Preparation of Colored Bi4Ti3O12−x Nanosheets with Enhanced Visible-Light Photocatalytic Hydrogen Evolution Activity
by Yizeng Zhang, Zhiwu Chen and Zhenya Lu
Nanomaterials 2018, 8(4), 261; https://doi.org/10.3390/nano8040261 - 21 Apr 2018
Cited by 26 | Viewed by 4951
Abstract
Bi4Ti3O12−x nanosheet photocatalysts with abundant oxygen vacancies are fabricated by a facile solid-state chemical reduction method for the first time. This method is simple in operation, has short reaction time, and can be conducted at mild temperatures [...] Read more.
Bi4Ti3O12−x nanosheet photocatalysts with abundant oxygen vacancies are fabricated by a facile solid-state chemical reduction method for the first time. This method is simple in operation, has short reaction time, and can be conducted at mild temperatures (300~400 °C). The electron paramagnetic resonance, thermogravimetric analysis, X-ray photoelectron spectrometer, and positron annihilation lifetime spectra results indicate that oxygen vacancies are produced in Bi4Ti3O12−x, and they can be adjusted by tuning the reduction reaction conditions. Control experiments show that the reduction time and temperature have great influences on the photocatalytic activities of Bi4Ti3O12−x. The optimal Bi4Ti3O12−x is the sample undergoing the reduction treatment at 350 °C for 60 min and it affords a hydrogen evolution rate of 129 μmol·g−1·h−1 under visible-light irradiation, which is about 3.4 times that of the pristine Bi4Ti3O12. The Bi4Ti3O12−x photocatalysts have good reusability and storage stability and can be used to decompose formaldehyde and formic acid for hydrogen production. The surface oxygen vacancies states result in the broadening of the valence band and the narrowing of the band gap. Such energy level structure variation helps promote the separation of photo-generated electron-hole pairs thus leading to enhancement in the visible-light photocatalytic hydrogen evolution. Meanwhile, the narrowing of the band gap leads to a broader visible light absorption of Bi4Ti3O12−x. Full article
(This article belongs to the Special Issue Synthesis and Applications of Nanomaterials for Photocatalysis and Electrocatalysis)
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16 pages, 32722 KiB  
Article
A Facile Approach to Prepare Black TiO2 with Oxygen Vacancy for Enhancing Photocatalytic Activity
by Shihao Chen, Yang Xiao, Yinhai Wang, Zhengfa Hu, Hui Zhao and Wei Xie
Nanomaterials 2018, 8(4), 245; https://doi.org/10.3390/nano8040245 - 16 Apr 2018
Cited by 134 | Viewed by 12106
Abstract
Black TiO2 has triggered worldwide research interest due to its excellent photocatalytic properties. However, the understanding of its structure–property relationships and a more effective, facile and versatile method to produce it remain great challenges. We have developed a facile approach to synthesize [...] Read more.
Black TiO2 has triggered worldwide research interest due to its excellent photocatalytic properties. However, the understanding of its structure–property relationships and a more effective, facile and versatile method to produce it remain great challenges. We have developed a facile approach to synthesize black TiO2 nanoparticles with significantly improved light absorption in the visible and infrared regions. The experimental results show that oxygen vacancies are the major factors responsible for black coloration. More importantly, our black TiO2 nanoparticles have no Ti3+ ions. These oxygen vacancies could introduce localized states in the bandgap and act as trap centers, significantly decreasing the electron–hole recombination. The photocatalytic decomposition of both rhodamine B and methylene blue demonstrated that, under ultraviolet light irradiation, better photocatalytic performance is achieved with our black TiO2 nanoparticles than with commercial TiO2 nanoparticles. Full article
(This article belongs to the Special Issue Synthesis and Applications of Nanomaterials for Photocatalysis and Electrocatalysis)
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20 pages, 29056 KiB  
Article
In-Situ Synthesis of Hydrogen Titanate Nanotube/Graphene Composites with a Chemically Bonded Interface and Enhanced Visible Photocatalytic Activity
by Juan Yang, Jun You, Jun Dai, Yumei Chen and Yao Li
Nanomaterials 2018, 8(4), 229; https://doi.org/10.3390/nano8040229 - 08 Apr 2018
Cited by 6 | Viewed by 4423
Abstract
Hydrogen titanate nanotube (HTT)/graphene nanocomposites are synthesized by hydrothermal reduction of graphene oxide (GO) and simultaneous preparation of nanotubular HTT via an alkaline hydrothermal process. By using this facile in-situ compositing strategy, HTT are densely supported upon the surface of graphene sheets with [...] Read more.
Hydrogen titanate nanotube (HTT)/graphene nanocomposites are synthesized by hydrothermal reduction of graphene oxide (GO) and simultaneous preparation of nanotubular HTT via an alkaline hydrothermal process. By using this facile in-situ compositing strategy, HTT are densely supported upon the surface of graphene sheets with close interface contacts. The as-prepared HTT/graphene nanocomposites possess significantly enhanced visible light catalytic activity for the partial oxidation of benzylic alcohols. The amount of graphene has significant influence on catalytic activity and the optimal content of graphene is 1.0 wt %, giving a normalized rate constant k of 1.71 × 10−3 g/m2·h, which exceeds that of pure HTT and HTT/graphene-1.0% mixed by a factor of 7.1 or 5.2. Other than the general role of graphene as a high-performance electron acceptor or transporter, the observed enhancement in photocatalytic activity over HTT/graphene can be ascribed to the improved interfacial charge migration from enhanced chemical bonding (Ti–C bonds) during the in-situ compositing process. The formation of Ti–C bonds is confirmed by XPS analysis and the resulting enhanced separation of photoinduced charge carriers is demonstrated by electrochemical impedance spectra and transient photocurrent response. Full article
(This article belongs to the Special Issue Synthesis and Applications of Nanomaterials for Photocatalysis and Electrocatalysis)
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15 pages, 2520 KiB  
Article
Zinc Tantalum Oxynitride (ZnTaO2N) Photoanode Modified with Cobalt Phosphate Layers for the Photoelectrochemical Oxidation of Alkali Water
by Prabhakarn Arunachalam, Maged N. Shaddad, Mohamed A. Ghanem, Abdullah M. Al-Mayouf and Mark T. Weller
Nanomaterials 2018, 8(1), 48; https://doi.org/10.3390/nano8010048 - 18 Jan 2018
Cited by 15 | Viewed by 5681
Abstract
Photoanodes fabricated by the electrophoretic deposition of a thermally prepared zinc tantalum oxynitride (ZnTaO2N) catalyst onto indium tin oxide (ITO) substrates show photoactivation for the oxygen evolution reaction (OER) in alkaline solutions. The photoactivity of the OER is further boosted by [...] Read more.
Photoanodes fabricated by the electrophoretic deposition of a thermally prepared zinc tantalum oxynitride (ZnTaO2N) catalyst onto indium tin oxide (ITO) substrates show photoactivation for the oxygen evolution reaction (OER) in alkaline solutions. The photoactivity of the OER is further boosted by the photodeposition of cobalt phosphate (CoPi) layers onto the surface of the ZnTaO2N photoanodes. Structural, morphological, and photoelectrochemical (PEC) properties of the modified ZnTaO2N photoanodes are studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet visible (UV−Vis) diffuse reflectance spectroscopy, and electrochemical techniques. The presence of the CoPi layer significantly improved the PEC performance of water oxidation in an alkaline sulphate solution. The photocurrent-voltage behavior of the CoPi-modified ZnTaO2N anodes was improved, with the influence being more prominent at lower oxidation potentials. A stable photocurrent density of about 2.3 mA·cm−2 at 1.23 V vs. RHE was attained upon visible light illumination. Relative to the ZnTaO2N photoanodes, an almost three-fold photocurrent increase was achieved at the CoPi/ZnTaO2N photoelectrode. Perovskite-based oxynitrides are modified using an oxygen-evolution co-catalyst of CoPi, and provide a new dimension for enhancing the photoactivity of oxygen evolution in solar-assisted water-splitting reactions. Full article
(This article belongs to the Special Issue Synthesis and Applications of Nanomaterials for Photocatalysis and Electrocatalysis)
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