Special Issue "Emerging Trends in TiO2 Photocatalysis and Applications"

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

Deadline for manuscript submissions: 31 December 2018

Special Issue Editors

Guest Editor
Prof. Dr. Trong-On Do

Department of Chemical Engineering, Laval University, Quebec G1V 0A6, Canada
Website | E-Mail
Interests: nanomaterials; TiO2-based nanocomposites; nano-plasmonics; photocatalysis; solar energy conversion; solar fuels; renewable energy; environmental remediation
Guest Editor
Dr. Sakar Mohan

Department of Chemical Engineering, Laval University, Quebec G1V 0A6, Canada
E-Mail
Interests: photocatalysis; biomass conversion; perovskites; multiferroics; plasmonics; nanomaterials for energy and environmental applications

Special Issue Information

Dear Colleagues,

       The photo-assisted catalytic reaction, which is conventionally known as “photocatalysis”, is blooming in the field of energy and environment due to its multifaceted applications, such as in pollutant degradation, water splitting, fuel conversion, anti-microbial activities, etc. The photocatalytic process involves the separation of excitons upon light irradiation, and their subsequent transfer to the respective band energies (electrons to the conduction band and holes to valence band) to perform reduction and oxidation processes in order to execute the required transformation reactions. The key requirement to achieve the required application is to engineer a photocatalytic material with suitable band edge positions to produce the appropriate redox species.

       In this direction, titanium dioxide (TiO2) is one of the well-established and renowned photocatalysts that has been explored for various possible photocatalytic applications. However, along with suitable band edge positions, an efficient photocatalyst should also have (i) a narrow band gap energy so as to absorb visible light energy, (ii) enhanced charge separation, so as to have high quantum efficiency, (iii) enhanced recombination resistance to have prolonged reactions, and (iv) effective interfacial interactions to have intimate contact between the surrounding media and the photocatalyst, towards total conversion of the reactant.

       To handle these requirements in a photocatalyst, several modifications strategies have been developed, which broadly include doping, composite, plasmon sensitization, co-catalyst loading, integration of carbon-based materials, anisotropic nanostructuring of the photocatalyst, etc. As TiO2 is a pioneering material for any developments in the field of photocatalysis, this Special Issue is going to be focused on “Emerging Trends in TiO2 Photocatalysis and Applications”, featuring the state-of-the-art in the field. Research findings focusing the fundamental exploration of the syntheses, characterizations and applications in technological- and industrial-scale development of TiO2 in the field of photocatalysis are of prime importance to this Special Issue.

       Above all, we are glad to highlight that Prof. Akira Fujishima will be contributing a review paper in this Special Issue highlighting the recent trends in the field and featuring the modern photocatalysis.

Prof. Dr. Trong-On Do
Dr. Sakar Mohan
Guest Editors

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Keywords

  • Honda-Fujishima effect
  • Band gap engineering
  • Doped TiO2
  • TiO2 based composites
  • Nanostructured TiO2 photocatalyst
  • Plasmonic TiO2 photocatalyst
  • Defective TiO2 photocatalyst
  • Visible light driven TiO2
  • Pollutant degradations
  • Water splitting
  • Fuel conversions

Published Papers (5 papers)

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Research

Open AccessFeature PaperArticle Mechanistic Study on Facet-Dependent Deposition of Metal Nanoparticles on Decahedral-Shaped Anatase Titania Photocatalyst Particles
Catalysts 2018, 8(11), 542; https://doi.org/10.3390/catal8110542
Received: 11 October 2018 / Revised: 8 November 2018 / Accepted: 9 November 2018 / Published: 13 November 2018
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Abstract
Facet-selective gold or platinum-nanoparticle deposition on decahedral-shaped anatase titania particles (DAPs) exposing {001} and {101} facets via photodeposition (PD) from metal-complex sources was reexamined using DAPs prepared with gas-phase reaction of titanium (IV) chloride and oxygen by quantitatively evaluating the area deposition density
[...] Read more.
Facet-selective gold or platinum-nanoparticle deposition on decahedral-shaped anatase titania particles (DAPs) exposing {001} and {101} facets via photodeposition (PD) from metal-complex sources was reexamined using DAPs prepared with gas-phase reaction of titanium (IV) chloride and oxygen by quantitatively evaluating the area deposition density on {001} and {101} and comparing with the results of deposition from colloidal metal particles in the dark (CDD) or under photoirradiation (CDL). The observed facet selectivity, more or less {101} preferable, depended mainly on pH of the reaction suspensions and was almost non-selective at low pH regardless of the deposition method, PD or CDL, and the metal-source materials. Based on the results, the present authors propose that facet selectivity is attributable to surface charges (zeta potential) depending on the kind of facets, {001} and {101}, and pH of the reaction mixture and that this concept can explain the observed facet selectivity and possibly the reported facet selectivity without taking into account facet-selective reaction of photoexcited electrons and positive holes on {101} and {001} facets, respectively. Full article
(This article belongs to the Special Issue Emerging Trends in TiO2 Photocatalysis and Applications)
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Open AccessArticle Solid-Phase Photocatalytic Degradation of Polyvinyl Borate
Catalysts 2018, 8(11), 499; https://doi.org/10.3390/catal8110499
Received: 28 September 2018 / Revised: 22 October 2018 / Accepted: 24 October 2018 / Published: 26 October 2018
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Abstract
In this study, polymer composites based on polyvinyl borate (PVB) with titanium dioxide (TiO2) nanoparticles were prepared through the condensation reaction of polyvinyl alcohol and boric acid in the presence of TiO2 nanoparticles. The solid-phase photocatalytic degradation of the polymer
[...] Read more.
In this study, polymer composites based on polyvinyl borate (PVB) with titanium dioxide (TiO2) nanoparticles were prepared through the condensation reaction of polyvinyl alcohol and boric acid in the presence of TiO2 nanoparticles. The solid-phase photocatalytic degradation of the polymer composites under UV light irradiation was investigated and compared with that of the pure PVB with the aid of weight loss measurements. The introduction of the photocatalyst nanoparticles in PVB enhanced the solid-phase photocatalytic degradation of the polymer matrix under UV light irradiation. The structural and morphological properties of PVB/TiO2 composites were analyzed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and UV-Vis spectroscopy, respectively. FTIR analysis revealed that PVB synthesis was successfully carried out in the presence of the photocatalyst nanoparticles. According to the morphological analyses, TiO2 nanoparticles were well dispersed in the PVB matrix. Full article
(This article belongs to the Special Issue Emerging Trends in TiO2 Photocatalysis and Applications)
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Open AccessArticle The Synergistic Effect of Pyridinic Nitrogen and Graphitic Nitrogen of Nitrogen-Doped Graphene Quantum Dots for Enhanced TiO2 Nanocomposites’ Photocatalytic Performance
Catalysts 2018, 8(10), 438; https://doi.org/10.3390/catal8100438
Received: 9 September 2018 / Revised: 29 September 2018 / Accepted: 30 September 2018 / Published: 4 October 2018
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Abstract
In this study, nitrogen-doped graphene quantum dots (N-GQDs) and a TiO2 nanocomposite were synthesized using a simple hydrothermal route. Ammonia water was used as a nitrogen source to prepare the N-GQDs. When optically characterized by UV-vis, N-GQDs reveal stronger absorption peaks in
[...] Read more.
In this study, nitrogen-doped graphene quantum dots (N-GQDs) and a TiO2 nanocomposite were synthesized using a simple hydrothermal route. Ammonia water was used as a nitrogen source to prepare the N-GQDs. When optically characterized by UV-vis, N-GQDs reveal stronger absorption peaks in the range of ultraviolet (UV) light than graphene quantum dots (GQDs). In comparison with GQDs/TiO2 and pure TiO2, the N-GQDs/TiO2 have significantly improved photocatalytic performance. In particular, it was found that, when the added amount of ammonia water was 50 mL, the content of pyridinic N and graphitic N were as high as 22.47% and 31.44%, respectively. Most important, the photocatalytic activity of N-GQDs/TiO2-50 was about 95% after 12 min. The results illustrated that pyridinic N and graphitic N play a significant role in photocatalytic performance. Full article
(This article belongs to the Special Issue Emerging Trends in TiO2 Photocatalysis and Applications)
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Open AccessArticle Photocatalytic Antibacterial Effectiveness of Cu-Doped TiO2 Thin Film Prepared via the Peroxo Sol-Gel Method
Catalysts 2018, 8(9), 352; https://doi.org/10.3390/catal8090352
Received: 23 July 2018 / Revised: 13 August 2018 / Accepted: 20 August 2018 / Published: 27 August 2018
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Abstract
Cu-doped titanium dioxide thin films (Cu/TiO2) were prepared on glass substrate via peroxo sol-gel method and dip-coating process with no subsequent calcination process for the degradation of organic dye and use as an antibacterial agent. The as-prepared materials were characterised using
[...] Read more.
Cu-doped titanium dioxide thin films (Cu/TiO2) were prepared on glass substrate via peroxo sol-gel method and dip-coating process with no subsequent calcination process for the degradation of organic dye and use as an antibacterial agent. The as-prepared materials were characterised using transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). For photocatalytic degradation of methylene blue in water, the samples were subjected to Ultraviolet C (UVC) and visible light irradiation. Degraded methylene blue concentration was measured using UV-Vis spectrophotometer. The antibacterial activities of the samples were tested against the gram-negative bacteria Escherichia coli (ATCC25922). Copper species were present in the form of CuO on the surface of modified TiO2 particles, which was confirmed using TEM and XPS. The optimal observed Cu/TiO2 weight ratio of 0.5 represents the highest photocatalytic activities under both UVC and visible light irradiation. Moreover, the same composition remarkably exhibited high antibacterial effectiveness against E. coli after illumination with ultraviolet A. The presence of CuO on TiO2 significantly enhanced photocatalytic activities. Therefore, active Cu-doped TiO2 can be used as a multipurpose coating material. Full article
(This article belongs to the Special Issue Emerging Trends in TiO2 Photocatalysis and Applications)
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Open AccessArticle Modification to L-H Kinetics Model and Its Application in the Investigation on Photodegradation of Gaseous Benzene by Nitrogen-Doped TiO2
Catalysts 2018, 8(8), 326; https://doi.org/10.3390/catal8080326
Received: 11 July 2018 / Revised: 3 August 2018 / Accepted: 6 August 2018 / Published: 9 August 2018
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Abstract
In this paper, the Langmuir-Hinshelwood (L-H) model has been used to investigate the kinetics of photodegradation of gaseous benzene by nitrogen-doped TiO2 (N-TiO2) at 25 °C under visible light irradiation. Experimental results show that the photoreaction coefficient kpm increased
[...] Read more.
In this paper, the Langmuir-Hinshelwood (L-H) model has been used to investigate the kinetics of photodegradation of gaseous benzene by nitrogen-doped TiO2 (N-TiO2) at 25 °C under visible light irradiation. Experimental results show that the photoreaction coefficient kpm increased from 3.992 × 10−6 mol·kg−1·s−1 to 11.55 × 10−6 mol·kg−1·s−1 along with increasing illumination intensity. However, the adsorption equilibrium constant KL decreased from 1139 to 597 m3·mol−1 when the illumination intensity increased from 36.7 × 104 lx to 75.1 × 104 lx, whereas it was 2761 m3·mol−1 in the absence of light. This is contrary to the fact that KL should be a constant if the temperature was fixed. This phenomenon can be attributed to the breaking of the adsorption-desorption equilibrium by photocatalytically decomposition. To compensate for the disequilibrium of the adsorption-desorption process, photoreaction coefficient kpm was introduced to the expression of KL and the compensation form was denoted as Km. KL is an indicator of the adsorption capacity of TiO2 while Km is only an indicator of the coverage ratio of TiO2 surface. The modified L-H model has been experimentally verified so it is expected to be used to predict the kinetics of the photocatalytic degradation of gaseous benzene. Full article
(This article belongs to the Special Issue Emerging Trends in TiO2 Photocatalysis and Applications)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Photocatalytic degradation of estriol using mesoporous iron-doped TiO2 under low and high UV-irradiation
Authors: Irwing M. Ramírez-Sánchez a,b, Erick R. Bandala c,d*
Affiliation:
a. Universidad de las Americas, Puebla. Sta. Catarina Martir, Cholula 72810 Puebla. Mexico.
b. Unidad Profesional Interdisciplinaria de Biotecnología - IPN, Barrio la Laguna, 07340, Mexico City, MX.
c. Desert Research Institute (DRI). 755 E. Flamingo Road. Las Vegas, 89119-7363 Nevada, USA. E-mail: erick.bandala@dri.edu
d. Graduate Program Hydrologic Sciences. University of Nevada, Reno. Reno, NV 89557, USA
Abstract: Iron doped TiO2 (Fe-TiO2) materials were studied under high and low UV-irradiation for evaluating hydroxyl radical (OH) generation and estriol (E3) degradation. The synthesis of Fe-TiO2 materials was using sodium dodecylsulfate (SDS) as a structure-directing, annealing at 276 K (3°C) and carrying out a programed thermal treatment to dry, heat, and cool. The procedure allowed to obtain a Fe-TiO2 MesoPorous material (MP). The structure of Fe-TiO2 MP´s was analyzed using SEM, TEM, XRD, XPS, BET, and diffuse reflectance techniques, showing nanoparticles and a red – shift. The X-ray photoelectron spectroscopy provided evidence that Fe3+ specie was in the lattice of TiO2 nanoparticles, and co-dopants no intentionally added were presents due to synthesis method. The photocatalytic performance was evaluated first with a probe of OH known as N,N-Dimethyl-4-nitrosoaniline (pNDA, also called RNO) and then with a estriol as a model compound. Degradation of estriol was achieved with undoped TiO2, Fe-TiO2 MP, and with Aeroxide TiO2 P25 used as a photocatalytic standard. The enhanced photocatalytic was obtained improved with 0.3 atomic percentage of Fe as a dopant of TiO2 under low UV-irradiation compared with undoped TiO2 and Aeroxide TiO2 P25.

Title: Renaissance of TiO2 in Photocatalysis Industries: Progress and Perspectives
Authors:
Sudhagar Pitchaimuthu a, Chiaki Terashima b, Akira Fujishima b
Affiliation:
a. Multi-functional Photocatalyst and Coatings Group, SPECIFIC, College of Engineering, Swansea University (Bay Campus), Swansea SA1 8EN, Wales, United Kingdom.
b. Photocatalysis International Research Center, Research Institute for Science & Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, JAPAN.
Abstract: The invention of groundbreaking scientific phenomena of producing oxygen gas on titanium dioxide (TiO2) semiconductor surface in aqueous solution upon light illumination, popularly coined as “Honda- Fujishima effect” in the year 1972, paves a new pathway in photocatalysis research. Since then, numerous semiconductor materials were tested in photocatalysis applications. However, TiO2 and its derivatives has been proven to be exceptional over other materials till date, due to their multifaceted properties such as outstanding photo catalytic activity, earth abundancy, biocompatibility, supreme chemical stability and low-cost. As a result, TiO2 offers versatile photocatalysis based technologies (self-cleaning coatings and environmental remediation) that are industrial-friendly resulting in a number of commercial products in Japan as well as around the world. Moreover, TiO2 has been proposed as benchmarking material in wide range of scientific research including solar cells, solar fuel, catalysis, batteries, biosensors, biomedical, water treatment, etc. This review summarizes the fundamental and advanced demonstration of TiO2 based photocatalysis industrial applications in recent years. In view of futuristic material world, current challenges in standardization and perspectives of utilizing TiO2 in new types of photocatalysis applications have also been discussed in this review. Therefore, this review will facilitate broad understanding and utilization of TiO2 with an emphasis towards futuristic industrial applications.

Title: Titanium dioxide (TiO2): A versatile material for photocatalytic energy and environmental applications
Authors: M. Sakar and Trong-On Do*
Affiliation: Department of Chemical Engineering, Laval University, Quebec G1V 0A8, Canada. *Email: Trong-On.Do@gch.ulaval.ca
Abstract: Photocatalysis is a multifunctional phenomenon that can be employed for energy applications such as H2 production, CO2 reduction into fuels and environmental applications such as pollutant degradations, antibacterial disinfection, etc. In this direction, it is not an exaggerated fact that the TiO2 is pioneering in the field of photocatalysis that largely explored for various photocatalytic applications as aforementioned. The deeper understanding of TiO2 photocatalysis has led to the design of new photocatalytic materials with multiple functionalities. Accordingly, this paper exclusively reviews the recent developments in the modification of TiO2 photocatalyst towards its application in the field of energy and environmental remediation. These modifications generally involve the physical and chemical changes in TiO2 such as anisotropic structuring and integration with other metal oxides, plasmonic materials, carbon based materials, etc. Such modifications essentially lead to the changes in the energy structure of TiO2 that largely boosts up the photocatalytic process via enhancing the band structure aligning, visible light absorption, carrier separation and transportation in the system. For instance, the ability to align the band structure in TiO2 makes it suitable for multiple photocatalytic processes such as degradation of various pollutants, H2 production, CO2 conversion, etc. For these reasons, TiO2 can be realized as a prototypical photocatalyst, which paves ways to develop new photocatalytic materials in the field. In this context, this review paper sheds light into the emerging trends in TiO2 in terms of its modifications towards multifunctional photocatalytic applications. 

Type of the paper:  Article
Tentative title: S-doped Graphene Quantum Dots Modifie TiO2 for Improved Photocatalytic Performance
Authors: a Fei Li, a Yi Luo, a Ming Li, a Yongjie Xu, a Yong Cheng, a Xinyu Li, a Tao Tang, b Liang Wang
Affiliation:
a College of Science, Guilin University of Technology, Guilin 541004, P.R. China
b Institute of Nanochemistry and Nanobiology, School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, P.R. China
Abstract: Titanium dioxide (TiO2) is a kind of typical semiconductor oxide with characteristic photocatalytic activity. Whereas, its photocatalytic activity is limited by continuous light exposure due to the rapid combination of carrier and optical corrosion. A facile hydrothermal method was to prepare titanium dioxide nanoparticles (TiO2 NPs) and S-doped graphene quantum dots (GQDs) and S-GQDs/ TiO2 NPs composite. The photocatalytic property of the TiO2, S-GQDs and S-GQDs/ TiO2 NPs were studied. As a result, the photocatalytic property of S-GQDs/ TiO2 shows marked improvement compared TiO2 NPs. The main reason for improving photocatalytic activity is that the S-GQDs coating on the surface of TiO2 NPs show the binding rate of generated electron-hole recombination, and reduces the photocorrosion phenomenon.

Title: Synergistic effect of Photocatalytic Degradation of Hexabromocyclododecane in Water by UV/TiO2/persulfate
Authors: Qiang Li1, Lifang Wang1, Hongyong Xie2*
Affiliations: 1 Northwestern Polytechnical University, School of Management, 127 West Youxi Road, Xian 710072, Shaanxi Province, China
2 School of Environment and Materials Engineering, College of Engineering, Shanghai Polytechnic University, Shanghai 201209, China
Correspondence: hyxie@sspu.edu.cn/hyxie@163.com
Abstract: Hexabromocyclododecane (HBCD) is a widely used flame retardants and is ubiquitous in various environmental matrices, such as water, sediment, air, dust and organisms, potentially inducing biotoxicity, including immunotoxicity, neurotoxicity, disruption of endocrine function and cytotoxicity, and therefore appropriate techniques for decontaminating HBCD are urgent need. In this study, degradation of HBCD is studied by using photocatalysis of homo/heterogeneous UV/TiO2/persulfate systems in alkaline solutions. By measuring the concentrations of HBCD, effects of pH values, load of TiO2, dosage of potassium persulfate and initial concentration of HBCD on degradation degree have been examined. Roles of radicals SO4•− and •OH in the photocatalysis systems are discussed based on experimental measurements and it was found that there exist synergistic effects in UV/TiO2/persulfate homo/heterogeneous photocatalysis.
Keywords: HBCD; homo/heterogeneous photocatalysis; TiO2 nanoparticles; persulfate; synergistic effects

Title: Carbon-Doped Titanium Dioxide with Enhanced Visible Light Photocatalytic Activity to Remove Atrazine and Its By-Products from Surface Water
Authors: Simon Komtchou1, Ahmad Dirany 2, Patrick Drogui*3, Didier Robert 4
Affiliations: 1 Ph.D. Student, Institut National de la Recherche Scientifique (INRS-Centre Eau, Terre et Environnement, Université du Québec, 490 rue de la Couronne, Québec, Qc, Canada, G1K 9A9, Phone : (418) 654-4478, Fax : (418) 654-2600, email : simon.komtchou@ete.inrs.ca
2Research associate, Institut National de la Recherche Scientifique (INRS-Centre Eau, Terre et Environnement), Université du Québec, 490 rue de la Couronne, Québec, Qc, Canada, G1K9A9, Phone: (418) 654-2550, Fax : (418) 654-2600, email : ahmad.dirany@ete.inrs.ca
3Professor, Institut National de la Recherche Scientifique (INRS-Centre Eau, Terre et Environnement), Université du Québec, 490 rue de la Couronne, Québec, Qc, Canada, G1K 9A9, Phone : (418) 654-3119, Fax : (418) 654-2600, email : patrick.drogui@ete.inrs.ca
4Professor, Institut de Chimie et Procédés pour l'Énergie, l'Environnement et la Santé (ICPEES), CNRS, Université de Lorraine, rue Victor Demange, 57500 Saint-Avold, France, Phone : (33) 3 87 93 91 85, email : didier.robert@univ-lorraine.fr
Correspondence: patrick.drogui@ete.inrs.ca; Tel: (418) 654-3119; Fax: (418) 654-2600
Abstract: Nanoparticles of titanium dioxide doped with carbon have been successfully prepared by sol-gel method using titanium tetrachloride as the precursor of titania and diethanolamine as dopant source. The obtained products were dry and calcined between at 400 °C and 500 °C. The physico-chemical properties of as-prepared C-TiO2 samples are characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption isotherms, and thermogravimetric analysis (TG) techniques. The results showed that the absorption edge of C-TiO2 samples is shifted from UV to visible light range and narrowing of the band gap. (XPS) results indicate that oxygen sites in the TiO2 lattice were substituted by carbon atoms and an O-Ti-C bond is formed. Moreover, the crystallinity of anatase was improved upon carbon doping. The photocatalytic activities of C-doped TiO2 powders samples were evaluated to remove atrazine (100 µg L-1) from synthetic solution and real agricultural surface water under visible light irradiation. The C-TiO2 nanopowders with 4% of carbon calcined at 450°C show the best degradation of atrazine (99% after 60 min treatment).

Title: Progress in Research on TiO2 photocatalysts and Development of Visible Light-responsive TiO2 Photocatalysts
Authors: Masakazu Anpo*, Masaya Matsuoka, Masato Takeuchi, Yu. Horiuchi
Affiliation: Graduate School of Engineering, Faculty of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai Osaka 599-8531, Japan
Abstract: Energy depletion and environmental pollution on a global scale are the most serious and urgent issues facing mankind in recent times. It is vital to design novel energy production and conversion systems that utilize natural energy and allow sustainable development without environmental destruction or pollution. The decomposition of H2O to produce H2 and O2 as well as the related reactions using visible light-responsive photocatalysts under sunlight irradiation has been intensively investigated to address these issues. In the past half century, research on various photocatalytic systems using metal oxides such as TiO2 have been carried out. However, to achieve higher efficiency in the production of H2 from H2O, more innovative breakthroughs in the development of new types of photocatalytic materials have been strongly desired. In this review article, I will show first the research progress of photocatalysis and then introduce the successful development of Ti-oxide photocatalysts which enable the absorption of visible light to operate as an efficient environmentally-friendly photocatalyst. Special attention will be focused on efficient H2 production from H2O involving biomass using visible light-responsive TiO2 thin film photocatalysts for the separate evolution of H2 and CO2 under sunlight irradiation, and will be discussed by its integration into an artificial light-type plant factory as a clean, carbon-neutral and sustainable chemical system in the effective utilization of sunlight.

Title: Photoinduced supersaturated adsorption of NO2 on TiO2
Authors:
Cao Thang Dinh,† F. Pelayo García de Arquer,† Xueli Zheng, Oleksandr Voznyy, Rafael Quintero-Bermudez, James Fan, Sjoerd Hoogland, Edward H. Sargent,*
Affiliation:
Department of Electrical and Computer Engineering, University of Toronto, 35 St George Street, Toronto, Ontario M5S 1A4, Canada
Abstract: The adsorption of atmospheric gases on solid surfaces play an important role in atmospheric chemistry. Particularly, the interaction of nitrogen oxide gases which are major causes of acid rain, photochemical smog, and depletion of the ozone layer, with the surface of a photoactive TiO2 has received great interest because TiO2 is widely used as white pigment in paint, plastic, and paper. Here, we demonstrate photoinduced supersaturated adsorption wherein the adsorption of NO2 molecules on TiO2 surfaces increases beyond its (dark) saturation capacity when UV-illuminated. This phenomenon stems from a photon-switchable hydrophilicity behaviour of TiO2 anatase nanoparticles that promotes complete surface saturation with -OH radicals.

Title: Photocatalytic Degradation of Microcystins by TiO2 Using UV-LED Pulse Width Modulation
Authors: Olivia Schneider 1,†, Robert Liang1,2,†,*, Leslie Bragg 3, Ivana Jaciw-Zurakowsky 1, Peng Peng 4,  Mark R. Servos 3, Y. Norman Zhou 1,2
Affiliations: 1 Centre for Advanced Materials Joining, Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1
2 Waterloo Institute of Nanotechnology, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1
3 Department of Biology, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1
4 School of Mechanical Engineering and Automation, International Research Institute for Multidisciplinary Science, Beihang University, 37 Xueyuan Rd, Beijing, 100191
† denotes equal contribution
Abstract: Toxic microcystins (MCs) produced by freshwater Microcystis aeruginosa are of concern because of both the health and economic impacts all over the world. An advanced oxidation process using UV/TiO2 is a promising treatment option for small organic pollutants such as microcystins. The following work details the successful degradation of MC-LA, MC-LR, and MC-RR using a porous titanium-titanium dioxide (PTT) membrane under UV-LED light. Microcystin quantitation was done by sample concentration and subsequent LC-MS/MS analysis. The PTT membrane offers a treatment option that eliminates the need for additional filtration or separation steps required by traditional catalysts. Controlled periodic illumination was successfully used to decrease total light exposure time and improve the photonic efficiency for a more cost-effective treatment system. Individual degradation rates were influenced by electrostatic forces between the catalyst and differently charged microcystins, which can potentially be adjusted by modifying the solution pH and catalyst’s isoelectric point.

Title: CO2 photoreduction with catalysts synthesized in supercritical medium. A review
Authors: Jesusa Rincón, Rafael Camarillo*, Susana Tostón, Fabiola Martínez, Carlos Jiménez
Affiliation: University of Castilla-La Mancha, Department of Chemical Engineering, Faculty of Environmental Sciences and Biochemistry, Av. Carlos III, s/n, 45071 – Toledo (Spain). *e-mail: rafael.camarillo@uclm.es
Abstract: Photocatalytic reduction of CO2 to fuels and chemicals is a promising strategy to address problems related to both climate change and energy supply. However, although last decade achievements in using sunlight to reduce CO2 are sounded, its practical application with current photocatalysts is still hindered by issues such as low energy conversion efficiency (mmol h-1 gcat-1), low selectivity, and poor control in suppressing competing reactions. In this context, considering that catalyst properties depend on its synthesis process, a possible strategy to improve catalyst performance is to produce it by new synthetic routes like those based on the use of supercritical fluids. Thus, the development of efficient and robust photocatalysts to drive solar-to-fuel conversion efficiencies from current values (1-2%) to figures above natural photosynthesis (3-5%), with high product selectivity, are key challenges for the supercritical technology. The main goal of this work is to summarize the literature on the photocatalytic reduction of CO2 with water vapor using TiO2 and TiO2-based catalysts synthesized in supercritical medium in order to provide evidences to answer the question on whether supercritical technology may produce superior catalysts to classical methods. Further, in order to provide a basis for improved catalytic materials, special attention will be given to the analysis of catalyst properties and their impact on CO2 photoreduction.

Title: Titanium Dioxide-based visible-light sensitive photocatalyst: Recent Advances and Applications
Author: Shinya Higashimoto
Affiliation:
Department of Applied Chemistry, Faculty of Engineering, Osaka Institute of Technology, 5-16-1 Omiya, Asahi-ku, Osaka 535-8585, Japan; shinya.higashimoto@oit.ac.jp
Abstract:
It is known that titanium dioxide (TiO2) exhibits photocatalysis by band-gap excitation (hv > 3.2 eV) of TiO2. However, in order to take advantage of the unlimited solar light available, TiO2 photocatalytic systems which work under visible light (400 - 800 nm) irradiation is strongly desired. Herein, we review the recent advances and applications of TiO2 based visible-light sensitive photocatalysis (See Scheme 1): by doping with nitrogen (N), carbon (C) and sulfur (S) ions etc. (1); by grafting with Fe3+ or Cu2+ ions via interfacial charge transfer (2); by surface plasmonic effects with Au or Ag nano-metal particles (3), by coupling with visible-light sensitive hetero-semiconductors (cadmium sulfide, carbon nitride etc.) (4), by the interfacial charge transfer surface complex (alcoholate species, etc.) through the interaction of TiO2 surface and reactant molecules (5). These visible-light responsive TiO2 photocatalyst would be applied for mineralization of volatile organic compounds (VOC), water splitting to produce H2 and fine organic synthesis.

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Scheme 1. Several visible-light photocatalytic system.

Title: Comparing the Efficiency of N-doped TiO2 and N-doped Bi2MoO6 Photo Catalysts for MB and Lignin Photodegradation.
Authors: R. Rangel1, V. J. Cedeño1, J. Espino1, J. J. Alvarado-Gil2, P. Bartolo-Pérez2, G. Rodríguez-Gattorno2
1 División de estudios de Posgrado, Facultad de Ingeniería Química, Universidad Michoacana de SNH., Morelia, México
2 Departamento de Física Aplicada, CINVESTAV-IPN, Unidad Mérida, Mérida, Yuc, México
Abstract: Nitrogen-doped titanium dioxide (N-TiO2) and nitrogen-doped bismuth molybdate (N-Bi2MoO6) compounds have been prepared and their efficiency to degrade methylene blue and lignin molecule under UV irradiation and visible light irradiation further studied. It was also established a comparison among TiO2, Bi2MoO6 catalysts prepared by means of chemical coprecipitation vs. N-TiO2 and N-Bi2MoO6 compounds. The catalysts were prepared starting from Ti(OCH2CH2CH3)4, Bi(NO3)3.5H2O, (NH4)6Mo7O24 reagents. N-doping was achieved in a continuous reflux system, using ethylenediamine as nitrogen source. The resulting materials were characterized by means of SEM, X-Ray diffraction, IR, XPS and photocatalytic activity measurements for MB and lignin under Visible light and UV radiation. It was observed a decreasing in particle size after the compounds were processed in the reflux system. The results regarding photocatalytic degradation tests show 90% of degradation for nitrogen doped samples.
Keywords: photocatalysis; titanium dioxide; bismuth molybdate; UV energy; visible light

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