Submit to Materials Review for Materials Propose a Special Issue

Journal Menu

Journal Browser

TiO2-Based Nanostructures, Composites and Hybrid Photocatalysts

Print Special Issue Flyer
Special Issue Editors
Special Issue Information
Keywords
Published Papers

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Advanced Nanomaterials and Nanotechnology".

Deadline for manuscript submissions: closed (30 June 2021) | Viewed by 38676

Share This Special Issue

Special Issue Editors

Dr. Stefano Lettieri

E-Mail Website
Guest Editor

National Research Council of Italy, Institute of Applied Sciences and Intelligent Systems "Eduardo Caianiello" (ISASI-CNR), Pozzuoli, Italy
Interests: multifunctional metal oxides; semiconductor nanostructures; photocatalytic materials; titanium dioxide; semiconductor optics; non-linear optical spectroscopy; photoluminescence; gas sensing; optical sensors
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Michele Pavone

E-Mail Website
Guest Editor

Department of Chemical Sciences, University of Napoli "Federico II", 80131 Naples, Italy
Interests: physical chemistry; quantum chemistry; functional oxides; energy materials; ab-initio calculations

Special Issue Information

Dear Colleagues,

Environmental pollution and depletion of fossil fuels represent two crucial obstacles for the sustainable development of contemporary human society. It is becoming more and more imperative to accelerate the develompment of green technologies capable to control and reduce pollution growth. Hence, it can be easily foreseen that confronting these issues will engage increasing efforts and resources.

Among the research and development fields dealing with the mentioned issues, those employing photocatalysis are likely to grow in relevance and spread new applications and technologies. Titanium dioxide (TiO₂) is nowdays one of the most widely used photocatalytic materials due to its ability to oxidatively decompose organic pollutants, low cost, durability and corrosion resistance. It is employed in several applications in the energy and environmental fields, including, for example: hydrogen evolution, photoelectrochemical conversion, photodegradation of organic contaminants, air and water purification systems, sterilization and bacterial detoxification. TiO₂ also proved to be useful for other applications, such as gas sensing, bone implant fixation, drug delivery, etc.

Much effort is nowdays focusing on TiO₂ modifications enambling to extend the TiO₂ optical absorption toward the visible range (in order to operate effectively under natural sunlight irradiation) and to improve the spatial separation of photogenerated charges. To these aims, several TiO₂ doping strategies and TiO₂-based hybrid composites have been scrutinized. In these kind of studies, foundational knowledge of the basic physical and chemical properties of the involved materials/components involved is required, as well as exhaustive investigations of the targeted application.

The aim of this Special Issue is to cover the main aspects of fundamental and applied research of TiO₂ and TiO₂-based materials and composites, such as (but not limited to) the following:

Fundamental properties of TiO₂ nanostructures: electronic states, defects, structural properties, optical properties, etc.
Synthesis of bulk TiO₂ crystals, TiO₂ nanoparticles and thin films
Modification of TiO₂ nanostructures through doping, including non-metal doping (e.g. nitrogen-doped TiO₂, fluorine-doped TiO₂, carbon-doped TiO₂, etc.) and metal doping (e.g. Fe/TiO₂, Cu/TiO₂, Au/TiO₂, Ag/TiO₂, Pd/TiO₂, Pt/TiO₂, etc.)
Self-doped TiO₂ nanostructures: oxygen vacancies, black titania, etc.
Composites and hybrid photocatalysts based on TiO₂ and carbon nanomaterials (e.g. TiO₂/graphene, TiO₂/graphene oxide, TiO₂/carbon nanotubes, TiO₂/g-C₃N₄, etc.) or on TiO₂ and inorganic materials (e.g. TiO₂/MoS₂ and other 2D transition metal dichalcogenides)
Applications, including water remediation, degradation of dyes and/or farmaceuticals, CO₂ reduction, hydrogen evolution, fuels production, plasmonic photocatalysis, TiO₂-based composites in perovskite solar cells, gas sensors, biosensors and biomedical applications, etc.

It is our pleasure to invite you to submit a manuscript for this Special Issue. Full papers, communications, and reviews are all welcome.

Dr. Stefano Lettieri
Assoc. Prof. Michele Pavone
Guest Editors

Manuscript Submission Information

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. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short 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 thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly 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 2600 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

TiO₂-based nanostructures and composites
photocatalysis
TiO₂-based hybrid photocatalysts
water remediation
environmental applications and green technologies
CO₂ reduction
hydrogen production
energy applications

Published Papers (11 papers)

Download All Papers

Order results

Result details

Show export options Show export options

Select all

Export citation of selected articles as:

Editorial

Jump to: Research, Review

6 pages, 227 KiB

Open AccessEditorial

TiO₂-Based Nanostructures, Composites and Hybrid Photocatalysts

by Stefano Lettieri and Michele Pavone

Materials 2022, 15(4), 1271; https://doi.org/10.3390/ma15041271 - 09 Feb 2022

Cited by 5 | Viewed by 1306

Abstract

The field of materials sciences has always been strongly interconnected with the most significant technological developments in the modern era, and such an interconnection is absolutely evident at least since the 1950s revolution of electronics and microelectronics, driven by advances in the science [...] Read more.

(This article belongs to the Special Issue TiO2-Based Nanostructures, Composites and Hybrid Photocatalysts)

Research

Jump to: Editorial, Review

9 pages, 2032 KiB

Open AccessArticle

Synthesis and Characterization of Anatase TiO₂ Microspheres Self-Assembled by Ultrathin Nanosheets

by Jian Di, Haibo Yan, Zhuoyu Liu and Xing Ding

Materials 2021, 14(11), 2870; https://doi.org/10.3390/ma14112870 - 27 May 2021

Cited by 5 | Viewed by 1794

Abstract

In this paper, we report a novel and simple method for synthesizing the microspheres self-assembled from ultrathin anatase TiO₂ nanosheets with a high percentage of (001) facets via the hydrolysis process of the single-reagent (potassium fluorotitanate). We then used optical microscopy, scanning electron microscopy, and high-resolution confocal laser Raman spectroscopy to characterize the microspheres generated under different conditions. The study found that the size of the anatase TiO₂ microspheres synthesized was 0.5–3 μm. As the synthesis time increased, the corroded surface of the microspheres gradually increased, resulting in the gradual disappearance of the edges and corners of the anatase nanosheets. The exposure percentage of the (001) facets of ultrathin anatase nanosheets synthesized for 2 h at 180–200 °C are close to 100%. The microsphere whose surface is completely covered by these anatase nanosheets also has nearly 100% exposed (001) facets. This new anatase nanosheet-based self-assembled microsphere will have great application potential in pollution prevention, environmental protection, and energy fields. Full article

(This article belongs to the Special Issue TiO2-Based Nanostructures, Composites and Hybrid Photocatalysts)

► Show Figures

Figure 1

13 pages, 4225 KiB

Open AccessArticle

(Ti,Sn) Solid Solution Based Gas Sensors for New Monitoring of Hydraulic Oil Degradation

by Ambra Fioravanti, Pietro Marani, Giorgio Paolo Massarotti, Stefano Lettieri, Sara Morandi and Maria Cristina Carotta

Materials 2021, 14(3), 605; https://doi.org/10.3390/ma14030605 - 28 Jan 2021

Cited by 11 | Viewed by 2184

Abstract

The proper operation of a fluid power system in terms of efficiency and reliability is directly related to the fluid state; therefore, the monitoring of fluid ageing in real time is fundamental to prevent machine failures. For this aim, an innovative methodology based on fluid vapor analysis through metal oxide (shortened: MOX) gas sensors has been developed. Two apparatuses were designed and realized: (i) a dedicated test bench to fast-age the fluid under controlled conditions; (ii) a laboratory MOX sensor system to test the headspace of the aged fluid samples. To prepare the set of MOX gas sensors suitable to detect the analytes’ concentrations in the fluid headspace, different functional materials were synthesized in the form of nanopowders, characterizing them by electron microscopy and X-ray diffraction. The powders were deposited through screen-printing technology, realizing thick-film gas sensors on which dynamical responses in the presence of the fluid headspace were obtained. It resulted that gas sensors based on solid solution Ti_xSn_1–xO₂ with x = 0.9 and 0.5 offered the best responses toward the fluid headspace with lower response and recovery times. Furthermore, a decrease in the responses (for all sensors) with fluid ageing was observed. Full article

(This article belongs to the Special Issue TiO2-Based Nanostructures, Composites and Hybrid Photocatalysts)

► Show Figures

Figure 1

10 pages, 3723 KiB

Open AccessArticle

Accelerated Life Testing of a Palladium-Doped Tin Oxide Electrode for Zn Electrowinning

by Jung Eun Park, Ho Kim and Eun Sil Lee

Materials 2020, 13(8), 1969; https://doi.org/10.3390/ma13081969 - 23 Apr 2020

Cited by 1 | Viewed by 1982

Abstract

Electrowinning is a technique that can be used to obtain high-purity elements through electrolysis. The degradation of accelerated life testing for Pd-based electrodes is discussed in this study. The lifetime of the electrodes was examined by multiplying the acceleration rate with the current to measure the voltage of the electrodes. The acceleration rate was set to 10, 20, and 30 times. Four components were deposited on the TiO₂ plate. The ratio of Ir to Sn was fixed at 1:1, while Ta was deposited at 10 wt.%. Pd was deposited at 2, 4, 8 and 10 wt.% to create Pd-Ir/Sn-Ta. The initial voltage decreased as the Pd deposition amount increased irrespective of the acceleration rate. The lower the acceleration rate, the lower the voltage. An increase in the Pd content caused the initial voltage to be low. The multiple of the acceleration rate slightly increased for all cases of life testing for one year. When the test was conducted by increasing the current density by 20 times, the increase in voltage was proportional to the Pd deposition amount. However, for the 30 times acceleration rate, the lifetime of the electrodes was shortened as the Pd content increased. It can be inferred that the content of Pd and the ratio of Ir to Sn can influence the lifetime of the electrodes. According to these results, if the multiple of the acceleration rate is too extreme, the lifetime of the electrodes cannot be evaluated because they are damaged in an extreme situation. Full article

(This article belongs to the Special Issue TiO2-Based Nanostructures, Composites and Hybrid Photocatalysts)

► Show Figures

Figure 1

19 pages, 6597 KiB

Open AccessArticle

Study of the Effect of Titanium Dioxide Hydrosol on the Photocatalytic and Mechanical Properties of Paper Sheets

by Roberta Grazia Toro, Mohamed Diab, Tilde de Caro, Mona Al-Shemy, Abeer Adel and Daniela Caschera

Materials 2020, 13(6), 1326; https://doi.org/10.3390/ma13061326 - 14 Mar 2020

Cited by 60 | Viewed by 3371

Abstract

Different amounts of a stable aqueous TiO₂ hydrosol were used to fabricate paper sheets having photocatalytic activity. The TiO₂ hydrosol was prepared in aqueous medium using titanium butoxide as precursor and acetic acid as catalyst for the hydrolysis of titanium butoxide. An aging process at room temperature and atmospheric pressure was finally applied to obtain crystalline anatase TiO₂ hydrosol. The effects of different TiO₂ hydrosol loadings on the mechanical strength and barrier properties of modified paper sheets were investigated in detail. The photocatalytic behavior of TiO₂-modified paper sheets was investigated as well using methylene blue (MB) as target pollutant. Full article

(This article belongs to the Special Issue TiO2-Based Nanostructures, Composites and Hybrid Photocatalysts)

► Show Figures

Figure 1

11 pages, 2151 KiB

Open AccessArticle

Successful Immobilization of Lanthanides Doped TiO₂ on Inert Foam for Repeatable Hydrogen Generation from Aqueous Ammonia

by Miroslava Edelmannová, Martin Reli, Lenka Matějová, Ivana Troppová, Lada Dubnová, Libor Čapek, Dana Dvoranová, Piotr Kuśtrowski and Kamila Kočí

Materials 2020, 13(5), 1254; https://doi.org/10.3390/ma13051254 - 10 Mar 2020

Cited by 4 | Viewed by 2538

Abstract

We describe the successful possibility of the immobilization of a photocatalyst on foam, which is beneficial from a practical point of view. An immobilized photocatalyst is possible for use in a continuous experiment and can be easily separated from the reactor after the reaction concludes. Parent TiO₂, La/TiO₂, and Nd/TiO₂ photocatalysts (containing 0.1 wt.% of lanthanide) were prepared by the sol-gel method and immobilized on Al₂O₃/SiO₂ foam (VUKOPOR A) by the dip-coating method. The photocatalysts were investigated for the photocatalytic hydrogen generation from an aqueous ammonia solution under UVA light (365 nm). The evolution of hydrogen was compared with photolysis, which was limited to zero. The higher hydrogen generation was observed in the presence of 0.1 wt.% La/TiO₂ than in 0.1 wt.% Nd/TiO₂. This is, besides other things, related to the higher level of the conduction band, which was observed for 0.1 wt.% La/TiO₂. The higher conduction band’s position is more effective for hydrogen production from ammonia decomposition. Full article

(This article belongs to the Special Issue TiO2-Based Nanostructures, Composites and Hybrid Photocatalysts)

► Show Figures

Graphical abstract

13 pages, 2228 KiB

Open AccessArticle

TiO₂ and N-TiO₂ Sepiolite and Zeolite Composites for Photocatalytic Removal of Ofloxacin from Polluted Water

by Michela Sturini, Federica Maraschi, Alice Cantalupi, Luca Pretali, Stefania Nicolis, Daniele Dondi, Antonella Profumo, Valentina Caratto, Elisa Sanguineti, Maurizio Ferretti and Angelo Albini

Materials 2020, 13(3), 537; https://doi.org/10.3390/ma13030537 - 23 Jan 2020

Cited by 21 | Viewed by 2418

Abstract

TiO₂ sepiolite and zeolite composites, as well the corresponding N-doped composites, synthesized through a sol–gel method, were tested for the photocatalytic degradation of a widespread fluoroquinolone antibiotic (ofloxacin) under environmental conditions. The catalysts were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS) analyses. A complete drug degradation occurred in 10–15 min in the presence of both TiO₂ sepiolite and zeolite catalysts, and in 20–30 min with the N-doped ones. Sepiolite proved to be a better TiO₂ support compared to the most common zeolite both in terms of adsorption capacity and photocatalytic efficiency in pollutants degradation. The influence of nitrogen doping (red shift from 3.2 to 3.0 eV) was also investigated. Although it was blurred by a marked increase of the particle dimension and thus a decrease of the specific surface area of the doped catalysts, it allowed a faster drug removal than direct photolysis. The photochemical paths and photoproducts were investigated, too. Full article

(This article belongs to the Special Issue TiO2-Based Nanostructures, Composites and Hybrid Photocatalysts)

► Show Figures

Graphical abstract

16 pages, 4252 KiB

Open AccessFeature PaperArticle

Photocatalytic Degradation of Azithromycin by Nanostructured TiO₂ Film: Kinetics, Degradation Products, and Toxicity

by Mirta Čizmić, Davor Ljubas, Marko Rožman, Danijela Ašperger, Lidija Ćurković and Sandra Babić

Materials 2019, 12(6), 873; https://doi.org/10.3390/ma12060873 - 15 Mar 2019

Cited by 33 | Viewed by 4684

Abstract

In this paper, nanostructured TiO₂ film was prepared by the by sol-gel process and dip-coating technique with titanium tetraisopropoxide as a precursor. After heat treatment at 550 °C, the deposited film was characterized by means of micro-Raman spectroscopy and atomic force microscopy (AFM). It was found that the TiO₂ film consisted of only the TiO₂ anatase phase and showed a granular microstructure. Photocatalytic degradation of azithromycin by using sol-gel nanostructured TiO₂ film was studied to define the most effective degradation process for potential use in wastewater treatment. Different factors were evaluated during photocatalysis, such as pH (3, 7, and 10), water matrix (ultrapure water and synthetic municipal waste water effluent), influence of another pharmaceutically active compound (sulfamethoxazole, one of the most often detected pharmaceutic compounds in waste waters), and radiation sources (low pressure ultraviolet (UV) mercury lamps with a UV-A and UV-C range; a light-emitting diode (LED) lamp with a radiation peak at 365 nm). The most effective degradation process was achieved with the UV-C irradiation source in matrices at pH 10. The water matrix had little effect on the photocatalytic degradation rates of azithromycin. The presence of sulfamethoxazole in the water matrix decreased the degradation rate of azithromycin, however, only in matrices with a pH level adjusted to 10. During the experiments, five azithromycin degradation products were identified and none of them showed toxic properties, suggesting effective removal of azithromycin. LED 365 nm as the irradiation source was not as effective as the UV-C lamp. Nevertheless, considering the cost, energy efficiency, and environmental aspects of the irradiation source, the LED lamp could be a “real-life” alternative. Full article

(This article belongs to the Special Issue TiO2-Based Nanostructures, Composites and Hybrid Photocatalysts)

► Show Figures

Figure 1

10 pages, 3206 KiB

Open AccessArticle

Effect of Ru, Rh, Mo, and Pd Adsorption on the Electronic and Optical Properties of Anatase TiO₂(101): A DFT Investigation

by Peng Gao, Libin Yang, Songtao Xiao, Lingyu Wang, Wei Guo and Jinghao Lu

Materials 2019, 12(5), 814; https://doi.org/10.3390/ma12050814 - 10 Mar 2019

Cited by 27 | Viewed by 4750

Abstract

Adsorbed metal atoms and metal doping onto TiO₂ can effectively enhance the optical and photocatalytic activity of photocatalytic efficiency of titanium dioxide (TiO₂), favoring the extension of its optical absorption spectrum and the efficiency of hydrogen generation. To investigate the possible mechanism causing potential improvement of photocatalytic activity, the electronic and optical properties of the anatase TiO₂(101) plane with different adsorbed metal atom have been theoretically calculated through density functional theory (DFT) method. Adsorption of Pd and Ru atoms increases the delocalization of the density of states, with an impurity state near the Fermi level. Moreover, the investigated adsorbed metal atoms (Mo, Pd, Ru, Rh) narrow the band gap of anatase TiO₂, thus enhancing the probability of photoactivation by visible light. The orbital hybridization of the d orbit from the adsorbed metal atom and the p orbit from the O of the defect site increases the Schottky barrier of the electronic structure. Full article

(This article belongs to the Special Issue TiO2-Based Nanostructures, Composites and Hybrid Photocatalysts)

► Show Figures

Graphical abstract

Review

Jump to: Editorial, Research

57 pages, 11428 KiB

Open AccessReview

Charge Carrier Processes and Optical Properties in TiO₂ and TiO₂-Based Heterojunction Photocatalysts: A Review

by Stefano Lettieri, Michele Pavone, Ambra Fioravanti, Luigi Santamaria Amato and Pasqualino Maddalena

Materials 2021, 14(7), 1645; https://doi.org/10.3390/ma14071645 - 27 Mar 2021

Cited by 118 | Viewed by 8922

Abstract

Photocatalysis based technologies have a key role in addressing important challenges of the ecological transition, such as environment remediation and conversion of renewable energies. Photocatalysts can in fact be used in hydrogen (H₂) production (e.g., via water splitting or photo-reforming of organic substrates), CO₂ reduction, pollution mitigation and water or air remediation via oxidation (photodegradation) of pollutants. Titanium dioxide (TiO₂) is a “benchmark” photocatalyst, thanks to many favorable characteristics. We here review the basic knowledge on the charge carrier processes that define the optical and photophysical properties of intrinsic TiO₂. We describe the main characteristics and advantages of TiO₂ as photocatalyst, followed by a summary of historical facts about its application. Next, the dynamics of photogenerated electrons and holes is reviewed, including energy levels and trapping states, charge separation and charge recombination. A section on optical absorption and optical properties follows, including a discussion on TiO₂ photoluminescence and on the effect of molecular oxygen (O₂) on radiative recombination. We next summarize the elementary photocatalytic processes in aqueous solution, including the photogeneration of reactive oxygen species (ROS) and the hydrogen evolution reaction. We pinpoint the TiO₂ limitations and possible ways to overcome them by discussing some of the “hottest” research trends toward solar hydrogen production, which are classified in two categories: (1) approaches based on the use of engineered TiO₂ without any cocatalysts. Discussed topics are highly-reduced “black TiO₂”, grey and colored TiO₂, surface-engineered anatase nanocrystals; (2) strategies based on heterojunction photocatalysts, where TiO₂ is electronically coupled with a different material acting as cocatalyst or as sensitizer. Examples discussed include TiO₂ composites or heterostructures with metals (e.g., Pt-TiO₂, Au-TiO₂), with other metal oxides (e.g., Cu₂O, NiO, etc.), direct Z-scheme heterojunctions with g-C₃N₄ (graphitic carbon nitride) and dye-sensitized TiO₂. Full article

(This article belongs to the Special Issue TiO2-Based Nanostructures, Composites and Hybrid Photocatalysts)

► Show Figures

Figure 1

21 pages, 6661 KiB

Open AccessReview

1D Titanium Dioxide: Achievements in Chemical Sensing

by Navpreet Kaur, Mandeep Singh, Abderrahim Moumen, Giorgio Duina and Elisabetta Comini

Materials 2020, 13(13), 2974; https://doi.org/10.3390/ma13132974 - 03 Jul 2020

Cited by 31 | Viewed by 3434

Abstract

For the last two decades, titanium dioxide (TiO₂) has received wide attention in several areas such as in medicine, sensor technology and solar cell industries. TiO₂-based gas sensors have attracted significant attention in past decades due to their excellent physical/chemical properties, low cost and high abundance on Earth. In recent years, more and more efforts have been invested for the further improvement in sensing properties of TiO₂ by implementing new strategies such as growth of TiO₂ in different morphologies. Indeed, in the last five to seven years, 1D nanostructures and heterostructures of TiO₂ have been synthesized using different growth techniques and integrated in chemical/gas sensing. Thus, in this review article, we briefly summarize the most important contributions by different researchers within the last five to seven years in fabrication of 1D nanostructures of TiO₂-based chemical/gas sensors and the different strategies applied for the improvements of their performances. Moreover, the crystal structure of TiO₂, different fabrication techniques used for the growth of TiO₂-based 1D nanostructures, their chemical sensing mechanism and sensing performances towards reducing and oxidizing gases have been discussed in detail. Full article

(This article belongs to the Special Issue TiO2-Based Nanostructures, Composites and Hybrid Photocatalysts)

► Show Figures

Journal Menu

Journal Browser

TiO2-Based Nanostructures, Composites and Hybrid Photocatalysts

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Published Papers (11 papers)

Editorial

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI