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Catalysts
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Photocatalysis and Environment
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Photocatalysis and Environment

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

Deadline for manuscript submissions: closed (20 November 2021) | Viewed by 50479

Special Issue Editors

Dr. Sami Rtimi

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Guest Editor
Global Institute for Water, Environment and Health, Geneva, Switzerland
Interests: catalytic materials; environmental remediation; emergent pollutants; antimicrobials; green new-deal
Special Issues, Collections and Topics in MDPI journals
Dr. Daria Camilla Boffito

E-Mail Website
Guest Editor
Department of Chemical Engineering, Polytechnique Montréal, Montreal, QC, Canada
Interests: heterogeneous catalysis; process intensification; photocatalysis; biomass; sonochemistry
Special Issues, Collections and Topics in MDPI journals
Dr. Aymen Amine Assadi

E-Mail Website
Guest Editor
Laboratory "Sciences Chimiques de Rennes"– Team "Chimie et Ingénierie des Procédés", 11 allée de Beaulieu, CS 50837, 35708 Rennes, CEDEX 7, France
Interests: chemical and environmental engineering; process intensification; photocatalysis
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

According to the UN-2030-SDGs, water depollution and sanitation is urgently needed. New methods for water and air depollution are under investigation. Among these methods, solar photocatalysis is showing huge potential for the removal of micropollutants and the inactivation of microorganisms.

A large number of studies have appeared that are devoted to the issue of the photocatalytic activity of TiO2 suspensions. Many other materials were used for pollutant degradation and/or microbial inactivation in water and air. During the last decade, attention has been drawn towards the design, synthesis and characterization of visible/solar light active catalysts. This allows the use of low-cost illumination sources and the exploitation of the lavish solar energy. The use of sunlight allows the design of low-cost solutions for water treatment, especially in the least developed countries (LDCs).

We invite authors to contribute original research articles as well as review articles that seek to address the mechanisms and significance of photocatalytic materials for environmental remediation. Particular interest will be given to papers exploring the preparation and engineering of innovative photocatalysts.

In particular, the topics of interest include but are not limited to:

  • Antimicrobial photocatalysts,
  • Photocatalytic coatings,
  • Indoor air quality,
  • Photocatalysis for VOC removal,
  • Water/wastewater treatment under solar light.

Dr. Sami Rtimi
Dr. Daria Camilla Boffito
Dr. Aymen Amine Assadi
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. Catalysts 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 2700 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

  • Photocatalytic materials
  • Environment
  • Materials characterization
  • Mechanism
  • Interfacial charge transfer

Published Papers (16 papers)

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11 pages, 1655 KiB  
Article
Accelerating the Design of Photocatalytic Surfaces for Antimicrobial Application: Machine Learning Based on a Sparse Dataset
by Heesoo Park, El Tayeb Bentria, Sami Rtimi, Abdelilah Arredouani, Halima Bensmail and Fedwa El-Mellouhi
Catalysts 2021, 11(8), 1001; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11081001 - 20 Aug 2021
Cited by 5 | Viewed by 2749
Abstract
Nowadays, most experiments to synthesize and test photocatalytic antimicrobial materials are based on trial and error. More often than not, the mechanism of action of the antimicrobial activity is unknown for a large spectrum of microorganisms. Here, we propose a scheme to speed [...] Read more.
Nowadays, most experiments to synthesize and test photocatalytic antimicrobial materials are based on trial and error. More often than not, the mechanism of action of the antimicrobial activity is unknown for a large spectrum of microorganisms. Here, we propose a scheme to speed up the design and optimization of photocatalytic antimicrobial surfaces tailored to give a balanced production of reactive oxygen species (ROS) upon illumination. Using an experiment-to-machine-learning scheme applied to a limited experimental dataset, we built a model that can predict the photocatalytic activity of materials for antimicrobial applications over a wide range of material compositions. This machine-learning-assisted strategy offers the opportunity to reduce the cost, labor, time, and precursors consumed during experiments that are based on trial and error. Our strategy may significantly accelerate the large-scale deployment of photocatalysts as a promising route to mitigate fomite transmission of pathogens (bacteria, viruses, fungi) in hospital settings and public places. Full article
(This article belongs to the Special Issue Photocatalysis and Environment)
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12 pages, 3406 KiB  
Article
Immobilization of Exfoliated g-C3N4 for Photocatalytical Removal of Organic Pollutants from Water
by Jakub Rusek, Šárka Paušová, Petr Praus and Josef Krýsa
Catalysts 2021, 11(2), 203; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11020203 - 03 Feb 2021
Cited by 4 | Viewed by 2421
Abstract
Graphitic carbon nitride (g-C3N4) was synthesized from melamine and exfoliated by thermal treatment. Exfoliated g-C3N4 particles were immobilized by electrophoretic deposition from an ultrasonically treated ethanolic suspension aged up to 12 weeks. During the aging of [...] Read more.
Graphitic carbon nitride (g-C3N4) was synthesized from melamine and exfoliated by thermal treatment. Exfoliated g-C3N4 particles were immobilized by electrophoretic deposition from an ultrasonically treated ethanolic suspension aged up to 12 weeks. During the aging of the suspension, the separation of particles bigger than 10 μm was observed. The separated stable part of the suspension contained particles with a relatively uniform size distribution, enabling the fabrication of g-C3N4 films that were stable in a stirred aqueous solution. Such stable immobilized particles of exfoliated g-C3N4 are reported for the first time. The photocatalytic activity of such layers was evaluated using aqueous solutions of Acid Orange 7 (AO7) and 4-chlorophenol (4-CP). The photocatalytic decomposition of AO7 was faster in comparison with the decomposition of 4-CP. Mineralization was observed in the case of AO7, but not in the case of 4-CP, where the decrease of 4-CP concentration is due to 4-CP polymerization and the formation of a dimer, C12H8Cl2O2. This indicates that the use of g-C3N4 as a photocatalyst for oxidative degradation of organic compounds in water is limited. Full article
(This article belongs to the Special Issue Photocatalysis and Environment)
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11 pages, 2396 KiB  
Article
Synthesis of Titanium Dioxide/Silicon Dioxide from Beach Sand as Photocatalyst for Cr and Pb Remediation
by Diana Rakhmawaty Eddy, Soraya Nur Ishmah, Muhamad Diki Permana and M. Lutfi Firdaus
Catalysts 2020, 10(11), 1248; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10111248 - 29 Oct 2020
Cited by 25 | Viewed by 3718
Abstract
Heavy metals are non-biodegradable and have a high toxicity effect on microorganisms which makes their presence in the environment extremely dangerous. The method of handling heavy metal waste by photocatalysis techniques using TiO2/SiO2 composite showed a good performance in reducing [...] Read more.
Heavy metals are non-biodegradable and have a high toxicity effect on microorganisms which makes their presence in the environment extremely dangerous. The method of handling heavy metal waste by photocatalysis techniques using TiO2/SiO2 composite showed a good performance in reducing harmful pollutants. In this study, SiO2 from Bengkulu beach sand, Indonesia, was used as a support material for TiO2 photocatalyst to remove Cr(VI) and Pb(II). SiO2 was obtained through leaching techniques using NaOH as a solvent. The TiO2/SiO2 composite photocatalyst was synthesized using a solvothermal method at 130 °C and then characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and a particle size analyzer (PSA). Based on the XRD diffractogram, the synthesized TiO2 showed the anatase structure while the SiO2 showed the amorphous structure. The Ti–O–Si bond is defined in the infrared (IR) spectra, which indicates that the relationship between TiO2 and SiO2 is a chemical interaction. The results of SEM and PSA characterizations show agglomerated spherical (round) particles with a mean particle size of 616.9 nm. The TiO2/SiO2 composite of 7:1 ratio showed the highest photocatalytic activity after 180 min of ultraviolet (UV) irradiation, with a concentration-decrease percentage of 93.77% and 93.55% for Cr(VI) and Pb(II), respectively. Full article
(This article belongs to the Special Issue Photocatalysis and Environment)
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0 pages, 1650 KiB  
Article
Comparison of the Photocatalytic Activity of ZnO/CeO2 and ZnO/Yb2O3 Mixed Systems in the Phenol Removal from Water: A Mechanicistic Approach
by Erik Cerrato, Nuno Paulo Ferreira Gonçalves, Paola Calza and Maria Cristina Paganini
Catalysts 2020, 10(10), 1222; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10101222 - 21 Oct 2020
Cited by 6 | Viewed by 2200
Abstract
In this paper we compare the photocatalytic activity of two semiconductors based on ZnO: ZnO/CeO2 and ZnO/Yb2O3. The two samples were prepared via hydrothermal synthesis and fully characterized by X-ray diffraction technique, diffuse reflectance Ultra Violet- Visible spectroscopy [...] Read more.
In this paper we compare the photocatalytic activity of two semiconductors based on ZnO: ZnO/CeO2 and ZnO/Yb2O3. The two samples were prepared via hydrothermal synthesis and fully characterized by X-ray diffraction technique, diffuse reflectance Ultra Violet- Visible spectroscopy (UV-Vis), high resolution transmission electron microscopy and finally with electron paramagnetic resonance spectroscopy. The prepared materials were also tested in their photocatalytic performances both through Electron Paramagnetic Resonance (EPR) analyzing the formation of charge carriers and with the abatement of a probe molecule like phenol, in presence and in absence of scavengers. Full article
(This article belongs to the Special Issue Photocatalysis and Environment)
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11 pages, 7284 KiB  
Article
Facile Preparation of a Novel Bi2WO6/Calcined Mussel Shell Composite Photocatalyst with Enhanced Photocatalytic Performance
by Shijie Li, Chunchun Wang, Yanping Liu, Bing Xue, Jialin Chen, Hengwei Wang and Yu Liu
Catalysts 2020, 10(10), 1166; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10101166 - 12 Oct 2020
Cited by 89 | Viewed by 2955
Abstract
The exploration of cost-effective and highly efficient photocatalysts is still a great challenge. In this work, a cost-effective and highly active Bi2WO6/calcined mussel shell (CMS/BWO) composite photocatalyst was prepared by a facile solvothermal route, in which Bi2WO [...] Read more.
The exploration of cost-effective and highly efficient photocatalysts is still a great challenge. In this work, a cost-effective and highly active Bi2WO6/calcined mussel shell (CMS/BWO) composite photocatalyst was prepared by a facile solvothermal route, in which Bi2WO6 nanosheets were tightly, evenly, and vertically grown on waste calcined mussel shells (CMS). Multiple techniques are adopted to characterize the phases, morphology, and chemical properties of the as-fabricated catalysts. In contrast to the stacked Bi2WO6, CMS/BWO has numerous exposed edges and open transfer pathways, which can create more open space and reactive sites for photocatalytic reactions. Such favorable characteristics enable CMS/BWO to efficiently degrade organic pollutants (e.g., rhodamine B (RhB), methylene blue (MB), tetracycline hydrochloride (TC)) under visible light. Moreover, the generation of reactive species during the photocatalytic process is also examined by trapping experiments, disclosing the pivotal role of photo-generated holes (h+) and hydroxyl radicals (•OH) in the photo-degradation of pollutants. Above all, this study not only provides an efficient photocatalyst for environmental remediation, but it also opens up new possibilities for waste mussel shell reutilization. Full article
(This article belongs to the Special Issue Photocatalysis and Environment)
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17 pages, 3773 KiB  
Article
Catalytic Removal of Alizarin Red Using Chromium Manganese Oxide Nanorods: Degradation and Kinetic Studies
by Muhammad Hamza, Ataf Ali Altaf, Samia Kausar, Shahzad Murtaza, Nasir Rasool, Rukhsana Gul, Amin Badshah, Muhammad Zaheer, Syed Adnan Ali Shah and Zainul Amiruddin Zakaria
Catalysts 2020, 10(10), 1150; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10101150 - 06 Oct 2020
Cited by 16 | Viewed by 3021
Abstract
Dye removal through photocatalytic degradation employing nanomaterials as catalysts is a growing research area. In current studies, photocatalytic alizarin red (AR) dye degradation has been investigated by designing a series of Cr based manganese oxide nanomaterials (MH1–MH5). Synthesized nanomaterials were characterized by powder [...] Read more.
Dye removal through photocatalytic degradation employing nanomaterials as catalysts is a growing research area. In current studies, photocatalytic alizarin red (AR) dye degradation has been investigated by designing a series of Cr based manganese oxide nanomaterials (MH1–MH5). Synthesized nanomaterials were characterized by powder X-ray diffraction, scanning electron microscopy/energy dispersive x-ray, Brunauer–Emmett–Teller, and photoluminescence techniques and were utilized for photocatalytic AR dye degradation under UV light. AR dye degradation was monitored by UV–visible spectroscopy and percent degradation was studied for the effect of time, catalyst dose, different dye concentrations, and different pH values of dye solution. All the catalysts have shown more than 80% dye degradation exhibiting good catalytic efficiencies for dye removal. The catalytic pathway was analyzed by applying the kinetic model. A pseudo second-order model was found the best fitted kinetic model indicating a chemically-rate controlled mechanism. Values of constant R2 for all the factors studied were close to unity depicting a good correlation between experimental data. Full article
(This article belongs to the Special Issue Photocatalysis and Environment)
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15 pages, 1948 KiB  
Article
Impact of H2O2 on the Lactic and Formic Acid Degradation in Presence of TiO2 Rutile and Anatase Phases under UV and Visible Light
by Annika Holm, Marwa Hamandi, Karima Sahel, Frederic Dappozze and Chantal Guillard
Catalysts 2020, 10(10), 1131; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10101131 - 01 Oct 2020
Cited by 4 | Viewed by 1885
Abstract
The degradation rates of formic acid and lactic acid in the presence and absence of H2O2 were studied, utilizing several TiO2 catalysts: PC105 (100% anatase), MPT 625 (100% rutile), and P25 (80% anatase/20% rutile), and the results were discussed [...] Read more.
The degradation rates of formic acid and lactic acid in the presence and absence of H2O2 were studied, utilizing several TiO2 catalysts: PC105 (100% anatase), MPT 625 (100% rutile), and P25 (80% anatase/20% rutile), and the results were discussed with regards to the current literature. The impact of hydrogen peroxide on the photocatalytic efficiency of eleven TiO2 samples was then determined, using commercial anatase structures (PC105, PC500, UV100), commercial mixed anatase/rutile (P25 and P90), and six rutile (two commercial samples: MPT 625 and C-R160, and four home-made rutile samples were synthesized by TiCl4 hydrolysis). The effect of catalyst surface area and TiO2 phase on the degradation rate of lactic acid (LA) and the decomposition of H2O2 was studied and discussed in regard to the active species generated. The intermediate products formed in the absence and presence of H2O2 were also an important factor in the comparison. Finally, the efficiency of the degradation of LA and formic acid (FA) in the presence of rutile and H2O2 was determined under visible light, and their reactivity was compared. The intermediate products formed in the degradation of LA were identified and quantified and compared to those obtained under UV (Ultra-Violet). Full article
(This article belongs to the Special Issue Photocatalysis and Environment)
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11 pages, 3095 KiB  
Article
Tandem Synthesis of High Yield MoS2 Nanosheets and Enzyme Peroxidase Mimicking Properties
by Suresh Thangudu, Mu Tzu Lee and Sami Rtimi
Catalysts 2020, 10(9), 1009; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10091009 - 03 Sep 2020
Cited by 14 | Viewed by 3855
Abstract
Molybdenum Sulfide nanosheets (MoS2 NSs) have unique properties that allow its use in a wide range of applications. Unfortunately, a lack of green synthesis methods to achieve a high yield remains a challenge after decades. Herein we report a simple, ecofriendly, green [...] Read more.
Molybdenum Sulfide nanosheets (MoS2 NSs) have unique properties that allow its use in a wide range of applications. Unfortunately, a lack of green synthesis methods to achieve a high yield remains a challenge after decades. Herein we report a simple, ecofriendly, green and cost-effective approach to synthesize water soluble MoS2 NSs via probe/Tip sonication method. The sequential batch manner pathway allows us to attain a high yield of MoS2 NSs (~100%). The prepared MoS2 NSs were characterized using up-to-date surface science techniques. UV-visible-NIR spectroscopy allowed us to visualize the doublet peaks of pristine MoS2 at 610 and 680 nm concomitant with the inter-band transitions at 394 nm and 460 nm. Using Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS), the crystallites’ sizes were estimated. X-ray diffraction (XRD) and Raman Spectroscopy were performed with respect to the bulk MoS2. The energy difference between the Raman peaks revealed that our NSs are formed of 5–6 layers. Further, we explored enzyme peroxidase mimetic properties of the synthesized MoS2 NSs. Results showed that the present MoS2 NSs offer excellent peroxidase mimicking properties. Most importantly, we observed that the optical properties and characteristics of MoS2 NSs synthesized by the current green method are similar to those of MoS2 NSs synthesized using conventional harsh methods reported in the literature. So that we strongly assume that the present method is a green alternative for the existing low yield and harsh experimental procedures to achieve water soluble MoS2 NSs in high yield. The synthesized soluble NSs are promising catalysts for the detection of toxic chemicals in the environment and/or for following enzymatic chromogenic reactions. Full article
(This article belongs to the Special Issue Photocatalysis and Environment)
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17 pages, 2268 KiB  
Article
Suppression of Hydrophobic Recovery in Photo-Initiated Chemical Vapor Deposition
by Alessio Aufoujal, Ulrich Legrand, Jean-Luc Meunier and Jason Robert Tavares
Catalysts 2020, 10(5), 534; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10050534 - 12 May 2020
Viewed by 3207
Abstract
Photo-initiated chemical vapor deposition (PICVD) functionalizes carbon nanotube (CNT)-enhanced porous substrates with a highly polar polymeric nanometric film, rendering them super-hydrophilic. Despite its ability to generate fully wettable surfaces at low temperatures and atmospheric pressure, PICVD coatings normally undergo hydrophobic recovery. This is [...] Read more.
Photo-initiated chemical vapor deposition (PICVD) functionalizes carbon nanotube (CNT)-enhanced porous substrates with a highly polar polymeric nanometric film, rendering them super-hydrophilic. Despite its ability to generate fully wettable surfaces at low temperatures and atmospheric pressure, PICVD coatings normally undergo hydrophobic recovery. This is a process by which a percentage of oxygenated functional group diffuse/re-arrange from the top layer of the deposited film towards the bulk of the substrate, taking the induced hydrophilic property of the material with them. Thus, hydrophilicity decreases over time. To address this, a vertical chemical gradient (VCG) can be deposited onto the CNT-substrate. The VCG consists of a first, thicker highly cross-linked layer followed by a second, thinner highly functionalized layer. In this article, we show, through water contact angle and XPS measurements, that the increased cross-linking density of the first layer can reduce the mobility of polar functional groups, forcing them to remain at the topmost layer of the PICVD coating and to suppress hydrophobic recovery. We show that employing a bi-layer VCG suppresses hydrophobic recovery for five days and reduces its effect afterwards (contact angle stabilizes to 42 ± 1° instead of 125 ± 3°). Full article
(This article belongs to the Special Issue Photocatalysis and Environment)
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18 pages, 8705 KiB  
Article
Highly Efficient Photo-Degradation of Gaseous Organic Pollutants Catalyzed by Diatomite-Supported Titanium Dioxide
by Xuefei Liu, Yugan He, Beibei Yang, Qi Yan and Junjiao Yang
Catalysts 2020, 10(4), 380; https://0-doi-org.brum.beds.ac.uk/10.3390/catal10040380 - 01 Apr 2020
Cited by 8 | Viewed by 2000
Abstract
Volatile organic compounds (VOCs) are the most harmful contaminants that have been identified, most of which are gaseous organic pollutants. In this study, TiO2@diatomite catalysts with various loading amounts of TiO2 were fabricated using a facile solvothermal method with anhydrous [...] Read more.
Volatile organic compounds (VOCs) are the most harmful contaminants that have been identified, most of which are gaseous organic pollutants. In this study, TiO2@diatomite catalysts with various loading amounts of TiO2 were fabricated using a facile solvothermal method with anhydrous ethanol as a solvent for the removal of VOCs. X-ray diffraction analysis revealed that TiO2 has an anatase phase and the introduction of diatomite has no negative effect. The catalysts were characterized using scanning electron microscopy and transmittance electron microscopy techniques. The results indicate that after introducing diatomite, TiO2 nanoparticles are mostly square-like and intact, and are uniformly immobilized in the diatomite. Finally, their photocatalytic performance was investigated using liquid ultraviolet spectrometry and gas chromatography-mass spectrometry. Among the catalysts tested, 0.35TiO2@diatomite (with a mass ratio of TiO2 to diatomite of 0.35) exhibited higher photocatalytic activity than the other samples, i.e., pure TiO2 and diatomite, and could effectively remove acetone and benzene, demonstrating its potential market application and practical significance. Full article
(This article belongs to the Special Issue Photocatalysis and Environment)
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16 pages, 2962 KiB  
Article
Bioinspired ZnO-Based Solar Photocatalysts for the Efficient Decontamination of Persistent Organic Pollutants and Hexavalent Chromium in Wastewater
by Albert Serrà, Elvira Gómez and Laetitia Philippe
Catalysts 2019, 9(12), 974; https://0-doi-org.brum.beds.ac.uk/10.3390/catal9120974 - 20 Nov 2019
Cited by 28 | Viewed by 3017
Abstract
Biomimetic/bioinspired engineering and sulfidation processes are effective strategies for improving the visible light-driven photocatalytic performance of ZnO photocatalysts. A facile electrodeposition process in high oxygen-flux conditions was used to synthesize well-defined fractal micro/nanoferns, consequently increasing the photocatalyst’s light-trapping capability and the accessible active [...] Read more.
Biomimetic/bioinspired engineering and sulfidation processes are effective strategies for improving the visible light-driven photocatalytic performance of ZnO photocatalysts. A facile electrodeposition process in high oxygen-flux conditions was used to synthesize well-defined fractal micro/nanoferns, consequently increasing the photocatalyst’s light-trapping capability and the accessible active surface. Next, a simple sulfidation process was used to form a thin layer of ZnS, producing ZnO@ZnS core@shell micro/nanoferns, thereby tuning the optoelectronic properties and extending the photoresponse to the visible region. The ZnO@ZnS micro/nanoferns exhibited clear superiority over other ZnO photocatalysts in the photooxidation of persistent organic pollutants (POPs) and the photoreduction of Cr(VI). Their excellent photocatalytic performance allowed the photodegradation under UV-filtered sunlight of nearly 97% of methylene blue after 60 min; the mineralization of >98% of a mixture of methylene blue, 4-nitrophenol, and rhodamine-B after 210 min; and the removal of nearly 65% of Cr(VI) after 180 min. In addition, the ZnO@ZnS micro/nanoferns demonstrated a good ability to decontaminate an inorganic-organic bipollutant system, with promising potential to leverage synergistic effects. Finally, these micro/nanoferns presented great recyclability and reusability for both photooxidation and photoremediation processes. These findings support that sulfidation and biomimetic engineering can be a superior route for designing efficient sunlight-driven ZnO-photocatalysts for water decontamination. Full article
(This article belongs to the Special Issue Photocatalysis and Environment)
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20 pages, 3099 KiB  
Article
The Sonophotocatalytic Degradation of Pharmaceuticals in Water by MnOx-TiO2 Systems with Tuned Band-Gaps
by Zahra Khani, Dalma Schieppati, Claudia L. Bianchi and Daria C. Boffito
Catalysts 2019, 9(11), 949; https://0-doi-org.brum.beds.ac.uk/10.3390/catal9110949 - 12 Nov 2019
Cited by 25 | Viewed by 2813
Abstract
Advanced oxidation processes (AOPs) are technologies to degrade organic pollutants to carbon dioxide and water with an eco-friendly approach to form reactive hydroxyl radicals. Photocatalysis is an AOP whereby TiO2 is the most adopted photocatalyst. However, TiO2 features a wide (3.2 [...] Read more.
Advanced oxidation processes (AOPs) are technologies to degrade organic pollutants to carbon dioxide and water with an eco-friendly approach to form reactive hydroxyl radicals. Photocatalysis is an AOP whereby TiO2 is the most adopted photocatalyst. However, TiO2 features a wide (3.2 eV) and fast electron-hole recombination. When Mn is embedded in TiO2, it shifts the absorption wavelength towards the visible region of light, making it active for natural light applications. We present a systematic study of how the textural and optical properties of Mn-doped TiO2 vary with ultrasound applied during synthesis. We varied ultrasound power, pulse length, and power density (by changing the amount of solvent). Ultrasound produced mesoporous MnOx-TiO2 powders with a higher surface area (101–158 m2 g−1), pore volume (0-13–0.29 cc g−1), and smaller particle size (4–10 µm) than those obtained with a conventional sol-gel method (48–129 m2 g−1, 0.14–0.21 cc g−1, 181 µm, respectively). Surprisingly, the catalysts obtained with ultrasound had a content of brookite that was at least 28%, while the traditional sol-gel samples only had 7%. The samples synthesized with ultrasound had a wider distribution of the band-gaps, in the 1.6–1.91 eV range, while traditional ones ranged from 1.72 eV to 1.8 eV. We tested activity in the sonophotocatalytic degradation of two model pollutants (amoxicillin and acetaminophen). The catalysts synthesized with ultrasound were up to 50% more active than the traditional samples. Full article
(This article belongs to the Special Issue Photocatalysis and Environment)
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18 pages, 6913 KiB  
Article
Duality in the Mechanism of Hexagonal ZnO/CuxO Nanowires Inducing Sulfamethazine Degradation under Solar or Visible Light
by Jiajie Yu, John Kiwi, Tianhe Wang, Cesar Pulgarin and Sami Rtimi
Catalysts 2019, 9(11), 916; https://0-doi-org.brum.beds.ac.uk/10.3390/catal9110916 - 02 Nov 2019
Cited by 39 | Viewed by 3611
Abstract
This study presents the first evidence for the photocatalytic performance of ZnO/CuxO hexagonal nanowires leading to sulfamethazine (SMT) degradation. The chemical composition of the nanowires was determined by X-ray fluorescence (XRF). The sample with the composition ZnO/Cux = 1.25O [...] Read more.
This study presents the first evidence for the photocatalytic performance of ZnO/CuxO hexagonal nanowires leading to sulfamethazine (SMT) degradation. The chemical composition of the nanowires was determined by X-ray fluorescence (XRF). The sample with the composition ZnO/Cux = 1.25O led to faster SMT-degradation kinetics. The SMT-degradation kinetics were monitored by high performance liquid chromatography (HPLC). The morphology of the hexagonal nanowires was determined by scanning electron microscopy (SEM) and mapped by EDX. The redox reactions during SMT degradation were followed by X-ray photoelectron spectroscopy (XPS). The interfacial potential between the catalyst surface and SMT was followed in situ under solar and indoor visible light irradiation. SMT-degradation was mediated by reactive oxidative species (ROS). The interfacial charge transfer (IFCT) between ZnO and CuxO is shown to depend on the type of light used (solar or visible light). This later process was found to be iso-energetic due to the potential energy positions of ZnO and CuxO conduction bands (cb). The intervention of surface plasmon resonance (LSPR) species in the SMT degradation is discussed. Full article
(This article belongs to the Special Issue Photocatalysis and Environment)
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20 pages, 9159 KiB  
Article
NaBH4-Reduction Induced Evolution of Bi Nanoparticles from BiOCl Nanoplates and Construction of Promising Bi@BiOCl Hybrid Photocatalysts
by Yuxiang Yan, Hua Yang, Zao Yi and Tao Xian
Catalysts 2019, 9(10), 795; https://0-doi-org.brum.beds.ac.uk/10.3390/catal9100795 - 24 Sep 2019
Cited by 78 | Viewed by 5680
Abstract
In this work, we have synthesized BiOCl nanoplates (diameter 140–220 nm, thickness 60–70 nm) via a co-precipitation method, and then created Bi nanoparticles (diameter 35–50 nm) on the surface of BiOCl nanoplates via a NaBH4 reduction method. By varying the NaBH4 [...] Read more.
In this work, we have synthesized BiOCl nanoplates (diameter 140–220 nm, thickness 60–70 nm) via a co-precipitation method, and then created Bi nanoparticles (diameter 35–50 nm) on the surface of BiOCl nanoplates via a NaBH4 reduction method. By varying the NaBH4 concentration and reaction time, the evolution of Bi nanoparticles was systematically investigated. It is demonstrated that with increasing the NaBH4 concentration (at a fixing reaction time of 30 min), BiOCl crystals are gradually reduced into Bi nanoparticles, and pure Bi nanoparticles are formed at 120 mM NaBH4 solution treatment. At low-concentration NaBH4 solutions (e.g., 10 and 30 mM), with increasing the reaction time, BiOCl crystals are partially reduced into Bi nanoparticles, and then the Bi nanoparticles return to form BiOCl crystals. At high-concentration NaBH4 solutions (e.g., 120 mM), BiOCl crystals are reduced to Bi nanoparticles completely with a short reaction time, and further prolong the treatment time leads to the transformation of the Bi nanoparticles into a two-phase mixture of BiOCl and Bi2O3 nanowires. The photodegradation performances of the samples were investigated by choosing rhodamine B (RhB) as the model pollutant and using simulated sunlight as the light source. It is demonstrated that an enhanced photodegradation performance can be achieved for the created Bi@BiOCl hybrid composites with appropriate NaBH4 treatment. The underlying photocatalytic mechanism was systematically investigated and discussed. Full article
(This article belongs to the Special Issue Photocatalysis and Environment)
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13 pages, 5675 KiB  
Article
Investigation of Microstructure and Photocatalytic Performance of a Modified Zeolite Supported Nanocrystal TiO2 Composite
by Gang Liao, Wei He and Yuming He
Catalysts 2019, 9(6), 502; https://0-doi-org.brum.beds.ac.uk/10.3390/catal9060502 - 31 May 2019
Cited by 34 | Viewed by 3713
Abstract
A modified zeolite/TiO2 composite (MZTC) was prepared through a method of saturated infiltration and synthesis in situ. The crystalline phase, micromorphology, elementary composition, specific surface area, pore size distribution, chemical bond and band gap variation of the products were characterized by X-ray [...] Read more.
A modified zeolite/TiO2 composite (MZTC) was prepared through a method of saturated infiltration and synthesis in situ. The crystalline phase, micromorphology, elementary composition, specific surface area, pore size distribution, chemical bond and band gap variation of the products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), BET specific surface area and pore size distribution analysis (BET), Fourier transform infrared spectroscopy (FTIR) and UV–vis diffuse reflectance spectroscopy (UV-vis DRS), respectively. The microscopic characterization results showed that TiO2 was homogeneously dispersed in the structure of zeolite at the nanoscale range, and a strong chemical bond was established between TiO2 and zeolite. The photocatalytic performance of MZTC was evaluated by studying the degradation rate of methylene blue (MB) dye in aqueous solution under UV-light irradiation. The results of the degradation experiment showed that the MB degradation rate of MZTC-2.5 was the highest, reaching 93.6%, which was 2.4 times higher than hydrolysis TiO2 powder (HTOP) containing the same mass of pure TiO2. The MB degradation rate of MZTC-2.5 still maintained 86.5% after five tests, suggesting the excellent recyclability of MZTC-2.5. The possible mechanism of MB degradation was also discussed. Full article
(This article belongs to the Special Issue Photocatalysis and Environment)
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Review

Jump to: Research

22 pages, 5607 KiB  
Review
Update on Interfacial Charge Transfer (IFTC) Processes on Films Inactivating Viruses/Bacteria under Visible Light: Mechanistic Considerations and Critical Issues
by Sami Rtimi and John Kiwi
Catalysts 2021, 11(2), 201; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11020201 - 03 Feb 2021
Cited by 13 | Viewed by 2385
Abstract
This review presents an update describing binary and ternary semiconductors involving interfacial charge transfer (IFCT) in composites made up by TiO2, CuO, Ag2O and Fe2O3 used in microbial disinfection (bacteria and viruses). The disinfection mechanism, kinetics [...] Read more.
This review presents an update describing binary and ternary semiconductors involving interfacial charge transfer (IFCT) in composites made up by TiO2, CuO, Ag2O and Fe2O3 used in microbial disinfection (bacteria and viruses). The disinfection mechanism, kinetics and generation of reactive oxygen species (ROS) in solution under solar/visible light are discussed. The surface properties of the photocatalysts and their active catalytic sites are described in detail. Pathogenic biofilm inactivation by photocatalytic thin films is addressed since biofilms are the most dangerous agents of spreading pathogens into the environment. Full article
(This article belongs to the Special Issue Photocatalysis and Environment)
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