10th Anniversary of Catalysts—Feature Papers in Photocatalysis

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

Deadline for manuscript submissions: closed (31 January 2023) | Viewed by 109034

Special Issue Editors

Laboratory of Photoactive Nanocomposite Materials, Saint-Petersburg State University, Ulyanovskaya Str. 1, Peterhof, 198504 Saint-Petersburg, Russia
Interests: photocatalysis; self-cleaning; superhydrophilic; antibacterial surfaces; metal and semiconductor particles; nanocristalyne transparent coatings; functional test according to DIN; CEN and ISO
Special Issues, Collections and Topics in MDPI journals
Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Krakow, Poland
Interests: heterogeneous photocatalysis; advanced oxidation processes (AOPs); environmental purification; plasmonic nanoparticles; antimicrobial properties; visible-light-responsive materials
Special Issues, Collections and Topics in MDPI journals
Laboratory of Industrial Chemistry, Department of Chemistry, University of Ioannina, 45500 Ioannina, Greece
Interests: photocatalysis; photolytic processes in the environment; photodegradation pathways; identification of phototransformation products
Special Issues, Collections and Topics in MDPI journals
Engineering Department of Environmental Engineering Piastów 45, Szczecin Faculty of Civil and Environmental, West Pomeranian University of Technology, 70-311 Szczecin, Poland
Interests: photocatalysis; photoactive building materials; titanium dioxide; water and air purification
Special Issues, Collections and Topics in MDPI journals
Department of Industrial Engineering, University Salerno, Via Giovanni Paolo 2 132, I-84084 Fisciano, Salerno, Italy
Interests: photocatalysis for sustainable chemistry; photocatalytic and photo-fenton processes for pollutants removal in wastewater; catalytic combustion of sewage sludge; decomposition and oxidative decomposition of H2S; hydrolysis of COS in the liquid phase
Special Issues, Collections and Topics in MDPI journals
Division of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea
Interests: semiconductor photocatalysis for environmental and energy applications; solar fuel production; artificial photosynthesis; development of visible light active photocatalysts; photochemical purification of water and air; environmental (photo)chemistry; ice (photo)chemistry; redox processes of environmental significance
Institute of Advanced Energy and Powertrain Technology, Shanghai Jiao Tong University, Shanghai, China
Interests: heterogeneous catalysis; catalysis for energy and environment; in situ and operando spectroscopy

Special Issue Information

Dear Colleagues,

It is our pleasure to welcome you to our Special Issue “Photocatalysis”, celebrating the 10th Anniversary of Catalysts. As you all know, photocatalysis has become one of the key areas within the catalysis field. Since it adds just another feature to the already rather complex mechanism of heterogeneous catalysis, that is, the interaction with photons required to initiate the overall process, there is still a large number of unknowns regarding details of the underlying reaction mechanism(s). Therefore, contributions highlighting such mechanistic details are highly welcome in this Special Issue. Moreover, a photocatalyst often requires the presence of one or even several so-called co-catalysts to enable the desired chemical conversions. Therefore, we would like to invite you to submit to this Special Issue your explanations regarding the role of catalysis in a photocatalytic process. Other areas for which high-level contributions are needed—but are by no means limited to—plasmonic photocatalysis, nanocomposite materials, doped and co-doped semiconductor materials, photocatalytic synthesis, solar fuels, theoretical modeling of photocatalytic processes, photoreactor and reaction engineering, non-linear optical effects, decontamination and disinfection, and pilot and full-scale applications, to name but a few. We look forward to receiving your contribution(s) as soon as possible. In addition to original research articles, we welcome review and feature articles.

Prof. Dr. Detlef W. Bahnemann
Prof. Dr. Ewa Kowalska
Prof. Dr. Ioannis Konstantinou
Prof. Dr. Magdalena Janus
Prof. Dr. Vincenzo Vaiano
Prof. Dr. Wonyong Choi
Prof. Dr. Zhi Jiang
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

  • Mechanisms of photocatalysis
  • (co)-catalysts
  • Plasmonic photocatalysis
  • Nanocomposite materials
  • Doped and co-doped semiconductor materials
  • Photocatalytic synthesis
  • Solar fuels and artificial photosynthesis
  • Water splitting, CO2 and N2 conversion
  • Environmental photocatalysis
  • Selective synthesis of organic compounds
  • Theoretical modeling of photocatalytic processes
  • Photoreactor and reaction engineering
  • Non-linear optical effects
  • Photonic crystals
  • Antimicrobial properties
  • Degradation mechanisms and pathways
  • Pilot and full-scale photocatalytic applications

Published Papers (49 papers)

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Research

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21 pages, 4714 KiB  
Article
Water-Based Photocatalytic Sol–Gel TiO2 Coatings: Synthesis and Durability
by Umberto Bellè, Daniela Spini, Barbara Del Curto, MariaPia Pedeferri and Maria Vittoria Diamanti
Catalysts 2023, 13(3), 494; https://doi.org/10.3390/catal13030494 - 28 Feb 2023
Cited by 2 | Viewed by 1672
Abstract
The environmental impact of industrial technologies and related remediation methods are major research trend lines. Unfortunately, in the development of materials for wastewater treatment or air purification, hazardous reactants are often employed, reducing the overall beneficial contribution of such technology on the environment. [...] Read more.
The environmental impact of industrial technologies and related remediation methods are major research trend lines. Unfortunately, in the development of materials for wastewater treatment or air purification, hazardous reactants are often employed, reducing the overall beneficial contribution of such technology on the environment. We here synthesize stable titanium dioxide (TiO2) sols using a green route, with titanium tetraisopropoxide (TTIP) as precursor, water as solvent and acetic acid acting as catalyst, chelating agent and peptizing agent. The sol was deposited on glass by dip-coating and then analyzed using XRD, SEM and spectrophotometry. Wastewater purification ability was evaluated in the photocatalytic degradation of two organic dyes (Rhodamine B and Methylene Blue). Results on RhB showed > 85% degradation in 6 h maintained along a series of 7 tests, confirming good efficiency and reusability, and 100% in 3 h on MB; efficiency mostly depended on calcination temperature and layer thickness. High photodegradation efficiency was found in nonannealed samples, suggesting TiO2 nanoparticles crystallization during sol–gel production. Yet, such samples showed a gradual decrease in photoactivity in repeated tests, probably due to a partial release of TiO2 particles in solution, while on calcined samples a good adhesion was obtained, leading to a more durable photoactive layer. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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10 pages, 6865 KiB  
Article
Fabrication and Photocatalytic Activity of Single Crystalline TiO2 Hierarchically Structured Microspheres
by Haisheng Huang, Qi Kong, Xin Yue, Kunlei Wang, Zhishun Wei and Ying Chang
Catalysts 2023, 13(1), 201; https://doi.org/10.3390/catal13010201 - 15 Jan 2023
Cited by 1 | Viewed by 1142
Abstract
Single crystalline anatase TiO2 microspheres with co-exposed {001}/{101} facets were prepared by a facile one-pot hydrothermal method using NaF as a morphology controlling agent. The influences of the NaF amount on the morphology and also on the photocatalytic activity were investigated systematically. [...] Read more.
Single crystalline anatase TiO2 microspheres with co-exposed {001}/{101} facets were prepared by a facile one-pot hydrothermal method using NaF as a morphology controlling agent. The influences of the NaF amount on the morphology and also on the photocatalytic activity were investigated systematically. The obtained microspheres possessed better morphology when the concentration of NaF was chosen at 0.1 mol/L, and the experimental results indicated that the crystal structure and morphology played important roles on the photocatalytic activity, based on the experimental results it was found that the photocatalytic degradation efficiency of TiO2 microspheres on Tetracycline hydrochloride could reach 76.4% in 2 h. Finally, a growth mechanism was proposed by investigating the growth process, i.e., a synergistic effect of F ions modified Ostwald ripening and oriented attachment. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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17 pages, 4347 KiB  
Article
Heteroepitaxial Growth of GaP Photocathode by Hydride Vapor Phase Epitaxy for Water Splitting and CO2 Reduction
by Axel Strömberg, Yanqi Yuan, Feng Li, Balaji Manavaimaran, Sebastian Lourdudoss, Peng Zhang and Yanting Sun
Catalysts 2022, 12(11), 1482; https://doi.org/10.3390/catal12111482 - 20 Nov 2022
Cited by 3 | Viewed by 1409
Abstract
Heteroepitaxial Zn-doped p-GaP was grown on (001) GaAs, (001) Si and (111) Si substrates by hydride vapor phase epitaxy for solar-driven photoelectrochemical applications of hydrogen generation by water splitting and CO2 reduction. Growth of GaP on Si was realized through the implementation [...] Read more.
Heteroepitaxial Zn-doped p-GaP was grown on (001) GaAs, (001) Si and (111) Si substrates by hydride vapor phase epitaxy for solar-driven photoelectrochemical applications of hydrogen generation by water splitting and CO2 reduction. Growth of GaP on Si was realized through the implementation of a low-temperature buffer layer, and the morphology and crystalline quality were enhanced by optimizing the precursor flows and pre-heating ambient substrate. The p-GaP/GaAs and p-GaP/Si samples were processed to photoelectrodes with an amorphous TiO2 coating for CO2 reduction and a combination of TiO2 layer and mesoporous tungsten phosphide catalyst for water splitting. P-GaP/GaAs with suitable Zn-doping concentration exhibited photoelectrochemical performance comparable to homoepitaxial p-GaP/GaP for water splitting and CO2 reduction. Degradation of photocurrent in p-GaP/Si photoelectrodes is observed in PEC water splitting due to the high density of defects arising from heteroepitaxial growth. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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18 pages, 5021 KiB  
Article
Environmentally Friendly Fabrication of High-Efficient Fe-ZnO/Citric Acid-Modified Cellulose Composite and the Enhancement of Photocatalytic Activity in the Presence of H2O2
by Agnieszka Fiszka Borzyszkowska, Agnieszka Sulowska, Ivar Zekker, Jakub Karczewski, Kai Bester and Anna Zielińska-Jurek
Catalysts 2022, 12(11), 1370; https://doi.org/10.3390/catal12111370 - 04 Nov 2022
Cited by 5 | Viewed by 1563
Abstract
In the present study, a novel Fe-ZnO/citric acid-modified cellulose composite (x%Fe-ZnO-y%CAC) was synthesized using an environmentally friendly hydrothermal method. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FTIR), nitrogen [...] Read more.
In the present study, a novel Fe-ZnO/citric acid-modified cellulose composite (x%Fe-ZnO-y%CAC) was synthesized using an environmentally friendly hydrothermal method. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FTIR), nitrogen physisorption, and electrochemical and photocurrent density analyses. The influence of the additives from the series of x%Fe-ZnO-y%CAC photocatalysts with Fe content from 0 to 5% and CAC content from 0 to 80% on photocatalytic degradation of ibuprofen (IBU) under simulated solar light was investigated. The photocatalyst 0.5%Fe-ZnO-40%CAC showed high photocatalytic activity of 0.0632 min−1 first-order kinetic rate constant and 46% TOC reduction of IBU under simulated solar light irradiation. Additionally, H2O2-assisted photocatalytic process was investigated for facilitating the IBU degradation in the presence of 0.5%Fe-ZnO-40%CAC; the first-order kinetic rate constant was 2.7 times higher compared to the process without addition of H2O2. Moreover, the effect of radical scavengers was examined to explain the degradation mechanism of IBU by synthesized photocatalysts supported with H2O2. The demonstrated system provides a low-cost and green approach to improve the photocatalytic activity of x%Fe-ZnO-y%CAC photocatalysts. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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18 pages, 2555 KiB  
Article
Photoreactive Carbon Dots Modified g-C3N4 for Effective Photooxidation of Bisphenol-A under Visible Light Irradiation
by Anwar Iqbal, Fatimah Bukola Shittu, Mohamad Nasir Mohamad Ibrahim, N. H. H. Abu Bakar, Noorfatimah Yahaya, Kalaivizhi Rajappan, M. Hazwan Hussin, Wan Hazman Danial and Lee D. Wilson
Catalysts 2022, 12(11), 1311; https://doi.org/10.3390/catal12111311 - 25 Oct 2022
Cited by 3 | Viewed by 1739
Abstract
A series of carbon dots (CDs) modified g-C3N4 (xCDs/g-C3N4; x = 0.5, 1.0, and 1.5 mL CDs solution) was synthesized via the microwave-assisted hydrothermal synthesis method for the photooxidation of bisphenol-A (BPA) under visible [...] Read more.
A series of carbon dots (CDs) modified g-C3N4 (xCDs/g-C3N4; x = 0.5, 1.0, and 1.5 mL CDs solution) was synthesized via the microwave-assisted hydrothermal synthesis method for the photooxidation of bisphenol-A (BPA) under visible light irradiation. The X-ray diffraction (XRD) analysis indicates that the CDs may have a turbostratic structure and the resulting photocatalysts have distorted crystal structure, as compared with pure g-C3N4. The high-resolution transmission electron microscope (HR-TEM) analysis revealed amorphous, mono-disperse, spherical CDs with an average particle size of 3.75 nm. The distribution of CDs within the matrix of g-C3N4 appear as small dark dot-like domains. The N2 adsorption-desorption analysis indicates that the nanocomposites are mesoporous with a density functional theory (DFT) estimate of the pore size distribution between 2–13 nm. The CDs quantum yield (QY) was determined to be 12% using the UV-vis spectral analysis, where the CDs/g-C3N4 has improved absorption in the visible region than g-C3N4. The higher BET surface area of CDs/g-C3N4 provided more adsorption sites and the ability to yield photogenerated e/h+ pairs, which caused the 1.5 CDs/g-C3N4 to have better photocatalytic efficiency compared to the rest of the systems. The highest removal, 90%, was achieved at the following optimum conditions: BPA initial concentration = 20 mg L−1, catalyst dosage = 30 mg L−1, and pH = 10. The photooxidation process is mainly driven by photogenerated holes (h+) followed by OH and O2•−. The synthesis of the 1.5 CDs/g-C3N4 system is simple and cost-effective, where this photocatalyst is highly stable and reusable versus other systems reported in the literature. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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12 pages, 3308 KiB  
Article
Visible-Light-Sensitive Polymerizable and Polymeric Triazine-Based Photoinitiators with Enhanced Migration Stability
by Liqiang Li, Di Zhu, Xiaotong Peng and Pu Xiao
Catalysts 2022, 12(11), 1305; https://doi.org/10.3390/catal12111305 - 24 Oct 2022
Cited by 2 | Viewed by 1322
Abstract
Photopolymerization has attracted great interest because of its mild reaction conditions, spatiotemporal controllability, cost efficiency, and fast speed. However, with the raising environmental awareness and the increasing attention to life and health, the leachability of photoinitiators has become a growing concern. In this [...] Read more.
Photopolymerization has attracted great interest because of its mild reaction conditions, spatiotemporal controllability, cost efficiency, and fast speed. However, with the raising environmental awareness and the increasing attention to life and health, the leachability of photoinitiators has become a growing concern. In this research, a methacrylate functionalized triazine-based polymerizable visible light photoinitiator, 2-(((4-(2-(4,6-bis(trichloromethyl)-1,3,5-triazin-2-yl)vinyl)phenoxy)carbonyl)amino)ethyl methacrylate (CT) and its reversible addition–fragmentation chain transfer (RAFT) polymerized CT (pCT) were designed as the polymerizable and polymeric photoinitiators, respectively. The photoinitiation abilities of the investigated triazine derivatives were evaluated under violet LEDs. Due to the steric effect, pCT showed slightly reduced photoinitiation ability under both LED at 400 nm and 410 nm irradiation. Nevertheless, photopolymers initiated using CT and pCT showed excellent migration stability compared to those prepared by 2-(4-methoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine (MT) and 4-(2-(4,6-bis(trichloromethyl)-1,3,5-triazin-2-yl)vinyl)phenol (PT). Specifically, CT and pCT-based polymers prepared under the irradiation of LED at 400 nm exhibited only 1/3-fold and 1/14-fold of photoinitiators leachability, while 1/2-fold and 1/6-fold of photoinitiator leachability were obtained compared to the MT-based photocured polymers when using LED at 410 nm. The excellent migration stability of pCT reveals potential applications in the biomedical and food packaging fields. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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14 pages, 5047 KiB  
Article
Photocatalytic Degradation of Tetracycline under Visible Light Irradiation on BiVO4 Microballs Modified with Noble Metals
by Limeng Wu, Xin Yue, Ying Chang, Kunlei Wang, Jinyue Zhang, Jiajie Sun, Zhishun Wei and Ewa Kowalska
Catalysts 2022, 12(11), 1293; https://doi.org/10.3390/catal12111293 - 22 Oct 2022
Cited by 8 | Viewed by 1794
Abstract
Monoclinic scheelite bismuth vanadate (BVO) microballs were prepared by a facile hydrothermal method and subsequently modified with 2 wt% of noble metals (NM = Au, Ag, Cu, Pt and Pd) by a photodeposition route. All materials were characterized by diffuse reflectance spectroscopy (DRS), [...] Read more.
Monoclinic scheelite bismuth vanadate (BVO) microballs were prepared by a facile hydrothermal method and subsequently modified with 2 wt% of noble metals (NM = Au, Ag, Cu, Pt and Pd) by a photodeposition route. All materials were characterized by diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR). The photocatalytic performance was investigated by degradation of tetracycline antibiotic under visible light irradiation. Moreover, photocurrent generation under UV/vis was also examined. It was found that BVO modification with all tested NMs resulted in a significant improvement in photocatalytic performance. The highest activity was obtained for Cu/BVO with mainly oxidized forms of copper. Based on scavenger tests (∙O2 and ∙OH as the main responsible species for TC degradation) and redox properties, it was proposed that the Z-scheme mechanism between copper oxides and BVO was responsible for enhanced photocatalytic activity. However, the co-participation of zero-valent forms of NMs should also be considered, either as electron scavengers, plasmonic sensitizers or conductors. Presented data reveal that porous microballs, highly attractive for practical applications due to micro-sized diameter and efficient light harvesting inside the structure, could be efficiently used for environmental and energy purposes under solar radiation. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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14 pages, 2129 KiB  
Article
Behavior of N-Doped TiO2 and N-Doped ZnO in Photocatalytic Azo Dye Degradation under UV and Visible Light Irradiation: A Preliminary Investigation
by Olga Sacco, Antonietta Mancuso, Vincenzo Venditto, Stefania Pragliola and Vincenzo Vaiano
Catalysts 2022, 12(10), 1208; https://doi.org/10.3390/catal12101208 - 10 Oct 2022
Cited by 7 | Viewed by 1526
Abstract
N-doped TiO2 (N-TiO2) and N-doped ZnO (N-ZnO) were synthesized utilizing ammonia as a dopant source. The chemico-physical characteristics of synthesized samples were studied by Raman spectroscopy, X-ray diffraction, SEM analysis, N2 adsorption–desorption at −196 °C, and diffuse reflectance spectroscopy. [...] Read more.
N-doped TiO2 (N-TiO2) and N-doped ZnO (N-ZnO) were synthesized utilizing ammonia as a dopant source. The chemico-physical characteristics of synthesized samples were studied by Raman spectroscopy, X-ray diffraction, SEM analysis, N2 adsorption–desorption at −196 °C, and diffuse reflectance spectroscopy. Compared to undoped samples, the introduction of nitrogen in the semiconductor lattice resulted in a shift of band-gap energy to a lower value: 3.0 eV for N-ZnO and 2.35 eV for N-TiO2. The photocatalysts were tested for the degradation of Eriochrome Black T (EBT), which was selected as a model azo dye. Both N-doped semiconductors evidenced an improvement in photocatalytic activity under visible light irradiation (62% and 20% EBT discoloration for N-TiO2 and N-ZnO, respectively) in comparison with the undoped samples, which were inactive in the presence of visible light. Different behavior was observed under UV irradiation. Whereas N-TiO2 was more photoactive than commercial undoped TiO2, the introduction of nitrogen in ZnO wurtzite resulted in a drastic reduction in photocatalytic activity, with only 45% EBT discoloration compared to total color removal obtained with the commercial ZnO sample, suggesting intrinsic limitations for doping of this class of semiconductors. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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12 pages, 2389 KiB  
Article
Photocatalytic CO2 Conversion Using Anodic TiO2 Nanotube-CuxO Composites
by Timofey P. Savchuk, Ekaterina V. Kytina, Elizaveta A. Konstantinova, Vladimir G. Kytin, Olga Pinchuk, Andrey K. Tarhanov, Vladimir B. Zaitsev and Tomasz Maniecki
Catalysts 2022, 12(9), 1011; https://doi.org/10.3390/catal12091011 - 07 Sep 2022
Cited by 7 | Viewed by 1795
Abstract
Nanosized titanium dioxide (TiO2) is currently being actively studied by the global scientific community, since it has a number of properties that are important from a practical point of view. One of these properties is a large specific surface, which makes [...] Read more.
Nanosized titanium dioxide (TiO2) is currently being actively studied by the global scientific community, since it has a number of properties that are important from a practical point of view. One of these properties is a large specific surface, which makes this material promising for use in photocatalysts, sensors, solar cells, etc. In this work, we prepared photocatalysts based on TiO2 nanotubes for converting carbon dioxide (CO2) into energy-intensive hydrocarbon compounds. Efficient gas-phase CO2 conversion in the prepared single-walled TiO2 nanotube-CuxO composites was investigated. Parameters of defects (radicals) in composites were studied. Methanol and methane were detected during the CO2 photoreduction process. In single-walled TiO2 nanotubes, only Ti3+/oxygen vacancy defects were detected. The Cu2+ centers and O2 radicals were found in TiO2 nanotube-CuxO composites using the EPR technique. It has been established that copper oxide nanoparticles are present in the TiO2 nanotube-CuxO composites in the form of the CuO phase. A phase transformation of CuO to Cu2O takes place during illumination, as has been shown by EPR spectroscopy. It is shown that defects accumulate photoinduced charge carriers. The mechanism of methane and methanol formation is discussed. The results obtained are completely original and show high promise for the use of TiO2-CuxO nanotube composites as photocatalysts for CO2 conversion into hydrocarbon fuel precursors. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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11 pages, 13120 KiB  
Article
Microwave-Assisted Photocatalytic Degradation of Organic Pollutants via CNTs/TiO2
by Yuqing Ren, Yao Chen, Qinyu Li, Hexing Li and Zhenfeng Bian
Catalysts 2022, 12(9), 940; https://doi.org/10.3390/catal12090940 - 24 Aug 2022
Cited by 9 | Viewed by 1871
Abstract
Introducing microwave fields into photocatalytic technology is a promising strategy to suppress the recombination of photogenerated charge carriers. Here, a series of microwave-absorbing photocatalysts, xCNTs/TiO2, were prepared by combining titanium dioxide (TiO2) with carbon nanotubes (CNTs) using a typical [...] Read more.
Introducing microwave fields into photocatalytic technology is a promising strategy to suppress the recombination of photogenerated charge carriers. Here, a series of microwave-absorbing photocatalysts, xCNTs/TiO2, were prepared by combining titanium dioxide (TiO2) with carbon nanotubes (CNTs) using a typical alcoholic thermal method to study the promotion of microwave-generated thermal and athermal effects on the photocatalytic oxidation process. As good carriers that are capable of absorbing microwaves and conducting electrons, CNTs can form hot spots and defects under the action of the thermal effect from microwaves to capture electrons generated on the surface of TiO2 and enhance the separation efficiency of photogenerated electrons (e) and holes (h+). Excluding the influence of the reaction temperature, the athermal effect of the microwave field had a polarizing effect on the catalyst, which improved the light absorption rate of the catalyst. Moreover, microwave radiation also promoted the activation of oxygen molecules and hydroxyl groups on the catalyst surface to generate more reactive oxygen radicals. According to the mechanism analysis, the microwave effect significantly improved the photocatalytic advanced oxidation process, which lays a solid theoretical foundation for practical application. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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12 pages, 2294 KiB  
Article
Photocatalytic H2O2 Generation Using Au-Ag Bimetallic Alloy Nanoparticles loaded on ZnO
by Xinzhu Pang, Nathan Skillen, Detlef W. Bahnemann, David W. Rooney and Peter K. J. Robertson
Catalysts 2022, 12(9), 939; https://doi.org/10.3390/catal12090939 - 24 Aug 2022
Cited by 6 | Viewed by 1755
Abstract
Hydrogen peroxide (H2O2) is an important chemical as it is an environmentally friendly oxidant for organic synthesis and environmental remediation as well as a promising candidate for the liquid fuel. Photocatalytic generation of H2O2 is sustainable, [...] Read more.
Hydrogen peroxide (H2O2) is an important chemical as it is an environmentally friendly oxidant for organic synthesis and environmental remediation as well as a promising candidate for the liquid fuel. Photocatalytic generation of H2O2 is sustainable, and many efforts have been put into the development of new catalysts to gain high H2O2 yields. In this investigation, Au/ZnO, Ag/ZnO and Au-Ag/ZnO catalysts were prepared by the simultaneous impregnation of HAuCl4 and AgNO3 and they were used to generate H2O2 from a methanol/O2 system. It was demonstrated that Au/ZnO had the best performance at generating H2O2. The presence of Au on ZnO accelerated the generation of H2O2 on ZnO and facilitated H2O2 adsorption onto the catalyst surface, which resulted in the reaction kinetics changing from zero-order to first-order. Ag atoms on Ag/ZnO were unstable and would strip from the surface of ZnO during irradiation, decreasing the yield of H2O2. The stabilization of Ag on Au-Ag/ZnO depended on the ratio of Au and Ag. Au0.1Ag0.2/ZnO was a stable catalyst and it showed that the presence of Ag promoted the formation and decomposition of peroxide, simultaneously. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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9 pages, 1834 KiB  
Communication
The Shell Matters: Self-Organized CdS-ZnS/MnS-Core-Shell—Porphyrin-Polymer Nano-Assemblies for Photocatalysis
by Maximilian Wagner and Franziska Gröhn
Catalysts 2022, 12(8), 907; https://doi.org/10.3390/catal12080907 - 17 Aug 2022
Viewed by 1294
Abstract
A facile synthesis of catalytically tunable core-shell CdS-ZnxMn1-xS-nanoparticles in conjunction with poly(acrylic acid) (PAA) and porphyrin in an aqueous solution is described in the following: The shell composition of the inorganic nanoparticles is varied to tune the optical properties [...] Read more.
A facile synthesis of catalytically tunable core-shell CdS-ZnxMn1-xS-nanoparticles in conjunction with poly(acrylic acid) (PAA) and porphyrin in an aqueous solution is described in the following: The shell composition of the inorganic nanoparticles is varied to tune the optical properties and to optimize the catalytic activity. Further, the tetravalent cationic 5,10,15,20-tetrakis(4-trimethylammoniophenyl) porphyrin (TAPP) fulfills a triple functionality in the catalyst: as a photosensitizer, as an electrostatic linker connecting the nanoparticles and as a probe to investigate the surface composition of the II-VI semiconducting nanoparticles. Different nanoparticles with varying zinc sulfide/manganese sulfide shell ratios are tested with regard to their photocatalytic behavior by crocin bleaching. The results reveal that the shell composition can be a crucial key to optimize the catalytic activity, which can further be important in tuning the reactivity of related systems. Fundamentally, the stepwise multi-component self-assembly in an aqueous solution has been demonstrated to allow the tuning of optic and catalytic properties of core-shell nanoparticles, a general concept that may be widely applicable. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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24 pages, 7474 KiB  
Article
Photo-Oxidation of Glycerol Catalyzed by Cu/TiO2
by Osmín Avilés-García, Arisbeht Mendoza-Zepeda, Alejandro Regalado-Méndez, Jaime Espino-Valencia, Sandra L. Martínez-Vargas, Rubi Romero and Reyna Natividad
Catalysts 2022, 12(8), 835; https://doi.org/10.3390/catal12080835 - 29 Jul 2022
Cited by 6 | Viewed by 2363
Abstract
In the present study, glycerol was oxidized by photocatalysis to glyceraldehyde, formaldehyde, and formic acid. Copper-doped TiO2 was synthesized by the evaporation-induced self-assembly approach and it was used as catalyst during the glycerol photo-oxidation reactions. The prepared mesoporous material exhibited high specific [...] Read more.
In the present study, glycerol was oxidized by photocatalysis to glyceraldehyde, formaldehyde, and formic acid. Copper-doped TiO2 was synthesized by the evaporation-induced self-assembly approach and it was used as catalyst during the glycerol photo-oxidation reactions. The prepared mesoporous material exhibited high specific surface area (242 m2/g) and band gap energy reduction of 2.55 eV compared to pure titania (3.2 eV) by the synthesis method due to the presence of copper cations (Cu2+ identified by XPS). The catalyst showed only anatase crystalline phase with nanocrystals around 8 nm and irregular agglomerates below 100 μm. The selectivity and formation rate of the products were favored towards formaldehyde and glyceraldehyde. The variables studied were catalyst amount, reaction temperature, and initial glycerol concentration. The response surface analysis was used to evaluate the effect of the variables on the product’s concentration. The optimized conditions were 0.4 g/L catalyst, 0.1 mol/L glycerol, and temperature 313.15 K. The response values under optimal conditions were 3.23, 8.17, and 1.15 mM for glyceraldehyde, formaldehyde, and formic acid, respectively. A higher selectivity towards formaldehyde was observed when visible light was used as the radiation source. This study is useful to evaluate the best reaction conditions towards value-added products during the oxidation of glycerol by photocatalysis using Cu/TiO2. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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17 pages, 3259 KiB  
Article
Sustainable Solar Light Photodegradation of Diclofenac by Nano- and Micro-Sized SrTiO3
by Melissa G. Galloni, Giuseppina Cerrato, Alessia Giordana, Ermelinda Falletta and Claudia L. Bianchi
Catalysts 2022, 12(8), 804; https://doi.org/10.3390/catal12080804 - 22 Jul 2022
Cited by 14 | Viewed by 1633
Abstract
Currently, photocatalytic reactions under solar illumination have attracted worldwide attention due to the tremendous set of associated environmental problems. Taking sunlight into account, it is indispensable to develop highly effective photocatalysts. Strontium titanate, SrTiO3 (STO), is a cubic perovskite-type semiconductor, an inexpensive [...] Read more.
Currently, photocatalytic reactions under solar illumination have attracted worldwide attention due to the tremendous set of associated environmental problems. Taking sunlight into account, it is indispensable to develop highly effective photocatalysts. Strontium titanate, SrTiO3 (STO), is a cubic perovskite-type semiconductor, an inexpensive material with high thermal stability and corrosion resistance that exhibits a similar energy bandgap to TiO2 and can represent an interesting alternative in photocatalytic applications. Particle size can significantly affect both photocatalytic and photoelectrochemical properties of a photocatalyst, thus altering the photooxidation of organic pollutants in air or water. In this context, this research aims at investigating the photocatalytic features of nano- and micro-sized commercial STO powders towards the photodegradation of diclofenac (DFC), a non-steroidal, anti-inflammatory drug, widely used as analgesic, antiarthritic, and antirheumatic. Both nano- and micro-STO photocatalysts exhibited remarkable photocatalytic efficiency towards DCF, reaching photodegradation efficiency higher than 90% within one hour. Results obtained in simulated drinking water were also compared to those obtained in ultrapure water. Both STOs showed good stability during recycling tests, maintaining high performances after three cycles. Eventually, active species were identified using various scavengers by trapping holes and radicals generated during the photocatalytic degradation process. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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14 pages, 3998 KiB  
Article
Predicting Active Sites in Photocatalytic Degradation Process Using an Interpretable Molecular-Image Combined Convolutional Neural Network
by Zhuoying Jiang, Jiajie Hu, Anna Samia and Xiong (Bill) Yu
Catalysts 2022, 12(7), 746; https://doi.org/10.3390/catal12070746 - 07 Jul 2022
Cited by 3 | Viewed by 1690
Abstract
Machine-learning models have great potential to accelerate the design and performance assessment of photocatalysts, leveraging their unique advantages in detecting patterns and making predictions based on data. However, most machine-learning models are “black-box” models due to lack of interpretability. This paper describes the [...] Read more.
Machine-learning models have great potential to accelerate the design and performance assessment of photocatalysts, leveraging their unique advantages in detecting patterns and making predictions based on data. However, most machine-learning models are “black-box” models due to lack of interpretability. This paper describes the development of an interpretable neural-network model on the performance of photocatalytic degradation of organic contaminants by TiO2. The molecular structures of the organic contaminants are represented by molecular images, which are subsequently encoded by feeding into a special convolutional neural network (CNN), EfficientNet, to extract the critical structural features. The extracted features in addition to five other experimental variables were input to a neural network that was subsequently trained to predict the photodegradation reaction rates of the organic contaminants by TiO2. The results show that this machine-learning (ML) model attains a higher accuracy to predict the photocatalytic degradation rate of organic contaminants than a previously developed machine-learning model that used molecular fingerprint encoding. In addition, the most relevant regions in the molecular image affecting the photocatalytic rates can be extracted with gradient-weighted class activation mapping (Grad-CAM). This interpretable machine-learning model, leveraging the graphic interpretability of CNN model, allows us to highlight regions of the molecular structure serving as the active sites of water contaminants during the photocatalytic degradation process. This provides an important piece of information to understand the influence of molecular structures on the photocatalytic degradation process. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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13 pages, 3801 KiB  
Article
Indoor Air Photocatalytic Decontamination by UV–Vis Activated CuS/SnO2/WO3 Heterostructure
by Alexandru Enesca and Viorel Sisman
Catalysts 2022, 12(7), 728; https://doi.org/10.3390/catal12070728 - 30 Jun 2022
Cited by 4 | Viewed by 1402
Abstract
A titania-free heterostructure based on CuS/SnO2/WO3 was obtained by a three-step sol–gel method followed by spray deposition on the glass substrate. The samples exhibit crystalline structures and homogenous composition. The WO3 single-component sample morphology consists of fibers that serve [...] Read more.
A titania-free heterostructure based on CuS/SnO2/WO3 was obtained by a three-step sol–gel method followed by spray deposition on the glass substrate. The samples exhibit crystalline structures and homogenous composition. The WO3 single-component sample morphology consists of fibers that serve as the substrate for SnO2 development. The CuS/SnO2/WO3 heterostructure is characterized by a dense granular morphology. Photocatalytic activity was evaluated under UV–Vis radiation and indicates that the WO3 single-component sample is able to remove 41.1% of acetaldehyde (64.9 ppm) and 52.5% of formaldehyde (81.4 ppm). However, the CuS/SnO2/WO3 exhibits a superior photocatalytic activity due to a larger light spectrum absorption and lower charge carrier recombination rate, allowing the removal of 69.2% of acetaldehyde and 78.5% of formaldehyde. The reusability tests indicate that the samples have a stable photocatalytic activity after three cycle (12 h/cycle) assessments. During light irradiation, the heterostructure acted as a Z-scheme mechanism using the redox ability of the CuS conduction band electrons and the SnO2/WO3 valence band holes to generate the oxidative species required for VOC removal. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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17 pages, 4447 KiB  
Article
Photocatalytic Remediation of Harmful Alexandrium minutum Bloom Using Hybrid Chitosan-Modified TiO2 Films in Seawater: A Lab-Based Study
by Nur Hanisah Ibrahim, Anwar Iqbal, Normawaty Mohammad-Noor, Roziawati Mohd Razali, Srimala Sreekantan, Dede Heri Yuli Yanto, Abdul Hanif Mahadi and Lee D. Wilson
Catalysts 2022, 12(7), 707; https://doi.org/10.3390/catal12070707 - 27 Jun 2022
Cited by 2 | Viewed by 2008
Abstract
The uncontrolled growth of harmful algal blooms (HABs) can negatively impact the environment and pose threats to human health and aquatic ecosystems. Titanium dioxide (TiO2) is known to be effective in killing harmful algae through flocculation and sedimentation. However, TiO2 [...] Read more.
The uncontrolled growth of harmful algal blooms (HABs) can negatively impact the environment and pose threats to human health and aquatic ecosystems. Titanium dioxide (TiO2) is known to be effective in killing harmful algae through flocculation and sedimentation. However, TiO2 in a dispersed form can harm other non-target marine organisms, which has raised concerns by environmentalists and scientists. This research seeks to explore the utility of immobilized titanium oxide as a photocatalyst for mitigation of HABs, where the Alexandrium minutum bloom was used as a model system herein. Chitosan was modified with 0.2 wt.% TiO2 (Chi/TiO2 (x mL; x = 1, 3 and 5 mL) and the corresponding films were prepared via solvent casting method. Scanning electron microscope (SEM) images of the films reveal a highly uneven surface. X-ray diffraction (XRD) analysis indicates the reduction in chitosan crystallinity, where the presence of TiO2 was negligible, in accordance with its dispersion within the chitosan matrix. The photocatalytic mitigation of A.minutum was carried out via a physical approach in a laboratory-scale setting. The negative surface charge of the films was observed to repel the negatively charged A.minutum causing fluctuation in the removal efficiency (RE). The highest RE (76.1 ± 13.8%) was obtained when Chi/TiO2 (1 mL) was used at 72 h, where the hydroxyl radicals generated were inferred to contribute to the deactivation of the algae cells by causing oxidative stress. An outcome of this study indicates that such hybrid films have the potential to replace the non-immobilized (dispersed) TiO2 for HAB mitigation. However, further investigation is required to deploy these films for field applications at a larger scale. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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16 pages, 2033 KiB  
Article
Retention and Inactivation of Quality Indicator Bacteria Using a Photocatalytic Membrane Reactor
by Ana Paula Marques, Rosa Huertas, Jorge Bernardo, Beatriz Oliveira, João Goulão Crespo and Vanessa Jorge Pereira
Catalysts 2022, 12(7), 680; https://doi.org/10.3390/catal12070680 - 22 Jun 2022
Cited by 3 | Viewed by 1598
Abstract
The development of effective disinfection treatment processes is crucial to help the water industry cope with the inevitable challenges resulting from the increase in human population and climate change. Climate change leads to heavy rainfall, flooding and hot weather events that are associated [...] Read more.
The development of effective disinfection treatment processes is crucial to help the water industry cope with the inevitable challenges resulting from the increase in human population and climate change. Climate change leads to heavy rainfall, flooding and hot weather events that are associated with waterborne diseases. Developing effective treatment technologies will improve our resilience to cope with these events and our capacity to safeguard public health. A submerged hybrid reactor was used to test the efficiency of membrane filtration, direct photolysis (using ultraviolet-C low-pressure mercury lamps, as well as ultraviolet-C and ultraviolet-A light-emitting diodes panels) and the combination of both treatment processes (membrane filtration and photolysis) to retain and inactivate water quality indicator bacteria. The developed photocatalytic membranes effectively retained the target microorganisms that were then successfully inactivated by photolysis and advanced oxidation processes. The new hybrid reactor could be a promising approach to treat drinking water, recreational water and wastewater produced by different industries in small-scale systems. Furthermore, the results obtained with membranes coated with titanium dioxide and copper combined with ultraviolet-A light sources show that the process may be a promising approach to guarantee water disinfection using natural sunlight. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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16 pages, 3280 KiB  
Article
Photocatalytic Reduction of Nitrates and Combined Photodegradation with Ammonium
by Francesco Conte, Veronica Pellegatta, Alessandro Di Michele, Gianguido Ramis and Ilenia Rossetti
Catalysts 2022, 12(3), 321; https://doi.org/10.3390/catal12030321 - 11 Mar 2022
Cited by 3 | Viewed by 2270
Abstract
Bare titania and metal-promoted TiO2 catalysts were employed in the treatment of nitrates, which are ubiquitous pollutants of wastewater. The results show that the process can be carried out under visible light (from a white light LED lamp) and, in the best [...] Read more.
Bare titania and metal-promoted TiO2 catalysts were employed in the treatment of nitrates, which are ubiquitous pollutants of wastewater. The results show that the process can be carried out under visible light (from a white light LED lamp) and, in the best case, 23.5% conversion of nitrate was obtained over 4 h with full selectivity towards N2 by employing 0.1 mol% Ag/TiO2 prepared by flame spray pyrolysis. Moreover, the performance was worse when testing the same catalysts with tap water (11.3% conversion), due to the more complex composition of the matrix. Finally, it was found that photoreduction of nitrate can be effectively performed in combination with photo-oxidation of ammonium without loss in the activity, opening up the possibility of treating highly polluted wastewater with a single process. The latter treatment employs the two contaminants simultaneously as electron and holes scavengers, with very good selectivity, in a completely new process that we may call Photo-Selective Catalytic Reduction (Photo-SCR). Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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11 pages, 2603 KiB  
Article
Decomposition of Gaseous Styrene Using Photocatalyst and Ozone Treatment
by Kengo Hamada, Tsuyoshi Ochiai, Daisuke Aoki, Yasuhisa Akutsu and Yasuo Hirabayashi
Catalysts 2022, 12(3), 316; https://doi.org/10.3390/catal12030316 - 10 Mar 2022
Cited by 2 | Viewed by 4774
Abstract
Because photocatalysis has strong oxidation abilities in redox systems, it has been applied to indoor air purification. However, intermediate products are produced during the photocatalytic oxidative decomposition of aromatic compounds with benzene rings. Therefore, it is essential to improve decomposition performance and evaluate [...] Read more.
Because photocatalysis has strong oxidation abilities in redox systems, it has been applied to indoor air purification. However, intermediate products are produced during the photocatalytic oxidative decomposition of aromatic compounds with benzene rings. Therefore, it is essential to improve decomposition performance and evaluate the intermediate products produced for practical applications. Herein, we describe the decomposition performance of ozone, photocatalyst, and their combination, under the target gas of styrene. Using a one-pass mini reactor, decomposition performance was evaluated by analyzing the output gas in the reactor and observing the styrene removal, the amount of carbon dioxide produced, and the composition of a small amount of intermediate products. The combination of ozone and photocatalyst showed the most significant performance, completely decomposing in the photocatalyst and removing odor components in ozone. Moreover, we demonstrated that decomposition performance could be evaluated by observing slight amounts of intermediate products in the exhaust gas. We believe that this research provides insights into the practical application of photocatalysis and ozone oxidation technologies in air purifiers and their performance management, with particular emphasis on the decomposition of odor compounds. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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17 pages, 7708 KiB  
Article
Synthesis and Photoelectrocatalytic Applications of TiO2/ZnO/Diatomite Composites
by Beibei Yang, Zixu Ma, Qian Wang and Junjiao Yang
Catalysts 2022, 12(3), 268; https://doi.org/10.3390/catal12030268 - 28 Feb 2022
Cited by 5 | Viewed by 2499
Abstract
ZnO and TiO2 are semiconductor nanomaterials that are widely used in photocatalysis. However, the relatively high recombination rate and low quantum yield of photogenerated electron–hole pairs limit their practical applications. In this study, a series of TiO2/ZnO/diatomite composites with various [...] Read more.
ZnO and TiO2 are semiconductor nanomaterials that are widely used in photocatalysis. However, the relatively high recombination rate and low quantum yield of photogenerated electron–hole pairs limit their practical applications. In this study, a series of TiO2/ZnO/diatomite composites with various compositions were successfully prepared via a two-step precipitation method. They exhibited stronger UV–visible absorption properties and substantially lower fluorescence intensities than those of ZnO and ZnO/diatomite, which was mainly due to the low recombination rate of the photogenerated electron–hole pairs in the composite system. The reaction intermediates of methylene blue were detected by liquid chromatography–mass spectrometry, and the degradation process was determined. The best composite catalyst was used for the degradation of gaseous methylbenzene and gaseous acetone. The gaseous acetone degradation product was determined to be acetaldehyde via gas chromatography–mass spectrometry. The results show that the composite catalyst exhibited a good photocatalytic degradation of both liquid pollutants and harmful volatile gases. When applied to the hydrogen and oxygen evolution reactions, the composite catalyst retained a good photoresponsivity and electrolytic efficiency. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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12 pages, 4073 KiB  
Article
Effect of Heating Rate on the Photocatalytic Activity of Ag–TiO2 Nanocomposites by One-Step Process via Aerosol Routes
by Kusdianto Kusdianto, Meditha Hudandini, Dianping Jiang, Masaru Kubo and Manabu Shimada
Catalysts 2022, 12(1), 17; https://doi.org/10.3390/catal12010017 - 24 Dec 2021
Cited by 7 | Viewed by 2580
Abstract
Ag–TiO2 nanocomposite films, based of Ag and TiO2 nanoparticles, were fabricated in a one-step aerosol route employing the simultaneous plasma-enhanced chemical vapor deposition and physical vapor deposition systems. The as-fabricated films were subjected to different heating rates (3 to 60 °C/min) [...] Read more.
Ag–TiO2 nanocomposite films, based of Ag and TiO2 nanoparticles, were fabricated in a one-step aerosol route employing the simultaneous plasma-enhanced chemical vapor deposition and physical vapor deposition systems. The as-fabricated films were subjected to different heating rates (3 to 60 °C/min) with a constant annealing temperature of 600 °C to observe the significant changes in the properties (e.g., nanoparticle size, crystalline size, crystallite phase, surface area) toward the photocatalytic performance. The photocatalytic activity was evaluated by the measurement of the degradation of a methylene blue aqueous solution under UV light irradiation, and the results revealed that it gradually increased with the increase in the heating rate, caused by the increased Brunauer–Emmett–Teller (BET) specific surface area and total pore volume. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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20 pages, 2410 KiB  
Article
Effect of Calcination Conditions on the Properties and Photoactivity of TiO2 Modified with Biuret
by Aleksandra Piątkowska and Sylwia Mozia
Catalysts 2021, 11(12), 1546; https://doi.org/10.3390/catal11121546 - 18 Dec 2021
Cited by 2 | Viewed by 2266
Abstract
A simple wet impregnation-calcination method was used to obtain a series of novel non-metal doped TiO2 photocatalysts. Biuret was applied as C and N source, while raw titanium dioxide derived from sulfate technology process was used as TiO2 and S source. [...] Read more.
A simple wet impregnation-calcination method was used to obtain a series of novel non-metal doped TiO2 photocatalysts. Biuret was applied as C and N source, while raw titanium dioxide derived from sulfate technology process was used as TiO2 and S source. The influence of the modification with biuret and the effect of the atmosphere (air or argon) and temperature (500–800 °C) of calcination on the physicochemical properties and photocatalytic activity of the photocatalysts towards ketoprofen decomposition under simulated solar light was investigated. Moreover, selected photocatalysts were applied for ketoprofen photodecomposition under visible and UV irradiation. Crucial features affecting the photocatalytic activity were the anatase to rutile phase ratio, anatase crystallites size and non-metals content. The obtained photocatalysts revealed improved activity in the photocatalytic ketoprofen decomposition compared to the crude TiO2. The best photoactivity under all irradiation types exhibited the photocatalyst calcined in the air atmosphere at 600 °C, composed of 96.4% of anatase with 23 nm crystallites, and containing 0.11 wt% of C, 0.05 wt% of N and 0.77 wt% of S. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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19 pages, 6136 KiB  
Article
Effects of Preparation Conditions on the Efficiency of Visible-Light-Driven Hydrogen Generation Based on Cd0.25Zn0.75S Photocatalysts
by Maali-Amel Mersel, Lajos Fodor, Péter Pekker, Miklós Jakab, Éva Makó and Ottó Horváth
Catalysts 2021, 11(12), 1534; https://doi.org/10.3390/catal11121534 - 16 Dec 2021
Cited by 5 | Viewed by 2208
Abstract
Photocatalytic H2 production utilizing H2S, an industrial side-product, is regarded as an environmentally friendly process to produce clean energy through direct solar energy conversion. For this purpose, sulfide-based materials, such as photocatalysts, have been widely used due to their good [...] Read more.
Photocatalytic H2 production utilizing H2S, an industrial side-product, is regarded as an environmentally friendly process to produce clean energy through direct solar energy conversion. For this purpose, sulfide-based materials, such as photocatalysts, have been widely used due to their good solar response and high photocatalytic activity. In this work, a ZnS–CdS composite was studied, and special attention was dedicated to the influence of the preparation parameters on its H2 production activity. The ZnS–CdS composite, with an enhanced photoactivity for H2 production, was synthesized both from ammine complexes and, in a conventional way, directly from acetates at various pH values. Deviating from the traditional method, the photoactivity of ZnS–CdS prepared from ammine complexes was not affected by the pH. Besides, the hydrothermal treatment and the ammonia content strongly influenced the rate of H2 production in this system. DRS, TEM, SEM, XRD, and quantum yield measurements prove the dependence of the photoactivity of these catalysts on the structural and morphological properties determined by the preparation conditions. The promising photocatalytic efficiency achieved with the application of these ZnS–CdS catalysts, prepared without any metal deposition, encourages further investigations to enhance the rate of hydrogen generation by optimization of the reaction conditions for practical utilization. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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13 pages, 8178 KiB  
Article
Microcystis@TiO2 Nanoparticles for Photocatalytic Reduction Reactions: Nitrogen Fixation and Hydrogen Evolution
by Xuan Li, Jingcai Chang, Shijie Zhang, Lihui Xiao, Xiaoge Wu and Zuoli He
Catalysts 2021, 11(12), 1443; https://doi.org/10.3390/catal11121443 - 26 Nov 2021
Cited by 4 | Viewed by 1764
Abstract
Solar-driven photocatalysis has been known as one of the most potential technologies to tackle the energy shortage and environmental pollution issues. Utilizing bio-pollutants to prepare functional materials has been considered as a green option. Herein, we used Microcystis aeruginosa as a bio-template to [...] Read more.
Solar-driven photocatalysis has been known as one of the most potential technologies to tackle the energy shortage and environmental pollution issues. Utilizing bio-pollutants to prepare functional materials has been considered as a green option. Herein, we used Microcystis aeruginosa as a bio-template to fabricate a Microcystis@TiO2 photocatalyst using a calcination method. The as-prepared Microcystis@TiO2 showed prominent ability as well as favorable stability for photocatalytic reduction reactions including hydrogen evolution and nitrogen fixation. Under light illumination, Microcystis@TiO2 calcined at 550 °C exhibited optimal photo-reduced activity among all samples, with the highest hydrogen evolution (1.36 mmol·g−1·h−1) and ammonia generation rates (0.97 mmol·g−1·h−1). This work provides a feasible approach to prepare functional materials from disposed pollutants. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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12 pages, 1721 KiB  
Article
Effect of the Type of Heterostructures on Photostimulated Alteration of the Surface Hydrophilicity: TiO2/BiVO4 vs. ZnO/BiVO4 Planar Heterostructured Coatings
by Maria V. Maevskaya, Aida V. Rudakova, Alexandra V. Koroleva, Aleksandr S. Sakhatskii, Alexei V. Emeline and Detlef W. Bahnemann
Catalysts 2021, 11(12), 1424; https://doi.org/10.3390/catal11121424 - 23 Nov 2021
Cited by 4 | Viewed by 1787
Abstract
Here, we report the results of comparative studies of the photostimulated hydrophilic behavior of heterostructured TiO2/BiVO4 and ZnO/BiVO4, and monocomponent TiO2 and ZnO nanocoating surfaces. The chemical composition and morphology of the synthesized nanocoatings were characterized by [...] Read more.
Here, we report the results of comparative studies of the photostimulated hydrophilic behavior of heterostructured TiO2/BiVO4 and ZnO/BiVO4, and monocomponent TiO2 and ZnO nanocoating surfaces. The chemical composition and morphology of the synthesized nanocoatings were characterized by XPS, SEM, and AFM methods. The electronic energy structure of the heterostructure components (band gap, top of the valence band, bottom of the conduction band, and Fermi level position) was determined on the basis of experimental results obtained by XPS, UV-V absorption spectroscopy and Kelvin probe methods. According to their electronic energy structure, the ZnO/BiVO4 and TiO2/BiVO4 heterostructures correspond to type I and type II heterostructures, respectively. The difference in the type of heterostructures causes the difference in the charge transfer behavior at heterojunctions: the type II TiO2/BiVO4 heterostructure favors and the type I ZnO/BiVO4 heterostructure prevents the photogenerated hole transfer from BiVO4 to the outer layer of the corresponding metal oxide. The results of the comparative studies show that the interaction of the photogenerated holes with surface hydroxy-hydrated multilayers is responsible for the superhydrophilic surface conversion accompanying the increase of the surface free energy and work function. The formation of the type II heterostructure leads to the spectral sensitization of the photostimulated surface superhydrophilic conversion. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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17 pages, 1594 KiB  
Article
Figures of Merit for Photocatalysis: Comparison of NiO/La-NaTaO3 and Synechocystis sp. PCC 6803 as a Semiconductor and a Bio-Photocatalyst for Water Splitting
by Eike S. Welter, Sebastian Kött, Fabian Brandenburg, Jens Krömer, Michael Goepel, Andreas Schmid and Roger Gläser
Catalysts 2021, 11(11), 1415; https://doi.org/10.3390/catal11111415 - 22 Nov 2021
Cited by 5 | Viewed by 2025
Abstract
While photocatalysis is considered a promising sustainable technology in the field of heterogeneous catalysis as well as biocatalysis, figures of merit (FOM) for comparing catalytic performance, especially between disciplines, are not well established. Here, photocatalytic water splitting was conducted using a semiconductor (NiO/La-NaTaO [...] Read more.
While photocatalysis is considered a promising sustainable technology in the field of heterogeneous catalysis as well as biocatalysis, figures of merit (FOM) for comparing catalytic performance, especially between disciplines, are not well established. Here, photocatalytic water splitting was conducted using a semiconductor (NiO/La-NaTaO3) and a bio-photocatalyst (Synechocystis sp. PCC 6803) in the same setup under similar reaction conditions, eliminating the often ill-defined influence of the setup on the FOMs obtained. Comparing the results enables the critical evaluation of existing FOMs and a quantitative comparison of both photocatalytic systems. A single FOM is insufficient to compare the photocatalysts, instead a combination of multiple FOMs (reaction rate, photocatalytic space time yield and a redefined apparent quantum yield) is superior for assessing a variety of photocatalytic systems. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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15 pages, 3540 KiB  
Article
Au-Ag/TiO2 Thin Films Preparation by Laser Ablation and Sputtering Plasmas for Its Potential Use as Photoanodes in Electrochemical Advanced Oxidation Processes (EAOP)
by Luis Alejandro Martínez-Chávez, Eric Mauricio Rivera-Muñoz, Rodrigo Rafael Velázquez-Castillo, Luis Escobar-Alarcón and Karen Esquivel
Catalysts 2021, 11(11), 1406; https://doi.org/10.3390/catal11111406 - 20 Nov 2021
Cited by 9 | Viewed by 2183
Abstract
Titanium dioxide (TiO2) is widely used, studied, and synthesized using different methodologies. By a modification of the material, it can be applied to wastewater treatment. A combined sputtering-laser ablation setup was used to deposit TiO2 thin films modified, individually and [...] Read more.
Titanium dioxide (TiO2) is widely used, studied, and synthesized using different methodologies. By a modification of the material, it can be applied to wastewater treatment. A combined sputtering-laser ablation setup was used to deposit TiO2 thin films modified, individually and simultaneously, with gold (Au) and silver (Ag). To investigate the effect of the metal incorporation in titanium and its impact on the photocatalytic activity, with dye discoloration as a pollutant compound model, the deposited films were characterized by UV–Vis, photoluminescence, and Raman spectroscopies, as well as by parallel beam X-ray diffraction. The results showed that films with different Au and Ag loads, and an 18 nm average crystallite size, were obtained. These metals have an essential effect on the deposited film’s compositional, structural, and optical properties, directly reflected in its photocatalytic activity. The photocatalytic test results using UV-Vis showed that, after 1 h of applying a 4.8 V electric voltage, a discoloration of up to 80% of malachite green (MG) was achieved, using ultraviolet (UV) light. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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9 pages, 2942 KiB  
Article
Intra-Molecular Electrical Field Regulated Nonlinear Catalyst Charge Transfer in the Organic Conjugated Molecular System
by Quanjiang Li, Shenghui Chen, Li Wang, Yanli Liu, Di He, Meishan Wang and Jingang Wang
Catalysts 2021, 11(11), 1375; https://doi.org/10.3390/catal11111375 - 15 Nov 2021
Viewed by 1291
Abstract
The application of organic conjugated molecular systems to photocatalysis is based on the charge transition with different electronegative substituents and the electron–hole separation behavior of charge transfer under light excitation. In this work, the relationship between the intra-molecular electrical field and molecular second-order [...] Read more.
The application of organic conjugated molecular systems to photocatalysis is based on the charge transition with different electronegative substituents and the electron–hole separation behavior of charge transfer under light excitation. In this work, the relationship between the intra-molecular electrical field and molecular second-order nonlinear optical properties is investigated theoretically by the sum-of-states (SOS) method. We use substituents with different electron affinity energy to construct internal electric fields with different properties in similar conjugated systems. The studies of these systems reveal the intra-molecular electric field strength and mode regulation of nonlinear optical coefficients and explain its physical mechanism. The intra-molecular charge recombination caused by the electrostatic potential multipole field of different substituents changes the transition behavior of one-photon, resulting in the enhancement of nonlinear optical properties (second-harmonic generation and sum-frequency coefficient) greater than 104. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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22 pages, 7411 KiB  
Article
Development of a Novel Microgap Reactor System for the Photocatalytic Degradation of Micropollutants from Aqueous Solutions with TiO2-Based Photocatalysts Immobilized by Spray Coating
by Tony B. Engelhardt, Minrui Zhu, Claudia Heilmann, Sabine Schmitz-Stöwe, Thomas Schwarz and Klaus Stöwe
Catalysts 2021, 11(11), 1351; https://doi.org/10.3390/catal11111351 - 11 Nov 2021
Cited by 2 | Viewed by 1554
Abstract
The presented investigation focuses on the development of a novel microgap reactor concept for the photocatalytic degradation of micropollutants from aqueous solutions with titanium dioxide-based catalysts immobilized by spray coating. Combinatorial experiment designs were utilized in order to study the influence of the [...] Read more.
The presented investigation focuses on the development of a novel microgap reactor concept for the photocatalytic degradation of micropollutants from aqueous solutions with titanium dioxide-based catalysts immobilized by spray coating. Combinatorial experiment designs were utilized in order to study the influence of the microgap width, irradiance and catalyst layer thickness on the conversion of 17 α-ethinyl estradiol. The impact of catalyst-doping is discussed as well. Regarding conversion analyses, LC-MS/MS and GC-MS techniques were deployed, while XRD, ESEM and BET were utilized for catalyst characterization. The results show that the built-up microgap reactor system enables a conversion of 65% within a residence time of 2.7 min with UV-A irradiation and under steady flow conditions. Thus, the presented bench scale photocatalysis reactor provides promising fundamental findings for the future development of pilot scale approaches. With the deployment of industrial catalysts and base materials, microgap reactor photocatalytic degradation represents an attractive technology for large-scale application. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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20 pages, 2151 KiB  
Article
Influence of rGO and Preparation Method on the Physicochemical and Photocatalytic Properties of TiO2/Reduced Graphene Oxide Photocatalysts
by Agnieszka Wanag, Ewelina Kusiak-Nejman, Adam Czyżewski, Dariusz Moszyński and Antoni W. Morawski
Catalysts 2021, 11(11), 1333; https://doi.org/10.3390/catal11111333 - 02 Nov 2021
Cited by 8 | Viewed by 1949
Abstract
In this study, a series of TiO2/rGO photocatalysts were obtained with a two-step procedure: a solvothermal method and calcination at 300–900 °C in an argon atmosphere. It was noted that the presence of rGO in photocatalysts had an important role in [...] Read more.
In this study, a series of TiO2/rGO photocatalysts were obtained with a two-step procedure: a solvothermal method and calcination at 300–900 °C in an argon atmosphere. It was noted that the presence of rGO in photocatalysts had an important role in the changes in crystallite size and specific surface area. In TiO2/rGO samples, different surface functional groups, such as C−Cgraph, C−Caliph, C−OH, C=O, and CO(O), were found. It was observed that rGO modification suppressed the anatase-to-rutile phase transformation. The photocatalytic activity of the obtained nanomaterials was investigated through the decomposition of methylene blue under UV and artificial solar light irradiation. It was found that the adsorption degree played an important role in methylene blue decomposition. The experimental results revealed that TiO2/rGO samples exhibited superior removal efficiency after calcination for methylene blue compared toTiO2 without rGO, as well as a commercial photocatalyst KRONOClean 7000. It was noted that photocatalytic activity increased with the increase in the calcination temperature. The highest activity was observed for the sample calcined at 700 °C, which consisted of 76% anatase and 24% rutile. This study clearly demonstrated that TiO2/rGO samples calcined in argon can be used as efficient photocatalysts for the application of methylene blue decomposition. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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12 pages, 8300 KiB  
Article
Mitigation of Particulate Matter and Airborne Pathogens in Swine Barn Emissions with Filtration and UV-A Photocatalysis
by Myeongseong Lee, Jacek A. Koziel, Nubia R. Macedo, Peiyang Li, Baitong Chen, William S. Jenks, Jeffrey Zimmerman and R. Vincent Paris
Catalysts 2021, 11(11), 1302; https://doi.org/10.3390/catal11111302 - 28 Oct 2021
Cited by 7 | Viewed by 1960
Abstract
This study evaluated the use of filtration and UV-A photocatalysis for the reduction of particulate matter (PM) and airborne bacterial pathogens in swine barns. Two MERV filters (8 and 15) were used to mitigate PM concentrations measured at the PM 1, PM 2.5, [...] Read more.
This study evaluated the use of filtration and UV-A photocatalysis for the reduction of particulate matter (PM) and airborne bacterial pathogens in swine barns. Two MERV filters (8 and 15) were used to mitigate PM concentrations measured at the PM 1, PM 2.5, respirable PM, and PM 10 ranges. Filtration was also used to generate different levels of airborne pathogens to be treated by UV-A. Results show that MERV 8 and 15 filters effectively reduced PM concentrations (96–98%) in air exhausted from a swine barn (p ranged from <0.01 to 0.04). UV-A photocatalysis did not mitigate PM concentrations. UV-A photocatalysis treatment reduced measured colony-forming units (CFUs) by 15–95%. The CFU percent reduction was higher when airborne PM concentration was low. The numeric results suggested a real mitigation effect despite p-values that did not meet the usual statistical cut-off of <0.05 for significance due to the large variability of the CFU control samples. Normalization of measured airborne pathogen concentrations by smaller PM size range concentrations led to emerging significant treatment differences for CFUs. A significant decrease (~51% reduction; p < 0.02) in the concentration of viable airborne bacteria was shown for all PM below the 10 micron range. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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18 pages, 6463 KiB  
Article
Synthesis of Nano-ZnO/Diatomite Composite and Research on Photoelectric Application
by Beibei Yang, Xuefei Liu, Zixu Ma, Qian Wang and Junjiao Yang
Catalysts 2021, 11(10), 1232; https://doi.org/10.3390/catal11101232 - 13 Oct 2021
Cited by 4 | Viewed by 1684
Abstract
The key to the commercialization of sustainable energy conversion technologies is the development of high-performance catalysts. The discovery of a stable, efficient, and low-cost multi-function catalysts is the key. We used a simple green precipitation method to load nanozinc oxide particles onto a [...] Read more.
The key to the commercialization of sustainable energy conversion technologies is the development of high-performance catalysts. The discovery of a stable, efficient, and low-cost multi-function catalysts is the key. We used a simple green precipitation method to load nanozinc oxide particles onto a diatomite substrate. The ZnO is nano-sized. This precipitation method produces ZnO nanoparticles in situ on diatomite. The catalysts degraded 90% of Methylene blue solution and also degraded gaseous benzene and gaseous acetone. Not only can the catalysts be used for the organic degradation of wastewater, but it also has the potential to degrade volatile organic compounds. Photocatalytic efficiency is closely related to the generation and separation of photogenerated electrons and holes. The effective suppression of the recombination rate of photoliving carriers and thus improvement of the photocatalytic activity, has become a key research area. At present, photocatalysis is an effective technology to inhibit photogenerated carrier recombination, which is often studied in sewage treatment. Photoelectrochemical decomposition of water reduces the recombination of photogenerated electrons and holes by applying an external bias, thus improving the quantum efficiency for the complete mineralization of organic pollutants. The composite catalysts were used for oxygen and hydrogen extraction reactions, and a comparison of the catalysts with various loading ratios showed that the photoelectrochemical decomposition of water activity of the composite catalysts are due to pure ZnO, and the efficiency is highest when the loading ratio is 10%. This work provides new methods for the design and further optimization of the preparation of photoelectrochemical decomposition of water catalysts. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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21 pages, 25284 KiB  
Article
Mesoporous TiO2 Implanted ZnO QDs for the Photodegradation of Tetracycline: Material Design, Structural Characterization and Photodegradation Mechanism
by Anwar Iqbal, Usman Saidu, Srimala Sreekantan, Mohammad Norazmi Ahmad, Marzaini Rashid, Naser M. Ahmed, Wan Hazman Danial and Lee D. Wilson
Catalysts 2021, 11(10), 1205; https://doi.org/10.3390/catal11101205 - 08 Oct 2021
Cited by 7 | Viewed by 2233
Abstract
A sol-gel method was used to prepare a mesoporous TiO2 implanted with a ZnO quantum dot photocatalyst (TZQ) for the photodegradation of tetracycline (TC) under fluorescent light irradiation. Scanning electron microscopy (SEM) shows the presence of cavities on the photocatalyst surface due [...] Read more.
A sol-gel method was used to prepare a mesoporous TiO2 implanted with a ZnO quantum dot photocatalyst (TZQ) for the photodegradation of tetracycline (TC) under fluorescent light irradiation. Scanning electron microscopy (SEM) shows the presence of cavities on the photocatalyst surface due to the use of starch as a synthetic template, where the nitrogen sorption results indicate that TZQ contains mesopores with reduced size (ca. 4.3 nm) versus the pore size of the parent meso-TiO2 (ca. 7.5 nm). The addition of ZnO quantum dots (QDs) resulted in spherically-shaped binary composite particles in layers onto the surface of TiO2. The coexistence of the ZnO QDs and TiO2 phase was observed using high resolution-transmission electron microscopy (HR-TEM). The photodegradation of TC was carried out in a homemade reactor equipped with two fluorescent lights (24 W each) and within 90 min of irradiation, 94.6% of TC (40 mg L−1) was photodegraded using 250 mg L−1 of TZQ at pH 9. The major reactive oxygen species identified from the scavenging tests were O2●− followed by HO. The deconvolution of the photoluminescence spectrum of TZQ indicates the presence of a strong quantum confinement effect (QCE) of the ZnO QDs, a defect related to Ti-species and oxygen. The analysis of the intermediates detected by LC-time-of-flight/mass spectrometry (LC/TOF-MS) suggest two photodegradation pathways. The pathways were validated using the Fukui function approach and the Wheland localisation approach. This simple and efficient photocatalytic technology is anticipated to benefit small-scale animal husbandries and aquaculture operators that have limited access to sustainable water treatment technology. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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24 pages, 4368 KiB  
Article
Fe-TiO2/AC and Co-TiO2/AC Composites: Novel Photocatalysts Prepared from Waste Streams for the Efficient Removal and Photocatalytic Degradation of Cibacron Yellow F-4G Dye
by Roberto Machado Garcia, Robert Carleer, Maria Arada Pérez, Jeamichel Puente Torres, Ying Gu, Pieter Samyn and Jan Yperman
Catalysts 2021, 11(10), 1137; https://doi.org/10.3390/catal11101137 - 23 Sep 2021
Cited by 8 | Viewed by 2733
Abstract
Fe-TiO2/AC and Co-TiO2/AC composites were prepared from activated carbon (AC) derived from residues of peanut hulls and TiO2 photocatalyst, electrochemically prepared from titanium scrap, and doped with Fe and Co, respectively. The adsorption capacity and photocatalytic activity of [...] Read more.
Fe-TiO2/AC and Co-TiO2/AC composites were prepared from activated carbon (AC) derived from residues of peanut hulls and TiO2 photocatalyst, electrochemically prepared from titanium scrap, and doped with Fe and Co, respectively. The adsorption capacity and photocatalytic activity of the Fe-TiO2/AC and Co-TiO2/AC composites were studied for removing and degrading Cibacron Yellow F-4G (CYF-4G) from wastewater. Doped ACs were characterized by thermogravimetry (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), a new X-ray absorption technique (XRA), and elemental analysis (EA). Interesting relationships were found between SEM, XRA, and TGA data and the doped amount of catalyst on ACs. Optimal dye adsorption was found at a pH of 2.0. The CYF-4G adsorption kinetics are followed according to the pseudo-second order model. The experimental data revealed that the Langmuir model fits better than the Freundlich and Temkin models. A decrease in adsorption capacity was observed when the catalyst dope percentage increased. A removal and degradation efficiency of the dye close to 100% was achieved around 120 min. A synergistic adsorption and photocatalytic degradation effect of the Fe-TiO2/AC and Co-TiO2/AC composites could be observed when adsorption experiments were conducted under simulated visible radiation. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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15 pages, 3773 KiB  
Article
A Novel Machine Learning Model to Predict the Photo-Degradation Performance of Different Photocatalysts on a Variety of Water Contaminants
by Zhuoying Jiang, Jiajie Hu, Matthew Tong, Anna C. Samia, Huichun (Judy) Zhang and Xiong (Bill) Yu
Catalysts 2021, 11(9), 1107; https://doi.org/10.3390/catal11091107 - 15 Sep 2021
Cited by 15 | Viewed by 4145
Abstract
This paper describes an innovative machine learning (ML) model to predict the performance of different metal oxide photocatalysts on a wide range of contaminants. The molecular structures of metal oxide photocatalysts are encoded with a crystal graph convolution neural network (CGCNN). The structure [...] Read more.
This paper describes an innovative machine learning (ML) model to predict the performance of different metal oxide photocatalysts on a wide range of contaminants. The molecular structures of metal oxide photocatalysts are encoded with a crystal graph convolution neural network (CGCNN). The structure of organic compounds is encoded via digital molecular fingerprints (MF). The encoded features of the photocatalysts and contaminants are input to an artificial neural network (ANN), named as CGCNN-MF-ANN model. The CGCNN-MF-ANN model has achieved a very good prediction of the photocatalytic degradation rate constants by different photocatalysts over a wide range of organic contaminants. The effects of the data training strategy on the ML model performance are compared. The effects of different factors on photocatalytic degradation performance are further evaluated by feature importance analyses. Examples are illustrated on the use of this novel ML model for optimal photocatalyst selection and for assessing other types of photocatalysts for different environmental applications. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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14 pages, 1238 KiB  
Article
Degradation Efficiency and Kinetics Analysis of an Advanced Oxidation Process Utilizing Ozone, Hydrogen Peroxide and Persulfate to Degrade the Dye Rhodamine B
by Piotr Zawadzki and Małgorzata Deska
Catalysts 2021, 11(8), 974; https://doi.org/10.3390/catal11080974 - 14 Aug 2021
Cited by 14 | Viewed by 3234
Abstract
In this study, the effectiveness of a rhodamine B (RhB) dye degradation process at a concentration of 20 mg/L in different advanced oxidation processes—H2O2/UV, O3/UV and PDS/UV—has been studied. The use of UV in a photo-assisted ozonation [...] Read more.
In this study, the effectiveness of a rhodamine B (RhB) dye degradation process at a concentration of 20 mg/L in different advanced oxidation processes—H2O2/UV, O3/UV and PDS/UV—has been studied. The use of UV in a photo-assisted ozonation process (O3/UV) proved to be the most effective method of RhB decolorization (90% after 30 min at dye concentration of 100 mg/L). The addition of sulfate radical precursors (sodium persulfate, PDS) to the reaction environment did not give satisfactory effects (17% after 30 min), compared to the PDS/UV system (70% after 30 min). No rhodamine B decolorization was observed using hydrogen peroxide as a sole reagent, whereas an effect on the degree of RhB degradation was observed when UV rays strike the sample with H2O2 (33% after 30 min). The rhodamine B degradation process followed the pseudo-first-order kinetics model. The combined PDS/O3/UV process has shown 60% color removal after 30 min of reaction time at an initial dye concentration of 100 mg/L. A similar effectiveness was obtained by only applying ozone or UV-activated persulfate, but at a concentration 2–5 times lower (20 mg/L). The results indicated that the combined PDS/O3/UV process is a promising method for high RhB concentrations (50–100 mg/L) comparing to other alternative advanced oxidation processes. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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12 pages, 5029 KiB  
Article
Fabrication of Six Manganese Containing Polyoxometalate Modified Graphite C3N4 Nanosheets Catalysts Used to Catalyze Water Decomposition
by Yue Wu, Xiaoxia Yu, Zhijing Fu, Jianye Pei and Lihua Bi
Catalysts 2021, 11(7), 856; https://doi.org/10.3390/catal11070856 - 17 Jul 2021
Cited by 5 | Viewed by 2058
Abstract
With the increase in gas population, the demand for clean and renewable energy is increasing. Hydrogen energy has a high combustion conversion energy while water is its combustion product. In recent years, a way to convert water into hydrogen and oxygen has been [...] Read more.
With the increase in gas population, the demand for clean and renewable energy is increasing. Hydrogen energy has a high combustion conversion energy while water is its combustion product. In recent years, a way to convert water into hydrogen and oxygen has been found by human beings inspired by plant photosynthesis. However, water decomposition consumes a significant amount of energy and is expensive. People expect to obtain a water decomposition catalyst with low cost and high efficiency. This work selected a six-manganese containing polyoxometalate with a similar structure characteristic to photosynthesizing PSII to fabricate with graphite C3N4 nanosheets for the construction of composite film (Mn6SiW/g-C3N4NSs) electrode via layer by layer self-assembly technology, which was used for the photo-electrochemical decomposition of water under visible light conditions. The binary composite film electrode displayed good catalytic efficiency. The photoelectric density of the composite electrode is 46 μA/cm2 (at 1.23 V vs. Ag/AgCl) and 239 μA/cm2 (at 1.5 V vs. Ag/AgCl). Compared with the g-C3N4NSs electrode alone, the photoelectric density of the composite electrode increased by 1 time. The reason is attributed to the fact that Mn6SiW has a similar structure characteristic to photosynthesizing PSII and high electron transferability. The construction of the composite film containing low-cost Mn6SiW to modify g-C3N4NSs can effectively improve the photocatalytic decomposition of water, thus this study provides valuable reference information for the development of low-cost and high-performance photo-electrocatalytic materials. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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21 pages, 10418 KiB  
Article
Green Synthesis, Structural Characterization and Photocatalytic Applications of ZnO Nanoconjugates Using Heliotropium indicum
by Udari Wijesinghe, Gobika Thiripuranathar, Farid Menaa, Haroon Iqbal, Anam Razzaq and Hanadi Almukhlifi
Catalysts 2021, 11(7), 831; https://doi.org/10.3390/catal11070831 - 08 Jul 2021
Cited by 28 | Viewed by 3814
Abstract
In recent years, biosynthesized zinc oxide nanoparticles (ZnO NPs) have been gaining importance due to their unique properties and tremendous applications. This study aimed to fabricate ZnO NPs by using extracts from various parts of the traditional medicinal plant Heliotropium indicum (H. [...] Read more.
In recent years, biosynthesized zinc oxide nanoparticles (ZnO NPs) have been gaining importance due to their unique properties and tremendous applications. This study aimed to fabricate ZnO NPs by using extracts from various parts of the traditional medicinal plant Heliotropium indicum (H. indicum) and evaluate their photocatalytic activity. Further, their potential in photoluminescence and fluorescence resonance energy transfer (FRET) was assessed. The Ultraviolet-Visible spectrum exhibited a hypsochromic shifted absorption band between 350–380 nm. Transmission electron microscopy (TEM) analysis revealed spherical NPs, while X-ray diffraction (XRD) data revealed wurtzite, hexagonal and crystalline nature. The TEM and XRD consistently determined an average particle size range from 19 to 53 nm. The photocatalytic degradation reaches a maximum of 95% for biogenic ZnO NPs by monitoring spectrophotometrically the degradation of methylene blue dye (λmax = 662.8 nm) under solar irradiation. Photoluminescence analysis revealed differentiated spectra with high-intensity emission peaks for biogenic ZnO NPs compared with chemically synthesized ZnO NPs. Eventually, the highest efficiency of FRET (80%) was found in ZnO NPs synthesized from the leaves. This remains the first report highlighting the multifunctional ZnO NPs capabilities mediated by using H. indicum, which could lead to important potential environmental and biomedical applications. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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13 pages, 4981 KiB  
Article
WO3 Fibers/g-C3N4 Z-Scheme Heterostructure Photocatalysts for Simultaneous Oxidation/Reduction of Phenol/Cr (VI) in Aquatic Media
by Feidias Bairamis and Ioannis Konstantinou
Catalysts 2021, 11(7), 792; https://doi.org/10.3390/catal11070792 - 29 Jun 2021
Cited by 18 | Viewed by 2562
Abstract
A sequence of WO3/g-C3N4 composites was synthesized at various % weight ratios (1, 5, 6.5, 8, 10, and 15%) of WO3 into g-C3N4 via electrospinning and wet-mixing method. The prepared photocatalytic materials were characterized [...] Read more.
A sequence of WO3/g-C3N4 composites was synthesized at various % weight ratios (1, 5, 6.5, 8, 10, and 15%) of WO3 into g-C3N4 via electrospinning and wet-mixing method. The prepared photocatalytic materials were characterized by X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, UV–vis diffuse reflection spectroscopy (DRS), scanning electron microscopy (SEM), N2 porosimetry and dynamic light scattering (DLS). Electrospun fibers of WO3 with diameter 250–300 nm was prepared using polyvinylpyrrolidone (PVP) polymer and used for the synthesis of composite WO3/g-C3N4 heterojunction structures. Results showed mesoporous materials with triclinic WO3 crystal phase, surface areas up to 67.7 m2g−1 and band gaps lower than 2.5 eV confirming the absorption to visible light region. The photocatalytic performance of the prepared photocatalysts were assessed towards the oxidation of phenol and reduction of Cr (VI), in single and binary systems using simulated solar light illumination, that followed first-order kinetics. The WO3/g-C3N4 composites were found to exhibit improved photocatalytic performances compared to the pure WO3 and g-C3N4 with 6.5 wt% WO3/g-C3N4 and 5 wt% WO3/g-C3N4 composites being the most efficient catalysts for the oxidation of phenolics and reduction of Cr (VI), respectively. The improved performance was explained by a Z-scheme photocatalytic mechanism which was proposed based on scavenging experiments and the determination of the corresponding energy levels of valence and conduction bands. The study demonstrated that such composites present interesting photocatalytic properties that can be further expanded to other environmental depollution applications as well as in energy applications. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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15 pages, 4732 KiB  
Article
Bifunctional Polymeric Carbon Nitride via Tuning Fabrication Conditions for Photocatalysis
by Malgorzata Aleksandrzak, Daria Baranowska, Wojciech Kukulka, Magdalena Onyszko, Beata Zielinska and Ewa Mijowska
Catalysts 2021, 11(6), 651; https://doi.org/10.3390/catal11060651 - 21 May 2021
Cited by 5 | Viewed by 1942
Abstract
In this contribution, the hydrogen evolution reaction and photodegradation of Rhodamine B (RhB) dye were studied using urea-based polymeric carbon nitride (PCN) as photocatalyst. The effects of calcination temperature and heating rate of the PCN on structural, morphological, optical, photoelectrochemical, and photocatalytic properties [...] Read more.
In this contribution, the hydrogen evolution reaction and photodegradation of Rhodamine B (RhB) dye were studied using urea-based polymeric carbon nitride (PCN) as photocatalyst. The effects of calcination temperature and heating rate of the PCN on structural, morphological, optical, photoelectrochemical, and photocatalytic properties were addressed. Different properties were found to be crucial in boosting photocatalytic performance dependending on the reaction type. The highest efficiency in hydrogen evolution was observed in the presence of PCN characterized by the superior charge transport and charge lifetime properties arising from higher degree of structural arrangement and lower defect content in comparison to that of other photocatalysts. However, photocatalytic degradation of RhB was the most powerful when the catalyst exhibited the highest specific surface area as a key parameter determining its efficiency, although it presented lower charge transport and charge carrier properties. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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14 pages, 6186 KiB  
Article
ZnO Nanospheres Fabricated by Mechanochemical Method with Photocatalytic Properties
by Zhou Zhou, Jing Wang and Chul Gyu Jhun
Catalysts 2021, 11(5), 572; https://doi.org/10.3390/catal11050572 - 29 Apr 2021
Cited by 8 | Viewed by 1956
Abstract
The preparation of high specific area (86.5 m2/g) ZnO nanospheres with good photocatalytic efficiency via a simple, green and efficient mechanochemical method was reported in this work. The products were characterized by XRD, SEM, TEM, BET and UV–Vis. The ball milling [...] Read more.
The preparation of high specific area (86.5 m2/g) ZnO nanospheres with good photocatalytic efficiency via a simple, green and efficient mechanochemical method was reported in this work. The products were characterized by XRD, SEM, TEM, BET and UV–Vis. The ball milling parameters were improved to reduce the agglomeration hazard during the ball milling process, and the specific surface area, band gap and photocatalytic efficiency were investigated in relation to ball milling time. Our study developed the opportunity for the low-cost and facile synthesis of a high specific surface area photocatalyst on a large scale for future industrial applications. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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Review

Jump to: Research

42 pages, 16523 KiB  
Review
Recent Progress in WS2-Based Nanomaterials Employed for Photocatalytic Water Treatment
by Aseel Yousef, Zeineb Thiehmed, Rana Abdul Shakoor and Talal Altahtamouni
Catalysts 2022, 12(10), 1138; https://doi.org/10.3390/catal12101138 - 28 Sep 2022
Cited by 4 | Viewed by 2224
Abstract
Water pollution is one of the most serious environmental issues globally due to its harmful consequences on the ecosystem and public health. Various technologies have been developed for water treatment such as photocatalysis, which has recently drawn scientists’ attention. Photocatalytic techniques using semiconductors [...] Read more.
Water pollution is one of the most serious environmental issues globally due to its harmful consequences on the ecosystem and public health. Various technologies have been developed for water treatment such as photocatalysis, which has recently drawn scientists’ attention. Photocatalytic techniques using semiconductors have shown an efficient removal of various water contaminants during water treatment as well as cost effectivity and low energy consumption. Tungsten disulfide (WS2) is among the promising Transition Metal Dichalcogenides (TMDs) photocatalysts, as it has an exceptional nanostructure and special properties including high surface area and high carrier mobility. It is usually synthesized via hydrothermal technique, chemical vapor deposition (CVD), and liquid-phase exfoliation (LPE) to obtain a wide variety of nanostructures such as nanosheets and nanorods. Most common examples of water pollutants that can be removed efficiently by WS2-based nanomaterials through semiconductor photocatalytic techniques are organic contaminants, pharmaceuticals, heavy metals, and infectious microorganisms. This review summarizes the most recent work on employing WS2-based nanomaterials for different photocatalytic water treatment processes. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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27 pages, 4927 KiB  
Review
Waste Biomass Selective and Sustainable Photooxidation to High-Added-Value Products: A Review
by Liliana Llatance-Guevara, Nelly Esther Flores, Germán Omar Barrionuevo and José Luis Mullo Casillas
Catalysts 2022, 12(10), 1091; https://doi.org/10.3390/catal12101091 - 21 Sep 2022
Cited by 7 | Viewed by 2132
Abstract
Researchers worldwide seek to develop convenient, green, and ecological production processes to synthesize chemical products with high added value. In this sense, lignocellulosic biomass photocatalysis is an excellent process for obtaining various outcomes for the industry. One issue of biomass transformation via heterogeneous [...] Read more.
Researchers worldwide seek to develop convenient, green, and ecological production processes to synthesize chemical products with high added value. In this sense, lignocellulosic biomass photocatalysis is an excellent process for obtaining various outcomes for the industry. One issue of biomass transformation via heterogeneous catalysis into valuable chemicals is the selection of an adequate catalyst that ensures high conversion and selectivity at low costs. Titanium oxide (TiO2), is widely used for several applications, including photocatalytic biomass degradation, depolymerization, and transformation. Graphite carbon nitride (g-C3N4) is a metal-free polymeric semiconductor with high oxidation and temperature resistance and there is a recent interest in developing this catalyst. Both catalysts are amenable to industrial production, relatively easy to dope, and suited for solar light absorption. Recent investigations also show the advantages of using heterojunctions, for biomass derivates production, due to their better solar spectrum absorption properties and, thus, higher efficiency, conversion, and selectivity over a broader spectrum. This work summarizes recent studies that maximize selectivity and conversion of biomass using photocatalysts based on TiO2 and g-C3N4 as supports, as well as the advantages of using metals, heterojunctions, and macromolecules in converting cellulose and lignin. The results presented show that heterogeneous photocatalysis is an interesting technology for obtaining several chemicals of industrial use, especially when using TiO2 and g-C3N4 doped with metals, heterojunctions, and macromolecules because these modified catalysts permit higher conversion and selectivity, milder reaction conditions, and reduced cost due to solar light utilization. In order to apply these technologies, it is essential to adopt government policies that promote the use of photocatalysts in the industry, in addition to encouraging active collaboration between photooxidation research groups and companies that process lignocellulosic biomass. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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30 pages, 457 KiB  
Review
Synthesis and Application of Innovative and Environmentally Friendly Photocatalysts: A Review
by Antonietta Mancuso and Giuseppina Iervolino
Catalysts 2022, 12(10), 1074; https://doi.org/10.3390/catal12101074 - 20 Sep 2022
Cited by 10 | Viewed by 2169
Abstract
Modern society faces two major challenges: removing pollutants from water and producing energy from renewable sources. To do this, science proposes innovative, low-cost, and environmentally friendly methods. The heterogeneous photocatalysis process fits perfectly in this scenario. In fact, with photocatalysis, it is possible [...] Read more.
Modern society faces two major challenges: removing pollutants from water and producing energy from renewable sources. To do this, science proposes innovative, low-cost, and environmentally friendly methods. The heterogeneous photocatalysis process fits perfectly in this scenario. In fact, with photocatalysis, it is possible both to mineralize contaminants that are not easily biodegradable and to produce hydrogen from the water splitting reaction or from the conversion of organic substances present in water. However, the main challenge in the field of heterogeneous photocatalysis is to produce low-cost and efficient photocatalysts active under visible light or sunlight. The objective of this review is to compare the new proposals for the synthesis of innovative photocatalysts that reflect the requirements of green chemistry, applied both in the removal of organic contaminants and in hydrogen production. From this comparison, we want to bring out the strengths and weaknesses of the proposals in the literature, but above all, new ideas to improve the efficiency of heterogeneous photocatalysis guaranteeing the principles of environmental and economic sustainability. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
37 pages, 7269 KiB  
Review
Recent Advancements in Photocatalysis Coupling by External Physical Fields
by Yan Mi, Wenjian Fang, Yawei Jiang, Yang Yang, Yongsheng Liu and Wenfeng Shangguan
Catalysts 2022, 12(9), 1042; https://doi.org/10.3390/catal12091042 - 13 Sep 2022
Cited by 6 | Viewed by 3437
Abstract
Photocatalysis is one of the most promising green technologies to utilize solar energy for clean energy achievement and environmental governance, such as artificial photosynthesis, water splitting, pollutants degradation, etc. Despite decades of research, the performance of photocatalysis still falls far short of the [...] Read more.
Photocatalysis is one of the most promising green technologies to utilize solar energy for clean energy achievement and environmental governance, such as artificial photosynthesis, water splitting, pollutants degradation, etc. Despite decades of research, the performance of photocatalysis still falls far short of the requirement of 5% solar energy conversion efficiency. Combining photocatalysis with the other physical fields has been proven to be an efficient way around this barrier which can improve the performance of photocatalysis remarkably. This review will focus on the recent advances in photocatalysis coupling by external physical fields, including Thermal-coupled photocatalysis (TCP), Mechanical-coupled photocatalysis (MCP), and Electromagnetism-coupled photocatalysis (ECP). In this paper, coupling mechanisms, materials, and applications of external physical fields are reviewed. Specifically, the promotive effect on photocatalytic activity by the external fields is highlighted. This review will provide a detailed and specific reference for photocatalysis coupling by external physical fields in a deep-going way. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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28 pages, 8443 KiB  
Review
Engineered Nanostructured Photocatalysts for Cancer Therapy
by Javier Bonet-Aleta, Jose I. Garcia-Peiro and Jose L. Hueso
Catalysts 2022, 12(2), 167; https://doi.org/10.3390/catal12020167 - 28 Jan 2022
Cited by 11 | Viewed by 3126
Abstract
The present review aims at highlighting recent advances in the development of photocatalysts devoted to cancer therapy applications. We pay especial attention to the engineering aspects of different nanomaterials including inorganic semiconductors, organic-based nanostructures, noble metal-based systems or synergistic hybrid heterostructures. Furthermore, we [...] Read more.
The present review aims at highlighting recent advances in the development of photocatalysts devoted to cancer therapy applications. We pay especial attention to the engineering aspects of different nanomaterials including inorganic semiconductors, organic-based nanostructures, noble metal-based systems or synergistic hybrid heterostructures. Furthermore, we also explore and correlate structural and optical properties with their photocatalytic capability to successfully performing in cancer-related therapies. We have made an especial emphasis to introduce current alternatives to organic photosensitizers (PSs) in photodynamic therapy (PDT), where the effective generation of reactive oxidative species (ROS) is pivotal to boost the efficacy of the treatment. We also overview current efforts in other photocatalytic strategies to tackle cancer based on photothermal treatment, starvation therapy, oxidative stress unbalance via glutathione (GSH) depletion, biorthogonal catalysis or local relief of hypoxic conditions in tumor microenvironments (TME). Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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19 pages, 3471 KiB  
Review
Sulfide-Based Photocatalysts Using Visible Light, with Special Focus on In2S3, SnS2 and ZnIn2S4
by José C. Conesa
Catalysts 2022, 12(1), 40; https://doi.org/10.3390/catal12010040 - 30 Dec 2021
Cited by 6 | Viewed by 2492
Abstract
Sulfides are frequently used as photocatalysts, since they absorb visible light better than many oxides. They have the disadvantage of being more easily photocorroded. This occurs mostly in oxidizing conditions; therefore, they are commonly used instead in reduction processes, such as CO2 [...] Read more.
Sulfides are frequently used as photocatalysts, since they absorb visible light better than many oxides. They have the disadvantage of being more easily photocorroded. This occurs mostly in oxidizing conditions; therefore, they are commonly used instead in reduction processes, such as CO2 reduction to fuels or H2 production. Here a summary will be presented of a number of sulfides used in several photocatalytic processes; where appropriate, some recent reviews will be presented of their behaviour. Results obtained in recent years by our group using some octahedral sulfides will be shown, showing how to determine their wavelength-dependent photocatalytic activities, checking their mechanisms in some cases, and verifying how they can be modified to extend their wavelength range of activity. It will be shown here as well how using photocatalytic or photoelectrochemical setups, by combining some enzymes with these sulfides, allows achieving the photo-splitting of water into H2 and O2, thus constituting a scheme of artificial photosynthesis. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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44 pages, 4550 KiB  
Review
The Evolution of Photocatalytic Membrane Reactors over the Last 20 Years: A State of the Art Perspective
by Raffaele Molinari, Cristina Lavorato and Pietro Argurio
Catalysts 2021, 11(7), 775; https://doi.org/10.3390/catal11070775 - 26 Jun 2021
Cited by 14 | Viewed by 2861
Abstract
The research on photocatalytic membrane reactors (PMRs) started around the year 2000 with the study of wastewater treatment by degradation reactions of recalcitrant organic pollutants, and since then the evolution of our scientific knowledge has increased significantly, broadening interest in reactions such as [...] Read more.
The research on photocatalytic membrane reactors (PMRs) started around the year 2000 with the study of wastewater treatment by degradation reactions of recalcitrant organic pollutants, and since then the evolution of our scientific knowledge has increased significantly, broadening interest in reactions such as the synthesis of organic chemicals. In this paper, we focus on some initial problems and how they have been solved/reduced over time to improve the performance of processes in PMRs. Some know-how gained during these last two decades of research concerns decreasing/avoiding the degradation of the polymeric membranes, improving photocatalyst reuse, decreasing membrane fouling, enhancing visible light photocatalysts, and improving selectivity towards the reaction product(s) in synthesis reactions (partial oxidation and reduction). All these aspects are discussed in detail in this review. This technology seems quite mature in the case of water and wastewater treatment using submerged photocatalytic membrane reactors (SPMRs), while for applications concerning synthesis reactions, additional knowledge is required. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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