Structured Semiconductors in Photocatalysis

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

Deadline for manuscript submissions: closed (31 October 2022) | Viewed by 32661

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Chemical Engineering Department, Facultad de Ciencias, Universidad Autonoma de Madrid, Campus Cantoblanco, E-28049 Madrid, Spain
Interests: chemical engineering; metal–organic frameworks (MOFs); carbon materials; water treatment; adsorption; advanced oxidation processes (AOPs); photocatalysis
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Departamento de Ingeniería Química, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
Interests: chemical engineering; materials science; adsorption; photocatalysis; semiconductors; MOFs
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Photocatalysis appears as an interesting approach for different applications, with the possibility of using sunlight as a sustainable and renewable source of energy. This technology is based on the use of a semiconductor that can be excited by light with an energy higher than its band gap inducing the formation of energy-rich electron-hole pairs, which can be involved in redox reactions. Recent progress has explored the chemical nature of structured semiconductors with the object to improve their electronic and optical properties, enhancing their photoresponse under different conditions. This Special Issue collects original research papers, reviews and commentaries focused on the challenges for the design of structured semiconductors with photocatalytic applications; thus synthesis, characterization of new photocatalysts, studies of activity and stability, and the mechanisms of photocatalytic reactions are invited for submission.

Dr. Jorge Bedia
Prof. Dr. Carolina Belver
Guest Editors

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Keywords

  • Photocatalysis
  • Structured semiconductors
  • H2 production
  • Environmental remediation
  • CO2 valorization

Published Papers (16 papers)

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Editorial

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4 pages, 205 KiB  
Editorial
Structured Semiconductors in Photocatalysis
by Carolina Belver and Jorge Bedia
Catalysts 2023, 13(7), 1111; https://doi.org/10.3390/catal13071111 - 17 Jul 2023
Cited by 1 | Viewed by 850
Abstract
Photocatalysis appears as an interesting approach for different applications, with the possibility of using sunlight as a sustainable and renewable source of energy [...] Full article
(This article belongs to the Special Issue Structured Semiconductors in Photocatalysis)

Research

Jump to: Editorial, Review

20 pages, 8564 KiB  
Article
Green Synthesis of CuO-TiO2 Nanoparticles for the Degradation of Organic Pollutants: Physical, Optical and Electrochemical Properties
by Dineo A. Bopape, Sarah Mathobela, Nolubabalo Matinise, David E. Motaung and Nomso C. Hintsho-Mbita
Catalysts 2023, 13(1), 163; https://doi.org/10.3390/catal13010163 - 10 Jan 2023
Cited by 13 | Viewed by 2356
Abstract
CuO-TiO2 nanocomposites were successfully synthesized using the C. benghalensis plant extracts. The effect of the composition of CuO to TiO2 on the morphological, optical, electrochemical, and photodegradation efficiency in the composites was studied. SEM, XRD, UV-vis, FTIR, TGA, BET, and CV [...] Read more.
CuO-TiO2 nanocomposites were successfully synthesized using the C. benghalensis plant extracts. The effect of the composition of CuO to TiO2 on the morphological, optical, electrochemical, and photodegradation efficiency in the composites was studied. SEM, XRD, UV-vis, FTIR, TGA, BET, and CV were used to characterize these materials. The XRD data reported the tenorite structure of the CuO and the anatase phase of the TiO2. SEM showed the spherical morphologies for all the CuO-TiO2 NPs, and these were also mesoporous in nature, as depicted by BET. The voltammogram of the CuO-TiO2 30/70 electrode showed a higher response current density compared to the other two samples, suggesting a higher specific capacitance. Upon testing the photocatalytic efficiencies of the CuO-TiO2 nanocomposites against methylene blue (MB), ciprofloxacin (CIP), and sulfisoxazole (SSX), the highest degradation of 94% was recorded for SSX using the CuO-TiO2 30/70 nanocomposites. Hydroxyl radicals were the primary species responsible for the photodegradation of SSX, and the material could be reused once. The most active species in the photodegradation of SSX has been identified as OH•. From this study, it can be noted that the CuO-TiO2 nanocomposites were more selective toward the degradation of antibiotics (sulfisoxazole and ciproflaxin) as compared to dyes (methylene blue). Full article
(This article belongs to the Special Issue Structured Semiconductors in Photocatalysis)
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18 pages, 3536 KiB  
Article
Effect of Pd-Doping Concentrations on the Photocatalytic, Photoelectrochemical, and Photoantibacterial Properties of CeO2
by Shaidatul Najihah Matussin, Fazlurrahman Khan, Mohammad Hilni Harunsani, Young-Mog Kim and Mohammad Mansoob Khan
Catalysts 2023, 13(1), 96; https://doi.org/10.3390/catal13010096 - 03 Jan 2023
Cited by 16 | Viewed by 1825
Abstract
Cerium oxide (CeO2) can exhibit good photocatalytic and photoantibacterial activities. However, its light-harvesting property is rather limited due to its large band gap. In order to boost these properties, doping with metal ions can improve light absorption and charge mobility. In [...] Read more.
Cerium oxide (CeO2) can exhibit good photocatalytic and photoantibacterial activities. However, its light-harvesting property is rather limited due to its large band gap. In order to boost these properties, doping with metal ions can improve light absorption and charge mobility. In this report, CeO2 and palladium−doped CeO2 (Pd−CeO2) NPs were synthesized via the microwave-assisted synthesis method. The structural, optical, and morphological studies of CeO2 and Pd−CeO2 NPs were carried out using various techniques. Mixed phases of CeO2/Ce2O3 were observed in pure CeO2 (S−CeO2) and Pd−CeO2. However, the Ce2O3 phase gradually disappeared upon doping with a higher percentage of Pd. Almost spherical particles were observed with average sizes between 6 and 13 nm. It was found that the incorporation of Pd reduced the particle size. Moreover, band gap energies of S−CeO2 and Pd−CeO2 NPs were reduced from 2.56 to 2.27 eV, and the PL intensities were also quenched with more Pd doping. The shifts in the conduction band and valence band were found to cause the reduction in the band gap energies of S−CeO2 and Pd−CeO2 NPs. In the case of photocatalytic degradation of methylene blue, photoelectrochemical, and photoantibacterial activities, Pd−CeO2 NPs showed enhanced activities under visible light irradiation. Therefore, Pd−CeO2 NPs have been shown to be a visible-light active material. Full article
(This article belongs to the Special Issue Structured Semiconductors in Photocatalysis)
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16 pages, 5519 KiB  
Article
Preparation of CuS/PbS/ZnO Heterojunction Photocatalyst for Application in Hydrogen Production
by Ming-Huan Chiu, Cheng-Ching Kuo, Chao-Wei Huang and Wein-Duo Yang
Catalysts 2022, 12(12), 1677; https://doi.org/10.3390/catal12121677 - 19 Dec 2022
Cited by 5 | Viewed by 1591
Abstract
A hexagonal wurtzite ZnO photocatalyst was prepared via a precipitation method. CuS nanoparticles (NPs) and PbS quantum dots (QDs) were loaded onto ZnO via a hydrothermal method to obtain a CuS/PbS/ZnO heterojunction photocatalyst. The CuS/PbS/ZnO photocatalyst obtained via the abovementioned method has significant [...] Read more.
A hexagonal wurtzite ZnO photocatalyst was prepared via a precipitation method. CuS nanoparticles (NPs) and PbS quantum dots (QDs) were loaded onto ZnO via a hydrothermal method to obtain a CuS/PbS/ZnO heterojunction photocatalyst. The CuS/PbS/ZnO photocatalyst obtained via the abovementioned method has significant absorption capabilities in the ultraviolet to near-infrared spectral regions, and effectively reduced the recombination of electron–hole pairs during a photocatalytic reaction. Electron microscope images showed that in the CuS/PbS/ZnO photocatalyst prepared at 130 °C, the particle size of the PbS QDs was approximately 5.5–5.7 nm, and the bandgap determined from the Tauc plot was 0.84 eV; this catalyst demonstrated the best water splitting effect. Furthermore, after adding a 0.25 M mixed solution of Na2S and Na2SO3 as the sacrificial reagent in photocatalysis for 5 h, the hydrogen production efficiency from water splitting reached 6654 μmol g−1 h−1. Full article
(This article belongs to the Special Issue Structured Semiconductors in Photocatalysis)
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16 pages, 2625 KiB  
Article
Photocatalytic Degradation of Methyl Orange Dyes Using Green Synthesized MoS2/Co3O4 Nanohybrids
by Tsung-Mo Tien, Chao-Hsiang Chen, Chen-Tang Huang and Edward L. Chen
Catalysts 2022, 12(11), 1474; https://doi.org/10.3390/catal12111474 - 18 Nov 2022
Cited by 10 | Viewed by 2137
Abstract
In this work, a new binary MoS2/Co3O4 nanohybrids was successfully fabricated and the chemical structures, morphologies, electrochemical and optical characterizations were carried out. In addition, heterojunction nanoparticles present in S-scheme structures act as electron traps and promote light [...] Read more.
In this work, a new binary MoS2/Co3O4 nanohybrids was successfully fabricated and the chemical structures, morphologies, electrochemical and optical characterizations were carried out. In addition, heterojunction nanoparticles present in S-scheme structures act as electron traps and promote light absorption capacity for the degradation of Methyl orange (MO) with visible-light activity. MoS2/Co3O4 nanohybrids suggested excellent photocatalytic performance compared to bare MoS2 and Co3O4, where 95.6% of MO was degraded within 170 min, respectively. The results also showed excellent stability and recyclability over five consecutive cycles, without noticeable changes in the nanocomposite structure. The boosted photocatalytic degradation and redox activities of MoS2/Co3O4 can be attributed to the created S-scheme heterostructure to facilitate the separation of and to delay recombination of photoinduced charge carriers. We believe that this strategy of exploiting nanohybrid photocatalysts has great potential in the field of environmental catalysis and diverse applications. Full article
(This article belongs to the Special Issue Structured Semiconductors in Photocatalysis)
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17 pages, 3401 KiB  
Article
Magnetic TiO2/Fe3O4-Chitosan Beads: A Highly Efficient and Reusable Catalyst for Photo-Electro-Fenton Process
by Soumaya Rezgui, Aida M. Díez, Lotfi Monser, Nafaa Adhoum, Marta Pazos and M. Ángeles Sanromán
Catalysts 2022, 12(11), 1425; https://doi.org/10.3390/catal12111425 - 13 Nov 2022
Cited by 2 | Viewed by 1548
Abstract
Heterogeneous photo-electro-Fenton process is an attractive technology for the removal of recalcitrant pollutants. To better exploit the presence of an irradiation source, a bifunctional catalyst with TiO2 nanoparticles embedded into an iron–chitosan matrix was developed. The catalytic activity of the catalyst was [...] Read more.
Heterogeneous photo-electro-Fenton process is an attractive technology for the removal of recalcitrant pollutants. To better exploit the presence of an irradiation source, a bifunctional catalyst with TiO2 nanoparticles embedded into an iron–chitosan matrix was developed. The catalytic activity of the catalyst was improved by the optimization of the loaded TiO2 content. The prepared composite catalysts based on TiO2, Fe3O4 and chitosan were called TiO2/Fe3O4-CS beads. The best catalyst with an optimal ratio TiO2/Fe = 2 exhibited a high efficiency in the degradation and mineralization of chlordimeform (CDM) insecticide. Under the optimum conditions (concentration of catalyst equal to 1 g L−1 and applied current intensity equal to 70 mA), a real effluent doped with 30 mg L−1 of CDM was efficiently treated, leading to 80.8 ± 1.9% TOC reduction after 6 h of treatment, with total removal of CDM after only 1 h.The generated carboxylic acids and minerals were identified and quantified. Furthermore, the stability and reusability of the developed catalyst was examined, and an insignificant reduction in catalytic activity was noticed for four consecutive cycles of the photo-electro-Fenton process. Analyses using SEM, XRD and VSM showed a good stability of the physicochemical properties of the catalyst after use. Full article
(This article belongs to the Special Issue Structured Semiconductors in Photocatalysis)
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11 pages, 4811 KiB  
Article
Photocatalytic Activity of ZnO/Ag Nanoparticles Fabricated by a Spray Pyrolysis Method with Different O2:N2 Carrier Gas Ratios and Ag Contents
by Meditha Hudandini, Nurdiana Ratna Puri, Sugeng Winardi, Widiyastuti Widiyastuti, Manabu Shimada and Kusdianto Kusdianto
Catalysts 2022, 12(11), 1374; https://doi.org/10.3390/catal12111374 - 05 Nov 2022
Cited by 7 | Viewed by 1594
Abstract
Wastewaters of the textile industry, e.g., those generated in Gresik, Indonesia, are a possible threat to the environment and should be treated before disposal. Photodegradation is a more promising method to overcome this problem than conventional methods such as biodegradation. ZnO is widely [...] Read more.
Wastewaters of the textile industry, e.g., those generated in Gresik, Indonesia, are a possible threat to the environment and should be treated before disposal. Photodegradation is a more promising method to overcome this problem than conventional methods such as biodegradation. ZnO is widely used for photodegradation due to its unique physical and chemical properties and stability. In this study, Ag was loaded onto ZnO, which is non-toxic and inexpensive, can improve the electron–hole separation, and has a significant catalytic potential. Pristine ZnO and ZnO-Ag nanoparticles were fabricated by an ultrasonic spray pyrolysis system at different Ag contents (1, 5, and 10 wt%). The carrier gas ratio (O2:N2) was also changed (1:0, 1:2, 1:1, 2:1, and 0:1) to examine its effects on the nanoparticle characteristics. The nanoparticle characteristics were examined using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer, Emmett, and Teller (BET) specific surface area. The results were interpreted in relation to photodegradation under UV light irradiation. An increase in the ZnO-Ag activity compared with pristine ZnO was observed at a carrier gas ratio of 0:1 with reaction rate constants of 0.0059 and 0.0025 min−1, respectively. Full article
(This article belongs to the Special Issue Structured Semiconductors in Photocatalysis)
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18 pages, 4279 KiB  
Article
Synthesis and Characterization of SiO2/TiO2 as Photocatalyst on Methylene Blue Degradation
by Aleksandra Babyszko, Agnieszka Wanag, Marcin Sadłowski, Ewelina Kusiak-Nejman and Antoni W. Morawski
Catalysts 2022, 12(11), 1372; https://doi.org/10.3390/catal12111372 - 05 Nov 2022
Cited by 13 | Viewed by 2321
Abstract
The paper presents a modification of titanium dioxide with fumed silica. The SiO2/TiO2 photocatalysts were obtained by the sol-gel method and then were calcined under an argon atmosphere. Various SiO2 weights (2–17.2 wt.%) were used in the materials’ preparation [...] Read more.
The paper presents a modification of titanium dioxide with fumed silica. The SiO2/TiO2 photocatalysts were obtained by the sol-gel method and then were calcined under an argon atmosphere. Various SiO2 weights (2–17.2 wt.%) were used in the materials’ preparation stage. The obtained samples were characterized using advanced analytical methods, such as FT-IR/DRS infrared spectroscopy, X-ray diffraction, SEM scanning electron microscopy, and UV-Vis/DRS spectroscopy. The BET specific surface area and zeta potential of samples were also measured. Based on the obtained results, it was observed that the modification of titanium dioxide with SiO2 effectively inhibited the increase in crystallite size of anatase and brookite during calcination and the decrease in specific surface area values. Moreover, the presence of SiO2 in the nanomaterials contributed to the increase in the size of specific surface area and the change in band gap energy values. The photocatalytic activity was determined based on the decomposition of methylene blue under UV irradiation. Thermal modification in an inert gas atmosphere significantly increased the dye removal rate. It should be noted that all the obtained SiO2/TiO2 photocatalysts showed higher activity compared to the starting TiO2. It was also found that the photocatalytic activity increased along with the increase in SiO2 content in the sample (up to 14.3 wt.% of SiO2). The highest activity was recorded for SiO2(11.1%)/TiO2_400 and SiO2(14.3%)/TiO2_400 samples. Full article
(This article belongs to the Special Issue Structured Semiconductors in Photocatalysis)
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19 pages, 2687 KiB  
Article
Fluoride-Doped TiO2 Photocatalyst with Enhanced Activity for Stable Pollutant Degradation
by Aida M. Díez, Iván Núñez, Marta Pazos, M. Ángeles Sanromán and Yury V. Kolen’ko
Catalysts 2022, 12(10), 1190; https://doi.org/10.3390/catal12101190 - 07 Oct 2022
Cited by 5 | Viewed by 1687
Abstract
Fluoride-doped TiO2 (F-TiO2) was synthesized by an efficient and simple one-step synthesis and successfully used for the UV-photo-degradation of the toxic and stable pollutants methylene blue (MB) and bisphenol A (BPA). Initially, the synthesized catalyst was characterized and compared to [...] Read more.
Fluoride-doped TiO2 (F-TiO2) was synthesized by an efficient and simple one-step synthesis and successfully used for the UV-photo-degradation of the toxic and stable pollutants methylene blue (MB) and bisphenol A (BPA). Initially, the synthesized catalyst was characterized and compared to untreated TiO2 (P25 Degussa) by different physical–chemical analyses such as XRD, band gap calculation, SEM, EDS, FITR, ECSA, or EIS. F-TiO2 defeated commercial TiO2, and almost complete pollutant removal was achieved within 30 min. The energy consumption was reduced as a result of the suitable reactor set-up, which reduced light scattering, and by the application of a long-pulse radiation procedure, where the lamp was switched off during periods where the radical degradation continued. This enhanced the overall photocatalysis process performance. Under these conditions, 80% of MB removal was attained within 15 min radiation with an energy consumption of only 0.070 Wh min−1, demonstrating a much better efficiency when compared to previously reported data. The catalyst was reusable, and its performance can be improved by the addition of H2O2. The results were validated by BPA degradation and the treatment of real wastewaters with both pollutants. The results were so encouraging that a scale-up reactor has been proposed for future studies. Full article
(This article belongs to the Special Issue Structured Semiconductors in Photocatalysis)
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21 pages, 7454 KiB  
Article
Zinc–Acetate–Amine Complexes as Precursors to ZnO and the Effect of the Amine on Nanoparticle Morphology, Size, and Photocatalytic Activity
by Jerry D. Harris, Emily A. Wade, Emmaline G. Ellison, Cecelia C. Pena, Stephen C. Bryant, Nicholas L. McKibben, Allison J. Christy, Kevin O. Laughlin, Ashley E. Harris, Kenrik V. Goettsche, Chad E. Larson, Seth M. Hubbard, Jonathan E. Cowen, Josh Eixenberger, David Estrada and Jennifer R. Chase
Catalysts 2022, 12(10), 1099; https://doi.org/10.3390/catal12101099 - 23 Sep 2022
Cited by 2 | Viewed by 1875
Abstract
Zinc oxide is an environmentally friendly and readily synthesized semiconductor with many industrial applications. ZnO powders were prepared by alkali precipitation using different [Zn(acetate)2(amine)x] compounds to alter the particle size and aspect ratio. Slow precipitations from 95 °C solutions [...] Read more.
Zinc oxide is an environmentally friendly and readily synthesized semiconductor with many industrial applications. ZnO powders were prepared by alkali precipitation using different [Zn(acetate)2(amine)x] compounds to alter the particle size and aspect ratio. Slow precipitations from 95 °C solutions produced micron-scale particles with morphologies of hexagonal plates, rods, and needles, depending on the precursor used. Powders prepared at 65 °C with rapid precipitation yielded particles with minimal morphology differences, but particle size was dependent on the precursor used. The smallest particles were produced using precursors that yielded crystals with low aspect ratios during high-temperature synthesis. Particles produced during rapid synthesis had sizes ranging from 21–45 nm. The materials were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, BET, and diffuse reflectance. The materials prepared using precursors with less-volatile amines were found to retain more organic material than ZnO produced using precursors with more volatile amines. The amount of organic material associated with the nanoparticles influenced the photocatalytic activity of the ZnO, with powders containing less organic material producing faster rate constants for the decolorizing of malachite green solutions under ultraviolet illumination, independent of particle size. [Zn(acetate)2(hydrazine)2] produced ZnO with the fastest rate constant and was recycled five times for dye degradation studies that revealed minimal to no reduction in catalytic efficiency. Full article
(This article belongs to the Special Issue Structured Semiconductors in Photocatalysis)
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19 pages, 2722 KiB  
Article
Disinfection and Photocatalytic Degradation of Organic Contaminants Using Visible Light-Activated GCN/Ag2CrO4 Nanocomposites
by Olufemi Oluseun Akintunde, Linlong Yu, Jinguang Hu, Md Golam Kibria, Casey R. J. Hubert, Samuel Pogosian and Gopal Achari
Catalysts 2022, 12(9), 943; https://doi.org/10.3390/catal12090943 - 25 Aug 2022
Cited by 6 | Viewed by 1878
Abstract
Visible-light-driven photocatalysts have gained increasing attention in the past few decades in treating emerging contaminants in water and wastewater. In this work, the photocatalytic activity of the coupled graphitic carbon nitride (GCN) and silver chromate (Ag2CrO4), herein denoted as [...] Read more.
Visible-light-driven photocatalysts have gained increasing attention in the past few decades in treating emerging contaminants in water and wastewater. In this work, the photocatalytic activity of the coupled graphitic carbon nitride (GCN) and silver chromate (Ag2CrO4), herein denoted as GCN/Ag2CrO4, nanocomposites was evaluated for degrading organic pollutants and inactivating microorganisms under visible light irradiation using a royal blue light-emitting diode (LED). The organic pollutants studied were 2,4-dichlorophenoxyacetic acid (2,4-D) and methyl chlorophenoxy propionic acid (MCPP or Mecoprop-P) present in KillexR, a commercially available herbicide, bovine serum albumin (BSA) protein, and SARS-CoV-2 spike protein. The disinfection experiments were conducted on wastewater secondary effluent. The results showed that over 85% degradation was achieved for both 2,4-D and Mecoprop-P in 120 min while 100% of BSA protein and 77.5% of SARS-CoV-2 protein were degraded in 20 min and 30 min, respectively. Additionally, GCN/Ag2CrO4 nanocomposites led to over one log reduction of cellular ATP (cATP), total coliforms, and E. coli in wastewater treatment plant (WWTP) secondary effluent after 60 min of royal blue LED irradiation. It was observed that the degradation performance of a photocatalyst under light irradiation is contaminant-specific. The binding affinity of the released metal ions from GCN/Ag2CrO4 with protein and ATP functional groups was responsible for the degradation of proteins and the reduction of cATP, while the generated ROS was responsible for the disinfection of total coliforms and E. coli. Overall, the results indicate that GCN/Ag2CrO4 nanocomposite is a promising photocatalyst in degrading organic pollutants and disinfecting microorganisms under visible light irradiation within a reasonable time. Full article
(This article belongs to the Special Issue Structured Semiconductors in Photocatalysis)
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13 pages, 4333 KiB  
Article
Preparation of TiO2-CNT-Ag Ternary Composite Film with Enhanced Photocatalytic Activity via Plasma-Enhanced Chemical Vapor Deposition
by Jianghua Lang, Kazuma Takahashi, Masaru Kubo and Manabu Shimada
Catalysts 2022, 12(5), 508; https://doi.org/10.3390/catal12050508 - 30 Apr 2022
Cited by 10 | Viewed by 2238
Abstract
In this study, a TiO2-CNT-Ag ternary composite film was successfully synthesized using the plasma-enhanced chemical vapor deposition method by simultaneously feeding a carbon nanotube (CNT)/Ag suspension and titanium tetraisopropoxide gas. The prepared TiO2-CNT-Ag film was characterized by scanning electron [...] Read more.
In this study, a TiO2-CNT-Ag ternary composite film was successfully synthesized using the plasma-enhanced chemical vapor deposition method by simultaneously feeding a carbon nanotube (CNT)/Ag suspension and titanium tetraisopropoxide gas. The prepared TiO2-CNT-Ag film was characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and ultraviolet-visible spectroscopy. Moreover, the Ag/Ti ratio of the film was confirmed using an inductivity-coupled plasma optical emission spectrometer. The performance of the TiO2-composite film for the degradation of rhodamine 6G under simulated solar light irradiation was evaluated. The rate constant of the prepared TiO2-CNT-Ag for rhodamine 6G degradation was approximately 1.8 times greater than that of prepared TiO2. This result indicates that the addition of CNT and Ag significantly improved the photocatalytic activity of the prepared films. Full article
(This article belongs to the Special Issue Structured Semiconductors in Photocatalysis)
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8 pages, 3842 KiB  
Communication
Ag-Doped TiO2 Composite Films Prepared Using Aerosol-Assisted, Plasma-Enhanced Chemical Vapor Deposition
by Jianghua Lang, Kazuma Takahashi, Masaru Kubo and Manabu Shimada
Catalysts 2022, 12(4), 365; https://doi.org/10.3390/catal12040365 - 23 Mar 2022
Cited by 9 | Viewed by 2189
Abstract
TiO2 is a promising photocatalyst, but its large bandgap restricts its light absorption to the ultraviolet region. The addition of noble metals can reduce the bandgap and electron-hole recombination; therefore, we prepared TiO2-Ag nanoparticle composite films by plasma-enhanced chemical vapor [...] Read more.
TiO2 is a promising photocatalyst, but its large bandgap restricts its light absorption to the ultraviolet region. The addition of noble metals can reduce the bandgap and electron-hole recombination; therefore, we prepared TiO2-Ag nanoparticle composite films by plasma-enhanced chemical vapor deposition (PECVD) using a mixture of aerosolized AgNO3, which was used as a Ag nanoparticle precursor, and titanium tetraisopropoxide, which acted as the TiO2 precursor. Notably, the use of PECVD enabled a low process temperature and eliminated the need for pre-preparing the Ag nanoparticles, thereby increasing the process efficiency. The structures and morphologies of the deposited films were characterized by ultraviolet (UV)—visible spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray spectroscopy, and the effects of the AgNO3 concentration on the photocatalytic activity of the deposited films were determined by assessing the degradation of methylene blue under UV light irradiation. The Ag ions were successfully reduced to metallic nanoparticles and were embedded in the TiO2 film. The best photocatalytic activity was achieved for a 1 wt% Ag-loaded TiO2 composite film, which was 1.75 times that of pristine TiO2. Full article
(This article belongs to the Special Issue Structured Semiconductors in Photocatalysis)
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16 pages, 6480 KiB  
Article
Influence of Synthesis Approach on Controlled Microstructures and Photocatalytic Properties of Ag/AgBr-Activated Carbon Composites on Visible Light Degradation of Tetracycline
by Saheed O. Sanni, Hendrik G. Brink and Elvera L. Viljoen
Catalysts 2021, 11(11), 1396; https://doi.org/10.3390/catal11111396 - 18 Nov 2021
Cited by 4 | Viewed by 1726
Abstract
The influence of the synthesis approach (thermal polyol and deposition–precipitation) regarding the dispersion of Ag/AgBr nanoparticles dispersed on activated carbon prepared from chemical impregnated pinecone (TP-AABR-ACK, and DP-AABR-ACK) was studied, to increase their photocatalytic efficiency on the degradation of tetracycline (TC). The physicochemical [...] Read more.
The influence of the synthesis approach (thermal polyol and deposition–precipitation) regarding the dispersion of Ag/AgBr nanoparticles dispersed on activated carbon prepared from chemical impregnated pinecone (TP-AABR-ACK, and DP-AABR-ACK) was studied, to increase their photocatalytic efficiency on the degradation of tetracycline (TC). The physicochemical characterization evidenced the significance of the ACK catalyst promoter in enhancing controlled microstructures (morphologies and particle size distributions), synergistic interface interaction between AABR NPs and the carbonaceous support, and efficient photogenerated charge carriers separation within TP-AABR-ACK, and DP-AABR-ACK composites. The results revealed 92% removal of TC within 180 min under the LED visible light irradiation, which was achieved using TP-AABR-ACK when compared to DP-AABR-ACK composite and other catalysts in this study. Such superior results achieved with TP-AABR-ACK composite were attributed to controlled morphologies, reduced particle size and agglomeration, improved absorptivity, and superior cooperative effect between the AABR and ACK catalyst promoter as evidenced from SEM, EDX, TEM, UV-DRS, and electrochemical characterizations, respectively. Furthermore, enhanced TOC removal and abundance of reactive superoxide anion generation were achieved with the TP-AABR-ACK composite in this study. Full article
(This article belongs to the Special Issue Structured Semiconductors in Photocatalysis)
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Review

Jump to: Editorial, Research

37 pages, 6531 KiB  
Review
Tailoring Structure: Current Design Strategies and Emerging Trends to Hierarchical Catalysts
by Virginia Venezia, Giulio Pota, Brigida Silvestri, Aniello Costantini, Giuseppe Vitiello and Giuseppina Luciani
Catalysts 2022, 12(10), 1152; https://doi.org/10.3390/catal12101152 - 01 Oct 2022
Cited by 3 | Viewed by 1802
Abstract
Nature mimicking implies the design of nanostructured materials, which can be assembled into a hierarchical structure, thus outperforming the features of the neat components because of their multiple length scale organization. This approach can be effectively exploited for the design of advanced photocatalysts [...] Read more.
Nature mimicking implies the design of nanostructured materials, which can be assembled into a hierarchical structure, thus outperforming the features of the neat components because of their multiple length scale organization. This approach can be effectively exploited for the design of advanced photocatalysts with superior catalytic activity for energy and environment applications with considerable development in the recent six years. In this context, we propose a review on the state of the art for hierarchical photocatalyst production. Particularly, different synthesis strategies are presented, including template-free structuring, and organic, inorganic, and hybrid templating. Furthermore, emerging approaches based on hybrid and bio-waste templating are also highlighted. Finally, a critical comparison among available methods is carried out based on the envisaged application. Full article
(This article belongs to the Special Issue Structured Semiconductors in Photocatalysis)
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23 pages, 3739 KiB  
Review
Advancements in Solar Desalination of Seawater by Various Ti3C2 MXene Based Morphologies for Freshwater Generation: A Review
by Adem Sreedhar and Jin-Seo Noh
Catalysts 2021, 11(12), 1435; https://doi.org/10.3390/catal11121435 - 25 Nov 2021
Cited by 16 | Viewed by 3310
Abstract
For a few years, we have been witnessing ubiquitous fresh and drinking water scarcity in various countries. To mitigate these problematic situations, many countries relied on non-conventional freshwater generation technologies through solar desalination of seawater. In this manner, we excel the ability of [...] Read more.
For a few years, we have been witnessing ubiquitous fresh and drinking water scarcity in various countries. To mitigate these problematic situations, many countries relied on non-conventional freshwater generation technologies through solar desalination of seawater. In this manner, we excel the ability of new class 2D Ti3C2 MXenes as a photothermal material (solar absorber) for freshwater generation via the solar desalination technique. In this review, the air–water interfacial interaction is highlighted for improving the evaporation efficiency. To provide the dependence of the desalination efficiency on the microstructure of the solar absorbers, we summarized various forms of 2D Ti3C2 MXenes (aerosol, films, foam, hydrogel, membrane, monolith and porous structure) and their characteristics. These microstructures prevailed ultrahigh photoconversion efficiency. In this aspect, we further explained key features such as light absorption, reflection, multiple internal reflection, hydrophilicity, lower thermal conduction, light-to-heat generation, and salt rejection for achieving efficient desalination output throughout the visible and broadband region. Specifically, we targeted to explore the self-floating and salt rejection nature of various state-of-the-art 2D Ti3C2 MXene structures. Further, we highlighted the long-term stability. Among the above morphologies, Ti3C2 MXene in the form of a membrane is believed to be a promising morphology which effectively desalinates seawater into freshwater. Finally, we highlighted the challenges and future perspectives, which can pave a potential path for advancing the sustainable solar desalination of seawater into freshwater. Full article
(This article belongs to the Special Issue Structured Semiconductors in Photocatalysis)
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