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Degradation and Photocatalytic Properties of Nanocomposites

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A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Energy and Catalysis".

Deadline for manuscript submissions: closed (20 March 2024) | Viewed by 20453

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Dr. Peter Kasak

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Center for Advanced Materials, Qatar University, Doha 2713, Qatar
Interests: heterogenous catalysis; gels; surface modification

Special Issue Information

Dear Colleagues,

In recent years, a large interest is devoted to optimize the photocatalytic characteristic of nanostructural composite in order to employ maximum energy from the solar spectrum, especially for photocatalysis and degradation of organic pollutants and industrial effluents. The nanocomposites consist of wide band gap energy semiconductors such as TiO₂ coupled with narrow band gap semiconductors, co-doping with metals or the presence of the photoresponsive nanostructured carbon-based architecture have an auspicious role in photocatalytic application and degradation due to their multistructural characteristics. Moreover, the heterojunctions or presence of photoactive components in nanocomposites play an effective role to broaden the photoresponsive range of photocatalysts in order to promote charge separation, photoconversion efficiency and charge transference. Additionally, the nanocomposites can own a large interfacial area due to face-to-face contact of heterostructures leading to an effective separation, and low recombination rate of photogenerated electron-hole pairs. In addition, the nanostructural architecture can dictate and reduce energy for the excitation of electrons from the occupied valence band (VB) to the vacant conduction band (CB) resulting in photogenerated charge carriers and via redox reactions with water, oxygen leading to highly Reactive Oxygen Species (‘OH, O₂⁻,) responsible for the fast degradation of organic dyes, pollutants and/or industrial effluent.

This Special Issue focuses to present the wide field and the utilization of nanostructural composite for photocatalytic transformation and degradation including the photocatalytic transformation of industrially relevant compounds, organic pollutants and industrial effluents photodegradation, photocatalytic CO₂conversion and related technologies for solar energy transformation. We encourage authors to contribute original research articles and review articles covering the recent progress on nanostructured composites with impeccable degradation and/or photocatalytic properties.

Dr. Peter Kasak
Guest Editor

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Keywords

photodegradation
pollutant photodegradation
nanocomposite
photoactive carbon-based structure
heterojunction
interface engineering
photocatalysis
photocatalytic transformation

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Published Papers (10 papers)

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Editorial

Jump to: Research

4 pages, 156 KiB

Open AccessEditorial

Degradation and Photocatalytic Properties of Nanocomposites

by Peter Kasak

Nanomaterials 2024, 14(13), 1065; https://doi.org/10.3390/nano14131065 - 21 Jun 2024

Viewed by 795

Abstract

The world is suffering from energy consumption and environmental pollution challenges for the next generation era [...] Full article

(This article belongs to the Special Issue Degradation and Photocatalytic Properties of Nanocomposites)

Research

Jump to: Editorial

18 pages, 5914 KiB

Open AccessArticle

Mixed Metal Oxide W-TiO₂ Nanopowder for Environmental Process: Synergy of Adsorption and Photocatalysis

by Khley Cheng, Socheata Heng, Siteng Tieng, Ford David, Sarah Dine, Oriana Haddad, Christophe Colbeau-Justin, Mamadou Traore and Andrei Kanaev

Nanomaterials 2024, 14(9), 765; https://doi.org/10.3390/nano14090765 - 26 Apr 2024

Cited by 2 | Viewed by 2140

Abstract

A mixed metal oxide W-TiO₂ nanopowder photocatalyst was prepared by using the sol–gel method with a broad range of elemental compositions x = C_W/(C_W + C_Ti), including TiO₂ and WO₃. The material was structurally characterized and evaluated in adsorption and photocatalytic processes by testing its removal capacity of a representative pollutant methylene blue (MB) in aqueous solutions and under UV-A and sunlight illuminations. The nanopowders appeared to be more effective adsorbents than pure TiO₂ and WO₃ materials, showing a maximum at 15 mol% W, which was set as the tungsten solubility limit in anatase titania. At the same time, the photocatalytic decomposition of MB peaked at 2 mol% W. The examination of different compositions showed that the most effective MB removal took place at 15 mol% W, which was attributed to the combined action of adsorption and heterogeneous photocatalysis. Moreover, MB decomposition under sunlight was stronger than under UV-A, suggesting photocatalyst activation by visible light. The pollutant removal efficiency of the material with 15 mol% W was enhanced by a factor of ~10 compared to pure TiO₂ at the beginning of the process, which shows its high potential for use in depollution processes in emergency cases of a great pollutant leak. As a result, a W_x=0.15-TiO₂ catalyst could be of high interest for wastewater purification in industrial plants. Full article

(This article belongs to the Special Issue Degradation and Photocatalytic Properties of Nanocomposites)

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18 pages, 5619 KiB

Open AccessArticle

Exploring the Remarkably High Photocatalytic Efficiency of Ultra-Thin Porous Graphitic Carbon Nitride Nanosheets

by Zahra Kalantari Bolaghi, Cristina Rodriguez-Seco, Aycan Yurtsever and Dongling Ma

Nanomaterials 2024, 14(1), 103; https://doi.org/10.3390/nano14010103 - 1 Jan 2024

Cited by 4 | Viewed by 2388

Abstract

Graphitic carbon nitride (g-C₃N₄) is a metal-free photocatalyst used for visible-driven hydrogen production, CO₂ reduction, and organic pollutant degradation. In addition to the most attractive feature of visible photoactivity, its other benefits include thermal and photochemical stability, cost-effectiveness, and simple and easy-scale-up synthesis. However, its performance is still limited due to its low absorption at longer wavelengths in the visible range, and high charge recombination. In addition, the exfoliated nanosheets easily aggregate, causing the reduction in specific surface area, and thus its photoactivity. Herein, we propose the use of ultra-thin porous g-C₃N₄ nanosheets to overcome these limitations and improve its photocatalytic performance. Through the optimization of a novel multi-step synthetic protocol, based on an initial thermal treatment, the use of nitric acid (HNO₃), and an ultrasonication step, we were able to obtain very thin and well-tuned material that yielded exceptional photodegradation performance of methyl orange (MO) under visible light irradiation, without the need for any co-catalyst. About 96% of MO was degraded in as short as 30 min, achieving a normalized apparent reaction rate constant (k) of 1.1 × 10⁻² min⁻¹mg⁻¹. This represents the highest k value ever reported using C₃N₄-based photocatalysts for MO degradation, based on our thorough literature search. Ultrasonication in acid not only prevents agglomeration of g-C₃N₄ nanosheets but also tunes pore size distribution and plays a key role in this achievement. We also studied their performance in a photocatalytic hydrogen evolution reaction (HER), achieving a production of 1842 µmol h⁻¹ g⁻¹. Through a profound analysis of all the samples’ structure, morphology, and optical properties, we provide physical insight into the improved performance of our optimized porous g-C₃N₄ sample for both photocatalytic reactions. This research may serve as a guide for improving the photocatalytic activity of porous two-dimensional (2D) semiconductors under visible light irradiation. Full article

(This article belongs to the Special Issue Degradation and Photocatalytic Properties of Nanocomposites)

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11 pages, 4339 KiB

Open AccessArticle

Graphitic Carbon Nitride Nanosheets Decorated with Zinc-Cadmium Sulfide for Type-II Heterojunctions for Photocatalytic Hydrogen Production

by Ammar Bin Yousaf, Muhammad Imran, Muhammad Farooq, Samaira Kausar, Samina Yasmeen and Peter Kasak

Nanomaterials 2023, 13(18), 2609; https://doi.org/10.3390/nano13182609 - 21 Sep 2023

Cited by 1 | Viewed by 1527

Abstract

In this study, we fabricated graphitic carbon nitride (g-C₃N₄) nanosheets with embedded ZnCdS nanoparticles to form a type II heterojunction using a facile synthesis approach, and we used them for photocatalytic H₂ production. The morphologies, chemical structure, and optical properties of the obtained g-C₃N₄–ZnCdS samples were characterized by a battery of techniques, such as TEM, XRD, XPS, and UV-Vis DRS. The as-synthesized g-C₃N₄–ZnCdS photocatalyst exhibited the highest hydrogen production rate of 108.9 μmol·g⁻¹·h⁻¹ compared to the individual components (g-C₃N₄: 13.5 μmol·g⁻¹·h⁻¹, ZnCdS: 45.3 μmol·g⁻¹·h⁻¹). The improvement of its photocatalytic activity can mainly be attributed to the heterojunction formation and resulting synergistic effect, which provided more channels for charge carrier migration and reduced the recombination of photogenerated electrons and holes. Meanwhile, the g-C₃N₄–ZnCdS heterojunction catalyst also showed a higher stability over a number of repeated cycles. Our work provides insight into using g-C₃N₄ and metal sulfide in combination so as to develop low-cost, efficient, visible-light-active hydrogen production photocatalysts. Full article

(This article belongs to the Special Issue Degradation and Photocatalytic Properties of Nanocomposites)

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15 pages, 5353 KiB

Open AccessArticle

Influence of Different Capping Agents on the Structural, Optical, and Photocatalytic Degradation Efficiency of Magnetite (Fe₃O₄) Nanoparticles

by Thandi B. Mbuyazi and Peter A. Ajibade

Nanomaterials 2023, 13(14), 2067; https://doi.org/10.3390/nano13142067 - 14 Jul 2023

Cited by 4 | Viewed by 1787

Abstract

Octylamine (OTA), 1-dodecanethiol (DDT), and tri-n-octylphosphine (TOP) capped magnetite nanoparticles were prepared by co-precipitation method. Powder X-ray diffraction patterns confirmed inverse spinel crystalline phases for the as-prepared iron oxide nanoparticles. Transmission electron microscopic micrographs showed iron oxide nanoparticles with mean particle sizes of 2.1 nm for Fe₃O₄-OTA, 5.0 nm for Fe₃O₄-DDT, and 4.4 nm for Fe₃O₄-TOP. The energy bandgap of the iron oxide nanoparticles ranges from 2.25 eV to 2.76 eV. The iron oxide nanoparticles were used as photocatalysts for the degradation of methylene blue with an efficiency of 55.5%, 58.3%, and 66.7% for Fe₃O₄-OTA, Fe₃O₄-DDT, and Fe₃O₄-TOP, respectively, while for methyl orange the degradation efficiencies were 63.8%, 47.7%, and 74.1%, respectively. The results showed that tri-n-octylphosphine capped iron oxide nanoparticles are the most efficient iron oxide nano-photocatalysts for the degradation of both dyes. Scavenger studies show that electrons (e⁻) and hydroxy radicals (•OH) contribute significantly to the photocatalytic degradation reaction of both methylene blue and methyl orange using Fe₃O₄-TOP nanoparticles. The influence of the dye solution’s pH on the photocatalytic reaction reveals that a pH of 10 is the optimum for methylene blue degradation, whereas a pH of 2 is best for methyl orange photocatalytic degradation using the as-prepared iron oxide nano-photocatalyst. Recyclability studies revealed that the iron oxide photocatalysts can be recycled three times without losing their photocatalytic activity. Full article

(This article belongs to the Special Issue Degradation and Photocatalytic Properties of Nanocomposites)

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13 pages, 3756 KiB

Open AccessArticle

High-Crystallinity BiOCl Nanosheets as Efficient Photocatalysts for Norfloxacin Antibiotic Degradation

by Dongxue Song, Mingxia Li, Lijun Liao, Liping Guo, Haixia Liu, Bo Wang and Zhenzi Li

Nanomaterials 2023, 13(12), 1841; https://doi.org/10.3390/nano13121841 - 12 Jun 2023

Cited by 11 | Viewed by 1982

Abstract

Semiconductor photocatalysts are essential materials in the field of environmental remediation. Various photocatalysts have been developed to solve the contamination problem of norfloxacin in water pollution. Among them, a crucial ternary photocatalyst, BiOCl, has attracted extensive attention due to its unique layered structure. In this work, high-crystallinity BiOCl nanosheets were prepared using a one-step hydrothermal method. The obtained BiOCl nanosheets showed good photocatalytic degradation performance, and the degradation rate of highly toxic norfloxacin using BiOCl reached 84% within 180 min. The internal structure and surface chemical state of BiOCl were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman, Fourier transform infrared spectroscopy (FTIR), UV–visible diffuse reflectance (UV-vis), Brunauer–Emmett–Teller (BET), X-ray photoelectron spectra (XPS), and photoelectric techniques. The higher crystallinity of BiOCl closely aligned molecules with each other, which improved the separation efficiency of photogenerated charges and showed high degradation efficiency for norfloxacin antibiotics. Furthermore, the obtained BiOCl nanosheets possess decent photocatalytic stability and recyclability. Full article

(This article belongs to the Special Issue Degradation and Photocatalytic Properties of Nanocomposites)

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15 pages, 6337 KiB

Open AccessArticle

Gamma Radiation Synthesis of Ag/P25 Nanocomposites for Efficient Photocatalytic Degradation of Organic Contaminant

by Zihua Zeng, Shuangxiao Li, Xueyan Que, Jing Peng, Jiuqiang Li and Maolin Zhai

Nanomaterials 2023, 13(10), 1666; https://doi.org/10.3390/nano13101666 - 18 May 2023

Cited by 3 | Viewed by 2221

Abstract

Titanium dioxide (TiO₂) has garnered significant attention among various photocatalysts, whereas its photocatalytic activity is limited by its wide bandgap and inefficient charge separation, making the exploration of new strategies to improve its photocatalytic performance increasingly important. Here, we report the synthesis of Ag/P25 nanocomposites through a one-step gamma-ray radiation method using AgNO₃ and commercial TiO₂ (Degussa P25). The resulting products were characterized by powder X-ray diffraction, UV-Vis diffused reflectance spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The effect of free radical scavengers, feed ratios of Ag/P25, and dose rates on the photocatalytic activity of the Ag/P25 nanocomposites were systematically investigated using rhodamine B under Xenon light irradiation. The results showed that the Ag/P25 photocatalyst synthesized with a feed ratio of 2.5 wt% and isopropyl alcohol as the free radical scavenger at a dose rate of 130 Gy/min exhibited outstanding photocatalytic activity, with a reaction rate constant of 0.0674 min⁻¹, much higher than that of P25. Additionally, we found that the particle size of Ag could be effectively controlled by changing the dose rate, and the Ag/P25 nanocomposites doped with smaller size of Ag nanoparticles performed higher photocatalytic activities. The synthesis strategy presented in this study offers new insight into the future development of highly efficient photocatalysts using radiation techniques. Full article

(This article belongs to the Special Issue Degradation and Photocatalytic Properties of Nanocomposites)

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18 pages, 3652 KiB

Open AccessArticle

Degradation of Organic Methyl Orange (MO) Dye Using a Photocatalyzed Non-Ferrous Fenton Reaction

by Sifani Zavahir, Tasneem Elmakki, Nourhan Ismail, Mona Gulied, Hyunwoong Park and Dong Suk Han

Nanomaterials 2023, 13(4), 639; https://doi.org/10.3390/nano13040639 - 6 Feb 2023

Cited by 11 | Viewed by 2820

Abstract

Removal of recalcitrant organic pollutants by degradation or mineralization from industrial waste streams is continuously being explored to find viable options to apply on the commercial scale. Herein, we propose a titanium nanotube array (based on a non-ferrous Fenton system) for the successful degradation of a model contaminant azo dye, methyl orange, under simulated solar illumination. Titanium nanotube arrays were synthesized by anodizing a titanium film in an electrolyte medium containing water and ethylene glycol. Characterization by SEM, XRD, and profilometry confirmed uniformly distributed tubular arrays with 100 nm width and 400 nm length. The non-ferrous Fenton performance of the titanium nanotube array in a minimal concentration of H₂O₂ showed remarkable degradation kinetics, with a 99.7% reduction in methyl orange dye concentration after a 60 min reaction time when illuminated with simulated solar light (100 mW cm⁻², AM 1.5G). The pseudo-first-order rate constant was 0.407 µmol⁻¹ min⁻¹, adhering to the Langmuir–Hinshelwood model. Reaction product analyses by TOC and LC/MS/MS confirmed that the methyl orange was partially fragmented, while the rest was mineralized. The facile withdrawal and regeneration observed in the film-based titanium nanotube array photocatalyst highlight its potential to treat real industrial wastewater streams with a <5% performance drop over 20 reaction cycles. Full article

(This article belongs to the Special Issue Degradation and Photocatalytic Properties of Nanocomposites)

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20 pages, 6266 KiB

Open AccessArticle

Facile Preparation of a Bispherical Silver–Carbon Photocatalyst and Its Enhanced Degradation Efficiency of Methylene Blue, Rhodamine B, and Methyl Orange under UV Light

by Md. Akherul Islam, Jeasmin Akter, Insup Lee, Santu Shrestha, Anil Pandey, Narayan Gyawali, Md. Monir Hossain, Md. Abu Hanif, Se Gyu Jang and Jae Ryang Hahn

Nanomaterials 2022, 12(22), 3959; https://doi.org/10.3390/nano12223959 - 10 Nov 2022

Cited by 4 | Viewed by 1751

Abstract

The combination of organic and inorganic materials is attracting attention as a photocatalyst that promotes the decomposition of organic dyes. A facile thermal procedure has been proposed to produce spherical silver nanoparticles (AgNPs), carbon nanospheres (CNSs), and a bispherical AgNP–CNS nanocomposite. The AgNPs and CNSs were each synthesized from silver acetate and glucose via single- and two-step annealing processes under sealed conditions, respectively. The AgNP–CNS nanocomposite was synthesized by the thermolysis of a mixture of silver acetate and a mesophase, where the mesophase was formed by annealing glucose in a sealed vessel at 190 °C. The physicochemical features of the as-prepared nanoparticles and composite were evaluated using several analytical techniques, revealing (i) increased light absorption, (ii) a reduced bandgap, (iii) the presence of chemical interfacial heterojunctions, (iv) an increased specific surface area, and (v) favorable band-edge positions of the AgNP–CNS nanocomposite compared with those of the individual AgNP and CNS components. These characteristics led to the excellent photocatalytic efficacy of the AgNP–CNS nanocomposite for the decomposition of three pollutant dyes under ultraviolet (UV) radiation. In the AgNP–CNS nanocomposite, the light absorption and UV utilization capacity increased at more active sites. In addition, effective electron–hole separation at the heterojunction between the AgNPs and CNSs was possible under favorable band-edge conditions, resulting in the creation of reactive oxygen species. The decomposition rates of methylene blue were 95.2, 80.2, and 73.2% after 60 min in the presence of the AgNP–CNS nanocomposite, AgNPs, and CNSs, respectively. We also evaluated the photocatalytic degradation efficiency at various pH values and loadings (catalysts and dyes) with the AgNP–CNS nanocomposite. The AgNP–CNS nanocomposite was structurally rigid, resulting in 93.2% degradation of MB after five cycles of photocatalytic degradation. Full article

(This article belongs to the Special Issue Degradation and Photocatalytic Properties of Nanocomposites)

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12 pages, 3795 KiB

Open AccessArticle

Z-Scheme Heterojunction of SnS₂/Bi₂WO₆ for Photoreduction of CO₂ to 100% Alcohol Products by Promoting the Separation of Photogenerated Charges

by Yong Xu, Juanjuan Yu, Jianfei Long, Lingxiao Tu, Weili Dai and Lixia Yang

Nanomaterials 2022, 12(12), 2030; https://doi.org/10.3390/nano12122030 - 13 Jun 2022

Cited by 9 | Viewed by 2352

Abstract

Using sunlight to convert CO₂ into solar fuel is an ideal solution to both global warming and the energy crisis. The construction of direct Z-scheme heterojunctions is an effective method to overcome the shortcomings of single-component or conventional heterogeneous photocatalysts for photocatalytic CO₂ (carbon dioxide) reduction. In this work, a composite photocatalyst of narrow-gap SnS₂ and stable oxide Bi₂WO₆ were prepared by a simple hydrothermal method. The combination of Bi₂WO₆ and SnS₂ narrows the bandgap, thereby broadening the absorption edge and increasing the absorption intensity of visible light. Photoluminescence, transient photocurrent, and electrochemical impedance showed that the coupling of SnS₂ and Bi₂WO₆ enhanced the efficiency of photogenerated charge separation. The experimental results show that the electron transfer in the Z-scheme heterojunction of SnS₂/Bi₂WO₆ enables the CO₂ reduction reactions to take place. The photocatalytic reduction of CO₂ is carried out in pure water phase without electron donor, and the products are only methanol and ethanol. By constructing a Z-scheme heterojunction, the photocatalytic activity of the SnS₂/Bi₂WO₆ composite was improved to 3.3 times that of pure SnS₂. Full article

(This article belongs to the Special Issue Degradation and Photocatalytic Properties of Nanocomposites)

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