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Visible Light Active Photocatalysts for Environmental Remediation and Organic Synthesis

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A special issue of Photochem (ISSN 2673-7256).

Deadline for manuscript submissions: closed (23 December 2021) | Viewed by 40867

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Dr. Vincenzo Vaiano

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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
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Dear Colleagues,

In recent years the formulation of innovative photocatalysts activated by visible or solar light has been attracting increasing attention because of their interesting potential for environmental remediation and in organic synthesis reactions. Generally, the strategies for the development of visible light active photocatalysts are mainly focused on enhancing the degradation efficiency (in the case of environmental remediation) or increasing the selectivity towards the desired product (in the case of organic synthesis). These goals can be achieved by doping the semiconductor lattice with metal and/or non-metal elements in order to reduce the band gap energy, making the semiconductor able to absorb light at a wavelength higher than the UV range. Other interesting options are the formulation of different types of heterojunctions (to increase visible absorption properties and the concentration of photoactive surface sites), or to develop alternative catalytic materials, such as metal-organic frameworks (MOFs). This Special Issue is focused on “Visible Light Active Photocatalysts for environmental remediation and organic synthesis”, featuring the state-of-the-art in this field. Research and review papers related to the preparation and characterization of novel catalytic materials and their use in the visible (or solar light) driven photocatalytic removal of pollutants from liquid and gaseous phases are welcome in this Special Issue. Moreover, innovative photocatalyst formulations studied in chemical reactions devoted to the selective synthesis of organic compounds (e.g., phenol from benzene, aniline from nitrobenzene, methanol from methane, etc.) will be considered.

Dr. Vincenzo Vaiano
Guest Editor

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Keywords

photocatalysis
visible or solar light
doped and co-doped semiconductors
heterojunctions
Metal-Organic Framework (MOFs)
water and wastewater treatment
gaseous pollutant removal
organic synthesis

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Published Papers (12 papers)

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Editorial

Jump to: Research, Review

2 pages, 149 KiB

Open AccessEditorial

Visible-Light-Active Photocatalysts for Environmental Remediation and Organic Synthesis

by Vincenzo Vaiano

Photochem 2021, 1(3), 460-461; https://doi.org/10.3390/photochem1030029 - 11 Nov 2021

Cited by 2 | Viewed by 2126

Abstract

In recent years, the formulation of innovative photocatalysts activated by visible or solar light has been attracting increasing attention because of their notable potential for environmental remediation and use in organic synthesis reactions [...] Full article

(This article belongs to the Special Issue Visible Light Active Photocatalysts for Environmental Remediation and Organic Synthesis)

Research

Jump to: Editorial, Review

12 pages, 2474 KiB

Open AccessArticle

Study of the Response Surface in the Photocatalytic Degradation of Acetaminophen Using TiO₂

by Adriana Marizcal-Barba, Jorge Alberto Sanchez-Burgos, Victor Zamora-Gasga and Alejandro Perez Larios

Photochem 2022, 2(1), 225-236; https://doi.org/10.3390/photochem2010017 - 10 Mar 2022

Cited by 6 | Viewed by 2285

Abstract

An effective way to obtain the optimal parameters of a process or experiment is the response surface method. Using the Box–Behnken design further decreases the number of experiments needed to obtain sufficient data to obtain a reliable equation. From the equation, it is possible to predict the behavior of the response with respect to the combination of variables involved. In this study we evaluated the photocatalytic activity of the synthesized TiO₂ for the degradation of acetaminophen, a frequently used and uncontrolled drug that has been detected with increasing frequency in wastewater effluents. The variables used for this study were pH, contaminant concentration (acetaminophen) and catalyst dose. We found, with a 95% confidence level, that 99% of the contaminant can be degraded to pH 10, contaminant to 35 mg/L and a catalyst dose of 0.15 g TiO₂. Full article

(This article belongs to the Special Issue Visible Light Active Photocatalysts for Environmental Remediation and Organic Synthesis)

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12 pages, 15283 KiB

Open AccessArticle

Enhanced Photocatalytic Activity of TiO₂ Thin Film Deposited by Reactive RF Sputtering under Oxygen-Rich Conditions

by Takaya Ogawa, Yuekai Zhao, Hideyuki Okumura and Keiichi N. Ishihara

Photochem 2022, 2(1), 138-149; https://doi.org/10.3390/photochem2010011 - 18 Feb 2022

Cited by 3 | Viewed by 2702

Abstract

TiO₂ thin films are promising as photocatalysts to decompose organic compounds. In this study, TiO₂ thin films were deposited by reactive radio-frequency (RF) magnetron sputtering under various flow rates of oxygen and argon gas. The results show that the photocatalytic activity decreases as the oxygen-gas ratio is increased to 30% or less, while the activity increases under oxygen-rich conditions. It was observed that the crystal structure changed from anatase to a composite of anatase and rutile, where the oxygen-gas ratio during RF sputtering is more than 40%. Interestingly, the oxygen vacancy concentration increased under oxygen-rich conditions, where the oxygen-gas ratio is more than 40%. The sample prepared under the most enriched oxygen condition, 70%, among our experiments exhibited the highest concentration of oxygen vacancy and the highest photocatalytic activity. Both the oxygen vacancies and the composite of anatase and rutile structure in the TiO₂ films deposited under oxygen-rich conditions are considered responsible for the enhanced photocatalysis. Full article

(This article belongs to the Special Issue Visible Light Active Photocatalysts for Environmental Remediation and Organic Synthesis)

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11 pages, 8119 KiB

Open AccessArticle

Effect of Photolysis on Zirconium Amino Phenoxides for the Hydrophosphination of Alkenes: Improving Catalysis

by Bryan T. Novas, Jacob A. Morris, Matthew D. Liptak and Rory Waterman

Photochem 2022, 2(1), 77-87; https://doi.org/10.3390/photochem2010007 - 18 Jan 2022

Cited by 3 | Viewed by 2734

Abstract

A comparative study of amino phenoxide zirconium catalysts in the hydrophosphination of alkenes with diphenylphosphine reveals enhanced activity upon irradiation during catalysis, with conversions up to 10-fold greater than reactions in ambient light. The origin of improved reactivity is hypothesized to result from substrate insertion upon an n→d charge transfer of a Zr–P bond in the excited state of putative phosphido (Zr–PR₂) intermediates. TD-DFT analysis reveals the lowest lying excited state in the proposed active catalysts are dominated by a P 3p→Zr 4d MLCT, presumably leading to enhanced catalysis. This hypothesis follows from triamidoamine-supported zirconium catalysts but demonstrates the generality of photocatalytic hydrophosphination with d⁰ metals. Full article

(This article belongs to the Special Issue Visible Light Active Photocatalysts for Environmental Remediation and Organic Synthesis)

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17 pages, 3251 KiB

Open AccessArticle

Remazol Black Decontamination Study Using a Novel One-Pot Synthesized S and Co Co-Doped TiO₂ Photocatalyst

by Riska Dwiyanna, Roto Roto and Endang Tri Wahyuni

Photochem 2021, 1(3), 488-504; https://doi.org/10.3390/photochem1030032 - 26 Nov 2021

Cited by 3 | Viewed by 2358

Abstract

This study investigated the decolorization of Remazol Black (RBB) using a TiO₂ photocatalyst modified by S and Co co-doped TiO₂ (S-Co-TiO₂) from a single precursor. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and UV–Vis specular reflectance spectroscopy were used to characterize the photocatalysts. The results revealed that the band-gap energy of the doped and co-doped TiO₂ decreased, with the S-Co-TiO₂ 8% showing the greatest one, and was found to be 2.78 eV while undoped TiO₂ was 3.20 eV. The presence of S and Co was also identified through SEM-EDX. An activity study on RBB removal revealed that the S-Co-TiO₂ photocatalyst showed the best result compared to undoped TiO₂, S-TiO₂, and Co-TiO₂. The S-Co-TiO₂ 8% photocatalyst reduced RBB concentration (20 mg L⁻¹) up to 96% after 90 min of visible light irradiation, whereas S-TiO₂, Co-TiO₂, and undoped TiO₂ reduced it to 89%, 56%, and 39%, respectively. A pH optimization study showed that the optimum pH of RBB decolorization by S-Co-TiO₂ was 3.0, the optimum mass was 0.6 g L⁻¹, and reuse studies show that S-Co-TiO₂ 8% has the potential to be used repeatedly to remove colored pollutants. The results obtained indicate that the modification of S, Co co-doped titania synthesized using a single precursor has been successfully carried out and showed excellent characteristics and activity compared to undoped or doped TiO₂. Full article

(This article belongs to the Special Issue Visible Light Active Photocatalysts for Environmental Remediation and Organic Synthesis)

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13 pages, 5949 KiB

Open AccessArticle

g-C₃N₄/MoS₂ Heterojunction for Photocatalytic Removal of Phenol and Cr(VI)

by Ilaeira Rapti, Feidias Bairamis and Ioannis Konstantinou

Photochem 2021, 1(3), 358-370; https://doi.org/10.3390/photochem1030023 - 15 Oct 2021

Cited by 21 | Viewed by 3560

Abstract

In this study, molybdenum disulfide (MoS₂) decorated on graphitic carbon nitride (g-C₃N₄) heterostructure catalysts at various weight ratios (0.5%, 1%, 3%, 10%, w/w) were successfully prepared via a two-step hydrothermal synthesis preparation method. The properties of the synthesized materials were studied by X-ray diffraction (XRD), attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FT-IR), UV–Vis diffuse reflection spectroscopy (DRS), scanning electron microscopy (SEM) and N₂ porosimetry. MoS₂ was successfully loaded on the g-C₃N₄ forming heterojunction composite materials. N₂ porosimetry results showed mesoporous materials, with surface areas up to 93.7 m²g⁻¹, while determined band gaps ranging between 1.31 and 2.66 eV showed absorption over a wide band of solar light. The photocatalytic performance was evaluated towards phenol oxidation and of Cr(VI) reduction in single and binary systems under simulated sunlight irradiation. The optimum mass loading ratio of MoS₂ in g-C₃N₄ was 1%, showing higher photocatalytic activity under simulated solar light in comparison with bare g-C₃N₄ and MoS₂ for both oxidation and reduction processes. Based on scavenging experiments a type-II photocatalytic mechanism is proposed. Finally, the catalysts presented satisfactory stability (7.8% loss) within three catalytic cycles. Such composite materials can receive further applications as well as energy conversion. Full article

(This article belongs to the Special Issue Visible Light Active Photocatalysts for Environmental Remediation and Organic Synthesis)

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13 pages, 7979 KiB

Open AccessArticle

Electrospun Carbon Nanofibers Decorated with Ag₃PO₄ Nanoparticles: Visible-Light-Driven Photocatalyst for the Photodegradation of Methylene Blue

by Gopal Panthi and Mira Park

Photochem 2021, 1(3), 345-357; https://doi.org/10.3390/photochem1030022 - 10 Oct 2021

Cited by 6 | Viewed by 3865

Abstract

For the first time, heterostructures of electrospun carbon nanofibers decorated with Ag₃PO₄ nanoparticles (Ag₃PO₄/CNFs) were successfully fabricated by the combination of simple and versatile electrospinning technique followed by carbonization and incorporation of Ag₃PO₄ nanoparticles via colloidal and precipitation synthesis approaches. The as-fabricated heterostructures were characterized by FESEM with EDS, XRD, TEM with HRTEM, FTIR and UV-vis diffuse reflectance spectroscopy. Experimental results revealed that the heterostructure obtained by colloidal synthesis approach (Ag₃PO₄/CNFs-1) was decorated with small-sized (~20 nm) and uniformly distributed Ag₃PO₄ nanoparticles on the surface of CNFs without any evident agglomeration, while in the heterostructure obtained by the precipitation synthesis approach (Ag₃PO₄/CNFs-2), CNFs were decorated with agglomerated and bigger-sized Ag₃PO₄ nanoparticles. The visible-light-driven photocatalytic investigation signified that the Ag₃PO₄/CNFs-1 heterostructure can exhibit higher performance towards the photodegradation of MB dye solution compared to the Ag₃PO₄/CNFs-2 heterostructure, which could be attributed to the synergistic effect between the uniformity and small size of Ag₃PO₄ nanoparticles and CNFs that can serve as a conductivity network to prevent the recombination of charge carriers. Moreover, the mechanism of the photocatalytic activity as-prepared heterostructure is proposed. Full article

(This article belongs to the Special Issue Visible Light Active Photocatalysts for Environmental Remediation and Organic Synthesis)

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11 pages, 2491 KiB

Open AccessArticle

Structural and Optical Properties of Bi₁₂NiO₁₉ Sillenite Crystals: Application for the Removal of Basic Blue 41 from Wastewater

by Billal Brahimi, Hamza Kenfoud, Yasmine Benrighi and Oussama Baaloudj

Photochem 2021, 1(3), 319-329; https://doi.org/10.3390/photochem1030020 - 27 Sep 2021

Cited by 12 | Viewed by 3213

Abstract

This article covers the structural and optical property analysis of the sillenite Bi₁₂NiO₁₉ (BNO) in order to characterize a new catalyst that could be used for environmental applications. BNO crystals were produced by the combustion method using Polyvinylpyrrolidone as a combustion reagent. Different approaches were used to characterize the resulting catalyst. Starting with X-ray diffraction (XRD), the structure was refined from XRD data using the Rietveld method and then the structural form of this sillenite was illustrated for the first time. This catalyst has a space group of I23 with a lattice parameter of a = 10.24 Å. In addition, the special surface area (SSA) of BNO was determined by the Brunauer-Emmett-Teller (BET) method. It was found in the range between 14.56 and 20.56 cm²·g⁻¹. Then, the morphology of the nanoparticles was visualized by Scanning Electron Microscope (SEM). For the optical properties of BNO, UV-VIS diffusion reflectance spectroscopy (DRS) was used, and a 2.1 eV optical bandgap was discovered. This sillenite′s narrow bandgap makes it an effective catalyst for environmental applications. The photocatalytic performance of the synthesized Bi₁₂NiO₁₉ was examined for the degradation of Basic blue 41. The degradation efficiency of BB41 achieved 98% within just 180 min at pH ~9 and with a catalyst dose of 1 g/L under visible irradiation. The relevant reaction mechanism and pathways were also proposed in this work. Full article

(This article belongs to the Special Issue Visible Light Active Photocatalysts for Environmental Remediation and Organic Synthesis)

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18 pages, 4729 KiB

Open AccessArticle

Metal-Free g-C₃N₄/Nanodiamond Heterostructures for Enhanced Photocatalytic Pollutant Removal and Bacteria Photoinactivation

by Natalya Kublik, Luiz E. Gomes, Luiz F. Plaça, Thalita H. N. Lima, Thais F. Abelha, Julio A. P. Ferencz, Anderson R. L. Caires and Heberton Wender

Photochem 2021, 1(2), 302-318; https://doi.org/10.3390/photochem1020019 - 14 Sep 2021

Cited by 9 | Viewed by 3752

Abstract

Heterogeneous photocatalysis has emerged as a promising alternative for both micropollutant removal and bacterial inactivation under solar irradiation. Among a variety of photocatalysts explored in the literature, graphite carbon nitride (g-C₃N₄) is a metal-free semiconductor with acceptable chemical stability, low toxicity, and excellent cost-effectiveness. To minimize its high charge recombination rate and increase the photocatalyst adsorption capacity whilst keeping the metal-free photocatalyst system idea, we proposed the heterojunction formation of g-C₃N₄ with diamond nanocrystals (DNCs), also known as nanodiamonds. Samples containing different amounts of DNCs were assessed as photocatalysts for pollutant removal from water and as light-activated antibacterial agents against Staphylococcus sureus. The sample containing 28.3 wt.% of DNCs presented the best photocatalytic efficiency against methylene blue, removing 71% of the initial dye concentration after 120 min, with a pseudo-first-order kinetic and a constant rate of 0.0104 min⁻¹, which is nearly twice the value of pure g-C₃N₄ (0.0059 min⁻¹). The best metal-free photocatalyst was able to promote an enhanced reduction in bacterial growth under illumination, demonstrating its capability of photocatalytic inactivation of Staphylococcus aureus. The enhanced photocatalytic activity was discussed and attributed to (i) the increased adsorption capacity promoted by the presence of DNCs; (ii) the reduced charge recombination rate due to a type-II heterojunction formation; (iii) the enhanced light absorption effectiveness; and (iv) the better charge transfer resistance. These results show that g-C₃N₄/DNC are low-cost and metal-free photoactive catalysts for wastewater treatment and inactivation of bacteria. Full article

(This article belongs to the Special Issue Visible Light Active Photocatalysts for Environmental Remediation and Organic Synthesis)

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17 pages, 4563 KiB

Open AccessArticle

Photocatalytic Decomposition of Nitrobenzene in Aqueous Solution by Ag/Cu₂O Assisted with Persulfate under Visible Light Irradiation

by Wen-Shing Chen and Jyun-Yang Chen

Photochem 2021, 1(2), 220-236; https://doi.org/10.3390/photochem1020013 - 27 Aug 2021

Cited by 3 | Viewed by 2619

Abstract

The mineralization of nitrobenzene was executed using an innovative method, wherein Ag/Cu₂O semiconductors stimulated by visible light irradiation were supported with persulfate anions. Batch-wise experiments were performed for the evaluation of effects of silver metal contents impregnated, persulfate concentrations and Ag/Cu₂O dosages on the nitrobenzene removal efficiency. The physicochemical properties of fresh and reacted Ag/Cu₂O were illustrated by X-ray diffraction analyses, FE-SEM images, EDS Mapping analyses, UV–Vis diffuse reflectance spectra, transient photocurrent analyses and X-ray photoelectron spectra, respectively. Because of intense scavenging effects caused by benzene, 1-propanol and methanol individually, the predominant oxidant was considered to be sulfate radicals, originated from persulfate anions via the photocatalysis of Ag/Cu₂O. As regards oxidation pathways, nitrobenzene was initially transformed into hydroxycyclohexadienyl radicals, followed with the production of 2-nitrophenol, 3-nitrophenol or 4-nitrophenol. Afterwards, phenol compounds descended from denitration of nitrophenols were converted into hydroquinone and p-benzoquinone. Full article

(This article belongs to the Special Issue Visible Light Active Photocatalysts for Environmental Remediation and Organic Synthesis)

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13 pages, 5575 KiB

Open AccessArticle

Preparation of Activated Carbon/TiO₂ Nanohybrids for Photodegradation of Reactive Red-35 Dye Using Sunlight

by Bappy Mondol, Anupam Sarker, A. M. Shareque, Shaikat Chandra Dey, Mohammad Tariqul Islam, Ajoy Kumar Das, Sayed Md. Shamsuddin, Md. Ashraful Islam Molla and Mithun Sarker

Photochem 2021, 1(1), 54-66; https://doi.org/10.3390/photochem1010006 - 18 May 2021

Cited by 44 | Viewed by 4483

Abstract

Activated carbon/titanium dioxide (AC/TiO₂) nanohybrids were synthesized by a hydrothermal technique using various weight percent of commercial AC and were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA). The synthesized nanohybrids were applied to photodegradation of Reactive Red-35 (RR-35) dye in aqueous solution using sunlight. Due to the synergistic effect of adsorption and photodegradation activity, AC/TiO₂ nanohybrids were more efficient in treating the aqueous dye solution than that of AC and TiO₂. The maximum (95%) RR-35 dye removal from the water was obtained with 20 wt% AC/TiO₂ within 30 min at natural pH of 5.6. The possible photodegradation mechanism of RR-35 dye with AC/TiO₂ was discussed from the scavenger test. Moreover, AC/TiO₂ was found to be suitable for long-term repeated applications through recyclability experiments. Therefore, AC/TiO₂ nanohybrid is a promising photocatalyst for treating azo dyes especially RR-35 from water. Full article

(This article belongs to the Special Issue Visible Light Active Photocatalysts for Environmental Remediation and Organic Synthesis)

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Review

Jump to: Editorial, Research

20 pages, 3576 KiB

Open AccessReview

Green Synthesis of Heterogeneous Visible-Light-Active Photocatalysts: Recent Advances

by Alessio Zuliani and Camilla Maria Cova

Photochem 2021, 1(2), 147-166; https://doi.org/10.3390/photochem1020009 - 27 Jul 2021

Cited by 17 | Viewed by 4753

Abstract

The exploitation of visible-light active photocatalytic materials can potentially change the supply of energy and deeply transform our world, giving access to a carbon neutral society. Currently, most photocatalysts are produced through low-ecofriendly, energy dispersive, and fossil-based synthesis. Over the last few years, research has focused on the development of innovative heterogeneous photocatalysts by the design of sustainable and green synthetic approaches. These strategies range from the use of plant extracts, to the valorization and recycling of metals inside industrial sludges or from the use of solventless techniques to the elaboration of mild-reaction condition synthetic tools. This mini-review highlights progresses in the development of visible-light-active heterogeneous photocatalysts based on two different approaches: the design of sustainable synthetic methodologies and the use of biomass and waste as sources of chemicals embedded in the final photoactive materials. Full article

(This article belongs to the Special Issue Visible Light Active Photocatalysts for Environmental Remediation and Organic Synthesis)

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