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Nanomaterials for Photocatalysis and Piezo-Photocatalysis

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

Deadline for manuscript submissions: closed (12 May 2023) | Viewed by 24033

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Special Issue Editors

Dr. Rosanna Pagano

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Guest Editor

Department of Biological and Environmental Sciences and Technologies, (DISTEBA), University of Salento, Via Monteroni, I-73100 Lecce, Italy
Interests: development of nanomaterials for applications in photodegradation and piezo-photodegradation; preparation of molecular films using wet immobilization techniques for applications such as active layers for the construction of pollutant sensors and for applications in the field of photodegradation

Prof. Dr. Ludovico Valli

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Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Via Monteroni, I-73100 Lecce, Italy
Interests: immobilization of different materials by humid techniques; characterization by spectroscopic techniques; applications of the deposited active layers in photo-induced phenomena (charge and/or energy transfer); chemical sensors; drug delivery through nanoassemblies and nanoparticles
Special Issues, Collections and Topics in MDPI journals

Dr. Zois Syrgiannis

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Simpson Querrey Institute, Northwestern University, Chicago, IL 60611, USA
Interests: hybrid materials; supramolecular systems; photocatalysis; photoelectrodes; nanomaterials; photosensitization

Special Issue Information

Dear Colleagues,

Water pollution, due to increased agricultural and industrial activities, has affected the quality of life and the ecosystem in recent years. Major toxic pollutants include metal ions, personal care products, and in particular drugs that are largely used by modern populations. Photocatalysis is a method applied to photochemical reactions, carried out with a catalyst which is activated by the light of a suitable wavelength. Photocatalysis research is rising to develop green technologies for the remediation of pollutants and for energy production. Classical photocatalysts are represented by semiconductors, such as TiO_2,ZnO, CeO₂, Fe_xO_y, etc., or a combination of them.

ZnO is one of the most studied and characterized materials thanks to its piezoelectric features. By using piezoelectric materials, an increase in the photocatalytic efficiency can be achieved if piezoelectric photocatalysts are simultaneously subjected to light radiation and mechanical stress. In recent years, the dual use of these two features of ZnO has led to the rise of a new research ﬁeld, so-called piezo-photocatalysis. Additionally, interesting optical features have been reported for nanostructured carbon allotropes (such as carbon nanodots, graphene dots, etc.) making them suitable to be integrated in photocatalytic systems. Moreover, the synthetic procedures for carbon dots are totally in line with green and sustainable chemistry.

The purpose of the Special Issue is to describe novel, innovative, and environmentally friendly synthesis of nanomaterials (inorganic, organic or hybrid) for applications in photocatalysis. Articles, reviews, and opinion letters by experts in the field are also welcome.

Dr. Rosanna Pagano
Prof. Dr. Ludovico Valli
Dr. Zois Syrgiannis
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

photocatalysis
nanomaterials
hybrid nanostructures
pollutants
synthesis of new hybrid materials
piezo-photodegradation
environmental contaminant drugs
sustainable procedures
green chemistry

Published Papers (10 papers)

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Research

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16 pages, 7297 KiB

Open AccessFeature PaperArticle

Solar Light-Induced Photocatalytic Response of BiOCl/PANI Composite towards the Degradation of Tetracycline

by Janis Goyal, Surbhi Sharma and Soumen Basu

Catalysts 2023, 13(5), 795; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13050795 - 24 Apr 2023

Cited by 1 | Viewed by 1254

Abstract

Photocatalytic degradation has gained much attention as a means of reducing water contamination as, with increasing industrialization and population growth, water pollution is a menace to both individuals and the environment. In this respect, metal oxide photocatalysts demonstrate effectiveness due to their excellent properties, such as their narrow band gap and low recombination rate of charge carriers. Here, various weight ratios of BiOCl/PANI composites have been synthesized by the simple wet chemical method. The crystallinity, oxidation state and surface chemical composition of the elements were analyzed by XRD and XPS techniques. FESEM and HRTEM images verified the formation of BiOCl nanosheets, covered well with PANI nanofibers, while EDX spectra revealed the uniform distribution of elements. The high surface area of the photocatalyst with a mesoporous nature was revealed by BET analysis. Low recombination rate and narrow band gap, suitable for photocatalysis, were confirmed by PL and UV–DRS spectroscopy. The photocatalytic performance of the photocatalyst was tested for the photodegradation of rhodamine-B (Rh-B) and tetracycline (TC) under natural sunlight irradiation. Kinetic results demonstrated that the 15% BiOCl/PANI hybrid exhibits excellent photocatalytic activity, degrading 97% of Rh-B and 77% of TC with a high rate constant (for Rh-B 0.0236 min⁻¹ and for TC 0.0106 min⁻¹). Trapping experiments highlighted that O₂^•− radicals play a vital role in the photodegradation mechanism. The reusability studies confirmed the good stability of the catalyst for the degradation of Rh-B (~85%) after five sequential runs. Considering its superior properties and ease of preparation, the synthesized photocatalyst can be used for ecological remediation. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis and Piezo-Photocatalysis)

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18 pages, 6183 KiB

Open AccessArticle

Photocatalytic Activity and Reusability of F, Sm³⁺ Co-Doped TiO₂/MWCNTs Hybrid Heterostructure for Efficient Photocatalytic Degradation of Brilliant Black Bis-Azo Dye

by Sabastian Simbarashe Mukonza, Nhamo Chaukura and Ajay Kumar Mishra

Catalysts 2023, 13(1), 86; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13010086 - 31 Dec 2022

Cited by 4 | Viewed by 2010

Abstract

A global freshwater pollution catastrophe is looming due to pollutants of emerging concern (PECs). Conventional water treatment methods are limited in removing PECs such as pharmaceuticals and dye house effluent from aquatic systems. This study provides an effective potential solution by developing an innovative wastewater treatment method based on solar-light-responsive semiconductor-based photocatalysts. A sol-gel synthesis technique was used to produce Fluorine-Sm³⁺ co-doped TiO₂ (0.6% Sm³⁺) (FST3) photocatalysts. This was followed by loading multi-walled carbon nanotubes (MWCNTs) in the range of 0.25 to 1 wt% into the FST3 matrix. Solid state UV-visible spectroscopy measurements showed a bathochromic shift into the visible light region after the co-doping of TiO₂, whereas XRD analysis confirmed the presence of predominantly anatase polymorphs of TiO₂. The FT-IR and EDX results confirmed the presence of the F and Sm³⁺ dopants in the synthesised photocatalysts. XRD and TEM measurements confirmed that the crystallite sizes of all synthesised photocatalysts ranged from 12–19 nm. The resultant photocatalysts were evaluated for photocatalytic degradation of Brilliant Black BN bis-azo dye in aqueous solution under simulated solar irradiation. FST3 completely degraded the dye after 3 h, with a high apparent rate constant (K_a) value (2.73 × 10⁻² min⁻¹). The degree of mineralisation was evaluated using the total organic carbon (TOC) technique, which revealed high TOC removal (82%) after 3 h and complete TOC removal after 4 h. The incorporation of F improved the optical properties and the surface chemistry of TiO₂, whereas Sm³⁺ improved the quantum efficiency and the optical properties. These synergistic effects led to significantly improved photocatalytic efficiency. Furthermore, incorporating MWCNTs into the F and Sm³⁺ co-doped TiO₂ (0.6% Sm³⁺) improved the reaction kinetics of the FST3, effectively reducing the reaction time by over 30%. Recyclability studies showed that after 5 cycles of use, the FST3/C1 degradation efficiency dropped by 7.1%, whereas TiO₂ degradation efficiency dropped by 33.4% after the same number of cycles. Overall, this work demonstrates a sustainable and efficient dye-removal technique. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis and Piezo-Photocatalysis)

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12 pages, 5156 KiB

Open AccessArticle

In Situ Growth and UV Photocatalytic Effect of ZnO Nanostructures on a Zn Plate Immersed in Methylene Blue

by Ranjitha K. Hariharalakshmanan, Fumiya Watanabe and Tansel Karabacak

Catalysts 2022, 12(12), 1657; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12121657 - 16 Dec 2022

Cited by 1 | Viewed by 1483

Abstract

Nanostructures of zinc oxide (ZnO) are considered promising photocatalysts for the degradation of organic pollutants in water. This work discusses an in situ growth and UV photocatalytic effect of ZnO nanostructures on a Zn plate immersed in methylene blue (MB) at room temperature. First, the Zn surfaces were pretreated via sandblasting to introduce a micro-scale roughness. Then, the Zn plates were immersed in MB and exposed to UV light, to observe ZnO nanostructure growth and photocatalytic degradation of MB. Scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and UV-Vis diffuse reflectance spectroscopy were used to characterize the Zn surfaces. We observed the growth of stoichiometric and crystalline ZnO with a nano-leaf morphology and an estimated bandgap of 3.08 eV. The photocatalytic degradation of MB was also observed in the presence of the ZnO nanostructures and UV light. The average percentage degradation was 76% in 4 h, and the degradation rate constant was 0.3535 h⁻¹. The experimental results suggest that room temperature growth of ZnO nanostructures (on Zn surfaces) in organic dye solutions is possible. Furthermore, the nanostructured surface can be used simultaneously for the photocatalytic degradation of the organic dye. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis and Piezo-Photocatalysis)

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18 pages, 5452 KiB

Open AccessArticle

Photocatalytic Degradation of Methylene Blue and Ortho-Toluidine Blue: Activity of Lanthanum Composites La_xMO_y (M: Fe, Co, Ni)

by Mmabatho L. Mocwana, Puseletso P. Mokoena, Pontsho S. Mbule, Isaac N. Beas, Guy L. Kabongo, Simon N. Ogugua and Themba E. Tshabalala

Catalysts 2022, 12(11), 1313; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12111313 - 26 Oct 2022

Cited by 7 | Viewed by 2113

Abstract

Lanthanum (La) nanocomposites LaFeO₃, LaNiO₃, and LaCoO₃ were synthesized using a sol-gel method, and different La to-metal (Fe, Ni, or Co) ratios were attained using various concentrations of salts. The resulting composites were calcined at 540 °C and characterized by XRD, SEM-EDX, FT-IR spectroscopy, XPS, thermogravimetric analysis (TGA), and PL spectroscopy. The activity of the lanthanum composites (LaFeO₃, LaNiO₃, and LaCoO₃) was studied using the photocatalytic degradation of methylene blue (MB) and ortho-toluidine blue (o-TB) under visible light with a wavelength below 420 nm. The change in the concentration of dyes was monitored by using the UV-Vis spectroscopy technique. All composites appeared to have some degree of photocatalytic activity, with composites possessing an orthorhombic crystal structure having higher photocatalytic activity. The LaCoO₃ composite is more efficient compared with LaFeO₃ and LaNiO₃ for both dyes. High degradation percentages were observed for the La composites with a 1:1 metal ratio. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis and Piezo-Photocatalysis)

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15 pages, 5008 KiB

Open AccessArticle

Evaluation of Ni-Doped Tricobalt Tetroxide with Reduced Graphene Oxide: Structural, Photocatalysis, and Antibacterial Response

by João Otávio Donizette Malafatti, Ailton José Moreira, Elaine Cristina Paris, Leydi Julieta Cardenas Flechas, Otávio Augusto Poli Pereira and Miryam Rincón Joya

Catalysts 2022, 12(10), 1199; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12101199 - 09 Oct 2022

Cited by 5 | Viewed by 1589

Abstract

Cobalt oxide (Co₃O₄) nanoparticles were successfully prepared by sol–gel and hydrothermal methods for antibacterial and photocatalytic applications with the addition of 1%, 4% nickel (Ni), and reduced graphene oxide (rGO). The structural and morphological properties of the nanoparticles were obtained by XRD, TEM and FESEM techniques. Cobalt oxide showed typical crystallographic planes to cubic phase and particles with inferior diameter to 30 nm. The Ni-Co₃O₄ + rGO nanocrystals exhibit a band gap value of 2.0 eV. The bactericidal tests for S. aureus and E. coli revealed that the insertion rGO synthesized by the sol–gel method promoted the antimicrobial activity for both microorganisms. Afterward, the photocatalytic assay for the atrazine contaminant showed significant responses to pesticide removal attributed to the simultaneous adsorption and degradation process. In addition, the sol–gel process found a better response to Ni-Co₃O₄ in the presence of rGO, indicating a nanocomposite superior synergism. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis and Piezo-Photocatalysis)

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15 pages, 7050 KiB

Open AccessArticle

Controlled Synthesis of Europium-Doped SnS Quantum Dots for Ultra-Fast Degradation of Selective Industrial Dyes

by Govindhasamy Murugadoss, Jayavel Prakash, Manavalan Rajesh Kumar, Asma A. Alothman, Mohamed A. Habila and Shaik Gouse Peera

Catalysts 2022, 12(10), 1128; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12101128 - 27 Sep 2022

Cited by 4 | Viewed by 1942

Abstract

Herein, SnS and Eu-doped SnS QDs have been synthesized by a facile chemical co-precipitation method for efficient photocatalytic degradation of organic dye molecules. The structural, morphological, and optical properties of QDs were investigated by various physiochemical characterization techniques. The photocatalytic degradation of methylene blue (MB) and crystal violet (CV) dyes have been studied under visible light irradiation under direct sunlight using a spectrophotometer. Enhanced photodegradation efficiency of 87% and 94% were attained for SnS and Eu (4%)-doped SnS, respectively. For CV dye, the pure SnS showed only 70.7% however the Eu (4%)-doped SnS achieved 99% efficiency. The rate constant value of the doped SnS was found to be much higher than that of pure SnS for both dyes. The obtained results from various characterization studies provided the reason for the enhancement of the photocatalytic activity of Eu-doped SnS QDs due to the presence of Eu³⁺ in the SnS lattice, and also smaller crystallite size with high surface area and its morphological features. Moreover, the Eu³⁺ plays an essential role in reducing the band gap, hampering recombination, and the generation of free radicals, thus the QDs promoted attractive degradation activity and high stability. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis and Piezo-Photocatalysis)

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15 pages, 19109 KiB

Open AccessArticle

Biosynthesized Bimetallic (ZnOSnO₂) Nanoparticles for Photocatalytic Degradation of Organic Dyes and Pharmaceutical Pollutants

by Louisah M. Mahlaule-Glory, Sarah Mathobela and Nomso C. Hintsho-Mbita

Catalysts 2022, 12(3), 334; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12030334 - 16 Mar 2022

Cited by 9 | Viewed by 2230

Abstract

The quest for eco-friendly synthetic routes that can be used for the development of multifunctional materials, in particular for water treatment, has reinforced the use of plant extracts as replacement solvents. In this study, bimetallic ZnOSnO₂ nanoparticles of different ratios were synthesized using the Sutherlandia frutescens (S. frutescens) plant and tested for the degradation of methylene blue dye and the antibiotics sulfisoxazole and sulfamethoxazole. From the analysis, FTIR confirmed the formation of bimetallic nanoparticles in all ratios within the fingerprint region. SEM revealed homogenous and heterostructures of tubular and spherical structures, with the size distribution ranging from 5–60 nm, respectively. XRD confirmed the formation and the crystallinity of the bimetallic nanoparticles, UV-Vis confirmed the optical properties of the materials and the bandgap values were found between 3.08 and 3.3 eV. From the surface area analysis, type III isotherm and mesoporous structures were confirmed. The photocatalytic activity of these ratios was investigated against MB dye and the antibiotics SSX and SMX. The highest degradation of 88% for MB was obtained using the 50:50 loading ratio at 150 min with a fast kinetic rate of 0.0008 min⁻¹. Furthermore, the holes were the species found to be responsible for the degradation of MB. The SSX and SMX antibiotics exhibited a 66% and 70% degradation, respectively. From this analysis, it can be noted that it is possible to synthesize environmentally safe materials that can be used to degrade various pollutants in our water streams. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis and Piezo-Photocatalysis)

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16 pages, 6227 KiB

Open AccessArticle

Biophotocatalytic Reduction of CO₂ in Anaerobic Biogas Produced from Wastewater Treatment Using an Integrated System

by Emmanuel Kweinor Tetteh and Sudesh Rathilal

Catalysts 2022, 12(1), 76; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12010076 - 11 Jan 2022

Cited by 9 | Viewed by 1543

Abstract

This study presents the bio-photocatalytic upgrading of biogas utilising carbon dioxide (CO₂) as a potential option for beginning fossil fuel depletion and the associated environmental risks in the pursuit of sustainable development. Herein, magnetite photocatalyst (Fe-TiO₂) was employed with an integrated anaerobic-photomagnetic system for the decontamination of municipality wastewater for biogas production. The Fe-TiO₂ photocatalyst used, manufactured via a co-precipitation technique, had a specific surface area of 62.73 m²/g, micropore volume of 0.017 cm³/g and pore size of 1.337 nm. The results showed that using the ultraviolet-visible (UV-Vis) photomagnetic system as a post-treatment to the anaerobic digestion (AD) process was very effective with over 85% reduction in colour, chemical oxygen demand (COD) and turbidity. With an organic loading rate (OLR) of 0.394 kg COD/L·d and hydraulic retention time (HTR) of 21 days, a 92% degradation of the organic content (1.64 kgCOD/L) was attained. This maximised the bioenergy production to 5.52 kWh/m³ with over 10% excess energy to offset the energy demand of the UV-Vis lamp. Assuming 33% of the bioenergy produced was used as electricity to power the UV-Vis lamp, the CO₂ emission reduction was 1.74 kg CO₂ e/m³, with good potential for environmental conservation. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis and Piezo-Photocatalysis)

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20 pages, 3831 KiB

Open AccessArticle

Synthesis and Characterization of Zinc Oxide Nanoparticles Using Acacia caesia Bark Extract and Its Photocatalytic and Antimicrobial Activities

by Jayachandran Ashwini, Thankamani Ravikumar Aswathy, Anil Babu Rahul, Gautham M. Thara and Achuthsankar S. Nair

Catalysts 2021, 11(12), 1507; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11121507 - 10 Dec 2021

Cited by 28 | Viewed by 4657

Abstract

This paper presents the green synthesis and characterization of ZnO nanoparticles and their microbial and photocatalytic application. The green synthesis of ZnO nanoparticles was carried out using Zinc nitrate hexahydrate and the bark extract of Acacia caesia (L.) Willd. The nanoparticles were synthesized at an optimum temperature of 65 °C followed by calcination at 400 °C. The samples were characterized using UV-visible spectroscopy, SEM, XRD, FTIR and EDX analysis. UV-visible spectroscopy showed a characteristic peak at 338 nm and the bandgap energy was found to be 3 eV which is specific for ZnO. SEM confirmed the presence of ZnO on its nanoscale. EDX gave the elemental details of Zinc constituting to 37.77% and Oxygen comprising 20.77% of its atomic weight. XRD analysis gave the diffractogram indexed at various angles corresponding to ZnO nanoparticles. It also revealed the average crystalline size to be 32.32 nm and the shape was found to be hexagonal. The functional group present in the nanoparticles was characterized using FTIR, which gave a characteristic peak at 485 cm⁻¹. The synthesized nanoparticles exhibited significant photocatalytic (methyl blue under UV irradiation). The presence of nanoparticles induces changes in its kinetics, whose rate constants and correlation coefficients were analyzed during the photocatalytic degradation of the model pollutant Methyl Blue. Studies on antibacterial (Escherichia coli, Staphylococcus aureus), antifungal (Aspergillus niger, Candida albicans) and anti-inflammatory (COX assay) properties were also carried out. The nanoparticles were synthesized in an eco-friendly and cost-effective method. The study opens new horizons in the field of water treatment, biosensors and nanotechnology. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis and Piezo-Photocatalysis)

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Review

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29 pages, 3037 KiB

Open AccessReview

Transition Metal Dichalcogenides [MX₂] in Photocatalytic Water Splitting

by Paul O. Fadojutimi, Siziwe S. Gqoba, Zikhona N. Tetana and John Moma

Catalysts 2022, 12(5), 468; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12050468 - 22 Apr 2022

Cited by 12 | Viewed by 3770

Abstract

The quest for a clean, renewable and sustainable energy future has been highly sought for by the scientific community over the last four decades. Photocatalytic water splitting is a very promising technology to proffer a solution to present day environmental pollution and energy crises by generating hydrogen fuel through a “green route” without environmental pollution. Transition metal dichalcogenides (TMDCs) have outstanding properties which make them show great potential as effective co-catalysts with photocatalytic materials such as TiO₂, ZnO and CdS for photocatalytic water splitting. Integration of TMDCs with a photocatalyst such as TiO₂ provides novel nanohybrid composite materials with outstanding characteristics. In this review, we present the current state of research in the application of TMDCs in photocatalytic water splitting. Three main aspects which consider their properties, advances in the synthesis routes of layered TMDCs and their composites as well as their photocatalytic performances in the water splitting reaction are discussed. Finally, we raise some challenges and perspectives in their future application as materials for water-splitting photocatalysts. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis and Piezo-Photocatalysis)

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