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Recent Progress in the Synthesis and Applications of Photocatalysts

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Photochemistry".

Deadline for manuscript submissions: closed (31 January 2023) | Viewed by 19316

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Special Issue Editors

Dr. Muhammad Humayun

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Guest Editor

Wuhan National Laboratory for Optoelectronics, School of Optical and Electronics Information, Huazhong University of Science and Technology, Wuhan 430074, China
Interests: photocatalysis; photoelectrocatalysis

Prof. Dr. Chundong Wang

E-Mail Website
Guest Editor

School of Optical and Electronic Information, Wuhan National Laboratory for Optoelectronics, Optics Valley Laboratory, Huazhong University of Science and Technology, Wuhan 430074, China
Interests: photocatalysis; photoelectrocatalysis; electocatalysis; energy materials

Special Issue Information

Dear Colleagues,

In recent years, rapid advancement in industrialization and globalization has been mostly driven by fossil fuel consumption, which inevitably produces serious environmental hazards, such as carbon dioxide (green house gas) and organic wastes. Sustainable solar fuel production such as hydrogen from water splitting by semiconductor photocatalysis is a promising means for replacing traditional fossil fuels. The main scientific and technological challenges for effective photocatalysis include stability, robustness, and efficiency of semiconductor photocatalysts. Hence, for practical applications, researchers are trying to design and develop highly efficient and stable photocatalysts. Until now, numerous semiconductor photocatalysts have been fabricated and utilized in photocatalysis for clean energy production and environmental remediation.

The vision of this Special Issue is to present current research on the synthesis and application of newly designed photocatalysts. We invite researchers to contribute original articles and review articles that cover but are not limited to the following topics: Contributions on the synthesis, characterization, reaction mechanism, and photocatalytic applications of metal oxides, metal carbides, metal sulfides, and carbon materials; and plasmonic material-based photocatalysts.

Dr. Muhammad Humayun
Prof. Dr. Chundong Wang
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. Molecules is an international peer-reviewed open access semimonthly 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

synthesis
reaction mechanisms
CO₂ conversion
H₂ evolution
pollutants degradation

Published Papers (7 papers)

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Research

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18 pages, 8957 KiB

Open AccessArticle

ZnO Nanostructures Doped with Various Chloride Ion Concentrations for Efficient Photocatalytic Degradation of Methylene Blue in Alkaline and Acidic Media

by Razan A. Alshgari, Zaheer Ahmed Ujjan, Aqeel Ahmed Shah, Muhammad Ali Bhatti, Aneela Tahira, Nek Muhammad Shaikh, Susheel Kumar, Mazhar Hussain Ibupoto, Amal Elhawary, Ayman Nafady, Brigitte Vigolo and Zaffar Hussain Ibhupoto

Molecules 2022, 27(24), 8726; https://doi.org/10.3390/molecules27248726 - 09 Dec 2022

Cited by 3 | Viewed by 1458

Abstract

In this study, chloride (Cl⁻) ions were successfully doped into ZnO nanostructures by the solvothermal method. The effect of various Cl⁻ concentrations on the photocatalytic activity of ZnO towards the photodegradation of methylene blue (MB) under the illumination of ultraviolet light was studied. The as-prepared Cl⁻-doped ZnO nanostructures were analyzed in terms of morphology, structure, composition and optical properties. XRD data revealed an average crystallite size of 23 nm, and the XRD patterns were assigned to the wurtzite structure of ZnO even after doping with Cl⁻. Importantly, the optical band gap of various Cl ion-doped ZnO nanostructures was successively reduced from 3.42 to 3.16 eV. The photodegradation efficiency of various Cl⁻ ion-doped ZnO nanostructures was studied for MB in aqueous solution, and the relative performance of each Cl ion-doped ZnO sample was as follows: 20% Cl⁻-doped ZnO > 15% Cl⁻-doped ZnO > 10% Cl⁻-doped ZnO > 5% Cl⁻-doped ZnO > pristine ZnO. Furthermore, the correlation of the pH of the MB solution and each Cl ion dopant concentration was also investigated. The combined results of varying dopant levels and the effect of the pH of the MB solution on the photodegradation process verified the crucial role of Cl⁻ ions in activating the degradation kinetics of MB. Therefore, these newly developed photocatalysts could be considered as alternative materials for practical applications such as wastewater treatment. Full article

(This article belongs to the Special Issue Recent Progress in the Synthesis and Applications of Photocatalysts)

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13 pages, 2776 KiB

Open AccessArticle

Facile Synthesis of ZIF-67 for the Adsorption of Methyl Green from Wastewater: Integrating Molecular Models and Experimental Evidence to Comprehend the Removal Mechanism

by Muniba Ikram, Sadaf Mutahir, Muhammad Humayun, Muhammad Asim Khan, Jehan Y. Al-Humaidi, Moamen S. Refat and Amr S. Abouzied

Molecules 2022, 27(23), 8385; https://doi.org/10.3390/molecules27238385 - 01 Dec 2022

Cited by 5 | Viewed by 2437

Abstract

Organic dyes with enduring colors which are malodorous are a significant source of environmental deterioration due to their virulent effects on aquatic life and lethal carcinogenic effects on living organisms. In this study, the adsorption of methyl green (MG), a cationic dye, was achieved by using ZIF-67, which has been deemed an effective adsorbent for the removal of contaminants from wastewater. The characterization of ZIF-67 was done by FTIR, XRD, and SEM analysis. The adsorption mechanism and characteristics were investigated with the help of control batch experiments and theoretical studies. The systematical kinetic studies and isotherms were sanctioned with a pseudo-second-order model and a Langmuir model (R² = 0.9951), confirming the chemisorption and monolayer interaction process, respectively. The maximum removal capacities of ZIF-67 for MG was 96% at pH = 11 and T = 25 °C. DFT calculations were done to predict the active sites in MG by molecular electrostatic potential (MEP). Furthermore, both Molecular dynamics and Monte Carlo simulations were also used to study the adsorption mechanism. Full article

(This article belongs to the Special Issue Recent Progress in the Synthesis and Applications of Photocatalysts)

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14 pages, 3348 KiB

Open AccessArticle

Ni-Coated Diamond-like Carbon-Modified TiO₂ Nanotube Composite Electrode for Electrocatalytic Glucose Oxidation

by Yi Kang, Xuelei Ren, Yejun Li and Zhiming Yu

Molecules 2022, 27(18), 5815; https://doi.org/10.3390/molecules27185815 - 08 Sep 2022

Cited by 4 | Viewed by 1354

Abstract

In this paper, a Ni and diamond-like carbon (DLC)-modified TiO₂ nanotube composite electrode was prepared as a glucose sensor using a combination of an anodizing process, electrodeposition, and magnetron sputtering. The composition and morphology of the electrodes were analyzed by a scanning electron microscope and energy dispersive X-ray detector, and the electrochemical glucose oxidation performance of the electrodes was evaluated by cyclic voltammetry and chronoamperometry. The results show that the Ni-coated DLC-modified TiO₂ electrode has better electrocatalytic oxidation performance for glucose than pure TiO₂ and electrodeposited Ni on a TiO₂ electrode, which can be attributed to the synergistic effect between Ni and carbon. The glucose test results indicate a good linear correlation in a glucose concentration range of 0.99–22.97 mM, with a sensitivity of 1063.78 μA·mM⁻¹·cm⁻² and a detection limit of 0.53 μM. The results suggest that the obtained Ni-DLC/TiO₂ electrode has great application potential in the field of non-enzymatic glucose sensors. Full article

(This article belongs to the Special Issue Recent Progress in the Synthesis and Applications of Photocatalysts)

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16 pages, 5010 KiB

Open AccessArticle

Pyropheophorbide-a/(001) TiO₂ Nanocomposites with Enhanced Charge Separation and O₂ Adsorption for High-Efficiency Visible-Light Degradation of Ametryn

by Songtao Liu, Rui Yan, Muhammad Humayun, Huanli Zhang, Yang Qu and Yingxue Jin

Molecules 2022, 27(17), 5576; https://doi.org/10.3390/molecules27175576 - 30 Aug 2022

Cited by 2 | Viewed by 1140

Abstract

It is highly desired to enhance charge separation and O₂ adsorption of the pyropheophorbide-a (Ppa) to promote visible-light activity and stability. Herein, Ppa modified 001-facet-exposed TiO₂ nanosheets (Ppa/001T) nanocomposites with different weight ratios were fabricated via the self-assembly approach by OH induced. Compared with the bare Ppa, the 8% amount optimized 8Ppa/001T sample displayed 41-fold enhanced activity for degradation of Ametryn (AME) under visible-light irradiation. The promoted photoactivities could be attributed to the accelerated charge carrier’s separation by coupling TiO₂ as thermodynamic platform for accepting the photoelectrons with high energy from Ppa and the promoted O₂ adsorption because of the residual fluoride on TiO₂. As for this, a distinctive two radicals (•O₂⁻ and •OH) involved pathway of AME degradation is carried out, which is different from the radical pathway dominated by •O₂⁻ for the bare Ppa. This work is of utmost importance since it gives us detailed information regarding the charge carrier’s separation and the impact of the radical pathway that will pave a new approach toward the design of high activity visible-light driven photocatalysts. Full article

(This article belongs to the Special Issue Recent Progress in the Synthesis and Applications of Photocatalysts)

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13 pages, 6744 KiB

Open AccessArticle

Synthesis and Micromechanistic Studies of Sensitized Bentonite for Methyl Orange and Rhodamine-B Adsorption from Wastewater: Experimental and DFT-Based Analysis

by Sadaf Mutahir, Tayyaba Irfan, Nimra Nadeem, Muhammad Humayun, Muhammad Asim Khan, Moamen S. Refat, Chundong Wang and Tahir Ali Sheikh

Molecules 2022, 27(17), 5567; https://doi.org/10.3390/molecules27175567 - 29 Aug 2022

Cited by 10 | Viewed by 1673

Abstract

This work reports the formation of a novel adsorbent, prepared by activating bentonite with cinnamic acid, which is highly efficient to remove dyes from wastewater. The adsorption efficiency of the cinnamic acid activated bentonite was compared with unmodified bentonite by removing methyl orange and rhodamine-B from polluted water. The characterization was performed through X-ray diffraction (XRD) Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). The results indicated that acidic pH and low temperature were more suitable for the selected dyes adsorption. The analysis of the data was done by the Langmuir and Freundlich isotherms; the Freundlich isotherm showed more suitability for the equilibrium data. The data were further analyzed by pseudo-first and pseudo-second-order models to study adsorption kinetics. The results showed that methyl orange and rhodamine-B adsorption obeyed pseudo-order kinetics. The results obtained from this research suggested that acid activation of bentonite with cinnamic acid increased the surface area of the clay and hence enhanced its adsorption efficiency. The maximum adsorption efficiency for the removal of methyl orange and rhodamine-B was up to 99.3 mg g⁻¹ and 44.7 mg g⁻¹, respectively, at 25 °C. This research provides an economical modification technique of bentonite, which makes it cost-effective and a good adsorbent for wastewater treatment. Full article

(This article belongs to the Special Issue Recent Progress in the Synthesis and Applications of Photocatalysts)

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Review

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36 pages, 6643 KiB

Open AccessReview

MXenes as Emerging Materials: Synthesis, Properties, and Applications

by Ubaid Ur Rahman, Muhammad Humayun, Usman Ghani, Muhammad Usman, Habib Ullah, Adil Khan, Nashwa M. El-Metwaly and Abbas Khan

Molecules 2022, 27(15), 4909; https://doi.org/10.3390/molecules27154909 - 01 Aug 2022

Cited by 47 | Viewed by 6953

Abstract

Due to their unique layered microstructure, the presence of various functional groups at the surface, earth abundance, and attractive electrical, optical, and thermal properties, MXenes are considered promising candidates for the solution of energy- and environmental-related problems. It is seen that the energy conversion and storage capacity of MXenes can be enhanced by changing the material dimensions, chemical composition, structure, and surface chemistry. Hence, it is also essential to understand how one can easily improve the structure–property relationship from an applied point of view. In the current review, we reviewed the fabrication, properties, and potential applications of MXenes. In addition, various properties of MXenes such as structural, optical, electrical, thermal, chemical, and mechanical have been discussed. Furthermore, the potential applications of MXenes in the areas of photocatalysis, electrocatalysis, nitrogen fixation, gas sensing, cancer therapy, and supercapacitors have also been outlooked. Based on the reported works, it could easily be observed that the properties and applications of MXenes can be further enhanced by applying various modification and functionalization approaches. This review also emphasizes the recent developments and future perspectives of MXenes-based composite materials, which will greatly help scientists working in the fields of academia and material science. Full article

(This article belongs to the Special Issue Recent Progress in the Synthesis and Applications of Photocatalysts)

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17 pages, 4135 KiB

Open AccessReview

MoS₂ as a Co-Catalyst for Photocatalytic Hydrogen Production: A Mini Review

by Sayyar Ali Shah, Iltaf Khan and Aihua Yuan

Molecules 2022, 27(10), 3289; https://doi.org/10.3390/molecules27103289 - 20 May 2022

Cited by 27 | Viewed by 3527

Abstract

Molybdenum disulfide (MoS₂), with a two-dimensional (2D) structure, has attracted huge research interest due to its unique electrical, optical, and physicochemical properties. MoS₂ has been used as a co-catalyst for the synthesis of novel heterojunction composites with enhanced photocatalytic hydrogen production under solar light irradiation. In this review, we briefly highlight the atomic-scale structure of MoS₂ nanosheets. The top-down and bottom-up synthetic methods of MoS₂ nanosheets are described. Additionally, we discuss the formation of MoS₂ heterostructures with titanium dioxide (TiO₂), graphitic carbon nitride (g-C₃N₄), and other semiconductors and co-catalysts for enhanced photocatalytic hydrogen generation. This review addresses the challenges and future perspectives for enhancing solar hydrogen production performance in heterojunction materials using MoS₂ as a co-catalyst. Full article

(This article belongs to the Special Issue Recent Progress in the Synthesis and Applications of Photocatalysts)

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