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Catalysts
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Advances in Photocatalytic Degradation
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Advances in Photocatalytic Degradation

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

Deadline for manuscript submissions: 31 August 2025 | Viewed by 8161

Special Issue Editors

Dr. Socorro Oros-Ruiz

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Guest Editor
Investigadores por México, SECIHTI, Instituto de Física, Universidad Autónoma de San Luis Potosi, San Luis Potosi, SLP, Mexico
Interests: photocatalysis
Dr. Juan Carlos Durán-Álvarez

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Guest Editor
Department of Micro and Nanotechnologies, Institute of Applied Sciences and Technology, National Autonomous University of Mexico, Mexico City 04510, Mexico
Interests: photocatalytic processes
Special Issues, Collections and Topics in MDPI journals
Dr. Esmeralda Mendoza

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Guest Editor
Investigadores por México, Centro de Investigación y Estudios de Posgrado, Facultad de Ciencias Químicas, Universidad Autónoma de San Luis Potosí, Dr. Manuel Nava 6, San Luis Potosí 78210, Mexico
Interests: photocatalytic processes
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The rapid development of industrialization has led to excessive emissions of hazardous pollutants into our water and air resources, which has a negative impact on health and the environment. Photocatalysis is widely used to degrade and mineralize hazardous organic compounds, reduce toxic metal ions to their non-toxic states, deactivate and destroy waterborne microorganisms, decompose air pollutants including volatile organic compounds, NOx, CO, and NH3, remove pathogens from air, and degrade waste plastics.

This Special Issue is a collection of original research papers, reviews, and commentaries that address the development and application of innovative photocatalytic systems for environmental remediation. Submissions are welcome in, but are not limited to, the following areas:

  • Development of novel semiconductors and/or composites for environmental remediation;
  • Photocatalytic degradation of emerging contaminants in wastewater;
  • Photocatalytic hydrogen production
  • Use of photocatalysis for indoor and urban air quality intervention;
  • Scale-up approaches for photocatalytic degradation systems;
  • Economic and life cycle assessment for environmental remediation by photocatalysis.

Dr. Socorro Oros-Ruiz
Dr. Juan Carlos Durán-Álvarez
Dr. Esmeralda Mendoza
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 2200 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
  • composite materials
  • wastewater treatment
  • organic pollutants
  • dyes degradation
  • photocatalytic hydrogen production
  • emerging water contaminants
  • indoor air quality
  • urban air quality
  • life cycle analysis

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Published Papers (9 papers)

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Research

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24 pages, 6126 KiB  
Article
Enhanced H2 Production Efficiency in Photo-Reforming of PET Waste Plastic Using Dark-Deposited Atom/Nanocomposite Pt/TiO2 Photocatalysts
by E. M. N. Thiloka Edirisooriya, Punhasa S. Senanayake, Pei Xu and Huiyao Wang
Catalysts 2025, 15(4), 334; https://doi.org/10.3390/catal15040334 - 31 Mar 2025
Viewed by 247
Abstract
Photo-reforming waste polyethylene terephthalate (PET) in alkaline aqueous solutions is a novel approach for green hydrogen production. This study focuses on improving the catalytic efficiency of Pt/TiO2 for the photo-reforming of waste PET using an innovative dark deposition method to deposit Pt [...] Read more.
Photo-reforming waste polyethylene terephthalate (PET) in alkaline aqueous solutions is a novel approach for green hydrogen production. This study focuses on improving the catalytic efficiency of Pt/TiO2 for the photo-reforming of waste PET using an innovative dark deposition method to deposit Pt single atoms on nano TiO2 (Pt/TiO2), thereby increasing the catalytic efficiency while reducing the cost of the catalyst. The precursor concentration was optimized to control the size and distribution of the Pt clusters/atoms, and the TiO2 support was annealed at different temperatures to modify the properties of Pt/TiO2. Nine Pt/TiO2 catalysts were synthesized using different Pt precursor concentrations and annealing temperatures. The catalysts were characterized to measure their morphological, crystalline, and electronic properties, as well as their hydrogen yields via PET photo-reforming. The hydrogen conversion efficiency and external quantum yield (EQY) were calculated and compared with those of traditional direct-deposited catalysts. The correlation between the different characteristics of the dark-deposited and direct-deposited catalysts and their influence on the hydrogen yield in the photo-reforming process was statistically analyzed using principal component analysis. Catalysts deposited under dark conditions exhibited 5-fold and 7-fold enhancements in hydrogen conversion efficiency and EQY, respectively, compared to conventional catalytic systems. These findings indicate that the proposed catalytic system provides a viable solution for minimizing Pt loading, reducing the cost of the catalyst, and maintaining a higher hydrogen conversion efficiency. Full article
(This article belongs to the Special Issue Advances in Photocatalytic Degradation)
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23 pages, 4497 KiB  
Article
Eco-Friendly Mechanochemical Fabrication of Polypyrrole/Ag-ZnO Heterostructures for Enhanced Photocatalytic Degradation of Methyl Orange
by Muhammad Khalid Nazir, Muhammad Babar Taj, Azza A. Al-Ghamdi, Afaf Almasoudi, Fatimah Mohammad H. AlSulami, Hadeel M. Banbela, Omar Makram Ali, Muhammad Mahboob Ahmed, Muhammad Imran Khan, Abdallah Shanableh and Javier Fernandez-Garcia
Catalysts 2025, 15(3), 284; https://doi.org/10.3390/catal15030284 - 18 Mar 2025
Viewed by 523
Abstract
A Ppy/Ag-ZnO catalyst was successfully synthesized at room temperature using a novel, green methodology. It involves a mechanically assisted metathesis reaction. The Ppy/Ag-ZnO catalyst was analyzed via X-ray diffraction Technique (XRD), Thermogravimetric analysis (TGA), Differential scanning calorimetry (DSC), Fourier Transform Infrared (FTIR), Scanning [...] Read more.
A Ppy/Ag-ZnO catalyst was successfully synthesized at room temperature using a novel, green methodology. It involves a mechanically assisted metathesis reaction. The Ppy/Ag-ZnO catalyst was analyzed via X-ray diffraction Technique (XRD), Thermogravimetric analysis (TGA), Differential scanning calorimetry (DSC), Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM), UV–visible spectroscopy, Brunauer–Emmett–Teller (BET), and zeta potential. Debye Scherrer’s calculation suggested a crystallite size of 2.30 nm for Ppy/Ag-ZnO nanocomposite. SEM confirmed the production of aggregated particles with an average size of 2.65 μm, endorsing the -ve zeta potential value (−6.78 mV) due to the presence of Van der Waals forces among the particles of Ppy/Ag-ZnO. DSC confirms that the strong interfacial interaction between Ag-ZnO and the polar segments of Ppy is responsible for the higher Tg (107 °C) and Tm (270 °C) in Ppy/Ag-ZnO. The surface area and average pore size of Ppy/Ag-ZnO catalyst were determined to be 47.08 cm3/g and 21.72 Å, respectively. Methyl orange (MO) was used as a probe in a photocatalytic reaction of fabricated material, which demonstrated exceptional efficiency, exhibiting a removal rate of 91.11% with a rate constant of 0.028 min−1. Photocatalytic degradation of MO was shown to follow pseudo-first-order kinetics. Full article
(This article belongs to the Special Issue Advances in Photocatalytic Degradation)
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20 pages, 4800 KiB  
Article
Photodegradation of Emerging Pollutants Using a Quaternary Mixed Oxide Catalyst Derived from Its Corresponding Hydrotalcite
by L. V. Castro, B. Alcántar-Vázquez, M. E. Manríquez, E. Albiter and E. Ortiz-Islas
Catalysts 2025, 15(2), 173; https://doi.org/10.3390/catal15020173 - 13 Feb 2025
Cited by 1 | Viewed by 871
Abstract
This study aimed to synthesize a multicationic hydrotalcite and transform it into mixed oxide nanostructures (ZnO/TiO2/CeO2/Al2O3, referred to as MixO) to serve as a heterogeneous photocatalyst for degrading various pollutants, including methylene blue (MB), methyl [...] Read more.
This study aimed to synthesize a multicationic hydrotalcite and transform it into mixed oxide nanostructures (ZnO/TiO2/CeO2/Al2O3, referred to as MixO) to serve as a heterogeneous photocatalyst for degrading various pollutants, including methylene blue (MB), methyl orange (MO), paracetamol (PA), and paraquat (PQ). The hydrotalcite was synthesized via an ultrasound-assisted method and calcined at 700 °C to obtain the corresponding mixed metal oxide. A comprehensive characterization of both the multicationic hydrotalcite (MC-LDH) and the mixed metal oxides (MixO) was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), N2 adsorption–desorption, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and pHPZC analysis. The MixO sample exhibited an optical bandgap of 3.19 eV. Photocatalytic performance was evaluated during 240 min of UV irradiation, demonstrating high degradation efficiencies attributable to the synergistic interactions among ZnO, TiO2, and CeO2. Degradation efficiencies reached 99.3% for MO and 95.2% for MB, while PA and PQ showed moderate degradation rates of 60% and 15%, respectively. The degradation kinetics of all pollutant compounds followed the Langmuir–Hinshelwood model. Additionally, the MixO catalyst maintained consistent performance over four consecutive degradation cycles, highlighting its reusability and stability. These findings underscore the potential of MixO mixed oxide nanostructures as practical and recyclable photocatalysts for environmental remediation, particularly in wastewater treatment applications. Full article
(This article belongs to the Special Issue Advances in Photocatalytic Degradation)
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18 pages, 5386 KiB  
Article
Photocatalytic Oxidation of Pesticides with TiO2-CeO2 Thin Films Using Sunlight
by Tania Arelly Tinoco Pérez, Evaristo Salaya Gerónimo, José Gilberto Torres Torres, Gloria Alicia del Angel Montes, Israel Rangel Vázquez, Adrian Cordero García, Adrian Cervantes Uribe, Adib Abiu Silahua Pavon and Juan Carlos Arevalo Pérez
Catalysts 2025, 15(1), 46; https://doi.org/10.3390/catal15010046 - 6 Jan 2025
Viewed by 859
Abstract
TiO2 thin film coatings significantly improve catalyst separation in photocatalytic processes. They can be applied in heterogeneous photocatalysis under sunlight by mixing TiO2 with other oxides, such as CeO2, for the removal of pollutants in water. Here, TiO2 [...] Read more.
TiO2 thin film coatings significantly improve catalyst separation in photocatalytic processes. They can be applied in heterogeneous photocatalysis under sunlight by mixing TiO2 with other oxides, such as CeO2, for the removal of pollutants in water. Here, TiO2-CeO2 thin films deposited on borosilicate slides were analyzed and applied in solar heterogeneous photocatalysis for the oxidation of pesticides. The films were synthesized by the sol-gel method with spin coating. The waste solutions from the synthesis were used to prepare TiO2 and TiO2-CeO2 powders. These were analyzed by XRD and XPS to explain the behavior of the films. The thin films were characterized by UV-Vis spectroscopy with transmittance, UV-Vis spectroscopy with RDS, profilometry, AFM and SEM. The addition of CeO2 to TiO2 caused a decrease in the average crystal size and an increase in the strain index. The addition of a second layer made the TiO2-CeO2 thin films thinner. The CeO2 created surface and electronic defects in the titania films, which enhanced their photocatalytic properties under sunlight in the mineralization of diuron and methyl parathion. The TiO2-CeO2-5.0% single-layer thin film samples were the most active in this study and will undoubtedly be applied in larger-scale reaction systems. Full article
(This article belongs to the Special Issue Advances in Photocatalytic Degradation)
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25 pages, 7157 KiB  
Article
Green Synthesis of Photocatalytically Active ZnO Nanoparticles Using Chia Seed Extract and Mechanistic Elucidation of the Photodegradation of Diclofenac and p-Nitrophenol
by Yossra Ounis Dkhil, Tim Peppel, Michael Sebek, Jennifer Strunk and Ammar Houas
Catalysts 2025, 15(1), 4; https://doi.org/10.3390/catal15010004 - 24 Dec 2024
Viewed by 1083
Abstract
Zinc oxide nanoparticles (ZnO NPs) were synthesized using a simple and eco-friendly precipitation method, employing a capping agent derived from chia seeds (Salvia hispanica). X-ray diffraction (XRD) analysis confirmed the formation of ZnO with a hexagonal crystal structure and an average [...] Read more.
Zinc oxide nanoparticles (ZnO NPs) were synthesized using a simple and eco-friendly precipitation method, employing a capping agent derived from chia seeds (Salvia hispanica). X-ray diffraction (XRD) analysis confirmed the formation of ZnO with a hexagonal crystal structure and an average crystallite size of less than 30 nm. Scanning electron microscopy (SEM) revealed distinct quasi-spherical and nanorod-like morphologies, while energy-dispersive X-ray spectroscopy (EDX) verified the presence of zinc and oxygen. Diffuse reflectance spectroscopy (DRS) indicated significant activity in the UV region, with the nanoparticles exhibiting a band gap of 3.25 eV. The photocatalytic efficiency of the synthesized ZnO NPs was evaluated through their ability to degrade diclofenac sodium (DCF) and para-nitrophenol (4-nitrophenol, PNP) under UV-LED irradiation, achieving pollutant removal rates exceeding 98%. The degradation mechanism is clarified by a detailed characterization of the reaction intermediates. These findings highlight the potential of ZnO NPs synthesized from chia seed extract for effective environmental remediation of pharmaceutical and organic pollutants. Full article
(This article belongs to the Special Issue Advances in Photocatalytic Degradation)
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20 pages, 12643 KiB  
Article
Titanium Dioxide 1D Nanostructures as Photocatalysts for Degradation and Removal of Pollutants in Water
by Dora María Frías Márquez, José Ángel Méndez González, Rosendo López González, Cinthia García Mendoza, Francisco Javier Tzompantzi Morales, Patricia Quintana Owen and Mayra Angélica Alvarez Lemus
Catalysts 2024, 14(12), 896; https://doi.org/10.3390/catal14120896 - 6 Dec 2024
Viewed by 1048
Abstract
The oxidation of organic pollutants in water is the most reported application of a Titanium dioxide (TiO2) photocatalyst. During the last decade, photoreduction with TiO2 has also been explored but simultaneous capabilities for unmodified TiO2 have not been reported [...] Read more.
The oxidation of organic pollutants in water is the most reported application of a Titanium dioxide (TiO2) photocatalyst. During the last decade, photoreduction with TiO2 has also been explored but simultaneous capabilities for unmodified TiO2 have not been reported yet. Here, we reported on the fabrication of TiO2 nanorods using hydrothermal treatment and compared the effect of two different TiO2 powders as the starting material: P-25 and TiO2 sol–gel (N-P25 and N-TiO2, respectively) which were further calcined at 400 °C (N-P25-400 and N-TiO2-400). XPS and XRD analyses confirmed the presence of sodium and hydrogen titanates in N-P25, but also an anatase structure for N-TiO2. The specific surface area of the calcined samples decreased compared to the dried samples. Photocatalytic activity was evaluated using phenol and methyl orange for degradation, whereas 4-nitrophenol was used for photoreduction. Irradiation of the suspension was performed under UV light (λ = 254 nm). The results demonstrated that the nanorods calcined at 400 °C were more photoactive since methyl orange (20 ppm) degradation reached 86% after 2 h, when N-TiO2-400 was used. On the other hand, phenol (20 ppm) was completely degraded by the presence of N-P25-400 after 2 h. Photoreduction of 4-nitrophenol (5 ppm) was achieved by the N-TiO2-400 during the same period. These results demonstrate that the presence of Ti3+ and the source of TiO2 have a significant effect on the photocatalytic activity of TiO2 nanorods. Additionally, the removal of methylene blue (20 ppm) was performed, demonstrating that N-TiO2 exhibited a high adsorption capacity for this dye. Full article
(This article belongs to the Special Issue Advances in Photocatalytic Degradation)
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15 pages, 7227 KiB  
Article
Hydrogen Production Through Water Splitting Reactions Using Zn-Al-In Mixed Metal Oxide Nanocomposite Photocatalysts Induced by Visible Light
by Monserrat Suárez-Quezada, Víctor Manuel Suárez-Quezada, Fernando Tobola-Inchaurregui, Socorro Oros-Ruiz and Sandra Cipagauta-Díaz
Catalysts 2024, 14(11), 835; https://doi.org/10.3390/catal14110835 - 20 Nov 2024
Cited by 1 | Viewed by 1166
Abstract
In this study, the synthesis of hybrid photocatalysts of Zn-Al-In mixed metal oxides were activated by using visible light, derived from Zn-Al-In layered double hydroxide (ZnAlIn-LDH), and these nanocomposites demonstrated high efficiency for photocatalytic H2 production under UV light when using methanol [...] Read more.
In this study, the synthesis of hybrid photocatalysts of Zn-Al-In mixed metal oxides were activated by using visible light, derived from Zn-Al-In layered double hydroxide (ZnAlIn-LDH), and these nanocomposites demonstrated high efficiency for photocatalytic H2 production under UV light when using methanol as a sacrificial agent. The most active photocatalytic material produced 372 μmol h−1 g−1 of H2. The characterization of these materials included X-ray diffraction (DRX), infrared spectroscopy (FTIR), X-ray fluorescence spectroscopy (XRF), X-ray spectroscopy (XEDS), scanning electron microscopy analysis (SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy, and N2- physisorption. In addition, the materials were characterized by photoelectrochemical techniques to explain the photocatalytic behavior. Subsequently, the photocatalytic performance for the water-splitting reactions under visible irradiation was evaluated. The ZnAlIn-MMOs with an In/(Al + In) molar ratio of 0.45 exhibited the highest photocatalytic activity in tests under visible light, attributed to the efficient separation and transport of photogenerated charge carriers originating from the new nanocomposite. This discovery indicates a method for developing new types of heteronanostructured photocatalysts which are activated by visible light. Full article
(This article belongs to the Special Issue Advances in Photocatalytic Degradation)
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Review

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30 pages, 2863 KiB  
Review
Occurrence, Ecotoxicity, and Photocatalytic Remediation of Antiretroviral Drugs in Global Surface Water Matrices
by Phephile Ngwenya, Lehlogonolo S. Tabana, Shepherd M. Tichapondwa and Evans M. N. Chirwa
Catalysts 2025, 15(4), 381; https://doi.org/10.3390/catal15040381 - 15 Apr 2025
Viewed by 505
Abstract
The increasing presence of pharmaceuticals, particularly antiretroviral drugs (ARVs), in wastewater has raised concerns regarding their environmental and health impacts. Photocatalysis, driven by advanced photocatalysts, such as coloured TiO2, ZnO, and composites with carbon-based materials, has shown promise as an effective [...] Read more.
The increasing presence of pharmaceuticals, particularly antiretroviral drugs (ARVs), in wastewater has raised concerns regarding their environmental and health impacts. Photocatalysis, driven by advanced photocatalysts, such as coloured TiO2, ZnO, and composites with carbon-based materials, has shown promise as an effective method for degrading these pollutants. Despite significant laboratory-scale success, challenges remain in scaling this technology for real-world applications, particularly in terms of photocatalyst stability, the formation of toxic degradation by-products, and economic feasibility. This paper explores the current state of photocatalytic degradation for ARVDs, emphasizing the need for further research into degradation pathways, the development of more efficient and cost-effective photocatalysts, and the integration of photocatalysis into hybrid treatment systems. The future of photocatalysis in wastewater treatment hinges on improving scalability, reactor design, and hybrid systems that combine photocatalysis with traditional treatment methods to ensure comprehensive pollutant removal. Innovations in catalyst design and reactor optimization are essential for advancing photocatalysis as a viable solution for large-scale wastewater treatment. Full article
(This article belongs to the Special Issue Advances in Photocatalytic Degradation)
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21 pages, 1288 KiB  
Review
Recent Advances in Congo Red Degradation by TiO2-Based Photocatalysts Under Visible Light
by Gabriela Elizabeth Quintanilla-Villanueva, Analía Sicardi-Segade, Donato Luna-Moreno, Raisa Estefanía Núñez-Salas, Juan Francisco Villarreal-Chiu and Melissa Marlene Rodríguez-Delgado
Catalysts 2025, 15(1), 84; https://doi.org/10.3390/catal15010084 - 17 Jan 2025
Viewed by 1409
Abstract
Congo Red is a complex aromatic azo dye whose metabolites can be toxic due to their carcinogenicity, mutagenicity, and various associated toxic effects on flora, fauna, and humans. Different technologies have been employed to degrade this dye, including biodegradation, radiation-based degradation, and chemical [...] Read more.
Congo Red is a complex aromatic azo dye whose metabolites can be toxic due to their carcinogenicity, mutagenicity, and various associated toxic effects on flora, fauna, and humans. Different technologies have been employed to degrade this dye, including biodegradation, radiation-based degradation, and chemical degradation with catalysts and photocatalysis. Among these, the use of TiO2-based materials combined with photocatalysis has proven to be an effective technology for its degradation. However, the wide bandgap of TiO2 limits its efficiency under visible light, prompting the need for modifications such as doping with metals, metalloids, and organic compounds. These modifications enhance its photocatalytic performance under visible light, achieving degradation efficiencies of up to 100% under optimal conditions. This article explores recent advances (from 2020 to the present) in the degradation of Congo Red using TiO2-based photocatalysts under visible light, focusing on their characteristics, synthesis methods, and degradation efficiencies. Additionally, it compares the TiO2-based photocatalysis with visible light to other available technologies, emphasizing its potential as a sustainable and efficient approach while addressing the importance of monitoring degradation byproducts to prevent the generation of equally or more toxic compounds. Full article
(This article belongs to the Special Issue Advances in Photocatalytic Degradation)
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