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Recent Developments in Photo-/Electrocatalysis: A Themed Issue in Honor of Prof. Trong-On Do

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

Deadline for manuscript submissions: 31 October 2026 | Viewed by 16106

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Special Issue Editors

Dr. Sakar Mohan

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Guest Editor

Centre for Nano and Material Sciences, Jain University, Bengaluru 562112, Karnataka, India
Interests: photocatalysis; biomass conversion; perovskites; multiferroics; plasmonics; nanomaterials for energy and environmental applications
Special Issues, Collections and Topics in MDPI journals

Dr. Maria Vittoria Diamanti

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Guest Editor

Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Via Mancinelli 7, 20131 Milan, Italy
Interests: titanium dioxide; titanium anodizing; anodic oxidation; plasma electrolytic oxidation; TiO₂ nanotubes; TiO₂ coatings for photocatalysis; self-cleaning; corrosion resistance; self-cleaning materials for the built environment; interference colors in thin films
Special Issues, Collections and Topics in MDPI journals

Dr. Chinh Chien Nguyen

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Guest Editor

1. Center for Advanced Chemistry, Institute of Research and Development, Duy Tan University, Danang 550000, Vietnam
2. Faculty of Natural Sciences, Duy Tan University, Danang 550000, Vietnam
Interests: CO₂ hydrogenation; high-value chemicals; photocatalysts; electrocatalysts; reactor design

Special Issue Information

Dear Colleagues,

Photo-/electrocatalysis has emerged as a powerful and versatile technology for addressing global challenges related to energy, environment, and sustainability. Over the years, significant advancements have been made in the design and development of novel photo-/electrocatalysts with enhanced activity, selectivity, and stability under visible or solar light. This Special Issue of Catalysts, titled "Recent Developments in Photo-/Electrocatalysis: A Themed Issue in Honor of Prof. Trong-On Do", is dedicated to celebrating the impactful scientific contributions of Professor Trong-On Do, Department of Chemical Engineering, Laval University, Canada, in the field of catalysis and photo-/electrocatalysis.

Prof. Do is renowned for his pioneering work on the synthesis and application of advanced catalytic materials, including metal oxides, zeolites, hybrid nanostructures, and supported catalysts for environmental remediation, hydrogen production, CO₂ conversion, and biomass valorization. This Special Issue aims to highlight the recent developments and emerging trends in photo-/electrocatalysis, reflecting the breadth and depth of the field that Prof. Do has helped shape.

Areas of interest include but are not limited to the following:

Design and synthesis of novel photo-/electrocatalytic materials;
Mechanistic insights into photo-/electrocatalytic reactions;
Photocatalysis for environmental purification;
Photo-/electrocatalytic CO₂ reduction;
Solar-driven water splitting, hydrogen generation, and N₂ fixation;
Photocatalytic biomass conversion and valorization;
Heterojunction and Z-scheme photocatalysts;
Visible light and plasmonic photocatalysis;
Photo-/electrocatalyst characterization and structure–activity relationships;
Computational studies and modeling of photocatalytic systems;
Scale-up strategies and reactor design for practical photocatalytic applications.

We welcome original research articles, short communications, reviews, and perspectives that provide valuable insights into the current progress and future directions of photocatalysis. Contributions that reflect interdisciplinary approaches and explore novel concepts, mechanisms, and materials are particularly encouraged.

This Special Issue will serve not only as a tribute to Prof. Trong-On Do’s lasting legacy in the catalysis community but also as a platform to inspire future innovations in photo-/electrocatalysis.

Dr. Sakar Mohan
Dr. Maria Vittoria Diamanti
Dr. Chinh Chien Nguyen
Guest Editors

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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.

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Keywords

band-gap engineering
heterojunctions
doping
surface plasmon resonance
photocatalysis
photoelectrocatalysis
energy generation
environmental remediation

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Published Papers (13 papers)

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24 pages, 3258 KB

Open AccessArticle

Eco-Friendly Synthesis of Zn-Doped CuO Nanoparticles Using Aloysia citrodora Extract for Highly Efficient Fenton-like Dye Degradation

by Aicha Hazmoune, Chahra Boukaous, Mazen S. F. Al-Hazeef, Mohammed Salah Aida, Farid Fadhillah, Amine Aymen Assadi, Abdeltif Amrane, Fekri Abdulraqeb Ali, Jie Zhang and Hichem Tahraoui

Catalysts 2026, 16(4), 352; https://doi.org/10.3390/catal16040352 - 14 Apr 2026

Viewed by 516

Abstract

The development of efficient, sustainable, and low-cost catalysts for wastewater treatment remains a major environmental challenge. In this work, Zn-doped CuO nanostructures were successfully synthesized via a green route using Aloysia citrodora leaf extract as a natural reducing and stabilizing agent. The structural and morphological properties of the prepared catalysts were systematically characterized by XRD, Raman spectroscopy, FTIR, SEM, and EDX analyses. The results revealed the formation of highly crystalline monoclinic CuO nanoparticles, whose defect density and surface properties were significantly modified by Zn incorporation. The catalytic performance of the synthesized materials was evaluated through the heterogeneous Fenton-like degradation of Rhodamine B in aqueous solution under dark conditions. The Zn-doped CuO catalyst exhibited outstanding degradation efficiency (~99.97%) within only 30 min, using a low catalyst dosage of 15 mg and a minimal H₂O₂ amount of 25 μL. The enhanced catalytic activity is attributed to the synergistic interaction between Zn-induced lattice defects and the Cu²⁺/Cu⁺ redox cycle, which promotes efficient H₂O₂ activation and •OH radical generation. Radical scavenging experiments confirmed the dominant role of hydroxyl radicals in the degradation process. Compared with previously reported CuO-based catalysts, the present system demonstrates superior performance in terms of reaction rate, oxidant consumption, and energy efficiency. These findings highlight the potential of Zn-doped CuO synthesized via green chemistry as a promising and sustainable catalyst for advanced wastewater treatment applications. Full article

(This article belongs to the Special Issue Recent Developments in Photo-/Electrocatalysis: A Themed Issue in Honor of Prof. Trong-On Do)

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18 pages, 3770 KB

Open AccessArticle

A Multifunctional Nickel-Based Metal–Organic Framework (MOF) for Hydrogen Production, Supercapacitors, and Electrocatalysis

by Zeinab Hussein Hashem, Laila H. Abdel-Rahman, Santiago Gómez-Ruiz and Hani Nasser Abdelhamid

Catalysts 2026, 16(3), 283; https://doi.org/10.3390/catal16030283 - 22 Mar 2026

Viewed by 1106

Abstract

The nickel-derived metal–organic framework (MOF), Ni-BTB, synthesized from 4,4′,4″-benzene-1,3,5-tribenzoic acid (H₃BTB), was investigated as a multifunctional platform for enhanced energy applications including production and storage. In catalytic hydrogen generation by NaBH₄ hydrolysis, Ni-BTB attained a hydrogen generation rate (HGR) of 4640 mL H₂/g•min with 1 mg of catalyst, with an activation energy of 76.44 kJ/mol. Under optimized reaction conditions (60 °C, 20 mg catalyst, and 1 g NaBH₄), the HGR increased to 9542 mL H₂/g•min, while exhibiting high recyclability throughout four successive cycles. As a supercapacitor electrode, Ni-BTB achieved a specific capacitance of 156 F/g at 1 A/g and showed remarkable cycling stability, maintaining its capacitance after 10,000 charge–discharge cycles. Furthermore, Ni-BTB exhibited exceptional electrocatalytic activity for oxygen evolution reaction (OER), requiring only 106 mV overpotential to achieve 10 mA/cm², offering a time-of-flight (TOF) of 0.0585 s⁻¹ and demonstrating significant operational longevity of at least 12 h. These findings underscore Ni-BTB as a durable, reusable, and adaptable material for hydrogen production, energy storage, and electrocatalytic applications. Full article

(This article belongs to the Special Issue Recent Developments in Photo-/Electrocatalysis: A Themed Issue in Honor of Prof. Trong-On Do)

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18 pages, 4002 KB

Open AccessArticle

Hierarchical In₂MnS₄ Flower-like Architectures for Efficient Dye Degradation and Methanol Oxidation

by Nunna Guru Prakash, Zakia Hassan Alhashem, Surya Veerendra Prabhakar Vattikuti and Shrouq H. Aleithan

Catalysts 2026, 16(3), 216; https://doi.org/10.3390/catal16030216 - 1 Mar 2026

Viewed by 475

Abstract

Hierarchical In₂MnS₄ microflowers were synthesized via a hydrothermal approach and evaluated as multifunctional photo-/electrocatalysts for crystal violet (CV) dye degradation and methanol oxidation. The synthesis strategy produced three-dimensional flower-like architectures composed of nanoscale subunits with high crystallinity and uniform elemental distribution. Optical characterization revealed strong visible-light absorption with a bandgap of approximately 1.74 eV, indicating suitability for solar-driven photocatalysis. In₂MnS₄ microflowers achieved 96.6% degradation of CV dye within 100 min, whereas negligible activity was observed without the catalyst. Kinetic analysis followed a pseudo-first-order model with an apparent rate constant of 0.029 min⁻¹. The catalyst maintained stable performance over four consecutive cycles, confirming good recyclability. Photoelectrochemical measurements showed a stable photocurrent response and reduced charge-transfer resistance, indicating efficient separation and transport of photogenerated charge carriers. Furthermore, electrochemical measurements revealed increased anodic responses and sustained current behavior in the presence of methanol, suggesting an electrochemical response upon methanol addition. These results highlight In₂MnS₄ microflowers as promising visible-light-responsive materials for environmental remediation and energy-related catalytic applications. Full article

(This article belongs to the Special Issue Recent Developments in Photo-/Electrocatalysis: A Themed Issue in Honor of Prof. Trong-On Do)

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20 pages, 3086 KB

Open AccessArticle

H₂O₂-Assisted Sunlight Photocatalytic Degradation of Basic Fuchsin Using Green-Synthesized ZnO Nanowires

by Aicha Hazmoune, Chahra Boukaous, Sabrina Iaiche, Boubaker Benhaoua, Farid Fadhillah, Amine Aymen Assadi, Abdeltif Amrane, Fekri Abdulraqeb Ahmed Ali, Jie Zhang, Mohammed Kebir and Hichem Tahraoui

Catalysts 2026, 16(2), 193; https://doi.org/10.3390/catal16020193 - 18 Feb 2026

Cited by 1 | Viewed by 822

Abstract

The efficient removal of toxic dyes from wastewater remains a major environmental challenge. In this study, we report a green and facile one-pot synthesis of zinc oxide nanowires (ZnO-NWs) using lemon verbena leaf extract as a sustainable capping and stabilizing agent. The extract played a vital role in directing the 1D growth of the wurtzite hexagonal structure. Characterization confirmed a band gap of 3.12 eV and the characteristic Zn-O stretching at 375 cm⁻¹. Photocatalytic activity tests using 20 mg of biosynthesized ZnO-NWs demonstrated excellent degradation performance. A rate constant of 0.0067 min⁻¹ was achieved, with 99.95% degradation of Basic Fuchsin under natural sunlight for 3 h. Active species analysis highlighted the crucial roles of holes (h⁺), superoxide radicals (O₂•⁻), and hydroxyl radicals (•OH). Notably, the addition of 10 mM H₂O₂ produced a powerful synergistic effect, reducing the degradation time from 3 h to only 7 min and increasing the reaction rate by approximately 25-fold. These findings highlight the potential of biosynthesized ZnO-NWs as highly efficient, rapid, and sustainable photocatalysts for environmental remediation. Full article

(This article belongs to the Special Issue Recent Developments in Photo-/Electrocatalysis: A Themed Issue in Honor of Prof. Trong-On Do)

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14 pages, 1360 KB

Open AccessFeature PaperArticle

Electrochemical Reduction of CO₂ Using Polycrystalline Phosphorus-Doped Diamond Electrode

by Tomokiyo Moriguchi and Yasuaki Einaga

Catalysts 2026, 16(1), 54; https://doi.org/10.3390/catal16010054 - 2 Jan 2026

Viewed by 930

Abstract

In this study, we investigated the electrochemical reduction of carbon dioxide (CO₂) using a phosphorus-doped polycrystalline diamond (PDD) electrode and compared it with a conventional boron-doped diamond (BDD) electrode. In the reduction reaction of CO₂ in a 0.5 M KCl aqueous solution, the PDD electrode showed high selectivity for formic acid production over a wide potential range. This tendency was particularly evident at potentials below −1.8 V (vs. RHE). Moreover, at more negative potentials of −2.4 V and −2.6 V, formic acid remained the dominant product, while hydrogen evolution was the main reaction on the BDD electrode at the negative potentials. Similarly, in electrochemical reduction using an 0.1 M KClO₄ aqueous solution, carbon monoxide was confirmed to be a major product, and hydrogen generation was effectively suppressed in a more negative potential range. In other words, PDD is a promising electrode material that can efficiently convert CO₂ into valuable chemicals while suppressing hydrogen evolution, even in negative potential regions. Full article

(This article belongs to the Special Issue Recent Developments in Photo-/Electrocatalysis: A Themed Issue in Honor of Prof. Trong-On Do)

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20 pages, 3405 KB

Open AccessArticle

One-Pot Direct Synthesis of b-Axis-Oriented and Al-Rich ZSM-5 Catalyst via NH₄NO₃-Mediated Crystallization for CO₂ Hydrogenation

by Mohammad Rostamizadeh, Chi-Cong Tran, Trong-On Do and Serge Kaliaguine

Catalysts 2026, 16(1), 47; https://doi.org/10.3390/catal16010047 - 2 Jan 2026

Cited by 1 | Viewed by 934

Abstract

Al-rich NH₄-ZSM-5 with highly oriented crystals was directly synthesized through a one-pot hydrothermal technique, using ammonium nitrate as a metal-free mineralizer. The samples were characterized by XRD, N₂ adsorption–desorption, SEM, FTIR, Py-FTIR, ²⁷Al MAS NMR, ²⁹Si MAS NMR, ¹H MAS NMR, and TGA techniques. The impact of aluminum source, ammonium source, and H₂O/SiO₂ molar ratio was studied. XRD results showed that the ZSM-5 catalyst with a low Si/Al ratio (13) was successfully synthesized without any amorphous phase, including a microporous/mesoporous structure. A low H₂O/SiO₂ molar ratio (75) resulted in coffin-shape surface morphology, large b-axis-oriented particles (ca. 19 µm), and high specific surface area (>300 m² g⁻¹), providing a large portion of straight channels (90.5%). The catalytic activity of the catalysts was evaluated in the CO₂ hydrogenation reaction in tandem configuration with a Na/Fe₂O₃ catalyst. The results confirmed that highly b-oriented crystals improved the product shape selectivity to p-xylene by affecting the diffusion resistance. Therefore, the developed catalyst provided high CO₂ conversion (45%) and high aromatic selectivity (77%), with p-xylene accounting for 82% of the produced xylene compounds, over a long-term time on stream (17 h). These results demonstrate the effectiveness of the direct synthesis strategy in producing Al-rich ZSM-5 catalysts with tailored textural and acidic properties for tandem and shape-selective catalysis. Full article

(This article belongs to the Special Issue Recent Developments in Photo-/Electrocatalysis: A Themed Issue in Honor of Prof. Trong-On Do)

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15 pages, 5390 KB

Open AccessFeature PaperArticle

Sequential Multilayer Design with SnO₂-Layer Decoration for Inhibiting Photocorrosion of Cu₂O Photocathode

by Jiawei Yan, Kai Takagi, Zhidong Wei, Masaya Motodate, Jiasheng Chi, Yong Zhu, Chiaki Terashima, Wenfeng Shangguan and Akira Fujishima

Catalysts 2026, 16(1), 37; https://doi.org/10.3390/catal16010037 - 1 Jan 2026

Viewed by 623

Abstract

The Cu₂O-based photocathode has been widely applied in photoelectrocatalytic hydrogen evolution and carbon dioxide reduction systems. However, the poor stability of Cu₂O caused by photocorrosion highly restricts the application. In this work, a multilayer configuration is designed as Cu₂O/ZnO/SnO₂ via sequential depositions of electrodeposition and spin-coating. The liquid-phase epitaxial growths of the Cu₂O and ZnO layers are achieved by sequential electrodepositions on a FTO/Au substrate. The decoration of a uniform SnO₂ layer onto Cu₂O/ZnO is realized by a SnO₂ QDs coating and provides dual functions for boosted electron transfer and surface reaction. The protection of the SnO₂ layer is fulfilled by the inhibition of Cu⁺ transformation, resulted from the compact covering of SnO₂ QDs onto the exposed surface of the Cu₂O and ZnO layers. Consequently, the enhanced photocurrent density and improved stability are obtained for Cu₂O/ZnO/SnO₂ compared to bare Cu₂O and Cu₂O/ZnO sample photocathodes. The necessary role of SnO₂ QDs serving as electron transfer and protection layers studied in this work reveals the remarkable potential in the modification of other vulnerable electrode materials. Full article

(This article belongs to the Special Issue Recent Developments in Photo-/Electrocatalysis: A Themed Issue in Honor of Prof. Trong-On Do)

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Review

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25 pages, 2424 KB

Open AccessReview

Balancing Photocatalytic and Photothermal Elements for Enhanced Solar Evaporation—A Review

by Daniela Meroni, Hady Hamza, Vanni Lughi and Maria Vittoria Diamanti

Catalysts 2026, 16(2), 157; https://doi.org/10.3390/catal16020157 - 3 Feb 2026

Viewed by 1651

Abstract

Water is a critical resource underpinning natural, societal and economic development, and its importance will grow bigger in the next decades. Interfacial solar evaporators are a promising and cost-effective technology for the generation of freshwater from saline and polluted waters. Yet, although these devices effectively reject salts and non-volatile pollutants, the presence of volatile organic compounds in the water source may lead to low water quality of the distillate. This review addresses the introduction of photocatalytic materials in solar evaporator devices to improve water quality, highlighting in particular possible synergies and incompatibilities between the materials promoting these functionalities. The interactions of the photocatalyst with photothermal materials are described, along with an overview of the materials most commonly selected for both functionalities. A positive interaction clearly emerges, with the photothermal materials not only accelerating evaporation but also generally stimulating the photocatalytic degradation of VOCs. Limits to the implementation of such a combination are described, including those due to electrolyte content and salt accumulation, reaction rate and mass transfer. Finally, recommendations regarding testing conditions and future studies are presented. Full article

(This article belongs to the Special Issue Recent Developments in Photo-/Electrocatalysis: A Themed Issue in Honor of Prof. Trong-On Do)

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20 pages, 2248 KB

Open AccessReview

Solar-Driven CO₂ Conversion: A Review of Long-Chain Products

by Dinh Khang Vo and Nhat Truong Nguyen

Catalysts 2026, 16(2), 155; https://doi.org/10.3390/catal16020155 - 3 Feb 2026

Viewed by 951

Abstract

The solar-driven conversion of CO₂ into long-chain (C₃₊) products offers a sustainable pathway to mitigate climate change, produce carbon-neutral fuels and value-added chemicals. Over the past few decades, significant advances have been achieved in CO₂ photoreduction; however, most systems still favor C₁ products (CO, CH₄) or C₂ intermediates. However, the synthesis of C₃₊ products poses a formidable challenge due to the complex multi-electron transfer steps required for C–C bond formation. This review provides a concise overview of recent progress in solar-driven photocatalytic and photothermal CO₂ reduction, with a specific focus on the formation of C₃₊ products. The fundamental principles are discussed, including the critical role of C–C coupling mechanisms and the stepwise reaction pathways for C₃₊ products. It highlights how the extended carbon chain length significantly increases the complexity and reduces selectivity, with the suppression of side reactions being a primary research objective. Key catalytic strategies, such as the use of copper-based materials, are examined for their unique ability to facilitate these demanding transformations. Finally, the major challenges are outlined, and a future outlook for this field is provided, with an emphasis on the need for advanced catalyst design and in situ characterization to unlock the potential of solar fuels. Full article

(This article belongs to the Special Issue Recent Developments in Photo-/Electrocatalysis: A Themed Issue in Honor of Prof. Trong-On Do)

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21 pages, 2705 KB

Open AccessReview

Membranes for Electrochemical Carbon Dioxide Conversion to Multi-Carbon Products

by Thao-Nguyen Ho, Duc-Minh Phan-Pham, Anh-Dao Ho, Tuan Anh Bui, Guorui Gao and Cao-Thang Dinh

Catalysts 2026, 16(2), 139; https://doi.org/10.3390/catal16020139 - 2 Feb 2026

Viewed by 900

Abstract

Electrochemical carbon dioxide reduction reaction (CO₂RR) offers a promising route to mitigate climate change while simultaneously enabling renewable energy storage and the sustainable production of value-added chemicals. A wide variety of CO₂RR reactor designs have been developed, including both liquid-phase cells and gas-phase configurations. Among these, gas-phase systems, particularly flow-cell and membrane electrode assembly (MEA) designs, have become the primary focus of recent research due to their ability to overcome mass transport limitations and operate at high currents. While catalyst development has received considerable attention in advancing CO₂RR performance, the role of membranes in these gas-phase electrolyzers has been less systematically reviewed. This article addresses that gap by critically examining the functions, advantages, and limitations of the major membrane classes used in CO₂ electrolysis: anion exchange membranes, cation exchange membranes, bipolar membranes, and non-ion-exchange porous membranes within flow-cell and MEA configurations. We highlight how membrane properties influence local pH regulation, water management, crossover behavior, and overall reactor performance, while emphasizing that product identity is primarily catalyst-determined. By analyzing recent progress and remaining challenges, this review provides design insights for membrane selection and development toward efficient, stable, and scalable CO₂ electrolysis systems. Full article

(This article belongs to the Special Issue Recent Developments in Photo-/Electrocatalysis: A Themed Issue in Honor of Prof. Trong-On Do)

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36 pages, 7496 KB

Open AccessReview

Constructed Wetlands Beyond the Fenton Limit: A Systematic Review on the Circular Photo-Biochemical Catalysts Design for Sustainable Wastewater Treatment

by M. M. Nour, Maha A. Tony and Hossam A. Nabwey

Catalysts 2026, 16(1), 92; https://doi.org/10.3390/catal16010092 - 16 Jan 2026

Cited by 2 | Viewed by 1213

Abstract

Constructed wetlands (CWs) are signified as green, self-sustaining systems for wastewater treatment. To date, their conventional designs struggle with slow kinetics and poor removal of refractory pollutants. This review redefines CWs as photo-reactive engineered systems, integrating near-neutral Fenton and photo-Fenton processes and in-situ oxidant generation to overcome diffusion limits, acid dosing, and sludge formation. By coupling catalytic fillers, solar utilization, and plant–microbe–radical (ROS) synergies, the approach enables intensified pollutant degradation while preserving the low-energy nature of CWs. Bibliometric trends indicate a sharp rise in studies linking CWs with advanced oxidation and renewable energy integration, confirming the emergence of a circular treatment paradigm. A decision framework is proposed that aligns material selection, reactor hydrodynamics, and solar light management with sustainability indicators such as energy efficiency, Fe-leach budget, and ROS-to-photon yield. This synthesis bridges environmental biotechnology with solar-driven catalysis, paving the way for next-generation eco-engineered wetlands capable of operating efficiently beyond the classical Fenton constraints. This work introduces the concept of “Constructed Wetlands Beyond the Fenton Limit”, where CWs are reimagined as photo-reactive circular systems that unify catalytic, biological, and solar processes under near-neutral conditions. It provides the first integrated decision matrix and performance metrics connecting catalyst design, ROS efficiency, and circular sustainability that offers a scalable blueprint for real-world hybrid wetland applications. Full article

(This article belongs to the Special Issue Recent Developments in Photo-/Electrocatalysis: A Themed Issue in Honor of Prof. Trong-On Do)

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22 pages, 4227 KB

Open AccessReview

Current Status and Future Prospects of Photocatalytic Technology for Water Sterilization

by Nobuhiro Hanada, Manabu Kiguchi and Akira Fujishima

Catalysts 2026, 16(1), 40; https://doi.org/10.3390/catal16010040 - 1 Jan 2026

Cited by 1 | Viewed by 1147

Abstract

Photocatalytic water sterilization has emerged as a promising sustainable technology for addressing microbial contamination across diverse sectors including healthcare, food production, and environmental management. This review examines the fundamental mechanisms and recent advances in photocatalytic water sterilization, with a particular emphasis on the differential bactericidal pathways against Gram-negative and Gram-positive bacteria. Gram-negative bacteria undergo a two-step inactivation process involving initial outer membrane lipopolysaccharide (LPS) degradation followed by inner membrane disruption, whereas Gram-positive bacteria exhibit simpler kinetics due to direct oxidative attacks on their thick peptidoglycan layer. Escherichia coli has long been used as the gold standard in photocatalytic sterilization studies owing to its aerobic nature and suitability for the colony-counting method. In contrast, Lactobacillus casei, a facultative anaerobe, can be cultured statically and evaluated rapidly using turbidity-based optical density measurements. Therefore, both organisms serve complementary roles depending on the experimental objectives—E. coli for precise quantification and L. casei for rapid, practical assessments of Gram-positive bacterial inactivation under laboratory conditions. We also describe sterilization using light alone while comparing it to photocatalytic sterilization and then discuss two innovative suspension-based photocatalyst systems: polystyrene bead-supported TiO₂/SiO₂ composites offering balanced reactivity and separability and magnetic TiO₂-SiO₂/Fe₃O₄ nanoparticles enabling rapid magnetic recovery. Future research directions should prioritize enhancing visible-light efficiency using metal-doped TiO₂ such as Cu-doped systems; improving catalyst durability; developing new applications of photocatalysts, such as protecting RO membranes; and validating scalability across diverse industrial and medical water treatment applications. Full article

(This article belongs to the Special Issue Recent Developments in Photo-/Electrocatalysis: A Themed Issue in Honor of Prof. Trong-On Do)

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56 pages, 38197 KB

Open AccessReview

Advances in Composite Photocatalysts for Efficient Degradation of Organic Pollutants: Strategies, Challenges, and Future Perspectives

by Adnan Majeed, Muhammad Adnan Iqbal and Trong-On Do

Catalysts 2025, 15(9), 893; https://doi.org/10.3390/catal15090893 - 17 Sep 2025

Cited by 14 | Viewed by 3535

Abstract

The persistent release of synthetic dyes such as methylene blue (MB) into aquatic environments poses a significant ecological hazard due to their chemical stability and toxicity. In recent years, the application of engineered composite photocatalysts has emerged as a potent solution for efficient dye degradation under visible and UV light. This review comprehensively summarizes various advanced composites, including carbon-based, metal-doped, and heterojunction materials, tailored for MB degradation. Notably, composites such as TiO₂/C-550, WS₂/GO/Au, and MOF-derived α-Fe₂O₃/ZnO achieved near-complete degradation (>99%) within 30–150 min, while others, like ZnO/JSAC-COO⁻ and Ag/TiO₂/CNT, displayed enhanced charge separation and stability over five consecutive cycles. Band gap engineering (ranging from 1.7 eV to 3.2 eV) and reactive oxygen species (·OH, ·O₂⁻) generation were key to their photocatalytic performance. This review compares the structural attributes, synthetic strategies, and degradation kinetics across systems, highlighting the synergistic role of co-catalysts, surface area, and electron mobility. This work offers systematic insight into the state-of-the-art composite photocatalysts and provides a comparative framework to guide future material design for wastewater treatment applications. Full article

(This article belongs to the Special Issue Recent Developments in Photo-/Electrocatalysis: A Themed Issue in Honor of Prof. Trong-On Do)

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