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Recent Advances in Photocatalytic Degradation of Tetracycline Antibiotics
Properties, Industrial Applications and Future Perspectives of Catalytic Materials Based on Nickel and Alumina: A Critical Review

Journal Description

Catalysts

Catalysts is a peer-reviewed open access journal of catalysts and catalyzed reactions published monthly online by MDPI. The Romanian Catalysis Society (RCS) are partners of Catalysts journal and its members receive a discount on the article processing charge.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, SCIE (Web of Science), Inspec, CAPlus / SciFinder, CAB Abstracts, and other databases.
Journal Rank: JCR - Q2 (Chemistry, Physical) / CiteScore - Q1 (General Environmental Science )
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 12.9 days after submission; acceptance to publication is undertaken in 2.8 days (median values for papers published in this journal in the first half of 2024).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.

Impact Factor: 3.8 (2023); 5-Year Impact Factor: 3.9 (2023)

Imprint Information Journal Flyer Open Access ISSN: 2073-4344

Latest Articles

19 pages, 671 KiB

Open AccessArticle

A Green Chemistry Approach to Catalytic Synthesis of Ethyl Levulinate

by Martina Sušjenka, Fran Prašnikar, Martina Jakovljević Kovač, Maja Molnar, Luz Fernandes, Ana Vital Marques Nunes, Ana Rita Cruz Duarte and Małgorzata Ewa Zakrzewska

Catalysts 2024, 14(12), 842; https://doi.org/10.3390/catal14120842 - 21 Nov 2024

Esterification of levulinic acid with ethanol was investigated using deep eutectic systems based on choline chloride and oxalic or p-toluenesulfonic acid as catalysts under conventional heating and alternative energy inputs, namely microwave, ultrasound, and mechanochemical treatment. The experiments were performed under varying operating [...] Read more.

Esterification of levulinic acid with ethanol was investigated using deep eutectic systems based on choline chloride and oxalic or p-toluenesulfonic acid as catalysts under conventional heating and alternative energy inputs, namely microwave, ultrasound, and mechanochemical treatment. The experiments were performed under varying operating conditions such as catalyst type and loading, alcohol to carboxylic acid molar ratio, temperature, or time. The obtained results demonstrate the overall better catalytic performance of the p-toluenesulfonic acid-based deep eutectic mixture in comparison with the oxalic acid-based analogue. The best results: levulinic acid conversion of 76% and 58%, for p-toluenesulfonic and oxalic acid containing deep eutectic systems, respectively, with 100% selectivity for both cases, were achieved for microwave-assisted synthesis with 5 wt.% of catalyst and excess alcohol to acid (molar ratio 5), at 413.15 K and for 10 min. The main advantage of all of the alternative activation methods studied (microwaves, ultrasounds, and ball mill processing) was the significant reduction in the reaction time. Full article

(This article belongs to the Special Issue Ionic Liquids and Eutectic Mixtures for Green Catalytic Processes)

22 pages, 2578 KiB

Open AccessReview

Recent Advancements in Catalysts for Petroleum Refining

by Muhammad Saeed Akhtar, Sajid Ali and Wajid Zaman

Catalysts 2024, 14(12), 841; https://doi.org/10.3390/catal14120841 - 21 Nov 2024

In petroleum refining, catalysts are used to efficiently convert crude oil into valuable products such as fuels and petrochemicals. These catalysts are employed in a range of processes, including catalytic cracking, hydrotreating, and reforming to meet stringent fuel quality standards. This review explores [...] Read more.

In petroleum refining, catalysts are used to efficiently convert crude oil into valuable products such as fuels and petrochemicals. These catalysts are employed in a range of processes, including catalytic cracking, hydrotreating, and reforming to meet stringent fuel quality standards. This review explores recent advancements in refining catalysts, focusing on novel materials, enhanced synthesis methods, and their industrial applications. The development of nano-, hierarchically structured, and supported metal catalysts has led to significant improvements in catalyst selectivity, yield, and longevity. These innovations are particularly important for processes such as hydrocracking, fluid catalytic cracking, and catalytic reforming, where catalysts improve conversion rates, product quality, and environmental sustainability. Advances in synthesis techniques such as sol-gel processes, microwave-assisted synthesis, and atomic layer deposition have further optimized catalyst performance. Environmental considerations have also driven the development of catalysts that reduce harmful emissions, particularly sulfur oxides and nitrogen oxides while promoting green catalysis through the use of bio-based materials and recyclable catalysts. Despite these advancements, challenges remain, particularly in scaling novel materials for industrial use and integrating them with existing technologies. Future research should focus on the exploration of new catalytic materials, such as metal-organic frameworks and multi-functional catalysts, which promise to further revolutionize the refining industry. This review thus demonstrates the transformative potential of advanced catalysts in enhancing the efficiency and environmental sustainability of petroleum refining. Full article

(This article belongs to the Special Issue Feature Papers in "Industrial Catalysis" Section)

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14 pages, 2487 KiB

Open AccessArticle

Eco-Friendly Synthesis of Thiazole Derivatives Using Recyclable Cross-Linked Chitosan Hydrogel Biocatalyst Under Ultrasonic Irradiation as Anti-Hepatocarcinogenic Agents

by Sobhi M. Gomha, Nahed A. Abd El-Ghany, Manal S. Ebaid, Tariq Z. Abolibda, Magdi E. A. Zaki, Mohammad Alhilal, Suzan Alhilal and Nadia A. Mohamed

Catalysts 2024, 14(12), 840; https://doi.org/10.3390/catal14120840 - 21 Nov 2024

In the current study, pyromellitimide benzoyl thiourea cross-linked chitosan (PIBTU-CS) hydrogel, was evaluated as a green biocatalyst for the efficient synthesis of novel thiazole derivatives. The PIBTU-CS hydrogel showcased key advantages, such as an expanded surface area and superior thermal stability, establishing it [...] Read more.

In the current study, pyromellitimide benzoyl thiourea cross-linked chitosan (PIBTU-CS) hydrogel, was evaluated as a green biocatalyst for the efficient synthesis of novel thiazole derivatives. The PIBTU-CS hydrogel showcased key advantages, such as an expanded surface area and superior thermal stability, establishing it as a potent eco-friendly catalyst. By employing PIBTU-CS alongside ultrasonic irradiation, we successfully synthesized a series of novel thiazoles through the reaction of 2-(4-((2-carbamothioylhydrazineylidene)methyl)phenoxy)-N-(4-chlorophenyl)acetamide with a variety of hydrazonoyl halides (6a–f) and α-haloketones (8a–c or 10a,b). A comparative analysis with TEA revealed that PIBTU-CS hydrogel consistently delivered significantly higher yields. This synthetic strategy provided several benefits, including mild reaction conditions, reduced reaction times, and consistently high yields. The robustness of PIBTU-CS was further underscored by its ability to be reused multiple times without a substantial reduction in catalytic efficiency. The structures of the synthesized thiazole derivatives were meticulously characterized using a range of analytical techniques, including IR, ¹H-NMR, ¹³C-NMR, and mass spectrometry (MS), confirming their successful formation. These results underscore the potential of PIBTU-CS hydrogel as a sustainable and recyclable catalyst for the synthesis of heterocyclic compounds. Additionally, all synthesized products were tested for their anticancer activity against HepG2-1 cells, with several new compounds exhibiting good anticancer effects. Full article

(This article belongs to the Special Issue Catalytic Energy Conversion and Catalytic Environmental Purification)

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16 pages, 706 KiB

Open AccessArticle

Synthesis and Experimental Screening of Catalysts for H₂S to H₂ Decomposition Under Close-to-Industry Conditions

by Timur Palankoev, Anton Manakhov, Andrey Kovalskii, Ekaterina Sukhanova, Zakhar Popov, Dmitry Chareev, Konstantin Dement’ev, Anton Maximov and Abdulaziz Al-Qasim

Catalysts 2024, 14(11), 839; https://doi.org/10.3390/catal14110839 - 20 Nov 2024

The chemical engineering community has shown significant interest in investigating methods to decompose hydrogen sulfide into hydrogen and sulfur. However, there is still a lack of detailed experimental data enabling us to choose the optimal catalyst, reaction, and regeneration conditions, as well as [...] Read more.

The chemical engineering community has shown significant interest in investigating methods to decompose hydrogen sulfide into hydrogen and sulfur. However, there is still a lack of detailed experimental data enabling us to choose the optimal catalyst, reaction, and regeneration conditions, as well as the overall process design. The purpose of this work is to synthesize a series of catalysts and compare their catalytic activity under the same conditions, chosen on the basis of a possible large-scale H₂S conversion process. To achieve this, the obtained catalysts were characterized by BET, XRD, SEM, TEM, and XPS before and after the reaction. Decomposition was conducted in a laboratory fixed-bed reactor at a temperature of 500 °C, 10 vol% of H₂S in the feed, and a GHSV of 540–1000 h⁻¹. DFT calculations evaluated the H₂S bond cleavage on various catalyst surfaces. It was shown that the most promising catalyst was Ni₃S₂, offering an acceptable H₂S conversion of 40%. We also observed that Ni₃S₂ catalyst regeneration could be conducted at much milder conditions compared to those previously reported in the literature. These results highlight the viability of upscaling the process with the selected catalyst. Full article

(This article belongs to the Section Industrial Catalysis)

14 pages, 2519 KiB

Open AccessArticle

Electrochemical Ammonia Synthesis from Dilute Gaseous Nitric Oxide Reduction at Ambient Conditions

by Haroon Ur Rasheed, Jae Hyung Kim, Taek-Seung Kim, Kyungho Lee, Joonmok Shim, Sung Hyung Kim and Hyung Chul Yoon

Catalysts 2024, 14(11), 838; https://doi.org/10.3390/catal14110838 - 20 Nov 2024

Converting gaseous nitric oxide (NO) to ammonia (NH₃) is important because of its environmental and industrial implications. The electrochemical transformation of nitrogen (N₂) to NH₃ faces several challenges, including a slow reaction rate and low Faradaic efficiency (FE). [...] Read more.

Converting gaseous nitric oxide (NO) to ammonia (NH₃) is important because of its environmental and industrial implications. The electrochemical transformation of nitrogen (N₂) to NH₃ faces several challenges, including a slow reaction rate and low Faradaic efficiency (FE). This study presents an innovative approach by integrating NO elimination and NH₃ production by electrochemical gaseous NO reduction reaction (NORR) under ambient conditions. Co and Mo-based catalysts were investigated for the continuous reduction of diluted NO gas (1%) to NH₃ within a proton exchange membrane (PEM) cell under ambient conditions. In electrochemical NORR tests conducted without a catholyte, CoMo-NC demonstrated notable NORR performance, achieving an NH₃ yield rate of 23.2 × 10⁻¹⁰ mol s⁻¹ cm⁻² at −2.2 V_cell and FE_NH3 of 94.6% at −1.6 V_cell, along with enhanced durability. Notably, this performance represents one of the highest FE_NH3 achievements for electrochemical gas-phase NO reduction at room temperature. Full article

(This article belongs to the Section Electrocatalysis)

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15 pages, 2979 KiB

Open AccessArticle

Assessing the Degradation of Levofloxacin in Aqueous Media by Metal-Free g-C₃N₄ Photocatalyst Under Simulated Solar Light Irradiation

by Truong Nguyen Xuan, Dien Nguyen Thi, Cong Le Thanh, Thu Mai Thi, Thu Le Dieu, Trung Nguyen Duc and Ottó Horváth

Catalysts 2024, 14(11), 837; https://doi.org/10.3390/catal14110837 - 20 Nov 2024

Graphitic carbon nitride (g-C₃N₄) as a fascinating conjugated polymer has attracted considerable attention due to its outstanding electronic properties, high physicochemical stability, and unique structure. In this work, we reported the characterization of g-C₃N₄, which [...] Read more.

Graphitic carbon nitride (g-C₃N₄) as a fascinating conjugated polymer has attracted considerable attention due to its outstanding electronic properties, high physicochemical stability, and unique structure. In this work, we reported the characterization of g-C₃N₄, which was simply synthesized by thermal polymerization of thiourea, the photocatalytic degradation kinetics, and the pathway of levofloxacin (LEV) using the prepared g-C₃N₄. The XRD and SEM results confirmed a crystalline graphite structure with a tri-s-triazine unit and stacked sheet-like layers of g-C₃N₄. The efficacy factor (EF) was compared to different photocatalytic processes to assess the LEV removal performance. g-C₃N₄ exhibits good stability as a photocatalyst during LEV photodegradation. Radical scavenger experiments revealed that in the oxidative degradation of LEV, ^•O₂^– and h⁺ played the determining roles. Moreover, based on the identification of intermediates using liquid chromatography with tandem mass spectrometry (LC-MS/MS), the degradation pathway of LEV was proposed. Full article

(This article belongs to the Special Issue Environmental Catalysis in Advanced Oxidation Processes, 2nd Edition)

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13 pages, 3059 KiB

Open AccessFeature PaperArticle

Tetranuclear N-Heterocyclic Carbene Palladium Acetate—The Fast-Initiating Precatalyst of Suzuki Coupling

by Sylwia Ostrowska, Szymon Rogalski, Maciej Kubicki and Cezary Pietraszuk

Catalysts 2024, 14(11), 836; https://doi.org/10.3390/catal14110836 - 20 Nov 2024

A tetranuclear N-heterocyclic palladium carbene acetate, characterised by a [Pd]/[NHC] = 2/1 ratio, was synthesised and shown to be catalytically active in Suzuki coupling. Single crystal XRD studies of the complex revealed its unprecedented geometry, with the presence of three coordinated palladium [...] Read more.

A tetranuclear N-heterocyclic palladium carbene acetate, characterised by a [Pd]/[NHC] = 2/1 ratio, was synthesised and shown to be catalytically active in Suzuki coupling. Single crystal XRD studies of the complex revealed its unprecedented geometry, with the presence of three coordinated palladium centres. The catalytic activity of the complex is significantly higher than that of analogues containing the same N-heterocyclic carbene ligand. Preliminary studies have been carried out to determine the catalytic properties of the complex. Full article

(This article belongs to the Special Issue N-heterocyclic Carbenes (NHC) and NHC-Metal Complexes: Preparation, Characterization and Applications in Modern Catalysis)

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15 pages, 7227 KiB

Open AccessArticle

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

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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16 pages, 3607 KiB

Open AccessArticle

Integration of CO₂ Adsorbent with Ni-Al₂O₃ Catalysts for Enhanced Methane Production in Carbon Capture and Methanation: Cooperative Interaction of CO₂ Spillover and Heat Exchange

by Dong Seop Choi, Hye Jin Kim, Jiyull Kim, Hyeona Yu and Ji Bong Joo

Catalysts 2024, 14(11), 834; https://doi.org/10.3390/catal14110834 - 20 Nov 2024

In this study, we conducted a comparative analysis of the catalytic behavior of Ni-CaO-Al₂O₃ dual functional material (DFM) and a physical mixture of Ni-Al₂O₃ and CaO-Al₂O₃ in the integrated carbon capture methanation (ICCM) process [...] Read more.

In this study, we conducted a comparative analysis of the catalytic behavior of Ni-CaO-Al₂O₃ dual functional material (DFM) and a physical mixture of Ni-Al₂O₃ and CaO-Al₂O₃ in the integrated carbon capture methanation (ICCM) process for promoted methane production. H₂-temperature-programmed surface reaction (H₂-TPSR) analysis revealed that in Ni-CaO-Al₂O₃ DFM, CO₂ adsorbed on the CaO surface can spillover to metallic Ni surface, enabling direct hydrogenation without desorption of CO₂. Ni-CaO-Al₂O₃ DFM exhibited a rapid initial methanation rate due to CO₂ spillover. The Ni-CaO-Al₂O₃ DFM, with Ni and CO₂ adsorption sites in close distance, allows efficient utilization of the heat generated by methanation to desorb strongly adsorbed CO₂, leading to enhanced methane production. Consequently, Ni-CaO-Al₂O₃ DFM produced 1.3 mmol/g_Ni of methane at 300 °C, converting 35% of the adsorbed CO₂ to methane. Full article

(This article belongs to the Section Nanostructured Catalysts)

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15 pages, 7583 KiB

Open AccessArticle

Fabrication of Two-Dimensional B-Doped C₃N₄ Nanosheet-Encapsulated One-Dimensional Rod-like Mo-MOF-Derived MoS₂ Heterojunctions for Enhanced Photocatalytic Ethanol Conversion and Synergistic Hydrogen Production

by Caili Zhang, Jian Wang and Li Wang

Catalysts 2024, 14(11), 833; https://doi.org/10.3390/catal14110833 - 19 Nov 2024

The photocatalytic conversion of ethanol and the simultaneous development of hydrogen technology play a role in solving the energy crisis and reducing environmental pollution. In this research, rod-like M-MoS₂ serves as a channel for charge transfer, leading to superior photocatalytic activity compared [...] Read more.

The photocatalytic conversion of ethanol and the simultaneous development of hydrogen technology play a role in solving the energy crisis and reducing environmental pollution. In this research, rod-like M-MoS₂ serves as a channel for charge transfer, leading to superior photocatalytic activity compared to H-MoS₂. Further, two-dimensional (2D) B-doped C₃N₄ (BCN) nanosheets were anchored on the one-dimensional (1D) rod-like M-MoS₂ surface to form a 1D/2D heterojunction, with M-MoS₂/BCN-0.08 (mass ratio of M-MoS₂:BCN of 0.08:1) exhibiting the highest photocatalytic performance. Under visible light irradiation, the ethanol conversion rate reached 1.79% after 5 h of photocatalytic reaction per gram of catalyst, while generating 421 μmol of 2,3-butanediol (2,3-BDO), 5460 μmol of acetaldehyde (AA), and 5410 μmol of hydrogen gas (H₂). This different characterization provides evidence that a significant amount of photoinduced electrons generated in BCN under illumination conditions rapidly transfer to the conduction band (CB) of M-MoS₂ through the rod-like structure of M-MoS₂, and finally transfer to Pt to promote the production of hydrogen gas. The photoinduced holes in the valence band (VB) of M-MoS₂ are rapidly consumed by ethanol upon transferring to BCN, effectively separating the photoinduced electron–hole pairs and resulting in superior photocatalytic performance. Full article

(This article belongs to the Section Photocatalysis)

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18 pages, 4983 KiB

Open AccessArticle

Understanding the Negative Apparent Activation Energy for Cu₂O and CoO Oxidation Kinetics at High Temperature near Equilibrium

by Yang Wang, Haiyang Liu, Qiwei Duan and Zhenshan Li

Catalysts 2024, 14(11), 832; https://doi.org/10.3390/catal14110832 - 19 Nov 2024

The pairs of Cu₂O/CuO and CoO/Co₃O₄ as the carriers of transferring oxygen and storing heat are essential for the recently emerged high-temperature thermochemical energy storage (TCES) system. Reported research results of Cu₂O and CoO oxidation kinetics [...] Read more.

The pairs of Cu₂O/CuO and CoO/Co₃O₄ as the carriers of transferring oxygen and storing heat are essential for the recently emerged high-temperature thermochemical energy storage (TCES) system. Reported research results of Cu₂O and CoO oxidation kinetics show that the reaction rate near equilibrium decreases with the temperature, which leads to the negative activation energy obtained using the Arrhenius equation and apparent kinetics models. This study develops a first-principle-based theoretical model to analyze the Cu₂O and CoO oxidation kinetics. In this model, the density functional theory (DFT) is adopted to determine the reaction pathways and to obtain the energy barriers of elementary reactions; then, the DFT results are introduced into the transition state theory (TST) to calculate the reaction rate constants; finally, a rate equation is developed to describe both the surface elemental reactions and the lattice oxygen concentration in a grain. The reaction mechanism obtained from DFT and kinetic rate constants obtained from TST are directly implemented into the rate equation to predict the oxidation kinetics of Cu₂O without fitting experimental data. The accuracy of the developed theory is validated by experimental data obtained from the thermogravimetric analyzer (TGA). Comparing the developed theory with the traditional apparent models, the reasons why the latter cannot appropriately predict the true oxidation characteristics are explained. The reaction rate is jointly controlled by thermodynamics (reaction driving force) and kinetics (reaction rate constant). Without considering the effect of the reaction driving force, the negative apparent activation energy of Cu₂O oxidation is obtained. However, for CoO oxidation, the negative apparent activation energy is still obtained although the effect of the reaction driving force is considered. According to the DFT results, the activation energy of the overall CoO oxidation reaction is negative, but the energy barriers of the elementary reactions are positive. Moreover, according to the first-principle-based rate equation theory, the pre-exponential factor in the kinetic model is dependent on the partition function ratio and decreases with the temperature for the Cu₂O and CoO oxidation near equilibrium, which results in the apparent activation energy being slightly lower than the actual value. Full article

(This article belongs to the Section Computational Catalysis)

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36 pages, 5088 KiB

Open AccessArticle

Eco-Friendly Synthesis of ZnO Nanoparticles for Quinoline Dye Photodegradation and Antibacterial Applications Using Advanced Machine Learning Models

by Hayet Chelghoum, Noureddine Nasrallah, Hichem Tahraoui, Mahmoud F. Seleiman, Mustapha Mounir Bouhenna, Hayet Belmeskine, Meriem Zamouche, Souhila Djema, Jie Zhang, Amina Mendil, Fayçal Dergal, Mohammed Kebir and Abdeltif Amrane

Catalysts 2024, 14(11), 831; https://doi.org/10.3390/catal14110831 - 19 Nov 2024

Community drinking water sources are increasingly contaminated by various point and non-point sources, with emerging organic contaminants and microbial strains posing health risks and disrupting ecosystems. This study explores the use of zinc oxide nanoparticles (ZnO-NPs) as a non-specific agent to address groundwater [...] Read more.

Community drinking water sources are increasingly contaminated by various point and non-point sources, with emerging organic contaminants and microbial strains posing health risks and disrupting ecosystems. This study explores the use of zinc oxide nanoparticles (ZnO-NPs) as a non-specific agent to address groundwater contamination and combat microbial resistance effectively. The ZnO-NPs were synthesized via a green chemistry approach, employing a sol-gel method with lemon peel aqueous extract. The catalyst was characterized using techniques including XRD, ATR-FTIR, SEM-EDAX, UV-DRS, BET, and Raman spectroscopy. ZnO-NPs were then tested for photodegradation of quinoline yellow dye (QY) under sunlight irradiation, as well as for their antibacterial and antioxidant properties. The ZnO-NP photocatalyst showed significant photoactivity, attributed to effective separation of photogenerated charge carriers. The efficiency of sunlight dye photodegradation was influenced by catalyst dosage (0.1–0.6 mg L⁻¹), pH (3–11), and initial QY concentration (10–50 mg L⁻¹). The study developed a first-order kinetic model for ZnO-NPs using the Langmuir–Hinshelwood equation, yielding kinetic constants of equilibrium adsorption and photodegradation of Kc = 6.632 × 10⁻² L mg⁻¹ and kH = 7.104 × 10⁻² mg L⁻¹ min⁻¹, respectively. The results showed that ZnO-NPs were effective against Gram-positive bacterial strains and showed moderate antioxidant activity, suggesting their potential in wastewater disinfection to achieve sustainable development goals. A potential antibacterial mechanism of ZnO-NPs involving interactions with microbial cells is proposed. Additionally, Gaussian Process Regression (GPR) combined with an improved Lévy flight distribution (FDB-LFD) algorithm was used to model QY photodegradation by ZnO-NPs. The ARD-Exponential kernel function provided high accuracy, validated through residue analysis. Finally, an innovative MATLAB-based application was developed to integrate the GPR_FDB-LFD model and FDB-LFD algorithm, streamlining optimization for precise photodegradation rate predictions. The results obtained in this study show that the GPR and FDB-LFD approaches offer efficient and cost-effective methods for predicting dye photodegradation, saving both time and resources. Full article

(This article belongs to the Special Issue Cutting-Edge Photocatalysis)

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11 pages, 483 KiB

Open AccessArticle

Reformulated Kinetics of Immobilized Enzymes in Non-Conventional Media: A Case of Lipase-Catalyzed Esterification

by Emmanuel M. Papamichael and Panagiota-Yiolanda Stergiou

Catalysts 2024, 14(11), 830; https://doi.org/10.3390/catal14110830 - 18 Nov 2024

Several approaches have been reported that aim to achieve simplified standardizations of the kinetic behavior of immobilized enzymes under specific experimental conditions. We have previously published simplified rate equations based on the kinetics of immobilized enzymes. Recently, new experimental results have become available [...] Read more.

Several approaches have been reported that aim to achieve simplified standardizations of the kinetic behavior of immobilized enzymes under specific experimental conditions. We have previously published simplified rate equations based on the kinetics of immobilized enzymes. Recently, new experimental results have become available on the kinetics and mechanisms of esterifications catalyzed by immobilized lipase in unconventional media, and consequently, a reformulation of their kinetics is necessary. In this work, we report the development of simplified rate equations relating the aforementioned reaction conditions on a new basis, considering our kinetic and mechanistic results. We provide experimental evidence that two different mechanisms describe the esterifications catalyzed by immobilized lipase, either in anhydrous organic solvent (n-hexane) or under non-solvent conditions. A ping-pong bi–bi mechanism with double dead-end substrate inhibition by both the fatty acid and the alcohol has been found to apply in the former case, while in the latter case the esterification proceeds via an ordered bi–bi mechanism with single dead-end substrate inhibition by ethanol. This study may be biotechnologically useful, as the increased use of immobilized enzymes, whether in academic research or in industry, requires sustainable development of new and environmentally friendly synthetic processes. Full article

(This article belongs to the Special Issue Biocatalysis in Non-conventional Media 2024)

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22 pages, 8434 KiB

Open AccessArticle

Highly Efficient Visible-Light Photocatalysts: Bi₂O₃@TiO₂ Derived from Ti-MOFs for Eriochrome Black T Degradation: A Joint Experimental and Computational Study

by Jing Meng, Asmaa G. Ashry, Ahmed S. Abou-Elyazed, Zhe Zhang, Xiaolin Li, Tamer Z. Sharara and Safinaz H. El-Demerdash

Catalysts 2024, 14(11), 829; https://doi.org/10.3390/catal14110829 - 17 Nov 2024

Herein, we synthesized Ti-MOF through a solvothermal method and subsequently calcined it to form anatase TiO₂. We further developed a Bi₂O₃@TiO₂ mixed oxide using impregnation and calcination processes. These oxides showed significant photocatalytic activity for degrading [...] Read more.

Herein, we synthesized Ti-MOF through a solvothermal method and subsequently calcined it to form anatase TiO₂. We further developed a Bi₂O₃@TiO₂ mixed oxide using impregnation and calcination processes. These oxides showed significant photocatalytic activity for degrading Eriochrome Black T (EBT) dye under visible light irradiation. We characterized the prepared samples using various techniques, including XRD, XPS, FTIR, BET, SEM, EDX, TEM, and UV-DRS analyses. Our results indicated that TiO₂ and 10%Bi₂O₃@TiO₂ achieved 80% and 100% degradation of EBT dye solution (50 ppm) within 30 min in acidic medium with a 50 mg catalyst dose, respectively. The calcination of the Ti-MOF into TiO₂ improved its sensitivity to visible light. The Bi₂O₃@TiO₂ composite was also effective in degrading other organic pollutants, such as Congo Red (degradation ~99%), Malachite Green (degradation ~95%), Methylene Blue (degradation ~81%), and Safranine O (degradation ~69%). The impregnation of Bi₂O₃ increased the surface acidity of TiO₂, enhancing its photocatalytic activity by promoting hydroxyl group formation through increased water adsorption. Additionally, 10%Bi₂O₃@TiO₂ demonstrated excellent chemical stability and reusability, maintaining high degradation efficiency over four cycles. Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) calculations were performed to understand the degradation mechanisms. UV-Vis absorption spectrum simulations suggested that the anionic HEB⁻² (O24) or EB⁻³ forms of the EBT dye are likely to undergo degradation. This study highlights the potential of Bi₂O₃@TiO₂ composites for effective photocatalytic applications in environmental remediation. Full article

(This article belongs to the Section Photocatalysis)

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20 pages, 11208 KiB

Open AccessArticle

Facile Synthesis of a Micro–Nano-Structured FeOOH/BiVO₄/WO₃ Photoanode with Enhanced Photoelectrochemical Performance

by Ruixin Li, Faqi Zhan, Guochang Wen, Bing Wang, Jiahao Qi, Yisi Liu, Chenchen Feng and Peiqing La

Catalysts 2024, 14(11), 828; https://doi.org/10.3390/catal14110828 - 17 Nov 2024

In the realm of photoelectrocatalytic (PEC) water splitting, the BiVO₄/WO₃ photoanode exhibits high electron–hole pair separation and transport capacity, rendering it a promising avenue for development. However, the charge transport and reaction kinetics at the heterojunction interface are suboptimal. This [...] Read more.

In the realm of photoelectrocatalytic (PEC) water splitting, the BiVO₄/WO₃ photoanode exhibits high electron–hole pair separation and transport capacity, rendering it a promising avenue for development. However, the charge transport and reaction kinetics at the heterojunction interface are suboptimal. This study uses the hydrothermal–electrodeposition–dip coating–calcination method to prepare a microcrystalline WO₃ photoanode thin film as the substrate material and combines it with nanocrystalline BiVO₄ to form a micro–nano-structured heterojunction photoanode to enhance the intrinsic and surface/interface charge transport properties of the photoanode. Under the condition of 1.23 V vs. RHE, the photoelectric current density reaches 1.09 mA cm⁻², which is twice that of WO₃. Furthermore, by using a simple impregnation–mineralization method to load the amorphous FeOOH catalyst, a noncrystalline–crystalline composite structure is formed to increase the number of active sites on the surface and reduce the overpotential of water oxidation, lowering the onset potential from 0.8 V to 0.6 V (vs. RHE). The photoelectric current density is further increased to 2.04 mA cm⁻² (at 1.23 V vs. RHE). The micro–nano-structure and noncrystalline–crystalline composite structure proposed in this study will provide valuable insights for the design and synthesis of high-efficiency photoelectrocatalysts. Full article

(This article belongs to the Special Issue Catalysts for Energy Storage)

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15 pages, 7410 KiB

Open AccessArticle

Highly Efficient Hydrogenation of Guaiacol over Ru/Al₂O₃-TiO₂ Catalyst at Low Temperatures

by Yumeng Song, Ping Chen, Hui Lou, Xiaoming Zheng and Xiangen Song

Catalysts 2024, 14(11), 827; https://doi.org/10.3390/catal14110827 - 17 Nov 2024

In this work, the highly efficient hydrogenation of guaiacol catalyzed by ruthenium supported on Al₂O₃-TiO₂ (Ru/Al₂Ti₁) at very mild conditions was carried out. At temperatures as low as 25 °C and 2 MPa H [...] Read more.

In this work, the highly efficient hydrogenation of guaiacol catalyzed by ruthenium supported on Al₂O₃-TiO₂ (Ru/Al₂Ti₁) at very mild conditions was carried out. At temperatures as low as 25 °C and 2 MPa H₂, about 60% of guaiacol could be converted to 2-methoxycyclohexanol (MCH) with a selectivity as high as 94% on the Ru/Al₂Ti₁ catalyst with an appropriate hydrogen pressure. At temperatures above 50 °C, almost all of the guaiacol could be converted with the catalyst of Ru/Al₂Ti₁, mainly into hydrogenated products such as MCH. The surprisingly efficient hydrogenation of guaiacol at low temperatures was most likely due to the ability of Ru particles loaded on the specific complex metal oxide carriers, particularly the reduction of the edge effect of Ru, to activate phenyl and hydrogen and reduce the competition of the dimethoxy process. These findings about the high activity of the Ru/Al₂Ti₁ catalyst at nearly room temperature may be helpful to upgrading the industrial process of the pyrolysis bio-oils. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis for Biomass and Its Derivatives into Chemicals)

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16 pages, 4312 KiB

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Peptide-Functionalized Gold Nanoparticles as Organocatalysts for Asymmetric Aldol Reactions

by Thabo Peme, Dean Brady, Ndivhuwo P. Shumbula, Khanani Machumele, Nosipho Moloto, Taryn Adams and Maya M. Makatini

Catalysts 2024, 14(11), 826; https://doi.org/10.3390/catal14110826 - 16 Nov 2024

The use of high catalyst loading is required for most of the organocatalyzed asymmetric aldol reactions in organic synthesis, and this often presents challenges during purification and difficulties in catalyst recovery from the reaction mixture. The immobilization of the catalyst onto gold nanoparticles [...] Read more.

The use of high catalyst loading is required for most of the organocatalyzed asymmetric aldol reactions in organic synthesis, and this often presents challenges during purification and difficulties in catalyst recovery from the reaction mixture. The immobilization of the catalyst onto gold nanoparticles (AuNPs) can change the structural conformations of the catalyst, thereby improving its catalytic activity and reusability. Herein we report on the synthesis of aldolase mimetic peptide coupled to gold nanoparticles (AuNPs) as efficient organocatalysts for asymmetric aldol reaction. AuNPs were synthesized using the Turkevich method. The conjugation of the peptide to AuNPs was characterized using surface plasmon resonance (SPR), Raman and X-ray photoelectron spectroscopy, and transmission electron microscopy (TEM) was used for particle size determination. The produced nanoparticles, whose sizes depended on the reduction method, were quasi-spherical with a relatively narrow size distribution. The peptide–AuNP conjugates were evaluated for aldol reaction catalytic activity between carbonyls p-nitrobenzaldehyde and cyclohexanone. The products were obtained with good yields (up to 85%) and enantioselectivity (up to 94%). The influence of organic solvents, pH and buffer solutions was also investigated. The results showed that the buffer solutions regulated the colloidal stability of AuNPs, resulting in a significant enhancement in the catalytic rate of the peptide–AuNP conjugate. Full article

(This article belongs to the Section Catalysis in Organic and Polymer Chemistry)

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26 pages, 9406 KiB

Open AccessReview

g-C₃N₄-Based Heterojunction for Enhanced Photocatalytic Performance: A Review of Fabrications, Applications, and Perspectives

by Junxiang Pei, Haofeng Li, Dechao Yu and Dawei Zhang

Catalysts 2024, 14(11), 825; https://doi.org/10.3390/catal14110825 - 16 Nov 2024

In recent years, photocatalysts have attracted wide attention in alleviating energy problems and environmental governance, among which, g-C₃N₄, as an ideal photocatalyst, has shown excellent application potential in achieving the sustainable development of energy. However, its photocatalytic performance needs [...] Read more.

In recent years, photocatalysts have attracted wide attention in alleviating energy problems and environmental governance, among which, g-C₃N₄, as an ideal photocatalyst, has shown excellent application potential in achieving the sustainable development of energy. However, its photocatalytic performance needs to be further improved in some applications. Rational construction of heterostructures with two or more semiconductor materials can combine the advantages of multi-components to simultaneously improve the photo-induced charge separation, which is very conducive to improving the absorption of visible light and obtaining more efficient redox capacity. With the rapid development in photocatalysis of g-C₃N₄-based heterostructures, a systematic summary and prospection of performance improvement are urgent and meaningful. This review focuses on various kinds of effective methods of heterogeneous combination; as well, strategies for improving the photocatalytic performance are fully discussed. In addition, the applications in efficient photocatalytic hydrogen production, photocatalytic carbon dioxide reduction, and organic pollutant degradation are systematically demonstrated. Finally, the remaining issues and prospects of further development are proposed as a kind of guidance for g-C₃N₄-based heterostructures with high efficiency at photocatalysis. Full article

(This article belongs to the Special Issue Photocatalysis: Past, Present, and Future Outlook)

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16 pages, 8407 KiB

Open AccessArticle

SnO₂ Quantum Dot-Decorated g-C₃N₄ Ultrathin Nanosheets: A Dual-Function Photocatalyst for Pollutant Degradation and Hydrogen Evolution

by Surya Veerendra Prabhakar Vattikuti, Hemanth P. K. Sudhani, Mohamed A. Habila, P. Rosaiah and Jaesool Shim

Catalysts 2024, 14(11), 824; https://doi.org/10.3390/catal14110824 - 15 Nov 2024

The development of advanced functional composite materials for degrading industrial pollutants and achieving photocatalytic hydrogen (H₂) production using abundant solar energy is pivotal in new and renewable energy research. This study presents the synthesis of a nanostructure comprising SnO₂ quantum [...] Read more.

The development of advanced functional composite materials for degrading industrial pollutants and achieving photocatalytic hydrogen (H₂) production using abundant solar energy is pivotal in new and renewable energy research. This study presents the synthesis of a nanostructure comprising SnO₂ quantum dots (QDs) randomly dispersed on the surface of graphitic carbon nitride (C₃N₄) nanosheets (Sn-C₃N₄), achieved through the thermal decomposition of melamine and a tin precursor. The synthesized materials were extensively characterized using various analytical techniques, with HRTEM analysis confirming the strong interaction between SnO₂ QDs and C₃N₄. The influence of SnO₂ QDs on the nanocomposite’s photocatalytic performance was evaluated, particularly regarding H₂ production and the degradation of crystal violet (CV) dye under simulated solar-light irradiation. The SnO₂-loaded C₃N₄ nanostructure exhibited a marked enhancement in photocatalytic activity, attributed to the synergistic effects of the quantum-sized SnO₂ nanoparticles. The optimized photocatalyst, 3-Sn-C₃N₄, demonstrated superior photocatalytic efficiency, achieving 95% degradation of CV dye within 45 min under simulated sunlight, significantly outperforming bare C₃N₄. Furthermore, the 3-Sn-C₃N₄ nanostructure attained the highest H₂ yield of 1305.4 μmol/h/g, a 4.6-fold increase compared with bare C₃N₄ (281 μmol/h/g). Enhanced photocatalytic performance was corroborated by photocurrent and EIS studies, which highlighted reduced charge carrier recombination as a critical factor in the improved activity. The underlying photocatalytic mechanisms were also examined. Full article

(This article belongs to the Section Environmental Catalysis)

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19 pages, 5351 KiB

Open AccessArticle

Deactivation and Regeneration Studies of Molybdenum-Based Catalysts in the Oxidative Desulfurization of Marine Fuel Oil

by Teddy Roy, Joy Alakari, Christine Lancelot, Pascal Blanchard, Line Poinel and Carole Lamonier

Catalysts 2024, 14(11), 823; https://doi.org/10.3390/catal14110823 - 15 Nov 2024

The oxidative desulfurization (ODS) of heavy fuel oil (HFO) offers a promising solution for desulfurizing marine fuels under mild conditions, in line with current environmental regulations. While most studies focus on model or light fuels, explaining deactivation through leaching or sulfone adsorption, the [...] Read more.

The oxidative desulfurization (ODS) of heavy fuel oil (HFO) offers a promising solution for desulfurizing marine fuels under mild conditions, in line with current environmental regulations. While most studies focus on model or light fuels, explaining deactivation through leaching or sulfone adsorption, the deactivation mechanisms of catalysts in HFO remain poorly understood. In this work, Mo-based catalysts supported on alumina were extensively characterized before and after catalytic reactions, and regeneration through air calcination was considered. Techniques such as XRD, Raman spectroscopy, XRF, and TGA, alongside catalytic testing with H₂O₂ as an oxidant, revealed that Mo surface speciation significantly impacted both activity and deactivation. Contrary to well-dispersed polymolybdates, crystalline MoO₃ induced low activity and hindered regeneration. No leaching of the active phase was demonstrated during the reaction. Sulfone adsorption had minimal impact on deactivation, while non-sulphur compounds appeared to be the key contributors. Regeneration outcomes were found to be molybdenum content-dependent: 10Mo/Al recovered its activity, while 20Mo/Al formed inactive phases, like Al₂(MoO₄)₃. Using an organic oxidant (tBHP) during ODS influenced the regeneration, as it prevented Al₂(MoO₄)₃ formation and redispersed crystalline MoO₃, enhancing performance. These findings advance understanding of catalyst deactivation and suggest strategies to extend catalyst life in the ODS of HFO. Full article

(This article belongs to the Special Issue Designing Catalytic Desulfurization Processes to Prepare Clean Fuels, 2nd Edition)

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