Catalysts

16 pages, 1188 KiB

Open AccessFeature PaperArticle

Enhancing Photocatalytic Hydrogen Evolution with Oxygen Vacancy-Modified P/Ag/Ag₂O/Ag₃PO₄/TiO₂ by Using Optimized NaBH₄ Reduction Strategy

by Xiang Sun, Yunxin Zhu, Guangqi An, Guoping Chen and Yingnan Yang

Catalysts 2025, 15(2), 167; https://doi.org/10.3390/catal15020167 (registering DOI) - 11 Feb 2025

Abstract

The introduction of oxygen vacancies (OVs) is a promising strategy to enhance the hydrogen (H₂) evolution efficiency of photocatalysts. Sodium borohydride (NaBH₄) is widely used as a reducing agent to introduce OVs, particularly in composite materials. However, its impact [...] Read more.

The introduction of oxygen vacancies (OVs) is a promising strategy to enhance the hydrogen (H₂) evolution efficiency of photocatalysts. Sodium borohydride (NaBH₄) is widely used as a reducing agent to introduce OVs, particularly in composite materials. However, its impact on H₂ evolution remains underexplored. In this study, by employing various mass ratios of NaBH₄to P/Ag/Ag₂O/Ag₃PO₄/TiO₂ (PAgT), OVs modified PAgT (R-PAgT) composites, which were synthesized and systematically characterized by XRD, FT-IR, and XPS. R-PAgT-10 with an optimal mass ratio exhibited a superior H₂ evolution efficiency and stability, maintaining its performance over 20 cycles under visible light irradiation, while the higher mass ratio of NaBH₄/PAgT led to the disruption of the crystal structure with excessive OVs amounts, resulting in poor stability. This study highlighted the importance of utilizing the optimal mass ratio of NaBH₄ to prepare OVs-PAgT for successful and stable H₂ evolution under visible light irradiation, which holds promise for developing efficient and durable photocatalysts for renewable energy applications. Full article

(This article belongs to the Special Issue Photocatalytic/Photoelectrocatalysis Water Splitting)

20 pages, 4970 KiB

Open AccessArticle

The Effect of Vacuum Annealing on the Structural, Electric, and Optical Properties, and Photocatalytic Activities of Sputtered TiO₂ and Nb-Doped TiO₂ Films

by Mengna Li, Yingying Fang and Baoshun Liu

Catalysts 2025, 15(2), 166; https://doi.org/10.3390/catal15020166 - 11 Feb 2025

Abstract

TiO₂ is still a prototype material in photocatalytic studies. The defects, including the intrinsic and foreign defects, are reported to be important in determining the TiO₂ photocatalytic properties. In the current research, amorphous TiO₂- and Nb-doped TiO₂ (NTO) [...] Read more.

TiO₂ is still a prototype material in photocatalytic studies. The defects, including the intrinsic and foreign defects, are reported to be important in determining the TiO₂ photocatalytic properties. In the current research, amorphous TiO₂- and Nb-doped TiO₂ (NTO) films were firstly prepared through magnetron sputtering, which were then heated under vacuum. The as-deposited TiO₂ and NTO films were amorphous, and transferred to anatase after heating. The vacuum heating at a higher temperature caused an obvious reduction in TiO₂ films, and the NTO film was more prone to be reduced as Nb dopants decreased the thermal stability of the TiO₂ lattice. The structure change induced by vacuum annealing had a great effect on electric and optical properties. The conductivity of the NTO films was 10,000 times and 100 times higher than that of the undoped TiO₂ films after post-vacuum heating at 450 °C and 650 °C, respectively. In addition to an increase in the band tail absorption, the NTO films presented strong free-electron absorption after vacuum heating; this means that the NTO films presented a clear Bornstein moss shift after vacuum heating because of the high conduction electron density. The change in the photoinduced absorption spectra revealed a possible result that photo-induced electrons can be also trapped at Nb sites, indicating that the Nb-related defect forms deep gap states; this greatly limits the photo-induced electron interfacial transfer. The results showed that the photocatalytic degradation of methylene blue decreased after vacuum heating. Full article

(This article belongs to the Special Issue TiO₂ Photocatalysts: Design, Optimization and Application)

23 pages, 2168 KiB

Open AccessArticle

Excellent Photocatalytic Performance Against Amoxicillin Antibiotic and Pt-Free Hydrogen Production Using Fe-Doped ZnS Nanostructures: Reaction Kinetics and Mechanistic Insights

by Ali Raza, Syeda Takmeel Zahra, Hadia Noor, Shahzad Naseem, Saira Riaz, Mohammad Ehtisham Khan, Wahid Ali, Mohammad S. Alomar, Anwar Ulla Khan, Syed Kashif Ali, Nazim Hasan and Waleed Zakri

Catalysts 2025, 15(2), 165; https://doi.org/10.3390/catal15020165 (registering DOI) - 11 Feb 2025

Abstract

This research presents the synthesis of Fe-doped ZnS nanocomposites via a chemical route, exploring their photocatalytic activity against amoxicillin (AMX) and evaluating their hydrogen production potential. The synthesized nanocomposites were characterized by several state-of-the-art analytical techniques, such as XRD, SEM, PL, UV adsorption, [...] Read more.

This research presents the synthesis of Fe-doped ZnS nanocomposites via a chemical route, exploring their photocatalytic activity against amoxicillin (AMX) and evaluating their hydrogen production potential. The synthesized nanocomposites were characterized by several state-of-the-art analytical techniques, such as XRD, SEM, PL, UV adsorption, Raman, TEM, and AFM. The photocatalytic performance revealed significant degradation of AMX under optimal conditions. Specifically, Fe-doped ZnS nanocomposites achieved a degradation efficiency of 94% within 120 min at a photocatalyst dosage of 110 mg. The pristine ZnS nanoparticles exhibited a hydrogen production rate of 23.6 µmol·g⁻¹·h⁻¹, whereas Fe doping substantially enhanced this rate to 526.6 µmol·g⁻¹·h⁻¹ under optimized conditions. The optimal temperature for hydrogen production was 200 °C, with maximum efficiency at pH 7. Furthermore, the recyclability tests demonstrated that the photocatalyst maintained a considerable hydrogen production rate over multiple cycles, underscoring its potential for commercial nanotechnology and environmental science applications. Full article

(This article belongs to the Special Issue Photocatalytic/Photoelectrocatalysis Water Splitting)

19 pages, 10288 KiB

Open AccessArticle

Photocatalytic Properties of Ag-Modifying N-TiO₂ Films Prepared via Magnetron Sputtering

by Li Sun, Xiong Hu, Zhigang Yuan, Ying Liu, Shunqi Mei, Fanhe Meng, Zhuoqun Que, Yi Xiong, Ke Zhang and Zhen Chen

Catalysts 2025, 15(2), 164; https://doi.org/10.3390/catal15020164 - 11 Feb 2025

Viewed by 118

Abstract

TiO₂ films and N-doped TiO₂ films modified with silver (Ag/N-TiO₂) were synthesized using DC magnetron sputtering. By varying the N₂ flow rate and the Ag sputtering power, respectively, the degree of doping and modification was managed. The microstructure, [...] Read more.

TiO₂ films and N-doped TiO₂ films modified with silver (Ag/N-TiO₂) were synthesized using DC magnetron sputtering. By varying the N₂ flow rate and the Ag sputtering power, respectively, the degree of doping and modification was managed. The microstructure, morphology, and properties of the thin film were studied using X-ray diffraction, field emission scanning electron microscopy, UV visible diffuse reflectance spectroscopy, and atomic force microscopy. The results show that TiO₂ in Ag/N-TiO₂ composite has an anatase structure, and the absorption spectrum of (Ag/N-TiO₂) thin film shows a red shift. The best photocatalytic degradation effect regarding the N-TiO₂ films was observed with an N₂ flow rate of 16 sccm (standard cubic per minute). The degradation rate in MO (Methyl orange) pure solution (C₀ = 10 mg/L) can reach 100% in 85 min, and in the MO-Na₂SO₄ mixed solution (C₀ = 10 mg/L, C C_Na₂SO₄ = 12.5 g/L), it only takes 40 min. Ag/N-TiO₂ films exhibited the highest degradation efficiency at a 5 W sputtering power and 50 s of sputtering time, reaching a 100% degradation rate in MO pure solution that can reach 100% in 50 min, and in the MO-Na₂SO₄ mixed solution, it only takes 36 min. The photocatalytic decomposition of MO was greatly accelerated by the addition of Na₂SO₄, which worked best with a 12.5 g/L concentration. However, when the concentration of Na₂SO₄ is above or below 12.5 g/L, Na₂SO₄ exhibits significant inhibition of photocatalytic degradation. Photocatalytic cycling experiments showed that the photocatalyst still maintained an effective degradation performance after four cycles. The degradation mechanism was analyzed using first-order kinetics and energy band theory. Compared to powder particles, the photocatalyst on the films has high stability and can be recovered 100%. So, photocatalysts on films have great potential for industrial applications. Full article

(This article belongs to the Section Photocatalysis)

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17 pages, 4291 KiB

Open AccessArticle

Piezo-Photocatalytic Degradation of Ciprofloxacin Based on Flexible BiVO₄ PVDF Nanofibers Membrane

by He Lv, Pan Wang, Ying Lv, Lihong Dong, Linlin Li, Min Xu, Lihai Fu, Bin Yue and Dengguang Yu

Catalysts 2025, 15(2), 163; https://doi.org/10.3390/catal15020163 - 11 Feb 2025

Viewed by 125

Abstract

The excessive use of ciprofloxacin, an antibiotic, has led to environmental challenges such as drug resistance and severe water pollution, necessitating effective mitigation strategies. Piezo-photocatalytic technology offers a sustainable solution. In this study, BiVO₄, recognized for its exceptional visible light absorption [...] Read more.

The excessive use of ciprofloxacin, an antibiotic, has led to environmental challenges such as drug resistance and severe water pollution, necessitating effective mitigation strategies. Piezo-photocatalytic technology offers a sustainable solution. In this study, BiVO₄, recognized for its exceptional visible light absorption and conductivity, was embedded within polyvinylidene fluoride (PVDF) nanofibers to address issues of secondary water pollution and enhance material recovery. The addition of peroxymonosulfate (PMS) further improved the degradation process by generating highly reactive sulfate radicals (•SO₄⁻), which acted synergistically with piezoelectric effects to enhance pollutant breakdown. Under the combined effects of stir, illumination, and PMS activation, BiVO₄ achieved a 40% higher ciprofloxacin degradation efficiency compared to mechanical stir alone. This improvement is attributed to the generation of polarization charges at both ends of the material and the •SO₄⁻, which promoted efficient electron-hole separation and oxidative degradation. This study introduces a novel approach to piezo-photocatalytic water treatment using flexible BiVO₄ membrane materials with PMS enhancement. Full article

(This article belongs to the Section Photocatalysis)

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17 pages, 1190 KiB

Open AccessArticle

Experimental and Kinetic Studies on the Conversion of Glucose to Levulinic Acid Catalyzed by Synergistic Cr/HZSM −5 in GVL/H₂O Biphasic System

by Han Wu, Rui Zhang, Jiantao Li, Jing Chang, Zhihua Liu, Jiale Chen, Jian Xiong, Yina Qiao, Zhihao Yu and Xuebin Lu

Catalysts 2025, 15(2), 162; https://doi.org/10.3390/catal15020162 - 10 Feb 2025

Viewed by 196

Abstract

In this paper, modified HZSM-5 catalysts with different ratios of chromium (Cr/HZSM−5) were synthesized and the solvent effect of gamma valerolactone (GVL) on the enhancement of levulinic acid (LA) yield was investigated. Characterization of the Cr/HZSM−5 catalyst revealed that the introduction of Cr [...] Read more.

In this paper, modified HZSM-5 catalysts with different ratios of chromium (Cr/HZSM−5) were synthesized and the solvent effect of gamma valerolactone (GVL) on the enhancement of levulinic acid (LA) yield was investigated. Characterization of the Cr/HZSM−5 catalyst revealed that the introduction of Cr did not change the structure of HZSM−5. The LA yield was increased from 42.5% (H₂O solvent system) to 51.4% (GVL/H₂O solvent system) under optimal conditions. The influence of GVL on the reaction mechanism was investigated through kinetic analysis, revealing that the incorporation of GVL reduces the activation energy barrier for the conversion of glucose to LA, thereby enhancing the glucose dehydration process. The effect of GVL on the product (LA) was studied, based on molecular dynamics. It was found that the addition of GVL squeezes the water in the solvent system into the second solvation shell layer, which causes GVL to distribute around the carbonyl, hydroxyl, and carboxyl groups of LA, and reduces the likelihood of LA side reactions, thus increasing the yield of LA. Full article

(This article belongs to the Special Issue Catalysis on Zeolites and Zeolite-Like Materials, 3rd Edition)

16 pages, 3283 KiB

Open AccessArticle

Highly Stable Ni–Red Mud Catalysts for CO₂-Free Hydrogen and Valuable Carbon from Natural Gas

by Wasim Ullah Khan, Dwi Hantoko, Galal Nasser, Akolade Idris Bakare, Ahmed Al Shoaibi, Srinivasakannan Chandrasekar and Mohammad M. Hossain

Catalysts 2025, 15(2), 161; https://doi.org/10.3390/catal15020161 - 10 Feb 2025

Viewed by 258

Abstract

The utilization of red mud as a catalyst support has been investigated to produce high-value carbon and CO_x-free hydrogen from natural gas. Nickel impregnation between 10 wt% to 20 wt% over red mud generates more active species in the form of [...] Read more.

The utilization of red mud as a catalyst support has been investigated to produce high-value carbon and CO_x-free hydrogen from natural gas. Nickel impregnation between 10 wt% to 20 wt% over red mud generates more active species in the form of nickel oxide; however, nickel–red mud interaction also generates less active spinel species (NiFe₂O₄). The red mud itself deactivates quickly during the production of hydrogen from the decomposition of methane; however, nickel-based red mud-supported catalysts have shown significant improvement in the activity results. For instance, the catalyst with 20 wt% nickel supported by red mud demonstrates a stable methane conversion as high as 75%. The reduction kinetics analysis demonstrated the lowest reduction in activation energy of 83 kJ/mol for 20Ni-PRM which played a major role in the excellent activity and stability of this catalyst. The post-reaction catalyst characterization results indicate the formation of multi-walled carbon nanotubes, as evidenced by high resolution transition electron microscope and thermogravimetric analyses. Full article

(This article belongs to the Section Catalytic Reaction Engineering)

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19 pages, 2934 KiB

Open AccessReview

Advances in In Situ Investigations of Heterogeneous Catalytic Ammonia Synthesis

by Weiyi Su, Xi Cheng, Suokun Shang, Runze Pan, Miao Qi, Qinqin Sang, Zhen Xie, Honghua Zhang, Ke Wang and Yanrong Liu

Catalysts 2025, 15(2), 160; https://doi.org/10.3390/catal15020160 - 9 Feb 2025

Viewed by 378

Abstract

Ammonia is a key “platform” raw chemical for fertilizers and nitrogen-containing chemicals, with a global annual production of ~180 million tons. Recently, ammonia has also come to be seen as an excellent hydrogen-containing liquid promising for long-term, large-scale hydrogen storage and transport. Therefore, [...] Read more.

Ammonia is a key “platform” raw chemical for fertilizers and nitrogen-containing chemicals, with a global annual production of ~180 million tons. Recently, ammonia has also come to be seen as an excellent hydrogen-containing liquid promising for long-term, large-scale hydrogen storage and transport. Therefore, artificial N₂ fixation, an ammonia synthesis reaction, will play a pivotal role influencing food and energy for human society. Till now, industrial ammonia synthesis has relied on high temperature and high pressure (420~500 °C, 10~15 MPa). Researchers are devoted to developing new catalysts as well as optimizing the traditional Fe-based catalysts continuously. However, the relation between the catalysts’ detailed structure and ammonia production efficiency are not yet fully understood, which is crucial to provide guidance on further improving the efficacy of this importance reaction. Recently, in situ characterization techniques have achieved significant improvements and new understandings have been achieved on the central topic of catalysis. In this review, recent advances in in situ investigations of heterogeneous catalytic ammonia synthesis are summarized and the key results are discussed. In the end, a concluding remark and perspective are proposed, with the hope of inspiring future investigations dedicated to unveiling the principles of designing catalysts for ammonia synthesis. Full article

(This article belongs to the Special Issue Applications of Heterogeneous Catalysts in Green Chemistry, 2nd Edition)

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29 pages, 3374 KiB

Open AccessReview

Application of Pillared Clays for Water Recovery

by Rubi Romero

Catalysts 2025, 15(2), 159; https://doi.org/10.3390/catal15020159 - 9 Feb 2025

Viewed by 253

Abstract

In recent years, efforts have been made in developing new and more efficient water purification methods and the synthesis of catalysts with greater catalytic activity that are more stable and can be used in wide pH ranges. Pillared clays represent a viable alternative [...] Read more.

In recent years, efforts have been made in developing new and more efficient water purification methods and the synthesis of catalysts with greater catalytic activity that are more stable and can be used in wide pH ranges. Pillared clays represent a viable alternative for removing organic contaminants. The clays, usually smectites, are modified by inserting inorganic pillars (Al, Zr, Cr, Fe, Ti, Ga, and Mn) between the layers of the clay, increasing its surface area, porosity, catalytic activity, and thermal stability. This review describes the importance of using pillared clays with different polyoxycations in Fenton, photo-Fenton, ozonation, wet catalytic oxidation of hydrogen peroxide, and photocatalysis processes. Pillared iron clays (Fe-PILCs) are promising catalysts capable of generating hydroxyl radicals that can oxidize organic contaminants, thus facilitating their removal. The current challenges of the PILC application at industrial scale are also discussed. Full article

(This article belongs to the Special Issue Photocatalyzed and Electrochemical Processes for a Cleaner Environment)

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23 pages, 6949 KiB

Open AccessFeature PaperReview

A Mini-Review of Recent Progress in Zeolite-Based Catalysts for Photocatalytic or Photothermal Environmental Pollutant Treatment

by Shenhao Zhang, Le Xu, Jie Xu and Boxiong Shen

Catalysts 2025, 15(2), 158; https://doi.org/10.3390/catal15020158 - 9 Feb 2025

Viewed by 431

Abstract

Atmospheric and water pollution has led to serious harm to the global environment and human health. Photocatalysis and photothermal catalysis technologies have been considered as promising methods to handle pollutants in the atmosphere and water due to their energy savings and environmental friendliness. [...] Read more.

Atmospheric and water pollution has led to serious harm to the global environment and human health. Photocatalysis and photothermal catalysis technologies have been considered as promising methods to handle pollutants in the atmosphere and water due to their energy savings and environmental friendliness. Zeolite catalysts have been widely used in the field of photocatalytic and photothermal catalytic removal of environmental pollutants due to their well-developed pore structure, high stability, and tunable surface chemistry. In this review, we have elaborated the photocatalytic and photothermal catalytic mechanisms and summarized the recent progress in zeolite-based catalysts for photocatalytic or photothermal catalytic environmental pollutant treatment. In summary, it is found that the strategies of elemental doping and surface structure modification directly affect the adsorption performance of zeolite for target pollutants, and the construction of a bifunctional structure promotes the generation of intrinsic active species and photogenerated charge separation. Finally, the paper presents current challenges and perspectives on zeolite-based catalysts for photocatalytic and photothermal catalytic treatment of environmental pollutants. Full article

(This article belongs to the Special Issue Catalysis on Zeolites and Zeolite-Like Materials, 3rd Edition)

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10 pages, 4705 KiB

Open AccessArticle

Bi₂O₂Se Nanosheets for Efficient Piezocatalytic H₂O₂ Production

by Shun Li, Xinbo Liu, Xinyue Zhang and Yong Liu

Catalysts 2025, 15(2), 157; https://doi.org/10.3390/catal15020157 - 8 Feb 2025

Viewed by 271

Abstract

Piezocatalysis is a promising technology for converting mechanical energy to chemical energy. Two-dimensional (2D) piezoelectric materials, with their large surface area, high charge mobility, and good flexibility, are among the most promising candidates in piezocatalysis. In this work, for the first time, we [...] Read more.

Piezocatalysis is a promising technology for converting mechanical energy to chemical energy. Two-dimensional (2D) piezoelectric materials, with their large surface area, high charge mobility, and good flexibility, are among the most promising candidates in piezocatalysis. In this work, for the first time, we report Bi₂O₂Se nanosheets (NSs) with an average thickness of ~8 nm and a lateral size of ~160 nm for efficient piezocatalytic H₂O₂ production from water and oxygen under mechanical force induced by ultrasonication. The Bi₂O₂Se NSs achieved a high H₂O₂ production rate of 1033.8 μmol/g/h using ethanol as the sacrificial agent, significantly surpassing that of its bulk-sheet counterpart. Our results provide a novel potential 2D piezocatalytic material and offer valuable guidance for the design and development of high-efficiency H₂O₂ production driven by mechanical energy from water. Full article

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16 pages, 5926 KiB

Open AccessFeature PaperArticle

Precision Size Control of Supported Pd and Pt Nanoparticles via Controlled Electroless Deposition

by Haiying Zhou, Wen Xiong, Abolfazl Shakouri, Yu Lu, John R. Regalbuto, John R. Monnier and John Meynard M. Tengco

Catalysts 2025, 15(2), 156; https://doi.org/10.3390/catal15020156 - 8 Feb 2025

Viewed by 296

Abstract

Well-defined supported metal nanoparticle catalysts, with high uniformity in particle sizes of the dispersed metal, are crucial for studying their catalyzed reactions that exhibit structure sensitivity. For such catalysts, conventional methods of preparation may prove unsuitable in controlling the nanoparticle size and distribution. [...] Read more.

Well-defined supported metal nanoparticle catalysts, with high uniformity in particle sizes of the dispersed metal, are crucial for studying their catalyzed reactions that exhibit structure sensitivity. For such catalysts, conventional methods of preparation may prove unsuitable in controlling the nanoparticle size and distribution. In this work, the systematic growth of supported Pd and Pt particles was achieved through the method of electroless deposition (ED), in which additional metal was deposited on preexisting particles of the same metal. The ED process was investigated by varying the pump time, pump speed, and molar ratios of the reagents during the continuous addition of the metal precursor, as well as the reducing agent and stabilizer, which were hydrazine and ethylenediamine, respectively. This allowed for the precise control of deposition rates, thus regulating the supported metal particle size, size distribution, and particle density. A slower deposition rate was achieved by increasing the amount of the ethylenediamine stabilizer and lowering the pumping speed. Slower rates of deposition resulted in smaller particle sizes and tighter size distributions compared to other preparations with the same metal weight loading, as characterized via X-ray diffraction (XRD), chemisorption, and scanning-transmission electron microscopy (STEM) methods. Full article

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20 pages, 3311 KiB

Open AccessArticle

Coal Fly Ash and Acid Mine Drainage-Based Fe-BEA Catalysts for the Friedel–Crafts Alkylation of Benzene

by Tapiwa Hlatywayo, Leslie Petrik and Benoit Louis

Catalysts 2025, 15(2), 155; https://doi.org/10.3390/catal15020155 - 7 Feb 2025

Viewed by 322

Abstract

Coal fly ash and acid mine drainage are significant environmental issues in South Africa, causing storage constraints and impacting water quality. This study explores the use of coal fly ash and acid mine drainage in preparing zeolite HBEA-supported Fe catalysts. The Na-BEA parent [...] Read more.

Coal fly ash and acid mine drainage are significant environmental issues in South Africa, causing storage constraints and impacting water quality. This study explores the use of coal fly ash and acid mine drainage in preparing zeolite HBEA-supported Fe catalysts. The Na-BEA parent catalysts were synthesised hydrothermally using coal fly ash as a feedstock. The Fe was loaded upon the H-BEA form zeolite using liquid-phase ion exchange or wet impregnation, using Fe-rich acid mine drainage as the metal precursor. The ion-exchanged Fe-BEA catalysts exhibited excellent activity, with the highest selectivity achieved over the 25 AHW after 0.5 h on stream. The study also found that when impregnation was used to load Fe onto the zeolite support, other metals present in the AMD affected the overall activity, with Mn, Ca, Mg, and Na decreasing conversion and selectivity, while Ni had a promoting effect. This study demonstrates that green solid acid catalysts with high catalytic activity can be prepared using two waste materials, coal fly ash and acid mine drainage. To the best of our knowledge, we are reporting for the first time the use of acid mine drainage as a metal precursor in Fe-BEA catalyst preparation. Full article

(This article belongs to the Section Industrial Catalysis)

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23 pages, 9524 KiB

Open AccessArticle

Novel AlCo₂O₄/MWCNTs Nanocomposites for Efficient Degradation of Reactive Yellow 160 Dye: Characterization, Photocatalytic Efficiency, and Reusability

by Junaid Ahmad, Amir Ikhlaq, Muhammad Raashid, Uzma Ikhlaq, Umair Yaqub Qazi, Hafiz Tariq Masood, Tousif Hussain, Mohsin Kazmi, Naveed Ramzan, Asma Naeem, Ashraf Aly Hassan, Fei Qi and Rahat Javaid

Catalysts 2025, 15(2), 154; https://doi.org/10.3390/catal15020154 - 7 Feb 2025

Viewed by 399

Abstract

The purpose of this work was to consider the decolorization efficiency of reactive yellow 160 (Ry-160) dye utilizing cobalt aluminum oxide (AlCo₂O₄)-anchored Multi-Walled Carbon Nanotubes (AlCo₂O₄/MWCNTs) nanocomposites as catalysts for the first time in a [...] Read more.

The purpose of this work was to consider the decolorization efficiency of reactive yellow 160 (Ry-160) dye utilizing cobalt aluminum oxide (AlCo₂O₄)-anchored Multi-Walled Carbon Nanotubes (AlCo₂O₄/MWCNTs) nanocomposites as catalysts for the first time in a photocatalytic process under natural sunlight irradiation. The compositional, morphological, and functional group analyses of AlCo₂O₄ and AlCo₂O₄/MWCNTs were performed by utilizing Energy Dispersive Spectroscopy (EDS), Field Emission Scanning Electron Microscopy (FE-SEM), and Fourier Transform Infrared (FTIR) Spectroscopy, respectively. A UV-Vis (UV-Vis) spectrophotometer was used to investigate degradation efficiency. The results exhibited a reduction in the optical bandgap for AlCo₂O₄/MWCNTs nanocomposites as catalysts from 1.5 to 1.3 eV compared with pure spinel AlCo₂O₄ nanocomposites. AlCo₂O₄/MWCNTs nanocomposites showed excellent photocatalytic behavior, and around 96% degradation of Ry-160 dye was observed in just 20 min under natural sunlight, showing first-order kinetics with rate constant of 0.151 min⁻¹. The results exhibited outstanding stability and reusability for AlCo₂O₄/MWCNTs by maintaining more than 90% photocatalytic efficiency even after seven successive operational cycles. The betterment of the photocatalytic behavior of AlCo₂O₄/MWCNTs nanocomposites as compared to AlCo₂O₄ nanocomposites owes to the first-rate storage capacity of electrons in MWCNTs, due to which the catalyst became an excellent electron acceptor. Furthermore, the permeable structure of MWCNTs results in a greater surface area leading to the onset of more active sites, and, in turn, it also boosts conductivity and reduces the formation of agglomerates on the surface of catalysts, which inhibits e−/h⁺ pair recombination. Concisely, the synthesis of a novel AlCo₂O₄/MWCNTs catalyst with excellent and fast photocatalytic activity was the aim of this study. Full article

(This article belongs to the Special Issue Photocatalysis towards a Sustainable Future)

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13 pages, 1458 KiB

Open AccessArticle

Catalytic Performance of Waste-Based Metal Oxides Towards Waste-Based Combustion Process

by Notsawan Swadchaipong, Vut Tongnan, Ammarika Makdee, Unalome Wetwatana Hartley and Issara Sereewatthanawut

Catalysts 2025, 15(2), 153; https://doi.org/10.3390/catal15020153 - 7 Feb 2025

Viewed by 334

Abstract

The catalytic performance of mixed metal oxides in the combustion of paper industrial waste (bark, paper sludge, and waste paper reject) was investigated. The mixed metal oxide catalyst with, SiO₂, Al₂O₃, Fe₂O₃, and [...] Read more.

The catalytic performance of mixed metal oxides in the combustion of paper industrial waste (bark, paper sludge, and waste paper reject) was investigated. The mixed metal oxide catalyst with, SiO₂, Al₂O₃, Fe₂O₃, and CaO percentages of 78.57, 9.28, 4.28, and 7.85, respectively, was prepared by mixing iron mill scale, clinker, used cement, and bentonite clay, which were employed as metal oxide precursors. An analysis of the combustion behavior of bark, paper sludge, and waste paper reject with and without a mixed metal oxide catalyst, using the thermogravimetric analysis technique, showed that the ignition temperature remained unchanged after the addition of the catalyst. In contrast, the burnout temperature was reduced from 616.9 to 482.6 °C, 682.0 to 672.5 °C, and 678.1 to 669.9 °C for bark, paper sludge, and waste paper reject, respectively. These results indicated that adding a mixed metal oxide catalyst enhanced the combustion reactivity via the accelerated char combustion of biomass. Furthermore, the products formed during the combustion process with and without a catalyst were investigated in a packed-bed reactor. The gaseous products (H₂, CO, CH₄, C₂H₄, C₂H₆, and CO₂) were observed during the combustion process of bark, paper sludge, and waste paper reject at 700 °C, both with and without a mixed metal oxide catalyst. However, higher H₂ and CO₂ compositions, which are attributed to the catalyst addition, were found in the presence of a catalyst, which improved the tar decomposition and the water–gas shift reaction. Full article

(This article belongs to the Special Issue Recent Advances in Energy-Related Materials in Catalysts, 2nd Edition)

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18 pages, 4220 KiB

Open AccessArticle

Catalytic OBSiC Open Cell Foams for Methane-Rich Gas Production Through Hydrogasification of Plastic Waste

by Emilia Saraceno, Eugenio Meloni, Alberto Giaconia and Vincenzo Palma

Catalysts 2025, 15(2), 152; https://doi.org/10.3390/catal15020152 - 6 Feb 2025

Viewed by 501

Abstract

The shift toward sustainable energy sources is essential to curb greenhouse gas emissions and satisfy energy demands. Among renewable options, carbon-based materials—such as agricultural residues and municipal solid waste—provide a dual advantage by generating energy and fuels while also reducing landfill waste. A [...] Read more.

The shift toward sustainable energy sources is essential to curb greenhouse gas emissions and satisfy energy demands. Among renewable options, carbon-based materials—such as agricultural residues and municipal solid waste—provide a dual advantage by generating energy and fuels while also reducing landfill waste. A notable innovation is transforming plastic waste into methane-rich streams via catalytic hydrogasification, a process in which carbon-based feedstocks interact with hydrogen using a selective catalyst. In this study, a structured catalyst was developed, characterized, and tested for converting plastic waste samples. The thermal degradation properties of plastic waste were first studied using thermogravimetric analysis. The catalyst was prepared using an Oxygen Bonded Silicon Carbide (OBSiC) open-cell foam as the carrier, coated with γ-Al₂O₃-based washcoat, CeO₂, and Ni layers. It was characterized in terms of specific surface area, coating adhesion, pore distribution, acidity, and the strength of its active sites. Experimental tests revealed that a hydrogen-enriched atmosphere significantly enhances CH₄ formation. Specifically, during catalytic hydrogasification, methane selectivity reached approximately 59%, compared to 6.7%, 13.7%, and 7.8% observed during pyrolysis, catalyzed pyrolysis, and non-catalyzed hydrogasification tests, respectively. This study presents a novel and effective approach for converting plastic waste using a structured catalyst, a method rarely explored in literature. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis for Sustainable Conversion of Biomass, Carbon Dioxide and Plastic Waste into Fuels and Chemicals)

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14 pages, 5507 KiB

Open AccessArticle

Iron/Rhodium Bimetallic Lewis Acid/Transition Metal Relay Catalysis for Alkynylation/Cyclotrimerization Sequential Reactions Toward Isoindolinone Derivatives from N,O-Cyclic Acetals

by Sidi Mohamed Abdallahi, Ewies Fawzy Ewies, Mohamed El-Shazly, Brahim Ould Elemine, Abderrahmane Hadou, Ata Martin Lawson, Adam Daïch and Mohamed Othman

Catalysts 2025, 15(2), 151; https://doi.org/10.3390/catal15020151 - 6 Feb 2025

Viewed by 297

Abstract

A novel sequential one-pot bimetallic catalytic system combining Fe(III)-catalyzed alkynylation and a Rh(I)-catalyzed [2+2+2] reaction was successfully developed. The σ-Lewis acid properties of iron (III) and the π-Lewis acid properties of rhodium (I) catalysts were unified in an unprecedented intermolecular alkynylation/cyclotrimerization one-pot process. [...] Read more.

A novel sequential one-pot bimetallic catalytic system combining Fe(III)-catalyzed alkynylation and a Rh(I)-catalyzed [2+2+2] reaction was successfully developed. The σ-Lewis acid properties of iron (III) and the π-Lewis acid properties of rhodium (I) catalysts were unified in an unprecedented intermolecular alkynylation/cyclotrimerization one-pot process. Using this unique Fe/Rh bimetallic relay catalytic system, a variety of benzo and pyrridinoisoindolinone derivatives were obtained under mild conditions from easily available N-(propargyl) hydroxy aminals, as the simplest N-acyliminium ion precursors, and several alkynes. Full article

(This article belongs to the Special Issue New Insights into Transition Metal Catalysts for Green Organic Synthesis)

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8 pages, 783 KiB

Open AccessCommunication

Intramolecular [2+2+2] Cyclotrimerization of a Model Triyne to [7]Helical Indeno[2,1-c]Fluorene with Air-Stable Ni(0) and Other Precatalysts

by Marina Degač and Martin Kotora

Catalysts 2025, 15(2), 150; https://doi.org/10.3390/catal15020150 - 5 Feb 2025

Viewed by 359

Abstract

In this work, we demonstrated that air-stable Ni(0) complexes with phosphine ligands can effectively catalyze intramolecular cyclotrimerization of a triyne to a compound with a [7]helical indeno[2,1-c]fluorene skeleton. The obtained results are comparable to those achieved by using Rh-based catalytic systems. [...] Read more.

In this work, we demonstrated that air-stable Ni(0) complexes with phosphine ligands can effectively catalyze intramolecular cyclotrimerization of a triyne to a compound with a [7]helical indeno[2,1-c]fluorene skeleton. The obtained results are comparable to those achieved by using Rh-based catalytic systems. Screening of the reaction conditions showed that bidentate phosphine ligands with small bite angles (70–80°) gave the best results in terms of yields. The highest asymmetric induction with the investigated air-stable Ni(0) precatalyst was obtained using the PROPHOS ligand in HFIP (62% ee). Other catalytic systems, like [Rh(CH₂=CH₂)₂Cl]₂ and [CpCo(P{OEt}₃)(trans-MeO₂CHC=CHCO₂Me)], have also been investigated, showing promising results. Full article

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

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11 pages, 4547 KiB

Open AccessArticle

Enhanced the Catalytic Performance of Samarium and Cerium Co-Modified Mn-Based Oxide Catalyst for Soot Oxidation

by Long Tang, Danfeng He, Wenyi Wang, Zhongxin Jin, Qiang Song, Xiangshi Gu, Zheng Li and Baofang Jin

Catalysts 2025, 15(2), 149; https://doi.org/10.3390/catal15020149 - 5 Feb 2025

Viewed by 430

Abstract

Manganese-based oxides with good redox properties exhibit high soot oxidation activity. To further enhance their catalytic performance, introducing additional metal elements into manganese-based oxides is considered an effective approach. Herein, two rare earth elements (Sm and Ce)-modified MnO_x catalysts were prepared by [...] Read more.

Manganese-based oxides with good redox properties exhibit high soot oxidation activity. To further enhance their catalytic performance, introducing additional metal elements into manganese-based oxides is considered an effective approach. Herein, two rare earth elements (Sm and Ce)-modified MnO_x catalysts were prepared by the co-precipitation method. The synthesized MnO_x catalyst primarily consists of the Mn₃O₄ phase, with trace amounts of Mn₅O₈. The addition of Sm or Ce maintains the predominance of the Mn₃O₄ phase, increases the proportion of Mn₅O₈, and enhances the redox properties, thereby boosting the catalytic activity for NO and soot oxidation. Notably, the coexistence of Sm and Ce achieves optimal soot oxidation activity, with T₁₀ reaching 306 °C. Comprehensive physicochemical characterization elucidates the underlying structure–performance relationships of these catalysts. Full article

(This article belongs to the Special Issue Rare Metal Catalysis: From Synthesis to Sustainable Applications)

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25 pages, 3108 KiB

Open AccessFeature PaperReview

Recent Progress in g-C₃N₄-Based Photocatalysts for Organic Pollutant Degradation: Strategies to Improve Photocatalytic Activity

by Yang Ruan, Yuanan Hu and Hefa Cheng

Catalysts 2025, 15(2), 148; https://doi.org/10.3390/catal15020148 - 4 Feb 2025

Viewed by 583

Abstract

With unique photochemical properties, graphitic carbon nitride (g-C₃N₄) has gained significant attention for application in photocatalytic degradation of a wide range of organic pollutants. However, its performance is limited by the rapid electron–hole recombination and the relatively weak redox [...] Read more.

With unique photochemical properties, graphitic carbon nitride (g-C₃N₄) has gained significant attention for application in photocatalytic degradation of a wide range of organic pollutants. However, its performance is limited by the rapid electron–hole recombination and the relatively weak redox capability. Substantial progress has been made in the preparation of g-C₃N₄-based photocatalysts with enhanced photocatalytic activity. This review summarizes the recent advances in strategies to improve the photocatalytic activity of g-C₃N₄-based photocatalysts and their application in the photocatalytic degradation of organic pollutants. Morphology control, doping, functionalization, metal deposition, dye sensitization, defect engineering, and construction of heterojunctions can be used to improve the photocatalytic activity of g-C₃N₄ through promoting charge carrier separation, reducing the bandgap, and suppressing charge recombination. Furthermore, a range of oxidants, such as hydrogen peroxide and persulfate, can be coupled with g-C₃N₄-based photocatalysts to enhance the generation of reactive oxygen species and boost the photocatalytic degradation of organic pollutants. Precise control over the g-C₃N₄ structure during the synthesis process remains a challenge, and further improvements are required in photocatalyst stability and the mineralization rates of organic pollutants. More research and development effort is needed to address the existing challenges, refine the design of g-C₃N₄-based photocatalysts to improve their activity, and promote their practical application in pollutant degradation. Full article

(This article belongs to the Special Issue Feature Review/Perspective Papers in Photocatalysis)

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36 pages, 6968 KiB

Open AccessFeature PaperReview

Protein Engineering for Industrial Biocatalysis: Principles, Approaches, and Lessons from Engineered PETases

by Konstantinos Grigorakis, Christina Ferousi and Evangelos Topakas

Catalysts 2025, 15(2), 147; https://doi.org/10.3390/catal15020147 - 4 Feb 2025

Viewed by 786

Abstract

Protein engineering has emerged as a transformative field in industrial biotechnology, enabling the optimization of enzymes to meet stringent industrial demands for stability, specificity, and efficiency. This review explores the principles and methodologies of protein engineering, emphasizing rational design, directed evolution, semi-rational approaches, [...] Read more.

Protein engineering has emerged as a transformative field in industrial biotechnology, enabling the optimization of enzymes to meet stringent industrial demands for stability, specificity, and efficiency. This review explores the principles and methodologies of protein engineering, emphasizing rational design, directed evolution, semi-rational approaches, and the recent integration of machine learning. These strategies have significantly enhanced enzyme performance, even rendering engineered PETase industrially relevant. Insights from engineered PETases underscore the potential of protein engineering to tackle environmental challenges, such as advancing sustainable plastic recycling, paving the way for innovative solutions in industrial biocatalysis. Future directions point to interdisciplinary collaborations and the integration of emerging machine learning technologies to revolutionize enzyme design. Full article

(This article belongs to the Special Issue Feature Review Papers in Biocatalysis and Enzyme Engineering)

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22 pages, 6298 KiB

Open AccessArticle

Influence of Secondary Porosity Introduction via Top-Down Methods on MOR, ZSM-5, and Y Zeolites on Their Cumene Cracking Performance

by Josué C. Souza, Mariele I. S. Mello, Felipe F. Barbosa, Iane M. S. Souza, Alexander Sachse and Sibele B. C. Pergher

Catalysts 2025, 15(2), 146; https://doi.org/10.3390/catal15020146 - 4 Feb 2025

Viewed by 555

Abstract

The influence of secondary porosity and the dimensionality of zeolitic structures with 1D and 3D pore systems on the accessibility of cumene to Brønsted acid sites was evaluated in this study. Zeolites Y, ZSM-5, and MOR, obtained through NH4F leaching and basic and [...] Read more.

The influence of secondary porosity and the dimensionality of zeolitic structures with 1D and 3D pore systems on the accessibility of cumene to Brønsted acid sites was evaluated in this study. Zeolites Y, ZSM-5, and MOR, obtained through NH4F leaching and basic and acid treatments, were studied. Zeolites Y and ZSM-5 showed a significant increase in specific surface area while maintaining the micropore volume as well as an increase in the concentration of Brønsted acid sites following treatment. Zeolite MOR exhibited an increase in mesopore volume and retained Brønsted acidity. The impact of the treatments on catalytic properties was evaluated through cumene cracking, which yielded high catalytic conversion for the materials. This result is consistent with the goal of the model reaction to characterize Brønsted acid sites, enhance accessibility, and reduce diffusion paths. Full article

(This article belongs to the Special Issue Sustainable Catalysis for Green Chemistry and Energy Transition)

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34 pages, 6093 KiB

Open AccessFeature PaperReview

Cobalt Decarbonization Catalysts Turning Methane to Clean Hydrogen and Valuable Carbon Nanostructures: A Review

by Elpida Zeza, Eleni Pachatouridou, Angelos A. Lappas and Eleni F. Iliopoulou

Catalysts 2025, 15(2), 145; https://doi.org/10.3390/catal15020145 - 4 Feb 2025

Viewed by 556

Abstract

The continuous growth in world energy demands along with the urgent need for decarbonization are strong motivations for the development and usage of sustainable fuels. Hydrogen is highly anticipated to replace fossil fuels in energy production, as it is one of the cleanest [...] Read more.

The continuous growth in world energy demands along with the urgent need for decarbonization are strong motivations for the development and usage of sustainable fuels. Hydrogen is highly anticipated to replace fossil fuels in energy production, as it is one of the cleanest energy sources with high energy density per weight. Among the hydrogen production methods, catalytic methane pyrolysis (CMP) stands out as it can contribute to the decarbonization process, since the only co-products include valuable carbon structures and no greenhouse emissions. Cobalt has been shown to be a competent metallic catalytic material with high activity in relation to hydrogen production and selectivity towards valuable carbon nanotubes (CNTs), or carbon nanofibers (CNFs). This review article aims to offer insights relevant to future developments in CMP, by reporting the advantages of methane decomposition over cobalt catalysts. It provides a summary of the factors that influence both hydrogen yield and carbon growth. More specifically, the impacts of different metal loadings and the benefits of utilizing both support carriers and bimetallic systems are addressed. Last but not least, the findings on the most efficient preparation procedures and the optimum operating conditions are also revealed, as supported by published experimental data. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Catalytic Materials)

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25 pages, 18185 KiB

Open AccessArticle

On the Conceptualization of the Active Site in Selective Oxidation over a Multimetal Oxide Catalyst: From Atomistic to Black-Box Approximation

by José F. Durán-Pérez, José G. Rivera de la Cruz, Martín Purino, Julio C. García-Martínez and Carlos O. Castillo-Araiza

Catalysts 2025, 15(2), 144; https://doi.org/10.3390/catal15020144 - 4 Feb 2025

Viewed by 579

Abstract

Catalytic reactor engineering bridges the active-site scale and the industrial-reactor scale, with kinetics as the primary bottleneck in scale-up. The main challenge in kinetics is conceptualizing the active site and formulating the reaction mechanism, leading to multiple approaches without clear guidance on their [...] Read more.

Catalytic reactor engineering bridges the active-site scale and the industrial-reactor scale, with kinetics as the primary bottleneck in scale-up. The main challenge in kinetics is conceptualizing the active site and formulating the reaction mechanism, leading to multiple approaches without clear guidance on their reliability for industrial-reactor design. This work assesses different approaches to active-site conceptualization and reaction-mechanism formulation for selective oxidation over a complex multi-metal catalyst. It integrates atomistic-scale insights from periodic Density Functional Theory (DFT) calculations into kinetic-model development. This approach contrasts with the macroscopic classical method, which treats the catalyst as a black box, as well as with alternative atomistic methods that conceptualize the active site as a single metal atom on different catalytic-surface regions. As a case study, this work examines ethane oxidative dehydrogenation to ethylene over the multi-metal oxide catalyst MoVTeNbO, which has a complex structure. This analysis provides insights into the ability of DFT to accurately describe reactions on such materials. Additionally, it compares DFT predictions to experimental data obtained from a non-idealized MoVTeNbO catalyst synthesized and assessed under kinetic control at the laboratory scale. The findings indicate that while the black-box active-site conceptualization best describes observed trends, its reaction mechanism and parameters lack reliability compared to DFT calculations. Furthermore, atomistic active-site conceptualizations lead to different parameter sets depending on how the active site and reaction mechanism are defined. Unlike previous studies, our approach determines activation-energy profiles within the range predicted by DFT. The resulting kinetic model describes experimental trends while maintaining phenomenological and statistical reliability. The corrections required for primary parameters remain below 20 kJ mol

^{- 1}

, consistent with the inherent uncertainties in DFT calculations. In summary, this work demonstrates the feasibility of integrating atomistic insights into kinetic modeling, offering different perspectives on active-site conceptualization and reaction-mechanism formulation, paving the way for future studies on rational catalyst and industrial-reactor design. Full article

(This article belongs to the Section Catalytic Reaction Engineering)

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14 pages, 4727 KiB

Open AccessArticle

Ternary PdIrNi Telluride Amorphous Mesoporous Nanocatalyst for Efficient Electro-Oxidation of Ethylene Glycol

by Liang Fu, Manli Wang, Lulu Hao, Jinhua Lei, Tong Liu, Zelin Chen and Changjiu Li

Catalysts 2025, 15(2), 143; https://doi.org/10.3390/catal15020143 - 4 Feb 2025

Viewed by 469

Abstract

The development of efficient electrocatalysts for the complete oxidation of ethylene glycol (EG) is crucial for enhancing the practicality of direct EG fuel cells (DEGFCs). However, significant challenges persist in developing highly active Pd-based catalytic electrodes. In this work, PdIrNi ternary telluride nanospheres [...] Read more.

The development of efficient electrocatalysts for the complete oxidation of ethylene glycol (EG) is crucial for enhancing the practicality of direct EG fuel cells (DEGFCs). However, significant challenges persist in developing highly active Pd-based catalytic electrodes. In this work, PdIrNi ternary telluride nanospheres (PdIrNiTe-MNSPs) with mesoporous morphology and an amorphous structure were successfully synthesized and applied in electrocatalytic EG oxidation reaction. Brunauer–Emmett–Teller analysis revealed typical mesoporous characteristics, with a surface area of 8.33 m²·g⁻¹ and a total pore volume of 0.055 cm³·g⁻¹, respectively. Transmission electron microscopy characterization showed that the outer layer of PdIrNiTe-MNSPs is entirely amorphous in structure. Electrochemical tests demonstrated that PdIrNiTe-MNSPs exhibit enhanced electrocatalytic specific activity (16.75 mA·cm⁻²) and mass activity (1372.22 mA·mg⁻¹) for EG oxidation reaction (EGOR), achieving 3.17 and 2.09 times higher than commercial Pd/C, which can be attributed to its unique nanoarchitecture and optimized electron configuration. In situ spectroscopy revealed that with the incorporation of IrNi, PdIrNiTe-MNSPs facilitate C-C bond cleavage of EG, achieving a higher selectivity (≈93%) in oxidizing EG to C1 products, while PdTe-MNSPs demonstrated higher selectivity for glycolic acid in EGOR. Taken together, this work provides new insights into the application of Pd-based telluride nanomaterials in electrocatalysis for EGOR. Full article

(This article belongs to the Special Issue Advanced Electrocatalysts for Energy-Related Applications)

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20 pages, 5440 KiB

Open AccessFeature PaperArticle

Novel Ni/SBA-15 Catalyst Pellets for Tar Catalytic Cracking in a Dried Sewage Sludge Pyrolysis Pilot Plant

by Emmanuel Iro, Saeed Hajimirzaee, Takehiko Sasaki and Maria Olea

Catalysts 2025, 15(2), 142; https://doi.org/10.3390/catal15020142 (registering DOI) - 3 Feb 2025

Viewed by 504

Abstract

Novel Ni/SBA-15 catalysts were synthesised and their activity in the dry reforming of methane process was assessed. These materials were prepared into extrudates shaped like pellets and tested in a pyrolysis pilot plant fitted with a catalytic reactor for sewage sludge pyrolysis tar [...] Read more.

Novel Ni/SBA-15 catalysts were synthesised and their activity in the dry reforming of methane process was assessed. These materials were prepared into extrudates shaped like pellets and tested in a pyrolysis pilot plant fitted with a catalytic reactor for sewage sludge pyrolysis tar removal. The Ni/SBA-15 catalyst pellets remained highly active and stable throughout the test’s duration, converting 100% tar in the hot gas to smaller non-condensable gases, thereby increasing the pyrolysis gas fraction and eliminating the problematic tar in the vapour stream. Catalyst characterisation with Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray (EDX) analysis, Transmission Electron Microscopy (TEM), and Thermogravimetric Analysis (TGA) confirmed that both the Ni/SBA-15-powered catalyst and the pellets were resistant to sintering and carbon deposition and remained highly active even with relatively high-level sulphur in the feed stream. The Ni/SBA-15 catalyst extrudates were prepared by mixing the powdered catalyst with varied amounts of colloidal silica binder and fixed amounts of methyl cellulose and water. The highest mechanical strength of the extrudates was determined to be of those obtained with 36% of the inorganic binder. The physical properties and catalytic activity of Ni/SBA-15 pellets with 36% colloidal silica were compared with the original powdered Ni/SBA-15 catalyst to assess the binder inhibitory effect, if any. The results confirmed that colloidal silica binder did not inhibit the desired catalyst properties and performance in the reaction. Instead, enhanced catalytic performance was observed. Full article

(This article belongs to the Section Catalysis for Sustainable Energy)

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15 pages, 2440 KiB

Open AccessFeature PaperArticle

Synergistic Effects of Photocatalysis, Ozone Treatment, and Metal Catalysts on the Decomposition of Acetaldehyde

by Tsuyoshi Ochiai, Kengo Hamada and Michifumi Okui

Catalysts 2025, 15(2), 141; https://doi.org/10.3390/catal15020141 - 3 Feb 2025

Viewed by 791

Abstract

This study explores the synergistic interactions between photocatalysis, ozone treatment, and metal catalysts in the decomposition of acetaldehyde, a representative volatile organic compound (VOC). The study addresses the growing need for efficient air purification technologies by integrating advanced oxidation processes. Metal catalysts, particularly [...] Read more.

This study explores the synergistic interactions between photocatalysis, ozone treatment, and metal catalysts in the decomposition of acetaldehyde, a representative volatile organic compound (VOC). The study addresses the growing need for efficient air purification technologies by integrating advanced oxidation processes. Metal catalysts, particularly manganese oxide-based materials, were combined with photocatalysis and ozonation to investigate their impact on acetaldehyde removal efficiency. Experimental results revealed that the treatment integrating these methods significantly outperformed conventional single-process treatments. Metal catalysts facilitated the initial oxidation of acetaldehyde, while photocatalysis accelerated subsequent stages, including the mineralisation of intermediates. Ozone contributed additional reactive oxidative species, further enhancing decomposition rates. These findings provide valuable insights into the design of efficient VOC removal systems, demonstrating that integrating metal catalysts with photocatalytic and ozonation processes offers a promising strategy for improving air purification technologies. This approach has potential applications in environmental remediation and indoor air quality management. Full article

(This article belongs to the Special Issue TiO₂ Photocatalysts: Design, Optimization and Application)

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16 pages, 4142 KiB

Open AccessArticle

Preparation of Novel ACE Inhibitory Peptides from Skimmed Goat Milk Hydrolyzed by Multi-Enzymes: Process Optimization, Purification, and Identification

by Wenjing Hu, Guowei Shu, Huan Lei, Guanli Du, Zhengxin Liu and Li Chen

Catalysts 2025, 15(2), 140; https://doi.org/10.3390/catal15020140 - 3 Feb 2025

Viewed by 496

Abstract

This study optimizes the process conditions for preparing angiotensin-converting enzyme (ACE) inhibitory peptides from skimmed goat milk (SGM) hydrolyzed by multi-enzymes using response surface methodology. When the enzymatic hydrolysis time was 90 min, the optimal hydrolysis conditions were a pH of 8.49, enzyme-to-substrate [...] Read more.

This study optimizes the process conditions for preparing angiotensin-converting enzyme (ACE) inhibitory peptides from skimmed goat milk (SGM) hydrolyzed by multi-enzymes using response surface methodology. When the enzymatic hydrolysis time was 90 min, the optimal hydrolysis conditions were a pH of 8.49, enzyme-to-substrate ratio (E/S ratio) of 8.04%, and temperature of 61.54 °C. The hydrolysis degree and ACE inhibitory activity were 65.39% ± 0.01% and 84.65% ± 0.03%, respectively. After purification by ultrafiltration, macroporous resin, and gel filtration, the ACE inhibitory activity of F2-2 in the two components of F2 was higher, with the ACE inhibitory rate of 93.97% ± 0.15% and IC₅₀ of 0.121 ± 0.004 mg/mL. The content of hydrophobic amino acids, fatty amino acids, and aromatic amino acids in component F2-2 accounts for 73.17%, 33.86%, and 33.72%, respectively. Eleven peptides were isolated and identified from the F2-2 components of the enzymatic hydrolysate of SGM, including two peptides without an established database. The peptides mainly came from β casein, α_S1 casein, and α_S2 casein. Full article

(This article belongs to the Special Issue Enzyme and Biocatalysis Application)

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12 pages, 4747 KiB

Open AccessArticle

Sulfur Dioxide-Tolerant Core@shell Ru@Pt Catalysts Toward Oxygen Electro-Reduction

by Yuxin Liu, Changyuan Bao, Guodong Xu, Lei Du and Bing Huang

Catalysts 2025, 15(2), 139; https://doi.org/10.3390/catal15020139 - 3 Feb 2025

Viewed by 515

Abstract

Proton exchange membrane fuel cells (PEMFCs) have achieved milestones in performance improvements and commercial launches. In the typical commercialized PEMFCs, the compressed air to cathode is usually supplied from ambient air, assuming that no costly pre-purification system is applied. Therefore, the working PEMFCs [...] Read more.

Proton exchange membrane fuel cells (PEMFCs) have achieved milestones in performance improvements and commercial launches. In the typical commercialized PEMFCs, the compressed air to cathode is usually supplied from ambient air, assuming that no costly pre-purification system is applied. Therefore, the working PEMFCs may suffer from the negative effects of the air impurities. In this regard, SO₂, as the most poisonous species, may be fed along with air at the cathode and strongly adsorbed on the Pt surface, leading to Pt site deactivation. To address this challenge, we published a series of works in terms of poisoning mechanisms, regeneration protocols, and advanced poisoning-tolerant catalysts. Herein, we are aiming at developing a SO₂-tolerant electrocatalyst toward a cathodic oxygen reduction reaction (ORR). We reasonably incorporate the Ru, synthesize Ru@Pt core@shell catalysts and investigate the relationships among Ru incorporation, ORR activity and SO₂ tolerance. Impressively, the Ru@Pt/C exhibits higher initial ORR activity (0.288 A mg⁻¹_Pt), better SO₂ poisoning resistance (33% loss in initial activity) than that of commercial Pt/C catalysts (0.252 A mg⁻¹_Pt; 62% loss). The engineered affinity between Pt and SO₂ in the presence of Ru is uncovered to account for the improvement. Full article

(This article belongs to the Special Issue Advanced Electrocatalysts for Oxygen Reduction Reaction)

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33 pages, 4567 KiB

Open AccessReview

Modified Zeolites for the Removal of Emerging Bio-Resistive Pollutants in Water Resources

by Fatin Samara, Amer A. Al Abdel Hamid, Venkatesh Gopal, Lara Dronjak, Fares Feghaly and Sofian Kanan

Catalysts 2025, 15(2), 138; https://doi.org/10.3390/catal15020138 - 2 Feb 2025

Viewed by 471

Abstract

The increasing presence of pollutants, including pharmaceuticals and pesticides, in water resources necessitates the development of effective remediation technologies. Zeolites are promising agents for pollutant removal due to their high surface area, ion-exchange capacity, natural abundance, and diverse tailorable porous structures. This review [...] Read more.

The increasing presence of pollutants, including pharmaceuticals and pesticides, in water resources necessitates the development of effective remediation technologies. Zeolites are promising agents for pollutant removal due to their high surface area, ion-exchange capacity, natural abundance, and diverse tailorable porous structures. This review focuses on the efficient application of modified zeolites and mesoporous materials as photocatalysts and adsorbents for removing contaminants from water bodies. The adsorption and photodegradation of pesticides and selected non-steroidal anti-inflammatory drugs and antibiotics on various zeolites reveal optimal adsorption and degradation conditions for each pollutant. In most reported studies, higher SiO₂/Al₂O₃ ratio zeolites exhibited improved adsorption, and thus photodegradation activities, due to increased hydrophobicity and lower negative charge. For example, SBA-15 demonstrated high efficiency in removing diclofenac, ibuprofen, and ketoprofen from water in acidic conditions. Metal doped into the zeolite framework was found to be a very active catalyst for the photodegradation of organic pollutants, including pesticides, pharmaceuticals, and industrial wastes. It is shown that the photocatalytic activity depends on the zeolite-type, metal dopant, metal content, zeolite pore structure, and the energy of the irradiation source. Faujasite-type Y zeolites combined with ozone achieved up to 95% micropollutant degradation. Bentonite modified with cellulosic biopolymers effectively removed pesticides such as atrazine and chlorpyrifos, while titanium and/or silver-doped zeolites showed strong catalytic activity in degrading carbamates, highlighting their environmental application potential. Full article

(This article belongs to the Special Issue Recent Advances in Photocatalytic Treatment of Pollutants in Water)

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Catalysts, Volume 15, Issue 2 (February 2025) – 69 articles

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