Catalysts

15 pages, 3859 KiB

Open AccessEditor’s ChoiceArticle

Photothermal-Assisted Photocatalytic Degradation of Tetracycline in Seawater Based on the Black g-C₃N₄ Nanosheets with Cyano Group Defects

by Loic Jiresse Nguetsa Kuate, Zhouze Chen, Jialin Lu, Huabing Wen, Feng Guo and Weilong Shi

Catalysts 2023, 13(7), 1147; https://doi.org/10.3390/catal13071147 - 24 Jul 2023

Cited by 27 | Viewed by 1475

Abstract

As a broad-spectrum antibiotic, tetracycline (TC) has been continually detected in soil and seawater environments, which poses a great threat to the ecological environment and human health. Herein, a black graphitic carbon nitride (CN-B) photocatalyst was synthesized by the one-step calcination method of [...] Read more.

As a broad-spectrum antibiotic, tetracycline (TC) has been continually detected in soil and seawater environments, which poses a great threat to the ecological environment and human health. Herein, a black graphitic carbon nitride (CN-B) photocatalyst was synthesized by the one-step calcination method of urea and phloxine B for the degradation of tetracycline TC in seawater under visible light irradiation. The experimental results showed that the photocatalytic degradation rate of optimal CN-B-0.1 for TC degradation was 92% at room temperature within 2 h, which was 1.3 times that of pure CN (69%). This excellent photocatalytic degradation performance stems from the following factors: (i) ultrathin nanosheet thickness reduces the charge transfer distance; (ii) the cyanogen defect promotes photogenerated carriers’ separation; (iii) and the photothermal effect of CN-B increases the reaction temperature and enhances the photocatalytic activity. This study provides new insight into the design of photocatalysts for the photothermal-assisted photocatalytic degradation of antibiotic pollutants. Full article

(This article belongs to the Special Issue Development of g-C₃N₄-Based Photocatalysts: Environmental Purification and Energy Conversion)

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18 pages, 2124 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Recent Advances in Platinum and Palladium Solvent Extraction from Real Leaching Solutions of Spent Catalysts

by Ana Paula Paiva

Catalysts 2023, 13(7), 1146; https://doi.org/10.3390/catal13071146 - 24 Jul 2023

Cited by 2 | Viewed by 2049

Abstract

The strategic importance of platinum and palladium, two platinum-group metals (PGMs), is particularly supported by their technological applications, one of the most relevant being the role they perform as catalysts for several sorts of chemical reactions. The cumulative demand for these two PGMs [...] Read more.

The strategic importance of platinum and palladium, two platinum-group metals (PGMs), is particularly supported by their technological applications, one of the most relevant being the role they perform as catalysts for several sorts of chemical reactions. The cumulative demand for these two PGMs to be used as catalysts more than justifies increasing research efforts to develop sustainable recycling processes to maintain their supply. This critically appraised topic review describes the recent research trends (since 2010) developed by the world’s research communities to reach sustainable methods to recover platinum and palladium from spent catalysts in the liquid phase, namely those involving a solvent extraction (SX) step. The selected recycling processes are based on extensive fundamental research, but this paper intends to focus on information collected about SX procedures applied to real leaching samples of spent catalysts, either from automobile or industrial sources. A critical appraisal of the claimed success levels, the identified constraints, and open challenges is carried out, together with some perspectives on possible ways to redirect research efforts and minimize the gap between academia and industry on this matter. Full article

(This article belongs to the Special Issue Recent Advances Utilized in the Recycling of Catalysts II)

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13 pages, 3674 KiB

Open AccessArticle

High Performance of Nanostructured Cu₂O-Based Photodetectors Grown on a Ti/Mo Metallic Substrate

by Alhoda Abdelmoneim, Mohamed Sh. Abdel-wahab, June Key Lee, Meera Moydeen Abdul Hameed, Badr M. Thamer, Abdullah M. Al-Enizi, Rayana Ibrahim Alkhalifah and Wael Z. Tawfik

Catalysts 2023, 13(7), 1145; https://doi.org/10.3390/catal13071145 - 24 Jul 2023

Viewed by 1061

Abstract

In this work, cuprous oxide (Cu₂O) thin films were prepared using a simplistic sputtering technique. The films were grown on both traditional fluorine-doped tin oxide (FTO) and Ti-metallic substrates. X-ray diffraction applied for investigation of the crystal structure proved that the [...] Read more.

In this work, cuprous oxide (Cu₂O) thin films were prepared using a simplistic sputtering technique. The films were grown on both traditional fluorine-doped tin oxide (FTO) and Ti-metallic substrates. X-ray diffraction applied for investigation of the crystal structure proved that the Cu₂O layer acquires the cubic structure with a (111) main peak at 2θ of 36.46°. The optical absorption and transmission were detected through the utilization of a UV-Vis spectrophotometer, and the optical bandgap for the Cu₂O layer was determined to be ~2.15 eV using Tauc’s equation. XPS and scanning electron microscopy were also performed for chemical structure and morphological investigation, respectively. The optoelectronic behaviors for the prepared samples were carried out using a Keithley source meter; the photocurrent density was measured in a range of applied voltage between −1 and 1 volt under the illumination of a xenon lamp with a power density of 100 mWcm⁻². External quantum efficiency, sensitivity, responsivity, and detectivity were computed using proprietary models based on the experimental data. Full article

(This article belongs to the Topic Photosensitive and Optical Materials)

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16 pages, 2685 KiB

Open AccessArticle

Reaction Pathways of Gamma-Valerolactone Hydroconversion over Co/SiO₂ Catalyst

by Gyula Novodárszki, Ferenc Lónyi, Magdolna R. Mihályi, Anna Vikár, Róbert Barthos, Blanka Szabó, József Valyon and Hanna E. Solt

Catalysts 2023, 13(7), 1144; https://doi.org/10.3390/catal13071144 - 23 Jul 2023

Cited by 1 | Viewed by 1064

Abstract

The hydroconversion of γ-valerolactone (GVL) over Co/SiO₂ catalyst proceeds in a complex reaction network, resulting in 2-methyltetrahydrofuran (2-MTHF) as the main product, and C₄–C₅ alcohol and alkane side-products. The catalyst was shown to contain Co⁰ sites and Lewis [...] Read more.

The hydroconversion of γ-valerolactone (GVL) over Co/SiO₂ catalyst proceeds in a complex reaction network, resulting in 2-methyltetrahydrofuran (2-MTHF) as the main product, and C₄–C₅ alcohol and alkane side-products. The catalyst was shown to contain Co⁰ sites and Lewis acid (Co²⁺ ion)/Lewis base (O²⁻ ion) pair sites, active for hydrogenation/dehydrogenation and dehydration reactions, respectively. The initial reaction step was confirmed to be the hydrogenation of GVL to key intermediate 1,4-pentanediol (1,4-PD). Cyclodehydration of 1,4-PD led to the main product 2-MTHF, whereas its dehydration/hydrogenation gave 1-pentanol and 2-pentanol side-products, with about the same yield. In contrast, 2-pentanol was the favored alcohol product of 2-MTHF hydrogenolysis. 2-Butanol was formed by decarbonylation of 4-hydroxypentanal intermediate. The latter was the product of 1,4-PD dehydrogenation. Alkanes were formed from the alcohol side-products via dehydration/hydrogenation reactions. Full article

(This article belongs to the Special Issue Heterogeneous Catalytic Materials: Synthesis, Characterization and Applications for Energetic Purposes, 2nd Edition)

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14 pages, 2566 KiB

Open AccessArticle

Polyol Synthesis of Ag-Doped Copper Oxide Nanoparticles as a Methylene Blue-Degrading Agent

by Yogeshwar Baste, Vikram Jadhav, Arpita Roy, Saad Alghamdi, Mohamed Abbas, Jari S. Algethami, Mazen Almehmadi, Mamdouh Allahyani, Devvret Verma, Krishna Kumar Yadav, Byong-Hun Jeon and Hyun-Kyung Park

Catalysts 2023, 13(7), 1143; https://doi.org/10.3390/catal13071143 - 23 Jul 2023

Cited by 6 | Viewed by 1513

Abstract

The use of metal oxide nanomaterials as photocatalysts for wastewater treatment has received significant attention in recent years due to their unique physicochemical properties. In this study, we use a polyol-mediated refluxing method to synthesize silver-incorporated copper oxide nanomaterials (Ag@CuO NMs). The use [...] Read more.

The use of metal oxide nanomaterials as photocatalysts for wastewater treatment has received significant attention in recent years due to their unique physicochemical properties. In this study, we use a polyol-mediated refluxing method to synthesize silver-incorporated copper oxide nanomaterials (Ag@CuO NMs). The use of tetra butyl ammonium bromide (TBAB) as a capping agent and ethylene glycol as a reducing agent for Ag+ to Ag is elaborated upon. The prepared Ag@CuO NMs were tested for their ability to degrade water pollutants, specifically methylene blue (MB) dye. Two different Ag contents, weights of 3% and 5%, were used to produce modified CuO-based nanomaterials. The crystalline structures of the NMs were characterized via XRD diffraction, and the morphology of the materials was investigated using FE-SEM. The optical properties were studied using UV-vis spectroscopy. The photocatalytic activity of the Ag@CuO NMs was evaluated by analyzing the degradation of MB dye when exposed to UV-visible light. Our results showed that the 5% weight Ag@CuO NM sample exhibited the most efficient degradation activity against MB dye. Therefore, these nanomaterials hold potential for photocatalytic applications, particularly for wastewater purification. Full article

(This article belongs to the Special Issue Applications of Nanocatalytic Processes: Water, Wastewater and Air Treatment)

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11 pages, 4665 KiB

Open AccessArticle

Improving Separation Efficiency of Photogenerated Charges through Combination of Conductive Polythiophene for Selective Production of CH₄

by Yiqiang Deng, Lingxiao Tu, Ping Wang, Shijian Chen, Man Zhang, Yong Xu and Weili Dai

Catalysts 2023, 13(7), 1142; https://doi.org/10.3390/catal13071142 - 23 Jul 2023

Viewed by 859

Abstract

In today’s society, mankind is confronted with two major problems: the energy crisis and the greenhouse effect. Artificial photosynthesis can use solar energy to convert the greenhouse gas CO₂ into high-value compounds, which is an ideal solution to alleviate the energy crisis [...] Read more.

In today’s society, mankind is confronted with two major problems: the energy crisis and the greenhouse effect. Artificial photosynthesis can use solar energy to convert the greenhouse gas CO₂ into high-value compounds, which is an ideal solution to alleviate the energy crisis and solve the problem of global warming. The combination of ZnO and polythiophenes (PTh) can make up for each other’s drawbacks, thus improving the photoresponse behavior and separation efficiency of the photogenerated carriers. The PTh layer can transfer photogenerated electrons to ZnO, thereby extending the lifetime of the photogenerated charges. The production rate of CH₄ from the photoreduction of CO₂ with ZnO/PTh₁₀ is 4.3 times that of pure ZnO, and the selectivity of CH₄ is increased from 70.2% to 92.2%. The conductive PTh can absorb photons to induce π–π* transition, and the photogenerated electrons can transfer from the LUMO to the conduction band (CB) of ZnO, thus more electrons are involved in the reduction of CO₂. Full article

(This article belongs to the Special Issue Photocatalysis in Air Purification)

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19 pages, 7460 KiB

Open AccessArticle

A Comparative Study of the Antiviral Properties of Thermally Sprayed Coatings against Human Coronavirus HCoV-229E

by Elnaz Alebrahim, Hediyeh Khatibnezhad, Morvarid Mohammadian Bajgiran, Magan Solomon, Chen Liang, Selena M. Sagan, Rogerio S. Lima, Jörg Oberste Berghaus, Maniya Aghasibeig and Christian Moreau

Catalysts 2023, 13(7), 1141; https://doi.org/10.3390/catal13071141 - 22 Jul 2023

Cited by 2 | Viewed by 1150

Abstract

For decades, novel viral strains of respiratory tract infections have caused human pandemics and initiated widespread illnesses. The recent coronavirus disease 2019 (COVID-19) outbreak caused by the SARS-CoV-2 virus has raised an urgent need to develop novel antiviral coatings as one of the [...] Read more.

For decades, novel viral strains of respiratory tract infections have caused human pandemics and initiated widespread illnesses. The recent coronavirus disease 2019 (COVID-19) outbreak caused by the SARS-CoV-2 virus has raised an urgent need to develop novel antiviral coatings as one of the potential solutions to mitigate the transmission of viral pathogens. Titanium dioxide is considered an excellent candidate for viral disinfection under light irradiation, with the potential to be activated under visible light for indoor applications. This research assessed the antiviral performance of thermally sprayed TiO₂ coatings under UVA and ambient light. We also report the antiviral performance of TiO₂ composites with other oxides, such as Cu₂O and Al₂O₃, produced by suspension plasma spray, atmospheric plasma spray, and suspension high-velocity oxygen fuel techniques. To evaluate the antiviral performance of the above coatings in a containment level-2 laboratory, a human common cold coronavirus, HCoV-229E, was initially used as a relevant surrogate for SARS-CoV-2. Coatings were also analyzed using SEM and XRD and were classified based on their surface roughness, porosity, and phase composition. Collectively, the thermally sprayed coatings showed comparable or slightly better antiviral activity compared to copper. The most significant level of activity observed was approximately 20% to 50% higher than that of a pure copper plate. Full article

(This article belongs to the Special Issue Photocatalytic Nanomaterials for Abatement of Microorganisms)

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19 pages, 3397 KiB

Open AccessArticle

Highly Stable Photocatalytic Dry and Bi-Reforming of Methane with the Role of a Hole Scavenger for Syngas Production over a Defective Co-Doped g-C₃N₄ Nanotexture

by Muhammad Tahir, Azmat Ali Khan, Abdullah Bafaqeer, Naveen Kumar, Mohammad Siraj and Amanullah Fatehmulla

Catalysts 2023, 13(7), 1140; https://doi.org/10.3390/catal13071140 - 22 Jul 2023

Cited by 4 | Viewed by 1282

Abstract

Photocatalytic reduction of CO₂ with CH₄ through the dry reforming of methane (DRM) is an attractive approach to recycling greenhouse gases into valuable chemicals and fuels; however, this process is quite challenging. Although there is growing interest in designing efficient photocatalysts, [...] Read more.

Photocatalytic reduction of CO₂ with CH₄ through the dry reforming of methane (DRM) is an attractive approach to recycling greenhouse gases into valuable chemicals and fuels; however, this process is quite challenging. Although there is growing interest in designing efficient photocatalysts, they are less stable, and have lower photoactivity when employed for DRM reactions. Herein, we developed a noble metal-free hierarchical graphitic carbon nitride (HC₃N₄) loaded with cobalt (Co) for highly efficient and stable photocatalytic dry reforming of methane to produce synthesis gases (CO and H₂). The performance of the newly designed Co/HC₃N₄ composite was tested for different reforming systems such as the dry reforming of methane, bi-reforming of methane (BRM) and reforming of CO₂ with methanol–water. The performance of HC₃N₄ was much higher compared to bulk g-C₃N₄, whereas Co/HC₃N₄ was found to be promising for higher charge carrier separation and visible light absorption. The yield of CO and H₂ with HC₃N₄ was 1.85- and 1.81-fold higher than when using g-C₃N₄ due to higher charge carrier separation. The optimized 2% Co/HC₃N₄ produces CO and H₂ at an evolution rate of 555 and 41.2 µmol g⁻¹ h⁻¹, which was 18.28- and 1.74-fold more than using HC₃N₄ during photocatalytic dry reforming of methane (DRM), with a CH₄/CO₂ feed ratio of 1.0. This significantly enhanced photocatalytic CO and H₂ evolution during DRM was due to efficient charge carrier separation in the presence of Co. The CH₄/CO₂ feed ratio was further investigated, and a 2:1 ratio was best for CO production. In contrast, the highest H₂ was produced with a 1:1 feed ratio due to the competitive adsorption of the reactants over the catalyst surface. The performance of the composite was further investigated for bi-reforming methane and methanol. Using photocatalytic CO₂ reduction with CH₄/H₂O, the production of CO and H₂ was reduced, whereas significantly higher CO and H₂ evolved using the BRM process involving methanol. Using methanol with CO₂ and H₂O, 10.77- and 1.39-fold more H₂ and CO efficiency was achieved than when using dry reforming of methane. The composite was also very stable for continuous synthesis gas production during DRM in consecutive cycles. Thus, a co-assisted g-C₃N₄ nanotexture is promising for promoting photocatalytic activity and can be further explored in other solar energy applications. Full article

(This article belongs to the Special Issue Nanostructured Materials for Solar and Visible Light Driven Photocatalysis)

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15 pages, 2665 KiB

Open AccessArticle

Comparison of Photocatalytic Biocidal Activity of TiO₂, ZnO and Au/ZnO on Escherichia coli and on Aspergillus niger under Light Intensity Close to Real-Life Conditions

by Mohamad Al Hallak, Thomas Verdier, Alexandra Bertron, Kevin Castelló Lux, Ons El Atti, Katia Fajerwerg, Pierre Fau, Julie Hot, Christine Roques and Jean-Denis Bailly

Catalysts 2023, 13(7), 1139; https://doi.org/10.3390/catal13071139 - 22 Jul 2023

Cited by 1 | Viewed by 1966

Abstract

Microbial contamination of the surface of building materials and subsequent release of microbial particles into the air can significantly affect indoor air quality. Avoiding the development or, at least, reducing the quantity of microorganisms growing on building materials is a key point to [...] Read more.

Microbial contamination of the surface of building materials and subsequent release of microbial particles into the air can significantly affect indoor air quality. Avoiding the development or, at least, reducing the quantity of microorganisms growing on building materials is a key point to reduce health risks for building occupiers. In that context, the antimicrobial activity of TiO₂, ZnO and Au/ZnO was assessed by measuring log reductions of Escherichia coli and Aspergillus niger populations both in the dark and under a light intensity close to real-life conditions. The bactericidal activities (≥2.3 log reduction) of tested products were stronger than their fungicidal activities (≤1.4 log reduction) after 2 h of contact. Different parameters including concentration of photocatalyst, intensity of light (dark vs. 5 W/m² UV-A), and duration of contact between photocatalyst and microbial cells and spores were investigated. Results of this study confirmed bactericidal activities of TiO₂, ZnO and AuZnO on E. coli and brought new insight on their fungicidal activity on the spores of A. niger. They also confirmed the greatest antimicrobial efficiency of ZnO compared to TiO₂ and its increased photocatalytic activity when decorated with Au, leading to the highest log reductions detected after 2 h of contact for both tested microorganisms (4 and 1.4 for E. coli and A. niger, respectively). The antimicrobial activity was enhanced by the duration of contact between microorganisms and nanoparticles of the different tested photocatalytic products. Full article

(This article belongs to the Special Issue Photocatalytic Nanomaterials for Abatement of Microorganisms)

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14 pages, 3832 KiB

Open AccessArticle

Utilization of Loaded Cobalt onto MCM-48 Mesoporous Catalyst as a Heterogeneous Reaction in a Fixed Bed Membrane Reactor to Produce Isomerization Product from n-Heptane

by Nisreen S. Ali, Issam K. Salih, Hamed N. Harharah, Hasan Sh. Majdi, Hussein G. Salih, Khairi R. Kalash, Ali Al-Shathr, Farah T. Al-Sudani, Mahir A. Abdulrahman, Jamal M. Alrubaye, Talib M. Albayati, Noori M. Saady and Sohrab Zendehboudi

Catalysts 2023, 13(7), 1138; https://doi.org/10.3390/catal13071138 - 22 Jul 2023

Cited by 13 | Viewed by 1202

Abstract

The use of catalytic membranes as microstructured reactors without a separative function has proved effective. High catalytic activity is possible with minimal mass transport resistances if the reactant mixture is pushed to flow through the pores of a membrane that has been impregnated [...] Read more.

The use of catalytic membranes as microstructured reactors without a separative function has proved effective. High catalytic activity is possible with minimal mass transport resistances if the reactant mixture is pushed to flow through the pores of a membrane that has been impregnated with catalyst. In this study, n-heptane (C₇H₁₆) was hydrocracked and hydro-isomerized within a plug-flow zeolitic catalytic membrane-packed bed reactor. The metallic cobalt (Co) precursor at 3 wt.% was loaded onto support mesoporous materials MCM-48 to synthesize heterogeneous catalysis. The prepared MCM-48 was characterized by utilizing characterization techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), Fourier transform infrared (FTIR), nitrogen adsorption–desorption isotherms, and the Brunauer–Emmett–Teller (BET) surface area. The structural and textural characteristics of MCM-48 after encapsulation with Co were also investigated. The analyses were performed before and after metal loading. According to the results, the 3 wt.% Co/MCM-48 of metallic catalyst in a fixed bed membrane reactor (MR) appears to have an excellent catalytic activity of ~83% during converting C₇H₁₆ at 400 °C, whereas a maximum selectivity was approximately ~65% at 325 °C. According to our findings, the synthesized catalyst exhibits an acceptable selectivity to isomers with multiple branches, while making low aromatic components. In addition, a good catalytic stability was noticed for this catalyst over the reaction. Use of 3 wt.% Co/MCM-48 catalyst led to the highest isomerization selectivity as well as n-heptane conversion. Therefore, the heterogeneous catalysis MCM-48 is a promising option/ alternative for traditional hydrocracking and hydro-isomerization processes. Full article

(This article belongs to the Section Catalytic Reaction Engineering)

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27 pages, 44211 KiB

Open AccessFeature PaperReview

Core–Shell Catalysts for Conventional Oxidation of Alcohols: A Brief Review

by Luís M. M. Correia, Maxim L. Kuznetsov and Elisabete C. B. A. Alegria

Catalysts 2023, 13(7), 1137; https://doi.org/10.3390/catal13071137 - 21 Jul 2023

Viewed by 1146

Abstract

This review highlights recent research on the application of core–shell structured materials as catalysts in the oxidation of alcohols to value-added products, such as benzaldehyde, acetophenone, benzophenone, cinnamaldehyde, and vanillin, among others. While the application of various unconventional energy inputs (such as microwave [...] Read more.

This review highlights recent research on the application of core–shell structured materials as catalysts in the oxidation of alcohols to value-added products, such as benzaldehyde, acetophenone, benzophenone, cinnamaldehyde, and vanillin, among others. While the application of various unconventional energy inputs (such as microwave and ultrasound irradiation) was reported, this paper focuses on conventional heating. The oxidation of homocyclic aromatic, heterocyclic aromatic, aliphatic, and alicyclic alcohols catalyzed by core–shell composite catalysts is addressed. This work also highlights some unique advantages of core–shell nanomaterial catalysis, namely the flexibility of combining individual functions for specific purposes as well as the effect of various parameters on the catalytic performance of these materials. Full article

(This article belongs to the Special Issue Metallic Nanoparticles and Metal-Mediated Synthesis in Catalysis)

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13 pages, 6669 KiB

Open AccessArticle

Efficient and Stable Degradation of Triazophos Pesticide by TiO₂/WO₃ Nanocomposites with S-Scheme Heterojunctions and Oxygen Defects

by Wen Li, Chunxu Chen, Renqiang Yang, Shuangli Cheng, Xiaoyu Sang, Meiwen Zhang, Jinfeng Zhang, Zhenghua Wang and Zhen Li

Catalysts 2023, 13(7), 1136; https://doi.org/10.3390/catal13071136 - 21 Jul 2023

Cited by 2 | Viewed by 952

Abstract

The prevalent utilization of organophosphorus pesticides presents a profound risk to the global environment, necessitating the immediate development of a secure and reliable methodology to mitigate this hazard. Photocatalytic technology, through the generation of robust oxidizing free radicals by suitable catalysts, offers a [...] Read more.

The prevalent utilization of organophosphorus pesticides presents a profound risk to the global environment, necessitating the immediate development of a secure and reliable methodology to mitigate this hazard. Photocatalytic technology, through the generation of robust oxidizing free radicals by suitable catalysts, offers a viable solution by effectively oxidizing organophosphorus pesticides, thus preserving environmental well-being. In this study, we successfully synthesized TiO₂/WO₃ (TO/WO) nanocomposites characterized by oxygen defects and S-scheme heterojunctions, demonstrating superior photocatalytic activity in the degradation of triazophos. Notably, the 60-TO/WO nanocomposite, wherein the proportion of WO comprises 60% of the total, exhibited optimal photocatalytic degradation activity, achieving a degradation rate of 78% within 120 min, and demonstrating exceptional stability, maintaining impressive degradation activity across four cycles. This performance was notably superior to that of standalone TO and WO. The presence of oxygen defects in WO was corroborated by electron paramagnetic resonance (EPR) spectroscopy. The mechanism at the heterojunction of the 60-TO/WO nanocomposite, identified as an S-scheme, was also confirmed by EPR and theoretical computations. Oxygen defects expedite charge transfer and effectively enhance the photocatalytic reaction, while the S-scheme effectively segregates photogenerated electrons and holes, thereby optimizing the photocatalytic oxidation of triazophos. This study introduces a novel nanocomposite material, characterized by oxygen defects and the S-scheme heterojunction, capable of effectively degrading triazophos and promoting environmental health. Full article

(This article belongs to the Special Issue Advances in Photocatalysis and Electrocatalysis Applications)

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23 pages, 7690 KiB

Open AccessEditor’s ChoiceArticle

The Impact of Different Green Synthetic Routes on the Photocatalytic Potential of FeSnO₂ for the Removal of Methylene Blue and Crystal Violet Dyes under Natural Sunlight Exposure

by Arifa Shaukat, Muhammad Akhyar Farrukh, Kok-Keong Chong, Rabia Nawaz, Muhammad Tariq Qamar, Shahid Iqbal, Nasser S. Awwad and Hala A. Ibrahium

Catalysts 2023, 13(7), 1135; https://doi.org/10.3390/catal13071135 - 21 Jul 2023

Cited by 4 | Viewed by 1439

Abstract

FeSnO₂ nanocomposites were synthesized via the green method using aqueous leaf extracts of Lawsonia inermis and Phyllanthus embilica plants. The role of polyphenols based on reduction potentials for the synthesis of FeSnO₂ was also highlighted. The synthesized materials were examined by [...] Read more.

FeSnO₂ nanocomposites were synthesized via the green method using aqueous leaf extracts of Lawsonia inermis and Phyllanthus embilica plants. The role of polyphenols based on reduction potentials for the synthesis of FeSnO₂ was also highlighted. The synthesized materials were examined by using TGA and DSC, FT-IR, XRD, and SEM with EDX analysis. Tetragonal rutile and distorted hexagonal structures were observed in SEM images of the FeSnO₂ nanocomposites and compared with an FeSnO₂ nanocomposite prepared using the sol-gel method. Scherer’s formula yielded crystallite sizes of 29.49, 14.54, and 20.43 nm; however, the average crystallite size assessed employing the Williamson–Hall equation was found to be 20.85, 11.30, and 14.86 nm by using the sol-gel and green techniques, using extracts from Lawsonia inermis and Phyllanthus embilica. The band gap was determined by using the Tauc and Wood equations, and photocatalytic activity was analyzed to determine the degradation of methylene blue (MB) and crystal violet (CV) under the illumination of natural sunlight. It was observed that the sample prepared by means of the green method using the leaf extract of Lawsonia inermis showed the best photocatalytic activity of 84%, with a particle size of 14.54 nm, a 3.10 eV band gap, and a specific surface area of 55.68 m²g⁻¹. Full article

(This article belongs to the Special Issue Advanced Materials for Application in Catalysis)

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15 pages, 5679 KiB

Open AccessFeature PaperArticle

Photocatalytic Degradation of Ciprofloxacin with Supramolecular Materials Consisting of Nitrogenous Organic Cations and Metal Salts

by Chenfei Ren, Jian Li, Xingxing Zhang and Yunyin Niu

Catalysts 2023, 13(7), 1134; https://doi.org/10.3390/catal13071134 - 21 Jul 2023

Viewed by 926

Abstract

The design and synthesis of composite materials with new structures/properties have important practical significance for the degradation of organic pollutants in aquatic environments. On this basis, five new supramolecular materials {[L1]₂·[Cu₄I₈]}(1), {[L1 [...] Read more.

The design and synthesis of composite materials with new structures/properties have important practical significance for the degradation of organic pollutants in aquatic environments. On this basis, five new supramolecular materials {[L1]₂·[Cu₄I₈]}(1), {[L1]₂·[Ag₄I₈]}(2), {[L2]·[ZnBr₄]}(3), {[L3]₂·[AgI₅]}(4), {[L3]·[CdBr₃Cl]}(5) were synthesized by introducing an amino group into a series of nitrogen-containing cationic ligands (L1–L3) through the reaction of polybromomethylbenzene with 4-aminopyridine. The degradation effect of catalysts 1–5 on ciprofloxacin (CIP) under visible light was studied using their potential catalytic properties. The results showed that compounds 1 and 4 had better degradation effects compared to other compounds. Moreover, compounds 1 and 4 were proved to be excellent catalysts for the photocatalytic degradation of CIP with cyclic experiments. Through further exploration, it was found that neutral conditions and 20 mg compound dosage were more conducive to the photodegradation of CIP by the compound. Through free radical capture experiments, it was found that ·OH played a major role in the photodegradation of CIP. Full article

(This article belongs to the Special Issue Air and Water Purification Processes through Photocatalysis: Scale Up Perspectives, 2nd Edition)

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13 pages, 1933 KiB

Open AccessArticle

A New Pseudomonas aeruginosa Isolate Enhances Its Unusual 1,3-Propanediol Generation from Glycerol in Bioelectrochemical System

by Julia Pereira Narcizo, Lucca Bonjy Kikuti Mancilio, Matheus Pedrino, María-Eugenia Guazzaroni, Adalgisa Rodrigues de Andrade and Valeria Reginatto

Catalysts 2023, 13(7), 1133; https://doi.org/10.3390/catal13071133 - 20 Jul 2023

Viewed by 1144

Abstract

The ability of some bacteria to perform Extracellular Electron Transfer (EET) has been explored in bioelectrochemical systems (BES) to obtain energy or chemicals from pure substances or residual substrates. Here, a new pyoverdine-producing Pseudomonas aeruginosa strain was isolated from an MFC biofilm oxidizing [...] Read more.

The ability of some bacteria to perform Extracellular Electron Transfer (EET) has been explored in bioelectrochemical systems (BES) to obtain energy or chemicals from pure substances or residual substrates. Here, a new pyoverdine-producing Pseudomonas aeruginosa strain was isolated from an MFC biofilm oxidizing glycerol, a by-product of biodiesel production. Strain EL14 was investigated to assess its electrogenic ability and products. In an open circuit system (fermentation system), EL14 was able to consume glycerol and produce 1,3-propanediol, an unusual product from glycerol oxidation in P. aeruginosa. The microbial fuel cell (MFC) EL14 reached a current density of 82.4 mA m⁻² during the first feeding cycle, then dropped sharply as the biofilm fell off. Cyclic voltammetry suggests that electron transfer to the anode occurs indirectly, i.e., through a redox substance, with redox peak at 0.22 V (vs Ag/AgCl), and directly probably by membrane redox proteins, with redox peak at 0.05 V (vs Ag/AgCl). EL14 produced added-value bioproducts, acetic and butyric acids, as well as 1,3 propanediol, in both fermentative and anodic conditions. However, the yield of 1,3-PDO from glycerol was enhanced from 0.57 to 0.89 (mol of 1,3-PDO mol⁻¹ of glycerol) under MFC conditions compared to fermentation. This result was unexpected, since successful 1,3-PDO production is not usually associated with P. aeruginosa glycerol metabolism. By comparing EL14 genomic sequences related to the 1,3-PDO biosynthesis with P. aeruginosa reference strains, we observed that strain EL14 has three copies of the dhaT gene (1,3-propanediol dehydrogenase a different arrangement compared to other Pseudomonas isolates). Thus, this work functionally characterizes a bacterium never before associated with 1,3-PDO biosynthesis, indicating its potential for converting a by-product of the biodiesel industry into an emerging chemical product. Full article

(This article belongs to the Special Issue Catalytic Processes in Biofuel Production and Biomass Valorization, 2nd Edition)

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15 pages, 5212 KiB

Open AccessFeature PaperArticle

Templating Synthesis of Hierarchically Porous Carbon with Magnesium Salts for Electrocatalytic Reduction of 4-Nitrophenol

by Wanyi Gan, Ping Xiao and Junjiang Zhu

Catalysts 2023, 13(7), 1132; https://doi.org/10.3390/catal13071132 - 20 Jul 2023

Cited by 1 | Viewed by 1043

Abstract

Hierarchically porous carbon (PC) was synthesized by a templating method, using magnesium salts (Mg(HCO₃)₂, MgC₂O₄ and MgO) as template precursors and citric acid as carbon precursor. During the carbonization process, besides the production of MgO particles, [...] Read more.

Hierarchically porous carbon (PC) was synthesized by a templating method, using magnesium salts (Mg(HCO₃)₂, MgC₂O₄ and MgO) as template precursors and citric acid as carbon precursor. During the carbonization process, besides the production of MgO particles, many gases (e.g., CO₂/NO₂/H₂O) were also released and acted as a porogen to generate pores in carbon. The resulting composite (MgO@C) was subsequently treated with HCl solution to remove the MgO templates, yielding hierarchically porous carbon. The surface oxygen functional groups over porous carbon were characterized by TPD and XPS, which showed that the PC-bic, synthesized using Mg(HCO₃)₂ as the template precursor, had the highest value among the PCs. As expected, the PC-bic exhibited the best performances for electrocatalytic reduction of 4-nitrophenol, with a peak current of −135.5 μA at −0.679 V. The effects of 4-nitrophenol concentration, buffer solution pH and scanning rate on the electrocatalytic activities, as well as the stability of PC-bic for the reaction were investigated. Full article

(This article belongs to the Special Issue Graphene Related Materials for Catalytic Applications)

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31 pages, 3845 KiB

Open AccessFeature PaperArticle

Educational Scale-Bridging Approach towards Modelling of Electric Potential, Electrochemical Reactions, and Species Transport in PEM Fuel Cell

by Ambrož Kregar, Klemen Zelič, Andraž Kravos and Tomaž Katrašnik

Catalysts 2023, 13(7), 1131; https://doi.org/10.3390/catal13071131 - 20 Jul 2023

Viewed by 997

Abstract

The use of hydrogen fuel cells as a mobile source of electricity could prove key to the future decarbonisation of heavy-duty road and marine transportation. Due to the complex interplay of various physicochemical processes in fuel cells, further development of these devices will [...] Read more.

The use of hydrogen fuel cells as a mobile source of electricity could prove key to the future decarbonisation of heavy-duty road and marine transportation. Due to the complex interplay of various physicochemical processes in fuel cells, further development of these devices will depend on concerted efforts by researchers from various fields, who often lack in-depth knowledge of different aspects of fuel cell operation. These knowledge gaps can be filled by information that is scattered in a wide range of literature, but is rarely covered in a concise and condensed manner. To address this issue, we propose an educational-scale-bridging approach towards the modelling of most relevant processes in the fuel cell that aims to adequately describe the causal relations between the processes involved in fuel cell operation. The derivation of the model equations provides an intuitive understanding of the electric and chemical potentials acting on protons at the microscopic level and relates this knowledge to the terminology commonly used in fuel cell research, such as catalyst electric overpotential and internal membrane resistance. The results of the model agreed well with the experimental data, indicating that the proposed simple mathematical description is sufficient for an intuitive understanding of fuel cell operation. Full article

(This article belongs to the Topic Hydrogen Energy Technologies, 2nd Volume)

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18 pages, 4812 KiB

Open AccessArticle

Polymer-Grafted 3D-Printed Material for Enzyme Immobilization—Designing a Smart Enzyme Carrier

by Daniela Eixenberger, Aditya Kumar, Saskia Klinger, Nico Scharnagl, Ayad W. H. Dawood and Andreas Liese

Catalysts 2023, 13(7), 1130; https://doi.org/10.3390/catal13071130 - 20 Jul 2023

Cited by 3 | Viewed by 1087

Abstract

One way to enhance the flow properties of packed bed reactors, including efficient mass transfer and high catalyst conversion rates, is the use of 3D printing. By creating optimized structures that prevent channeling and high pressure drops, it is possible to achieve the [...] Read more.

One way to enhance the flow properties of packed bed reactors, including efficient mass transfer and high catalyst conversion rates, is the use of 3D printing. By creating optimized structures that prevent channeling and high pressure drops, it is possible to achieve the desired target. Nevertheless, additively manufactured structures most often possess a limited surface-area-to-volume-ratio, especially as porous printed structures are not standardized yet. One way to achieve surface-enhanced 3D-printed structures is surface modification to introduce surface-initiated polymers. In addition, when stimuli-sensitive polymers are chosen, autonomous process control is prospective. The current publication deals with the application of surface-induced polymerization on 3D-printed structures with the subsequent application as an enzyme carrier. Surface-induced polymerization can easily increase the number of enzymes by a factor of six compared to the non-modified 3D-printed structure. In addition, the swelling behavior of polyacrylic acid is proven, even with immobilized enzymes, enabling smart reaction control. The maximum activity of Esterase 2 (Est2) from Alicyclobacillus acidocaldarius per g carrier, determined after 2 h of polymer synthesis, is 0.61 U/g_support. Furthermore, universal applicability is shown in aqueous and organic systems, applying an Est2 and Candida antarctica lipase B (CalB) catalyzed reaction and leaving space for improvement due to compatibility of the functionalization process and the here chosen organic solvent. Overall, no enzyme leaching is detectable, and process stability for at least five subsequent batches is ensured. Full article

(This article belongs to the Special Issue Immobilized Biocatalysts II)

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18 pages, 10185 KiB

Open AccessFeature PaperArticle

Structured Catalyst for Indirect Internal Reforming (IIR) of Biogas in Solid Oxide Fuel Cell (SOFC)

by Anna Prioriello, Leonardo Duranti, Igor Luisetto, Frederick Sanna, Claudio Larosa, Maria Luisa Grilli and Elisabetta Di Bartolomeo

Catalysts 2023, 13(7), 1129; https://doi.org/10.3390/catal13071129 - 20 Jul 2023

Cited by 2 | Viewed by 1487

Abstract

The aim of this work is the development of a structured catalyst for the dry reforming of biogas to be used as a pre–reformer in the indirect internal reforming configuration (IIR) of solid oxide fuel cells (SOFCs). The structured catalyst is based on [...] Read more.

The aim of this work is the development of a structured catalyst for the dry reforming of biogas to be used as a pre–reformer in the indirect internal reforming configuration (IIR) of solid oxide fuel cells (SOFCs). The structured catalyst is based on NiCrAl foams coated with ruthenium (nominal loading 3.0 wt%) supported on a CaZr_0.85Sm_0.15O_3−δ (CZS) perovskite oxide. The powder is produced by solution combustion synthesis and deposited on metallic foams by the wash–coating method. Catalytic tests for the dry reforming of methane (DRM) reaction are carried out at 850 °C, 700 °C and 550 °C for an overall 50 h with CH₄/CO₂ = 1 and p = 1.3 bar at different gas hourly space velocities (GHSVs). The final goal is a proof–of–concept: a laboratory validation of an IIR–SOFC fed by biogas. The carbon amount on spent structured catalysts is evaluated by thermogravimetric analysis and microstructural/compositional investigation. Full article

(This article belongs to the Special Issue New Trends in Electrocatalysis for CO₂ Conversion)

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16 pages, 4349 KiB

Open AccessFeature PaperArticle

Benzene Oxidation over Pt Loaded on Fly Ash Zeolite X

by Yuri Kalvachev, Totka Todorova, Hristo Kolev, Daniel Merker and Cyril Popov

Catalysts 2023, 13(7), 1128; https://doi.org/10.3390/catal13071128 - 20 Jul 2023

Cited by 2 | Viewed by 928

Abstract

In the present study, zeolite X (FANaX) was synthesized from coal fly ash (FA) by a two-step high-temperature method. In order to follow the effect of different contaminants in the starting coal ash, zeolite X was also synthesized from pure chemicals according to [...] Read more.

In the present study, zeolite X (FANaX) was synthesized from coal fly ash (FA) by a two-step high-temperature method. In order to follow the effect of different contaminants in the starting coal ash, zeolite X was also synthesized from pure chemicals according to a classical recipe (NaX). Iron was loaded on this reference zeolite with the amount which was contained in the coal FA. The final catalytic samples were obtained by wet impregnation of Pt nanoparticles on both types of zeolite crystals. The most active samples in the benzene oxidation were the platinum-modified ones and, among them, the Pt-impregnated FA zeolite (Pt FANaX). The comparison of the catalytic activity of Pt FANaX with the reference PtFe NaX zeolite showed a temperature difference of 10 °C in favor of Pt FANaX at 50% benzene conversion. From these results, it can be concluded that FA zeolites are a good, cheaper and environmentally friendly alternative to traditional zeolites, synthesized from pure chemicals, which can be applied in the preparation of catalysts for the purification of gaseous mixtures from harmful organic compounds. Full article

(This article belongs to the Section Environmental Catalysis)

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11 pages, 1719 KiB

Open AccessFeature PaperArticle

Iron-Borophosphate Glass-Catalyzed Regioselective Hydrothiolation of Alkynes under Green Conditions

by Nicoli Catholico, Eduarda A. Tessari, Isis J. A. Granja, Martinho J. A. de Sousa, Jorlandio F. Felix, Flávia Manarin, Marcelo Godoi, Jamal Rafique, Ricardo Schneider, Sumbal Saba and Giancarlo V. Botteselle

Catalysts 2023, 13(7), 1127; https://doi.org/10.3390/catal13071127 - 20 Jul 2023

Viewed by 836

Abstract

Vinyl sulfides are an important class of organic compounds that have relevant synthetic and biological applications. The best-known approach to realize these compounds is the hydrothiolation of alkynes under different conditions using metals, toxic and carcinogenic solvents. The development of new catalysts using [...] Read more.

Vinyl sulfides are an important class of organic compounds that have relevant synthetic and biological applications. The best-known approach to realize these compounds is the hydrothiolation of alkynes under different conditions using metals, toxic and carcinogenic solvents. The development of new catalysts using materials that are environmentally friendly, low in cost, and easy to handle is highly desirable for this reaction. In this regard, glasses have become an important class of materials, since they can be used as a catalyst for chemical reactions. We prepared and characterized an inexpensive and robust iron-doped borophosphate glass (Fe@NaH₂PO₄-H₃BO₃ glass). This eco-friendly material was successfully applied as a catalyst for the hydrothiolation of alkynes under solvent-free conditions, affording the desired vinyl sulfides in good-to-excellent yields, with high stereoselectivity. This method of synthesis is attractive because it enables the reuse of the iron-glass catalyst and the scaling up of reactions. Full article

(This article belongs to the Special Issue Feature Papers in Catalysis in Organic and Polymer Chemistry)

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13 pages, 1348 KiB

Open AccessArticle

Atom Transfer Radical Addition via Dual Photoredox/Manganese Catalytic System

by Vladislav S. Kostromitin, Vitalij V. Levin and Alexander D. Dilman

Catalysts 2023, 13(7), 1126; https://doi.org/10.3390/catal13071126 - 19 Jul 2023

Viewed by 1490

Abstract

Atom transfer radical addition of bromonitromethane and 1,2-dibromotetrafluoroethane to alkenes is described. The reaction is performed under blue light irradiation using two catalysts: 4CzIPN and manganese (II) bromide. The cyanoarene photocatalyst serves for the redox activation of starting organic bromide, while the manganese [...] Read more.

Atom transfer radical addition of bromonitromethane and 1,2-dibromotetrafluoroethane to alkenes is described. The reaction is performed under blue light irradiation using two catalysts: 4CzIPN and manganese (II) bromide. The cyanoarene photocatalyst serves for the redox activation of starting organic bromide, while the manganese salt facilitates the trapping of the alkyl radical with the formation of the carbon–bromine bond. Full article

(This article belongs to the Special Issue Free Radicals in Catalysis, Organic Synthesis, and Material Science)

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23 pages, 5762 KiB

Open AccessArticle

Hydroisomerisation and Hydrocracking of n-Heptane: Modelling and Optimisation Using a Hybrid Artificial Neural Network–Genetic Algorithm (ANN–GA)

by Bashir Y. Al-Zaidi, Ali Al-Shathr, Amal K. Shehab, Zaidoon M. Shakor, Hasan Sh. Majdi, Adnan A. AbdulRazak and James McGregor

Catalysts 2023, 13(7), 1125; https://doi.org/10.3390/catal13071125 - 19 Jul 2023

Cited by 1 | Viewed by 1210

Abstract

In this paper, the focus is on upgrading the value of naphtha compounds represented by n-heptane (n-C₇H₁₆) with zero octane number using a commercial zeolite catalyst consisting of a mixture of 75% HY and 25% HZSM-5 [...] Read more.

In this paper, the focus is on upgrading the value of naphtha compounds represented by n-heptane (n-C₇H₁₆) with zero octane number using a commercial zeolite catalyst consisting of a mixture of 75% HY and 25% HZSM-5 loaded with different amounts, 0.25 to 1 wt.%, of platinum metal. Hydrocracking and hydroisomerisation processes are experimentally and theoretically studied in the temperature range of 300–400 °C and under various contact times. A feedforward artificial neural network (FFANN) based on two hidden layers was used for the purpose of process modelling. A total of 80% of the experimental results was used to train the artificial neural network, with the remaining results being used for evaluation and testing of the network. Tan-sigmoid and log-sigmoid transfer functions were used in the first and second hidden layers, respectively. The optimum number of neurons in hidden layers was determined depending on minimising the mean absolute error (MAE). The best ANN model, represented by the multilayer FFANN, had a 4–24–24–12 topology. The ANN model accurately simulates the process in which the correlation coefficient (R²) was found to be 0.9918, 0.9492, and 0.9426 for training, validation, and testing, respectively, and an average of 0.9767 for all data. In addition, the operating conditions of the process were optimised using the genetic algorithm (GA) towards increasing the octane number of the products. MATLAB^® Version 2020a was utilised to complete all required computations and predictions. Optimal operating conditions were found through the theoretical study: 0.85 wt.% Pt-metal loaded, 359.36 °C, 6.562 H₂/n-heptane feed ratio, and 3.409 h⁻¹ weight-hourly space velocity (WHSV), through which the maximum octane number (RON) of 106.84 was obtained. Finally, those operating conditions largely matched what was calculated from the results of the experimental study, where the highest percentage of the resulting isomers was found with about 78.7 mol% on the surface of the catalyst loaded with 0.75 wt.% Pt-metal at 350 °C using a feed ratio of 6.5 H₂/n-C₇ and WHSV of 2.98 h⁻¹. Full article

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26 pages, 5985 KiB

Open AccessFeature PaperReview

Solution Plasma for Surface Design of Advanced Photocatalysts

by Rui Wang, Changhua Wang, Yanmei Xing and Xintong Zhang

Catalysts 2023, 13(7), 1124; https://doi.org/10.3390/catal13071124 - 19 Jul 2023

Cited by 1 | Viewed by 1160

Abstract

Rational design of the surface of photocatalysts can conveniently modulate the photo-stimulated charge separation, influence the surface reaction kinetics, and other pivotal factors in the photocatalytic processes for efficient photocatalysis. Solution plasma, holding promise for mild modification of the surface structure of materials, [...] Read more.

Rational design of the surface of photocatalysts can conveniently modulate the photo-stimulated charge separation, influence the surface reaction kinetics, and other pivotal factors in the photocatalytic processes for efficient photocatalysis. Solution plasma, holding promise for mild modification of the surface structure of materials, has recently been recognized as an emerging technology for surface engineering of high-performance photocatalysts. In this review, we will briefly introduce the fundamentals of solution plasma and its applications in materials preparation and summarize the recent research progress in the surface design of advanced photocatalysts by solution plasma. Lastly, we will indicate some possible new directions. This review is expected to provide an instructive guideline for the surface design of heterogeneous photocatalysts by solution plasma. Full article

(This article belongs to the Special Issue Surface Microstructure Design for Advanced Catalysts)

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13 pages, 4230 KiB

Open AccessFeature PaperArticle

Tailoring Morphology in Hydrothermally Synthesized CdS/ZnS Nanocomposites for Extraordinary Photocatalytic H₂ Generation via Type-II Heterojunction

by Mianli Huang, Maoqing Yu, Ruiru Si, Xiaojing Zhao, Shuqin Chen, Kewei Liu and Xiaoyang Pan

Catalysts 2023, 13(7), 1123; https://doi.org/10.3390/catal13071123 - 19 Jul 2023

Cited by 3 | Viewed by 973

Abstract

CdS@ZnS core shell nanocomposites were prepared by a one-pot hydrothermal route. The morphology of the composite was tuned by simply changing the Zn²⁺ precursor concentration. To characterize the samples prepared, various techniques were employed, including XRD, FESEM, TEM, XPS and UV-vis DRS. [...] Read more.

CdS@ZnS core shell nanocomposites were prepared by a one-pot hydrothermal route. The morphology of the composite was tuned by simply changing the Zn²⁺ precursor concentration. To characterize the samples prepared, various techniques were employed, including XRD, FESEM, TEM, XPS and UV-vis DRS. The band gaps of CdS and ZnS were measured to be 2.26 and 3.32 eV, respectively. Compared with pure CdS, the CdS@ZnS samples exhibited a slight blue shift, which indicated an increased band gap of 2.29 eV. The CdS@ZnS core shell composites exhibited efficient photocatalytic performance for H₂ generation under simulated sunlight illumination in contrast to pure CdS and ZnS. Additionally, an optimized H₂ generation rate (14.44 mmol·h⁻¹·g⁻¹_cat) was acquired at CdS@ZnS-2, which was approximately 4.6 times greater than that of pure CdS (3.12 mmol·h⁻¹·g⁻¹_cat). Moreover, CdS@ZnS heterojunction also showed good photocatalytic stability. The process of charge separation over the photocatalysts was investigated using photoelectrochemical analysis. The findings indicate that the CdS@ZnS nanocomposite has efficient charge separation efficiency. The higher H₂ generation activity and stability for CdS@ZnS photocatalysts can be attributed to the intimate interface in the CdS@ZnS core–shell structure, which promoted the light absorption intensity and photoinduced charge separation efficiency. It is expected that this study will offer valuable insights into the development of efficient core shell composite photocatalysts. Full article

(This article belongs to the Special Issue Engineering Novel Heterojunctions for Photocatalytic Energy and Environmental Applications)

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15 pages, 4077 KiB

Open AccessArticle

Lithium–Sodium Fly Ash-Derived Catalyst for the In Situ Partial Deoxygenation of Isochrysis sp. Microalgae Bio-Oil

by Nur Adilah Abd Rahman, Fernando Cardenas-Lizana and Aimaro Sanna

Catalysts 2023, 13(7), 1122; https://doi.org/10.3390/catal13071122 - 19 Jul 2023

Viewed by 792

Abstract

The catalytic potential of Na and LiNa fly ash (FA) obtained through a simple solid-state synthesis was investigated for the pyrolysis of Isochrysis sp. microalgae using a fixed bed reactor at 500 °C. While both LiNa-FA and Na-FA catalysts reduced the bio-oil yield [...] Read more.

The catalytic potential of Na and LiNa fly ash (FA) obtained through a simple solid-state synthesis was investigated for the pyrolysis of Isochrysis sp. microalgae using a fixed bed reactor at 500 °C. While both LiNa-FA and Na-FA catalysts reduced the bio-oil yield and increased char and gas production, LiNa-FA was found to enhance the quality of the resulting bio-oil by decreasing its oxygen content (−25 wt.%), increasing paraffins and olefins and decreasing its acidity. The deoxygenation activity of LiNa-FA was attributed to the presence of weak and mild base sites, which enabled dehydration, decarboxylation, ketonisation, and cracking to form olefins. The bio-oil generated with LiNa-FA contained higher amounts of alkanes, alkenes, and carbonated esters, indicating its capacity to chemisorb and partially desorb CO₂ under the studied conditions. These findings suggest that LiNa-FA catalysts could be a cost-effective alternative to acidic zeolites for in situ deoxygenation of microalgae to biofuels. Full article

(This article belongs to the Special Issue Catalysis in Biomass Valorization for Fuel and Chemicals)

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13 pages, 3713 KiB

Open AccessArticle

Effect of Ultraviolet Illumination on the Fixation of Silver Ions on Zinc Oxide Films and Their Photocatalytic Efficiency

by Dobrina Ivanova, Ralitsa Mladenova, Hristo Kolev and Nina Kaneva

Catalysts 2023, 13(7), 1121; https://doi.org/10.3390/catal13071121 - 18 Jul 2023

Cited by 2 | Viewed by 1293

Abstract

This study focuses on the fabrication and characterization of nanostructured zinc oxide films deposited on glass substrates using sol–gel dip-coating methods. The thin films are functionalized with silver ions at various Ag⁺ concentrations (10⁻², 10⁻³, 10⁻⁴ M) [...] Read more.

This study focuses on the fabrication and characterization of nanostructured zinc oxide films deposited on glass substrates using sol–gel dip-coating methods. The thin films are functionalized with silver ions at various Ag⁺ concentrations (10⁻², 10⁻³, 10⁻⁴ M) through room temperature ion fixation process with and without ultraviolet (UV) illumination. Physicochemical characterization techniques, such as employing Scanning Electron Microscopy with Energy-dispersive X-ray spectroscopy (SEM-EDX), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Ultraviolet–Visible Spectroscopy and Electron Paramagnetic Resonance (EPR) techniques. The SEM-EDX and XRD confirmed a characteristic ganglia-like structure with a hexagonal crystalline structure. The photocatalytic performance and available surface area of the pure and Ag films are investigated in the removal of methylene blue dye under UV and visible light illumination and in darkness. It is observed that the photocatalytic activity increases proportionally to the Ag⁺ ion concentration: ZnO < Ag(10⁻⁴ M)/ZnO, < Ag(10⁻³ M)/ZnO < Ag(10⁻² M)/ZnO. Moreover, the catalysts modified under UV illumination during the fixation treatment (Ag-UV/ZnO) exhibited a higher photocatalytic efficiency and degraded the dye in comparison with those without a light source (Ag/ZnO). The experimental results are confirmed using total organic carbon (TOC) analysis. The optimal silver concentration (10⁻² M) is established, which shows the highest photocatalytic efficiency (in both cases of ion fixation treatment). The results can be used as a guideline for the development of co-catalyst-functionalized semiconductor photocatalysts. Full article

(This article belongs to the Special Issue Advances in the Synthesis and Applications of Transition/Noble Metal Oxide Photocatalysts, 2nd Edition)

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16 pages, 2683 KiB

Open AccessArticle

Structurally Rigid (8-(Arylimino)-5,6,7-trihydroquinolin-2-yl)-methyl Acetate Cobalt Complex Catalysts for Isoprene Polymerization with High Activity and cis-1,4 Selectivity

by Nighat Yousuf, Yanping Ma, Qaiser Mahmood, Wenjuan Zhang, Ming Liu, Rongyan Yuan and Wen-Hua Sun

Catalysts 2023, 13(7), 1120; https://doi.org/10.3390/catal13071120 - 18 Jul 2023

Cited by 8 | Viewed by 959

Abstract

A series of cobalt complexes bearing (8-(arylimino)-5,6,7-trihydroquinolin-2-yl)methyl acetate ligand framework were prepared using a one-pot synthesis method. These complexes were then extensively investigated for their catalytic performance in isoprene polymerization. In addition to the complexes being characterized via FT-IR spectrum and elemental analysis, [...] Read more.

A series of cobalt complexes bearing (8-(arylimino)-5,6,7-trihydroquinolin-2-yl)methyl acetate ligand framework were prepared using a one-pot synthesis method. These complexes were then extensively investigated for their catalytic performance in isoprene polymerization. In addition to the complexes being characterized via FT-IR spectrum and elemental analysis, the molecular structure of Co1 and Co5 was determined via X-ray diffraction analysis. The analysis revealed a chloride-bridged centrosymmetric binuclear species in which each cobalt center exhibited a distorted square pyramidal geometry. Among the prepared complexes, Co1 demonstrated the highest catalytic activity of 1.37 × 10⁵ g (mol of Co)⁻¹(h)⁻¹, achieving complete monomer conversion and resultant polyisoprene showed high molecular weight (M_n ≥ 2.6 × 10⁵ g/mol). All of the complexes showed preference for the cis-1,4 configuration ranging from 65% to 72%, while the 3,4 monomer insertion units constituted between 27% and 34% of the polymer structure. Moreover, extensive investigations were conducted to assess the impact of reaction parameters and ligand properties on the catalytic activities and microstructural characteristics of the resulting polymer. Full article

(This article belongs to the Special Issue Metal-Organic Catalyst for High Performance Materials)

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12 pages, 2554 KiB

Open AccessArticle

Application of a Response Surface Method for the Optimization of the Hydrothermal Synthesis of Magnetic NiCo₂O₄ Desulfurization Catalytic Powders

by Yinke Zhang, Lu Li, Zihan Shang and Hang Xu

Catalysts 2023, 13(7), 1119; https://doi.org/10.3390/catal13071119 - 18 Jul 2023

Viewed by 822

Abstract

In this study, nickel cobaltate (NiCo₂O₄) powders are employed as a catalyst in conjunction with persulfate for the development of a catalytic oxidation system to enhance fuel desulfurization. The hydrothermal synthesis conditions of NiCo₂O₄ powders, which [...] Read more.

In this study, nickel cobaltate (NiCo₂O₄) powders are employed as a catalyst in conjunction with persulfate for the development of a catalytic oxidation system to enhance fuel desulfurization. The hydrothermal synthesis conditions of NiCo₂O₄ powders, which significantly influenced the desulfurization efficiency, were optimized using a response surface methodology with a Box–Behnken design. These conditions were ranked in the following order: calcination temperature > hydrothermal temperature > calcination time > hydrothermal time. Through the optimization process, the ideal preparation conditions were determined as follows: a hydrothermal temperature of 143 °C, hydrothermal time of 6.1 h, calcination temperature of 330 °C, and calcination time of 3.7 h. Under these optimized conditions, the predicted desulfurization rate was approximately 85.8%. The experimental results closely matched the prediction, yielding a desulfurization rate of around 84%, with a minimal error of only 2.1%. To characterize the NiCo₂O₄ powders prepared under the optimal conditions, XRD, SEM, and TEM analyses were conducted. The analysis revealed that the microscopic morphology of NiCo₂O₄ exhibited a rectangular sheet structure, with an average particle size of 20 nm. Additionally, fan-shaped NiCo₂O₄ particles were observed as a result of linear and bundle agglomerations. Thus, this work is innovative in its ability to synthesize nano-catalysts using hydrothermal synthesis in a controllable manner and establishing a correlation between the hydrothermal synthesis conditions and catalytic activity. Full article

(This article belongs to the Section Catalytic Materials)

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13 pages, 9616 KiB

Open AccessFeature PaperArticle

Mitigating Co Metal Particle Agglomeration and Enhancing ORR Catalytic Activity through Nitrogen-Enriched Porous Carbon Derived from Biomass

by Yanling Wu, Qinggao Hou, Fangzhou Li, Yuanhua Sang, Mengyang Hao, Xi Tang, Fangyuan Qiu and Haijun Zhang

Catalysts 2023, 13(7), 1118; https://doi.org/10.3390/catal13071118 - 18 Jul 2023

Viewed by 1286

Abstract

Biomass-derived porous carbon has gained significant attention as a cost-effective and sustainable material in non-noble metal carbon-based electrocatalysts for the oxygen reduction reaction (ORR). However, during the preparation of transition metal catalysts based on biomass-derived porous carbon, the agglomeration of transition metal atoms [...] Read more.

Biomass-derived porous carbon has gained significant attention as a cost-effective and sustainable material in non-noble metal carbon-based electrocatalysts for the oxygen reduction reaction (ORR). However, during the preparation of transition metal catalysts based on biomass-derived porous carbon, the agglomeration of transition metal atoms often occurs, leading to a notable decline in catalytic activity. In this study, we present a straightforward synthetic approach for the preparation of nitrogen-enriched soybean-derived porous carbon (Co@SP-C-a) as an electrocatalyst for the ORR. To achieve this, we employed a two-step method. In the first step, a chemical activator (KCl) was utilized to enhance the porosity of the self-doped nitrogen biomass carbon material. In the second step, a constant pressure drop funnel technique was employed to uniformly disperse bimetal cobalt/zinc-based zeolitic imidazolium frameworks (ZIF-L and ZIF-67) containing different metal ions (Zn²⁺ and Co²⁺) into the activated biomass carbon material. Subsequent high-temperature calcination of the ZIF-L and ZIF-67@SP-C-a composite precursor yielded the Co@SP-C-a catalyst. The obtained catalyst exhibited remarkable ORR activity in an alkaline solution (E_onset = 0.89 V, E_1/2 = 0.83 V, J_L = −6.13 mA·cm⁻²) and exceptional long-term stability. This study presents an effective strategy to prevent the agglomeration of metal nanoparticles when integrating them with biomass-based carbon materials, thus leading to enhanced catalytic performance. Full article

(This article belongs to the Special Issue Morphological Effects on Catalytic Reactions)

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Catalysts, Volume 13, Issue 7 (July 2023) – 120 articles

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