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Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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20 pages, 2239 KiB  
Review
Contemporary Enzyme-Based Methods for Recombinant Proteins In Vitro Phosphorylation
by Marcela Slovakova and Zuzana Bilkova
Catalysts 2021, 11(8), 1007; https://doi.org/10.3390/catal11081007 - 20 Aug 2021
Cited by 6 | Viewed by 2926
Abstract
Phosphorylation is a reversible, enzyme-controlled posttranslational process affecting approximately one-third of all proteins in eukaryotic cells at any given time. Any deviation in the degree and/or site of phosphorylation leads to an abnormal conformation of proteins, resulting in a decline or loss of [...] Read more.
Phosphorylation is a reversible, enzyme-controlled posttranslational process affecting approximately one-third of all proteins in eukaryotic cells at any given time. Any deviation in the degree and/or site of phosphorylation leads to an abnormal conformation of proteins, resulting in a decline or loss of their function. Knowledge of phosphorylation-related pathways is essential for understanding the understanding of the disease pathogenesis and for the design of new therapeutic strategies. Recent availability of various kinases at an affordable price differs in activity, specificity, and stability and provides the opportunity of studying and modulating this reaction in vitro. We can exploit this knowledge for other applications. There is an enormous potential to produce fully decorated and active recombinant proteins, either for biomedical or cosmetic applications. Closely related is the possibility to exploit current achievements and develop new safe and efficacious vaccines, drugs, and immunomodulators. In this review, we outlined the current enzyme-based possibilities for in vitro phosphorylation of peptides and recombinant proteins and the added value that immobilized kinases provide. Full article
(This article belongs to the Special Issue Recent Advances in Biocatalysis and Metabolic Engineering)
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16 pages, 3397 KiB  
Article
The Activity Enhancement Effect of Ionic Liquids on Oxygen Reduction Reaction Catalysts: From Rotating Disk Electrode to Membrane Electrode Assembly
by Kan Huang, Oscar Morales-Collazo, Zhichao Chen, Tangqiumei Song, Liang Wang, Honghong Lin, Joan F. Brennecke and Hongfei Jia
Catalysts 2021, 11(8), 989; https://doi.org/10.3390/catal11080989 - 18 Aug 2021
Cited by 9 | Viewed by 2739
Abstract
Ionic liquids (ILs) have been explored as a surface modification strategy to promote the oxygen reduction reaction (ORR) on Pt/C and their chemical structures were identified to have strong influence on the ORR activities. To better understand the roles of anion and cation [...] Read more.
Ionic liquids (ILs) have been explored as a surface modification strategy to promote the oxygen reduction reaction (ORR) on Pt/C and their chemical structures were identified to have strong influence on the ORR activities. To better understand the roles of anion and cation of ILs on the catalytic reaction, two cations ([MTBD]+ and [bmim]+) were paired with three anions ([TFSI]−, [beti]−, and [C4F9SO3]−) to form various IL structures. By systematically varying the IL combinations and studying their effects on the electrochemical behaviors, such as electrochemical surface area and specific ORR activities, it was found that cation structure had a higher influence than anion, and the impact of the [MTBD]+ series was stronger than the [bmim]+ series. In addition to the investigation in the half-cell, studies were also extended to the membrane electrode assembly (MEA). Considerable performance enhancements were demonstrated in both the kinetic region and high current density region with the aid of IL. This work suggests that IL modification can provide a complementary approach to improve the performance of proton exchange membrane fuel cells. Full article
(This article belongs to the Special Issue Novel Developments in Fuel-Cell Oxygen Reduction Electrocatalysts)
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17 pages, 3102 KiB  
Article
LuxAB-Based Microbial Cell Factories for the Sensing, Manufacturing and Transformation of Industrial Aldehydes
by Thomas Bayer, Aileen Becker, Henrik Terholsen, In Jung Kim, Ina Menyes, Saskia Buchwald, Kathleen Balke, Suvi Santala, Steven C. Almo and Uwe T. Bornscheuer
Catalysts 2021, 11(8), 953; https://doi.org/10.3390/catal11080953 - 10 Aug 2021
Cited by 8 | Viewed by 4104
Abstract
The application of genetically encoded biosensors enables the detection of small molecules in living cells and has facilitated the characterization of enzymes, their directed evolution and the engineering of (natural) metabolic pathways. In this work, the LuxAB biosensor system from Photorhabdus luminescens was [...] Read more.
The application of genetically encoded biosensors enables the detection of small molecules in living cells and has facilitated the characterization of enzymes, their directed evolution and the engineering of (natural) metabolic pathways. In this work, the LuxAB biosensor system from Photorhabdus luminescens was implemented in Escherichia coli to monitor the enzymatic production of aldehydes from primary alcohols and carboxylic acid substrates. A simple high-throughput assay utilized the bacterial luciferase—previously reported to only accept aliphatic long-chain aldehydes—to detect structurally diverse aldehydes, including aromatic and monoterpene aldehydes. LuxAB was used to screen the substrate scopes of three prokaryotic oxidoreductases: an alcohol dehydrogenase (Pseudomonas putida), a choline oxidase variant (Arthrobacter chlorophenolicus) and a carboxylic acid reductase (Mycobacterium marinum). Consequently, high-value aldehydes such as cinnamaldehyde, citral and citronellal could be produced in vivo in up to 80% yield. Furthermore, the dual role of LuxAB as sensor and monooxygenase, emitting bioluminescence through the oxidation of aldehydes to the corresponding carboxylates, promises implementation in artificial enzyme cascades for the synthesis of carboxylic acids. These findings advance the bio-based detection, preparation and transformation of industrially important aldehydes in living cells. Full article
(This article belongs to the Special Issue Biocatalytic Cascade Reactions (in vivo and in vitro))
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14 pages, 33866 KiB  
Article
Enhanced Performance of Pt Nanoparticles on Ni-N Co-Doped Graphitized Carbon for Oxygen Reduction Reaction in Polymer Electrolyte Membrane Fuel Cells
by Won Suk Jung
Catalysts 2021, 11(8), 909; https://doi.org/10.3390/catal11080909 - 28 Jul 2021
Cited by 2 | Viewed by 2089
Abstract
Since the reaction rate and cost for cathodic catalyst in polymer electrolyte membrane fuel cells are obstacles for commercialization, the high-performance catalyst for oxygen reduction reaction is necessary. The Ni encapsulated with N-doped graphitic carbon (Ni@NGC) prepared with ethylenediamine and carbon black is [...] Read more.
Since the reaction rate and cost for cathodic catalyst in polymer electrolyte membrane fuel cells are obstacles for commercialization, the high-performance catalyst for oxygen reduction reaction is necessary. The Ni encapsulated with N-doped graphitic carbon (Ni@NGC) prepared with ethylenediamine and carbon black is employed as an efficient support for the oxygen reduction reaction. Characterizations show that the Ni@NGC has a large surface area and mesoporous structure that is suitable to the support for the Pt catalyst. The catalyst structure is identified and the size of Pt nanoparticles distributed in the narrow range of 2–3 nm. Four different nitrogen species are doped properly into graphitic carbon structure. The Pt/Ni@NGC shows higher performance than the commercial Pt/C catalyst in an acidic electrolyte. The mass activity of the Pt/Ni@NGC in fuel cell tests exhibits over 1.5 times higher than that of commercial Pt/C catalyst. The Pt/Ni@NGC catalyst at low Pt loading exhibits 47% higher maximum power density than the Pt/C catalyst under H2-air atmosphere. These results indicate that the Ni@NGC as a support is significantly beneficial to improving activity. Full article
(This article belongs to the Special Issue Novel Catalyst Materials for Low-Temperature Fuel Cells and Electrolyzers)
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35 pages, 3632 KiB  
Review
Green Synthesis of Metallic Nanoparticles: Applications and Limitations
by Pritam Kumar Dikshit, Jatin Kumar, Amit K. Das, Soumi Sadhu, Sunita Sharma, Swati Singh, Piyush Kumar Gupta and Beom Soo Kim
Catalysts 2021, 11(8), 902; https://doi.org/10.3390/catal11080902 - 26 Jul 2021
Cited by 248 | Viewed by 27171
Abstract
The past decade has witnessed a phenomenal rise in nanotechnology research due to its broad range of applications in diverse fields including food safety, transportation, sustainable energy, environmental science, catalysis, and medicine. The distinctive properties of nanomaterials (nano-sized particles in the range of [...] Read more.
The past decade has witnessed a phenomenal rise in nanotechnology research due to its broad range of applications in diverse fields including food safety, transportation, sustainable energy, environmental science, catalysis, and medicine. The distinctive properties of nanomaterials (nano-sized particles in the range of 1 to 100 nm) make them uniquely suitable for such wide range of functions. The nanoparticles when manufactured using green synthesis methods are especially desirable being devoid of harsh operating conditions (high temperature and pressure), hazardous chemicals, or addition of external stabilizing or capping agents. Numerous plants and microorganisms are being experimented upon for an eco–friendly, cost–effective, and biologically safe process optimization. This review provides a comprehensive overview on the green synthesis of metallic NPs using plants and microorganisms, factors affecting the synthesis, and characterization of synthesized NPs. The potential applications of metal NPs in various sectors have also been highlighted along with the major challenges involved with respect to toxicity and translational research. Full article
(This article belongs to the Special Issue Recent Advances on Nano-Catalysts for Biological Processes)
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17 pages, 3384 KiB  
Article
Shape Effects of Ceria Nanoparticles on the Water‒Gas Shift Performance of CuOx/CeO2 Catalysts
by Maria Lykaki, Sofia Stefa, Sónia A. C. Carabineiro, Miguel A. Soria, Luís M. Madeira and Michalis Konsolakis
Catalysts 2021, 11(6), 753; https://doi.org/10.3390/catal11060753 - 21 Jun 2021
Cited by 12 | Viewed by 2481
Abstract
The copper–ceria (CuOx/CeO2) system has been extensively investigated in several catalytic processes, given its distinctive properties and considerable low cost compared to noble metal-based catalysts. The fine-tuning of key parameters, e.g., the particle size and shape of individual counterparts, [...] Read more.
The copper–ceria (CuOx/CeO2) system has been extensively investigated in several catalytic processes, given its distinctive properties and considerable low cost compared to noble metal-based catalysts. The fine-tuning of key parameters, e.g., the particle size and shape of individual counterparts, can significantly affect the physicochemical properties and subsequently the catalytic performance of the binary oxide. To this end, the present work focuses on the morphology effects of ceria nanoparticles, i.e., nanopolyhedra (P), nanocubes (C), and nanorods (R), on the water–gas shift (WGS) performance of CuOx/CeO2 catalysts. Various characterization techniques were employed to unveil the effect of shape on the structural, redox and surface properties. According to the acquired results, the support morphology affects to a different extent the reducibility and mobility of oxygen species, following the trend: R > P > C. This consequently influences copper–ceria interactions and the stabilization of partially reduced copper species (Cu+) through the Cu2+/Cu+ and Ce4+/Ce3+ redox cycles. Regarding the WGS performance, bare ceria supports exhibit no activity, while the addition of copper to the different ceria nanostructures alters significantly this behaviour. The CuOx/CeO2 sample of rod-like morphology demonstrates the best catalytic activity and stability, approaching the thermodynamic equilibrium conversion at 350 °C. The greater abundance in loosely bound oxygen species, oxygen vacancies and highly dispersed Cu+ species can be mainly accounted for its superior catalytic performance. Full article
(This article belongs to the Special Issue Gold, Silver and Copper Catalysis)
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16 pages, 2662 KiB  
Article
Passivation of Co/Al2O3 Catalyst by Atomic Layer Deposition to Reduce Deactivation in the Fischer–Tropsch Synthesis
by José Antonio Díaz-López, Jordi Guilera, Martí Biset-Peiró, Dan Enache, Gordon Kelly and Teresa Andreu
Catalysts 2021, 11(6), 732; https://doi.org/10.3390/catal11060732 - 14 Jun 2021
Cited by 4 | Viewed by 2929
Abstract
The present work explores the technical feasibility of passivating a Co/γ-Al2O3 catalyst by atomic layer deposition (ALD) to reduce deactivation rate during Fischer–Tropsch synthesis (FTS). Three samples of the reference catalyst were passivated using different numbers of ALD cycles (3, [...] Read more.
The present work explores the technical feasibility of passivating a Co/γ-Al2O3 catalyst by atomic layer deposition (ALD) to reduce deactivation rate during Fischer–Tropsch synthesis (FTS). Three samples of the reference catalyst were passivated using different numbers of ALD cycles (3, 6 and 10). Characterization results revealed that a shell of the passivating agent (Al2O3) grew around catalyst particles. This shell did not affect the properties of passivated samples below 10 cycles, in which catalyst reduction was hindered. Catalytic tests at 50% CO conversion evidenced that 3 and 6 ALD cycles increased catalyst stability without significantly affecting the catalytic performance, whereas 10 cycles caused blockage of the active phase that led to a strong decrease of catalytic activity. Catalyst deactivation modelling and tests at 60% CO conversion served to conclude that 3 to 6 ALD cycles reduced Co/γ-Al2O3 deactivation, so that the technical feasibility of this technique was proven in FTS. Full article
(This article belongs to the Special Issue Heterogeneous Catalysts Optimization: From Material Design to Properties)
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44 pages, 4493 KiB  
Review
Application of TiO2-Based Photocatalysts to Antibiotics Degradation: Cases of Sulfamethoxazole, Trimethoprim and Ciprofloxacin
by Anastasiya Kutuzova, Tetiana Dontsova and Witold Kwapinski
Catalysts 2021, 11(6), 728; https://doi.org/10.3390/catal11060728 - 12 Jun 2021
Cited by 68 | Viewed by 6626
Abstract
The extensive application of antibiotics in human and veterinary medicine has led to their widespread occurrence in a natural aquatic environment. Global health crisis is associated with the fast development of antimicrobial resistance, as more and more infectious diseases cannot be treated more [...] Read more.
The extensive application of antibiotics in human and veterinary medicine has led to their widespread occurrence in a natural aquatic environment. Global health crisis is associated with the fast development of antimicrobial resistance, as more and more infectious diseases cannot be treated more than once. Sulfamethoxazole, trimethoprim and ciprofloxacin are the most commonly detected antibiotics in water systems worldwide. The persistent and toxic nature of these antibiotics makes their elimination by conventional treatment methods at wastewater treatment plants almost impossible. The application of advanced oxidation processes and heterogeneous photocatalysis over TiO2-based materials is a promising solution. This highly efficient technology has the potential to be sustainable, cost-efficient and energy-efficient. A comprehensive review on the application of various TiO2-based photocatalysts for the degradation of sulfamethoxazole, trimethoprim and ciprofloxacin is focused on highlighting their photocatalytic performance under various reaction conditions (different amounts of pollutant and photocatalyst, pH, light source, reaction media, presence of inorganic ions, natural organic matter, oxidants). Mineralization efficiency and ecotoxicity of final products have been also considered. Further research needs have been presented based on the literature findings. Among them, design and development of highly efficient under sunlight, stable, recyclable and cost-effective TiO2-based materials; usage of real wastewaters for photocatalytic tests; and compulsory assessment of products ecotoxicity are the most important research tasks in order to meet requirements for industrial application. Full article
(This article belongs to the Special Issue Environmental Remediation via Metal-Oxides-Mediated Heterogeneous Photocatalysis)
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13 pages, 3855 KiB  
Article
Octahedral Growth of PtPd Nanocrystals
by Diana Nelli, Cesare Roncaglia, Samuel Ahearn, Marcel Di Vece, Riccardo Ferrando and Chloé Minnai
Catalysts 2021, 11(6), 718; https://doi.org/10.3390/catal11060718 - 09 Jun 2021
Cited by 11 | Viewed by 2462
Abstract
PtPd nanoparticles are among the most widely studied nanoscale systems, mainly because of their applications as catalysts in chemical reactions. In this work, a combined experimental-theoretical study is presented about the dependence of growth shape of PtPd alloy nanocrystals on their composition. The [...] Read more.
PtPd nanoparticles are among the most widely studied nanoscale systems, mainly because of their applications as catalysts in chemical reactions. In this work, a combined experimental-theoretical study is presented about the dependence of growth shape of PtPd alloy nanocrystals on their composition. The particles are grown in the gas phase and characterized by STEM-HRTEM. PtPd nanoalloys present a bimodal size distribution. The size of the larger population can be tuned between 3.8 ± 0.4 and 14.1 ± 2.0 nm by controlling the deposition parameters. A strong dependence of the particle shape on the composition is found: Pd-rich nanocrystals present more rounded shapes whereas Pt-rich ones exhibit sharp tips. Molecular dynamics simulations and excess energy calculations show that the growth structures are out of equilibrium. The growth simulations are able to follow the growth shape evolution and growth pathways at the atomic level, reproducing the structures in good agreement with the experimental results. Finally the optical absorption properties are calculated for PtPd nanoalloys of the same shapes and sizes grown in our experiments. Full article
(This article belongs to the Special Issue Heterogeneous Catalysts Optimization: From Material Design to Properties)
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30 pages, 33501 KiB  
Review
Aftertreatment Technologies for Diesel Engines: An Overview of the Combined Systems
by Ferenc Martinovic, Lidia Castoldi and Fabio Alessandro Deorsola
Catalysts 2021, 11(6), 653; https://doi.org/10.3390/catal11060653 - 21 May 2021
Cited by 29 | Viewed by 7528
Abstract
The abatement of the pollutants deriving from diesel engines in the vehicle sector still represents an interesting scientific and technological challenge due to increasingly limiting regulations. Meeting the stringent limits of NOx and soot emissions requires a catalytic system with great complexity, [...] Read more.
The abatement of the pollutants deriving from diesel engines in the vehicle sector still represents an interesting scientific and technological challenge due to increasingly limiting regulations. Meeting the stringent limits of NOx and soot emissions requires a catalytic system with great complexity, size of units, and number of units, as well as increased fuel consumption. Thus, an after-treatment device for a diesel vehicle requires the use of an integrated catalyst technology for a reduction in the individual emissions of exhaust gas. The representative technologies devoted to the reduction of NOx under lean-burn operation conditions are selective catalytic reduction (SCR) and the lean NOx trap (LNT), while soot removal is mainly performed by filters (DPF). These devices are normally used in sequence, or a combination of them has been proposed to overcome the drawbacks of the individual devices. This review summarizes the current state of NOx and soot abatement strategies. The main focus of this review is on combined technologies for NOx removal (i.e., LNT–SCR) and for the simultaneous removal of NOx and soot, like SCR-on-Filter (SCRoF), in series LNT/DPF and SCR/DPF, and LNT/DPF and SCR/DPF hybrid systems. Full article
(This article belongs to the Special Issue Selective Catalytic Reduction of NOx by NH3)
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15 pages, 1792 KiB  
Review
Waste Animal Bones as Catalysts for Biodiesel Production; A Mini Review
by Fayaz Hussain, Saad Alshahrani, Muhammad Mujtaba Abbas, Haris Mahmood Khan, Asif Jamil, Haseeb Yaqoob, Manzoore Elahi M. Soudagar, Muhammad Imran, Mushtaq Ahmad and Mamoona Munir
Catalysts 2021, 11(5), 630; https://doi.org/10.3390/catal11050630 - 13 May 2021
Cited by 38 | Viewed by 7717
Abstract
Slaughterhouse waste is considered to be an emerging issue because of its disposal cost. As an alternative, it would be a great prospect for the bioeconomy society to explore new usages of these leftover materials. As per food safety rules mentioned by EU [...] Read more.
Slaughterhouse waste is considered to be an emerging issue because of its disposal cost. As an alternative, it would be a great prospect for the bioeconomy society to explore new usages of these leftover materials. As per food safety rules mentioned by EU legislation, all bone waste generated by slaughterhouses ought to be disposed of by rendering. The huge quantity of worldwide bone waste generation (130 billion kilograms per annum) is an environmental burden if not properly managed. The waste animal bones can be efficiently employed as a heterogeneous catalyst to produce biodiesel. This mini review summarized the recent literature reported for biodiesel generation using waste animal bones derived heterogeneous catalyst. It discusses the sources of bone waste, catalyst preparation methods, particularly calcination and its effects, and important characteristics of bones derived catalyst. It suggests that catalysts extracted from waste animal bones have suitable catalytic activity in transesterification of different oil sources to generate a good quality biodiesel. Full article
(This article belongs to the Special Issue Heterogeneous Catalysis in Green Chemistry)
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29 pages, 8877 KiB  
Review
Lipase Immobilization in Mesoporous Silica Nanoparticles for Biofuel Production
by Aniello Costantini and Valeria Califano
Catalysts 2021, 11(5), 629; https://doi.org/10.3390/catal11050629 - 13 May 2021
Cited by 37 | Viewed by 4747
Abstract
Lipases are ubiquitous enzymes whose physiological role is the hydrolysis of triacylglycerol into fatty acids. They are the most studied and industrially interesting enzymes, thanks to their versatility to promote a plethora of reactions on a wide range of substrates. In fact, depending [...] Read more.
Lipases are ubiquitous enzymes whose physiological role is the hydrolysis of triacylglycerol into fatty acids. They are the most studied and industrially interesting enzymes, thanks to their versatility to promote a plethora of reactions on a wide range of substrates. In fact, depending on the reaction conditions, they can also catalyze synthesis reactions, such as esterification, acidolysis and transesterification. The latter is particularly important for biodiesel production. Biodiesel can be produced from animal fats or vegetable oils and is considered as a biodegradable, non-toxic and renewable energy source. The use of lipases as industrial catalysts is subordinated to their immobilization on insoluble supports, to allow multiple uses and use in continuous processes, but also to stabilize the enzyme, intrinsically prone to denaturation with consequent loss of activity. Among the materials that can be used for lipase immobilization, mesoporous silica nanoparticles represent a good choice due to the combination of thermal and mechanical stability with controlled textural characteristics. Moreover, the presence of abundant surface hydroxyl groups allows for easy chemical surface functionalization. This latter aspect has the main importance since lipases have a high affinity with hydrophobic supports. The objective of this work is to provide an overview of the recent progress of lipase immobilization in mesoporous silica nanoparticles with a focus on biodiesel production. Full article
(This article belongs to the Special Issue Enzyme Immobilization and Biocatalysis)
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14 pages, 1424 KiB  
Article
Photocatalytic Degradation of Sulfolane Using a LED-Based Photocatalytic Treatment System
by Sripriya Dharwadkar, Linlong Yu and Gopal Achari
Catalysts 2021, 11(5), 624; https://doi.org/10.3390/catal11050624 - 12 May 2021
Cited by 12 | Viewed by 3196
Abstract
Sulfolane is an emerging industrial pollutant detected in the environments near many oil and gas plants in North America. So far, numerous advanced oxidation processes have been investigated to treat sulfolane in aqueous media. However, there is only a few papers that discuss [...] Read more.
Sulfolane is an emerging industrial pollutant detected in the environments near many oil and gas plants in North America. So far, numerous advanced oxidation processes have been investigated to treat sulfolane in aqueous media. However, there is only a few papers that discuss the degradation of sulfolane using photocatalysis. In this study, photocatalytic degradation of sulfolane using titanium dioxide (TiO2) and reduced graphene oxide TiO2 composite (RGO-TiO2) in a light-emitting diode (LED) photoreactor was investigated. The impact of different waters (ultrapure water, tap water, and groundwater) and type of irradiation (UVA-LED and mercury lamp) on photocatalytic degradation of sulfolane were also studied. In addition, a reusability test was conducted for the photocatalyst to examine the degradation of sulfolane in three consecutive cycles with new batches of sulfolane-contaminated water. The results show that LED-based photocatalysis was effective in degrading sulfolane in waters even after three photocatalytic cycles. UVA-LEDs displayed more efficient use of photon energy when compared with the mercury lamps as they have a narrow emission spectrum coinciding with the absorption of TiO2. The combination of UVA-LED and TiO2 yielded better performance than UVA-LED and RGO-TiO2 for the degradation of sulfolane. Much lower sulfolane degradation rates were observed in tap water and groundwater than ultrapure water. Full article
(This article belongs to the Special Issue Photo(electro)catalytic Reactions Combined with Ozone Oxidation Technique)
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14 pages, 4201 KiB  
Article
Atmospheric Pressure Tornado Plasma Jet of Polydopamine Coating on Graphite Felt for Improving Electrochemical Performance in Vanadium Redox Flow Batteries
by Song-Yu Chen, Yu-Lin Kuo, Yao-Ming Wang, Wei-Mau Hsu, Tzu-Hsuan Chien, Chiu-Feng Lin, Cheng-Hsien Kuo, Akitoshi Okino and Tai-Chin Chiang
Catalysts 2021, 11(5), 627; https://doi.org/10.3390/catal11050627 - 12 May 2021
Cited by 4 | Viewed by 3061
Abstract
The intrinsic hydrophobicity of graphite felt (GF) is typically altered for the purpose of the surface wettability and providing active sites for the enhancement of electrochemical performance. In this work, commercial GF is used as the electrodes. The GF electrode with a coated-polydopamine [...] Read more.
The intrinsic hydrophobicity of graphite felt (GF) is typically altered for the purpose of the surface wettability and providing active sites for the enhancement of electrochemical performance. In this work, commercial GF is used as the electrodes. The GF electrode with a coated-polydopamine catalyst is achieved to enhance the electrocatalytic activity of GF for the redox reaction of vanadium ions in vanadium redox flow battery (VRFB). Materials characteristics proved that a facile coating via atmospheric pressure plasma jet (APPJ) to alter the surface superhydrophilicity and to deposit polydopamine on GF for providing the more active sites is feasibly achieved. Due to the synergistic effects of the presence of more active sites on the superhydrophilic surface of modified electrodes, the electrochemical performance toward VO2+/VO2+ reaction was evidently improved. We believed that using the APPJ technique as a coating method for electrocatalyst preparation offers the oxygen-containing functional groups on the substrate surface on giving a hydrogen bonding with the grafted functional polymeric materials. Full article
(This article belongs to the Special Issue Catalysts and Electrode Functionalization for Redox Flow Battery)
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19 pages, 5187 KiB  
Article
Particle Number Emissions of a Euro 6d-Temp Gasoline Vehicle under Extreme Temperatures and Driving Conditions
by Barouch Giechaskiel, Victor Valverde, Anastasios Kontses, Anastasios Melas, Giorgio Martini, Andreas Balazs, Jon Andersson, Zisis Samaras and Panagiota Dilara
Catalysts 2021, 11(5), 607; https://doi.org/10.3390/catal11050607 - 10 May 2021
Cited by 21 | Viewed by 3417
Abstract
With the introduction of gasoline particulate filters (GPFs), the particle number (PN) emissions of gasoline direct-injection (GDI) vehicles are below the European regulatory limit of 6 × 1011 p/km under certification conditions. Nevertheless, concerns have been raised regarding emission levels at the [...] Read more.
With the introduction of gasoline particulate filters (GPFs), the particle number (PN) emissions of gasoline direct-injection (GDI) vehicles are below the European regulatory limit of 6 × 1011 p/km under certification conditions. Nevertheless, concerns have been raised regarding emission levels at the boundaries of ambient and driving conditions of the real-driving emissions (RDE) regulation. A Euro 6d-Temp GDI vehicle with a GPF was tested on the road and in the laboratory with cycles simulating congested urban traffic, dynamic driving, and towing a trailer uphill at 85% of maximum payload. The ambient temperatures covered a range from −30 to 50 °C. The solid PN emissions were 10 times lower than the PN limit under most conditions and temperatures. Only dynamic driving that regenerated the filter passively, and for the next cycle resulted in relatively high emissions although they were still below the limit. The results of this study confirmed the effectiveness of GPFs in controlling PN emissions under a wide range of conditions. Full article
(This article belongs to the Special Issue Present Challenges in Catalytic Emission Control for Internal Combustion Engines)
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18 pages, 3470 KiB  
Review
A Brief Review of Catalytic Cathode Materials for Na-CO2 Batteries
by Dong Sui, Meijia Chang, Haiyu Wang, Hang Qian, Yanliang Yang, Shan Li, Yongsheng Zhang and Yingze Song
Catalysts 2021, 11(5), 603; https://doi.org/10.3390/catal11050603 - 07 May 2021
Cited by 36 | Viewed by 4605
Abstract
As an emerging energy storage technology, Na-CO2 batteries with high energy density are drawing tremendous attention because of their advantages of combining cost-effective energy conversion and storage with CO2 clean recycle and utilization. Nevertheless, their commercial applications are impeded by unsatisfactory [...] Read more.
As an emerging energy storage technology, Na-CO2 batteries with high energy density are drawing tremendous attention because of their advantages of combining cost-effective energy conversion and storage with CO2 clean recycle and utilization. Nevertheless, their commercial applications are impeded by unsatisfactory electrochemical performance including large overpotentials, poor rate capability, fast capacity deterioration, and inferior durability, which mainly results from the inefficient electrocatalysts of cathode materials. Therefore, novel structured cathode materials with efficient catalytic activity are highly desired. In this review, the latest advances of catalytic cathode materials for Na-CO2 batteries are summarized, with a special emphasis on the electrocatalysts for CO2 reduction and evolution, the formation and decomposition of discharge product, as well as their catalytic mechanism. Finally, an outlook is also proposed for the future development of Na-CO2 batteries. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts: Achievements in Electrocatalysis for Sustainable Energy Technologies)
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16 pages, 4367 KiB  
Article
CpCo(III) Precatalysts for [2+2+2] Cycloadditions
by Fabian Fischer, Michael Eder and Marko Hapke
Catalysts 2021, 11(5), 596; https://doi.org/10.3390/catal11050596 - 04 May 2021
Cited by 2 | Viewed by 2991
Abstract
Catalysts applied in cobalt-catalyzed cyclotrimerizations reactions in general rely on the use of Co(I) precatalysts or the in situ generation of Co(I) catalysts from Co(II) sources by reduction in the presence of steering ligands, often by addition of less noble metals. In this [...] Read more.
Catalysts applied in cobalt-catalyzed cyclotrimerizations reactions in general rely on the use of Co(I) precatalysts or the in situ generation of Co(I) catalysts from Co(II) sources by reduction in the presence of steering ligands, often by addition of less noble metals. In this paper, we report the synthesis and properties of novel stable CpCo(III) complexes as precatalysts and their exemplary evaluation for application in catalytic [2+2+2] cycloadditions. The role of phosphite neutral ligands, as well as iodide and cyanide as anionic ligands, on the reactivity of the complexes was evaluated. A modified one-pot approach to the synthesis of Cp ring-functionalized Cp’Co(III) complexes was developed. The investigations demonstrated that CpCo(III) complexes can be directly applied as catalysts in catalytic cyclotrimerizations of triynes without reducing agents as additives. Full article
(This article belongs to the Special Issue Cobalt Catalysis: Recent Progress and Developments)
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23 pages, 7555 KiB  
Review
Toward Scaling-Up Photocatalytic Process for Multiphase Environmental Applications
by Mohamed Gar Alalm, Ridha Djellabi, Daniela Meroni, Carlo Pirola, Claudia Letizia Bianchi and Daria Camilla Boffito
Catalysts 2021, 11(5), 562; https://doi.org/10.3390/catal11050562 - 28 Apr 2021
Cited by 45 | Viewed by 4997
Abstract
Recently, we have witnessed a booming development of composites and multi-dopant metal oxides to be employed as novel photocatalysts. Yet the practical application of photocatalysis for environmental purposes is still elusive. Concerns about the unknown fate and toxicity of nanoparticles, unsatisfactory performance in [...] Read more.
Recently, we have witnessed a booming development of composites and multi-dopant metal oxides to be employed as novel photocatalysts. Yet the practical application of photocatalysis for environmental purposes is still elusive. Concerns about the unknown fate and toxicity of nanoparticles, unsatisfactory performance in real conditions, mass transfer limitations and durability issues have so far discouraged investments in full-scale applications of photocatalysis. Herein, we provide a critical overview of the main challenges that are limiting large-scale application of photocatalysis in air and water/wastewater purification. We then discuss the main approaches reported in the literature to tackle these shortcomings, such as the design of photocatalytic reactors that retain the photocatalyst, the study of degradation of micropollutants in different water matrices, and the development of gas-phase reactors with optimized contact time and irradiation. Furthermore, we provide a critical analysis of research–practice gaps such as treatment of real water and air samples, degradation of pollutants with actual environmental concentrations, photocatalyst deactivation, and cost and environmental life-cycle assessment. Full article
(This article belongs to the Special Issue Air and Water Purification Processes through Photocatalysis: Scale Up Perspectives)
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19 pages, 5354 KiB  
Article
The Effect of Co Incorporation on the CO Oxidation Activity of LaFe1−xCoxO3 Perovskites
by Maik Dreyer, Moritz Krebs, Sharif Najafishirtari, Anna Rabe, Klaus Friedel Ortega and Malte Behrens
Catalysts 2021, 11(5), 550; https://doi.org/10.3390/catal11050550 - 27 Apr 2021
Cited by 15 | Viewed by 2971
Abstract
Perovskite oxides are versatile materials due to their wide variety of compositions offering promising catalytic properties, especially in oxidation reactions. In the presented study, LaFe1−xCoxO3 perovskites were synthesized by hydroxycarbonate precursor co-precipitation and thermal decomposition thereof. Precursor and [...] Read more.
Perovskite oxides are versatile materials due to their wide variety of compositions offering promising catalytic properties, especially in oxidation reactions. In the presented study, LaFe1−xCoxO3 perovskites were synthesized by hydroxycarbonate precursor co-precipitation and thermal decomposition thereof. Precursor and calcined materials were studied by scanning electron microscopy (SEM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TG), and X-ray powder diffraction (XRD). The calcined catalysts were in addition studied by transmission electron microscopy (TEM) and N2 physisorption. The obtained perovskites were applied as catalysts in transient CO oxidation, and in operando studies of CO oxidation in diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). A pronounced increase in activity was already observed by incorporating 5% cobalt into the structure, which continued, though not linearly, at higher loadings. This could be most likely due to the enhanced redox properties as inferred by H2-temperature programmed reduction (H2-TPR). Catalysts with higher Co contents showing higher activities suffered less from surface deactivation related to carbonate poisoning. Despite the similarity in the crystalline structures upon Co incorporation, we observed a different promotion or suppression of various carbonate-related bands, which could indicate different surface properties of the catalysts, subsequently resulting in the observed non-linear CO oxidation activity trend at higher Co contents. Full article
(This article belongs to the Special Issue Surface Design of Metal Oxide Catalysts)
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31 pages, 3760 KiB  
Review
Main Hydrogen Production Processes: An Overview
by Marco Martino, Concetta Ruocco, Eugenio Meloni, Pluton Pullumbi and Vincenzo Palma
Catalysts 2021, 11(5), 547; https://doi.org/10.3390/catal11050547 - 25 Apr 2021
Cited by 82 | Viewed by 10174
Abstract
Due to its characteristics, hydrogen is considered the energy carrier of the future. Its use as a fuel generates reduced pollution, as if burned it almost exclusively produces water vapor. Hydrogen can be produced from numerous sources, both of fossil and renewable origin, [...] Read more.
Due to its characteristics, hydrogen is considered the energy carrier of the future. Its use as a fuel generates reduced pollution, as if burned it almost exclusively produces water vapor. Hydrogen can be produced from numerous sources, both of fossil and renewable origin, and with as many production processes, which can use renewable or non-renewable energy sources. To achieve carbon neutrality, the sources must necessarily be renewable, and the production processes themselves must use renewable energy sources. In this review article the main characteristics of the most used hydrogen production methods are summarized, mainly focusing on renewable feedstocks, furthermore a series of relevant articles published in the last year, are reviewed. The production methods are grouped according to the type of energy they use; and at the end of each section the strengths and limitations of the processes are highlighted. The conclusions compare the main characteristics of the production processes studied and contextualize their possible use. Full article
(This article belongs to the Special Issue Catalysts for Sustainable Hydrogen Production: Preparation, Applications and Process Integration)
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22 pages, 4501 KiB  
Review
Research Progress on Catalytic Water Splitting Based on Polyoxometalate/Semiconductor Composites
by Yue Wu and Lihua Bi
Catalysts 2021, 11(4), 524; https://doi.org/10.3390/catal11040524 - 20 Apr 2021
Cited by 15 | Viewed by 4755
Abstract
In recent years, due to the impact of global warming, environmental pollution, and the energy crisis, international attention and demand for clean energy are increasing. Hydrogen energy is recognized as one of the clean energy sources. Water is considered as the largest potential [...] Read more.
In recent years, due to the impact of global warming, environmental pollution, and the energy crisis, international attention and demand for clean energy are increasing. Hydrogen energy is recognized as one of the clean energy sources. Water is considered as the largest potential supplier of hydrogen energy. However, artificial catalytic water splitting for hydrogen and oxygen evolution has not been widely used due to its high energy consumption and high cost during catalytic cracking. Therefore, the exploitation of photocatalysts, electrocatalysts, and photo-electrocatalysts for rapid, cost effective, and reliable water splitting is essentially needed. Polyoxometalates (POMs) are regarded as the potential candidates for water splitting catalysis. In addition to their excellent catalytic properties and reversibly redox activities, POMs can also modify semiconductors to overcome their shortcomings, and improve photoelectric conversion efficiency and photocatalytic activity, which has attracted more and more attention in the field of photoelectric water splitting catalysis. In this review, we summarize the latest applications of POMs and semiconductor composites in the field of photo-electrocatalysis (PEC) for hydrogen and oxygen evolution by catalytic water splitting in recent years and take the latest applications of POMs and semiconductor composites in photocatalysis for water splitting. In the conclusion section, the challenges and strategies of photocatalytic and PEC water-splitting by POMs and semiconductor composites are discussed. Full article
(This article belongs to the Section Photocatalysis)
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15 pages, 1589 KiB  
Article
Microbial Removal of Pb(II) Using an Upflow Anaerobic Sludge Blanket (UASB) Reactor
by Jeremiah Chimhundi, Carla Hörstmann, Evans M. N. Chirwa and Hendrik G. Brink
Catalysts 2021, 11(4), 512; https://doi.org/10.3390/catal11040512 - 19 Apr 2021
Cited by 8 | Viewed by 2445
Abstract
The main objective of this study was to achieve the continuous biorecovery and bioreduction of Pb(II) using an industrially obtained consortia as a biocatalyst. An upflow anaerobic sludge blanket reactor was used in the treatment process. The bioremediation technique that was applied made [...] Read more.
The main objective of this study was to achieve the continuous biorecovery and bioreduction of Pb(II) using an industrially obtained consortia as a biocatalyst. An upflow anaerobic sludge blanket reactor was used in the treatment process. The bioremediation technique that was applied made use of a yeast extract as the microbial substrate and Pb(NO3)2 as the source of Pb(II). The UASB reactor exhibited removal efficiencies of between 90 and 100% for the inlet Pb concentrations from 80 to 2000 ppm and a maximum removal rate of 1948.4 mg/(L·d) was measured. XRD and XPS analyses of the precipitate revealed the presence of Pb0, PbO, PbS and PbSO4. Supporting experimental work carried out included growth measurements, pH, oxidation–reduction potentials and nitrate levels. Full article
(This article belongs to the Special Issue Biocatalysis for Green Chemistry)
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23 pages, 14979 KiB  
Article
A Thermally Conductive Pt/AAO Catalyst for Hydrogen Passive Autocatalytic Recombination
by Alina E. Kozhukhova, Stephanus P. du Preez, Aleksander A. Malakhov and Dmitri G. Bessarabov
Catalysts 2021, 11(4), 491; https://doi.org/10.3390/catal11040491 - 12 Apr 2021
Cited by 23 | Viewed by 3297
Abstract
In this study, a Pt/anodized aluminum oxide (AAO) catalyst was prepared by the anodization of an Al alloy (Al6082, 97.5% Al), followed by the incorporation of Pt via an incipient wet impregnation method. Then, the Pt/AAO catalyst was evaluated for autocatalytic hydrogen recombination. [...] Read more.
In this study, a Pt/anodized aluminum oxide (AAO) catalyst was prepared by the anodization of an Al alloy (Al6082, 97.5% Al), followed by the incorporation of Pt via an incipient wet impregnation method. Then, the Pt/AAO catalyst was evaluated for autocatalytic hydrogen recombination. The Pt/AAO catalyst’s morphological characteristics were determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The average Pt particle size was determined to be 3.0 ± 0.6 nm. This Pt/AAO catalyst was tested for the combustion of lean hydrogen (0.5–4 vol% H2 in the air) in a recombiner section testing station. The thermal distribution throughout the catalytic surface was investigated at 3 vol% hydrogen (H2) using an infrared camera. The Al/AAO system had a high thermal conductivity, which prevents the formation of hotspots (areas where localized surface temperature is higher than an average temperature across the entire catalyst surface). In turn, the Pt stability was enhanced during catalytic hydrogen combustion (CHC). A temperature gradient over 70 mm of the Pt/AAO catalyst was 23 °C and 42 °C for catalysts with uniform and nonuniform (worst-case scenario) Pt distributions. The commercial computational fluid dynamics (CFD) code STAR-CCM+ was used to compare the experimentally observed and numerically simulated thermal distribution of the Pt/AAO catalyst. The effect of the initial H2 volume fraction on the combustion temperature and conversion of H2 was investigated. The activation energy for CHC on the Pt/AAO catalyst was 19.2 kJ/mol. Prolonged CHC was performed to assess the durability (reactive metal stability and catalytic activity) of the Pt/AAO catalyst. A stable combustion temperature of 162.8 ± 8.0 °C was maintained over 530 h of CHC. To confirm that Pt aggregation was avoided, the Pt particle size and distribution were determined by TEM before and after prolonged CHC. Full article
(This article belongs to the Section Catalytic Materials)
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17 pages, 3576 KiB  
Review
Enantioselective Catalytic C-H Amidations: An Highlight
by Eleonora Tosi, Renata Marcia de Figueiredo and Jean-Marc Campagne
Catalysts 2021, 11(4), 471; https://doi.org/10.3390/catal11040471 - 06 Apr 2021
Cited by 12 | Viewed by 3186
Abstract
The crucial role played by compounds bearing amide functions, not only in biological processes but also in several fields of chemistry, life polymers and material sciences, has brought about many significant discoveries and innovative approaches for their chemical synthesis. Indeed, a plethora of [...] Read more.
The crucial role played by compounds bearing amide functions, not only in biological processes but also in several fields of chemistry, life polymers and material sciences, has brought about many significant discoveries and innovative approaches for their chemical synthesis. Indeed, a plethora of strategies has been developed to reach such moieties. Amides within chiral molecules are often associated with biological activity especially in life sciences and medicinal chemistry. In most of these cases, their synthesis requires extensive rethinking methodologies. In the very last years (2019–2020), enantioselective C-H functionalization has appeared as a straightforward alternative to reach chiral amides. Therein, an overview on these transformations within this timeframe is going to be given. Full article
(This article belongs to the Special Issue Catalytic Approaches for Amide Synthesis)
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13 pages, 2297 KiB  
Article
Multi-Scale Biosurfactant Production by Bacillus subtilis Using Tuna Fish Waste as Substrate
by Jiheng Hu, Jie Luo, Zhiwen Zhu, Bing Chen, Xudong Ye, Peng Zhu and Baiyu Zhang
Catalysts 2021, 11(4), 456; https://doi.org/10.3390/catal11040456 - 01 Apr 2021
Cited by 23 | Viewed by 3827
Abstract
As one of the most effective biosurfactants reported to date, lipopeptides exhibit attractive surface and biological activities and have the great potential to serve as biocatalysts. Low yield, high cost of production, and purification hinder the large-scale applications of lipopeptides. Utilization of waste [...] Read more.
As one of the most effective biosurfactants reported to date, lipopeptides exhibit attractive surface and biological activities and have the great potential to serve as biocatalysts. Low yield, high cost of production, and purification hinder the large-scale applications of lipopeptides. Utilization of waste materials as low-cost substrates for the growth of biosurfactant producers has emerged as a feasible solution for economical biosurfactant production. In this study, fish peptone was generated through enzyme hydrolyzation of smashed tuna (Katsuwonus pelamis). Biosurfactant (mainly surfactin) production by Bacillus subtilis ATCC 21332 was further evaluated and optimized using the generated fish peptone as a comprehensive substrate. The optimized production conduction was continuously assessed in a 7 L batch-scale and 100 L pilot-scale fermenter, exploring the possibility for a large-scale surfactin production. The results showed that Bacillus subtilis ATCC 21332 could effectively use the fish waste peptones for surfactin production. The highest surfactin productivity achieved in the pilot-scale experiments was 274 mg/L. The experimental results shed light on the further production of surfactins at scales using fish wastes as an economical substrate. Full article
(This article belongs to the Special Issue Biocatalysts and Their Environmental Applications)
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21 pages, 3341 KiB  
Review
Recent Developments in Dielectric Barrier Discharge Plasma-Assisted Catalytic Dry Reforming of Methane over Ni-Based Catalysts
by Xingyuan Gao, Ziting Lin, Tingting Li, Liuting Huang, Jinmiao Zhang, Saeed Askari, Nikita Dewangan, Ashok Jangam and Sibudjing Kawi
Catalysts 2021, 11(4), 455; https://doi.org/10.3390/catal11040455 - 01 Apr 2021
Cited by 50 | Viewed by 5905
Abstract
The greenhouse effect is leading to global warming and destruction of the ecological environment. The conversion of carbon dioxide and methane greenhouse gases into valuable substances has attracted scientists’ attentions. Dry reforming of methane (DRM) alleviates environmental problems and converts CO2 and [...] Read more.
The greenhouse effect is leading to global warming and destruction of the ecological environment. The conversion of carbon dioxide and methane greenhouse gases into valuable substances has attracted scientists’ attentions. Dry reforming of methane (DRM) alleviates environmental problems and converts CO2 and CH4 into valuable chemical substances; however, due to the high energy input to break the strong chemical bonds in CO2 and CH4, non-thermal plasma (NTP) catalyzed DRM has been promising in activating CO2 at ambient conditions, thus greatly lowering the energy input; moreover, the synergistic effect of the catalyst and plasma improves the reaction efficiency. In this review, the recent developments of catalytic DRM in a dielectric barrier discharge (DBD) plasma reactor on Ni-based catalysts are summarized, including the concept, characteristics, generation, and types of NTP used for catalytic DRM and corresponding mechanisms, the synergy and performance of Ni-based catalysts with DBD plasma, the design of DBD reactor and process parameter optimization, and finally current challenges and future prospects are provided. Full article
(This article belongs to the Special Issue Plasma-Catalysis for Environmental and Energy-Related Applications)
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25 pages, 2924 KiB  
Review
Facet-Dependent Reactivity of Ceria Nanoparticles Exemplified by CeO2-Based Transition Metal Catalysts: A Critical Review
by Michalis Konsolakis and Maria Lykaki
Catalysts 2021, 11(4), 452; https://doi.org/10.3390/catal11040452 - 31 Mar 2021
Cited by 35 | Viewed by 4372
Abstract
The rational design and fabrication of highly-active and cost-efficient catalytic materials constitutes the main research pillar in catalysis field. In this context, the fine-tuning of size and shape at the nanometer scale can exert an intense impact not only on the inherent reactivity [...] Read more.
The rational design and fabrication of highly-active and cost-efficient catalytic materials constitutes the main research pillar in catalysis field. In this context, the fine-tuning of size and shape at the nanometer scale can exert an intense impact not only on the inherent reactivity of catalyst’s counterparts but also on their interfacial interactions; it can also opening up new horizons for the development of highly active and robust materials. The present critical review, focusing mainly on our recent advances on the topic, aims to highlight the pivotal role of shape engineering in catalysis, exemplified by noble metal-free, CeO2-based transition metal catalysts (TMs/CeO2). The underlying mechanism of facet-dependent reactivity is initially discussed. The main implications of ceria nanoparticles’ shape engineering (rods, cubes, and polyhedra) in catalysis are next discussed, on the ground of some of the most pertinent heterogeneous reactions, such as CO2 hydrogenation, CO oxidation, and N2O decomposition. It is clearly revealed that shape functionalization can remarkably affect the intrinsic features and in turn the reactivity of ceria nanoparticles. More importantly, by combining ceria nanoparticles (CeO2 NPs) of specific architecture with various transition metals (e.g., Cu, Fe, Co, and Ni) remarkably active multifunctional composites can be obtained due mainly to the synergistic metalceria interactions. From the practical point of view, novel catalyst formulations with similar or even superior reactivity to that of noble metals can be obtained by co-adjusting the shape and composition of mixed oxides, such as Cu/ceria nanorods for CO oxidation and Ni/ceria nanorods for CO2 hydrogenation. The conclusions derived could provide the design principles of earth-abundant metal oxide catalysts for various real-life environmental and energy applications. Full article
(This article belongs to the Special Issue Commemorative Issue in Honor of Professor Gerhard Ertl on the Occasion of His 85th Birthday)
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26 pages, 5868 KiB  
Review
Review on the Visible Light Photocatalysis for the Decomposition of Ciprofloxacin, Norfloxacin, Tetracyclines, and Sulfonamides Antibiotics in Wastewater
by Samar Shurbaji, Pham Thi Huong and Talal Mohammed Altahtamouni
Catalysts 2021, 11(4), 437; https://doi.org/10.3390/catal11040437 - 29 Mar 2021
Cited by 67 | Viewed by 6269
Abstract
Antibiotics are chemical compounds that are used to kill or prevent bacterial growth. They are used in different fields, such as the medical field, agriculture, and veterinary. Antibiotics end up in wastewater, which causes the threat of developing antibacterial resistance; therefore, antibiotics must [...] Read more.
Antibiotics are chemical compounds that are used to kill or prevent bacterial growth. They are used in different fields, such as the medical field, agriculture, and veterinary. Antibiotics end up in wastewater, which causes the threat of developing antibacterial resistance; therefore, antibiotics must be eliminated from wastewater. Different conventional elimination methods are limited due to their high cost and effort, or incomplete elimination. Semiconductor-assisted photocatalysis arises as an effective elimination method for different organic wastes including antibiotics. A variety of semiconducting materials were tested to eliminate antibiotics from wastewater; nevertheless, research is still ongoing due to some limitations. This review summarizes the recent studies regarding semiconducting material modifications for antibiotic degradation using visible light irradiation. Full article
(This article belongs to the Special Issue Photocatalytic Oxidation/Ozonation Processes)
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53 pages, 6120 KiB  
Review
Advanced Two-Dimensional Heterojunction Photocatalysts of Stoichiometric and Non-Stoichiometric Bismuth Oxyhalides with Graphitic Carbon Nitride for Sustainable Energy and Environmental Applications
by Kishore Sridharan, Sulakshana Shenoy, S. Girish Kumar, Chiaki Terashima, Akira Fujishima and Sudhagar Pitchaimuthu
Catalysts 2021, 11(4), 426; https://doi.org/10.3390/catal11040426 - 26 Mar 2021
Cited by 47 | Viewed by 5836
Abstract
Semiconductor-based photocatalysis has been identified as an encouraging approach for solving the two main challenging problems, viz., remedying our polluted environment and the generation of sustainable chemical energy. Stoichiometric and non-stoichiometric bismuth oxyhalides (BiOX and BixOyXz where X [...] Read more.
Semiconductor-based photocatalysis has been identified as an encouraging approach for solving the two main challenging problems, viz., remedying our polluted environment and the generation of sustainable chemical energy. Stoichiometric and non-stoichiometric bismuth oxyhalides (BiOX and BixOyXz where X = Cl, Br, and I) are a relatively new class of semiconductors that have attracted considerable interest for photocatalysis applications due to attributes, viz., high stability, suitable band structure, modifiable energy bandgap and two-dimensional layered structure capable of generating an internal electric field. Recently, the construction of heterojunction photocatalysts, especially 2D/2D systems, has convincingly drawn momentous attention practicably owing to the productive influence of having two dissimilar layered semiconductors in face-to-face contact with each other. This review has systematically summarized the recent progress on the 2D/2D heterojunction constructed between BiOX/BixOyXz with graphitic carbon nitride (g-C3N4). The band structure of individual components, various fabrication methods, different strategies developed for improving the photocatalytic performance and their applications in the degradation of various organic contaminants, hydrogen (H2) evolution, carbon dioxide (CO2) reduction, nitrogen (N2) fixation and the organic synthesis of clean chemicals are summarized. The perspectives and plausible opportunities for developing high performance BiOX/BixOyXz-g-C3N4 heterojunction photocatalysts are also discussed. Full article
(This article belongs to the Special Issue Commemorative Issue in Honor of Professor Akira Fujishima)
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34 pages, 6186 KiB  
Review
Direct Synthesis of Dimethyl Ether from CO2: Recent Advances in Bifunctional/Hybrid Catalytic Systems
by Noelia Mota, Elena Millán Ordoñez, Bárbara Pawelec, José Luis G. Fierro and Rufino M. Navarro
Catalysts 2021, 11(4), 411; https://doi.org/10.3390/catal11040411 - 24 Mar 2021
Cited by 52 | Viewed by 9879
Abstract
Dimethyl ether (DME) is a versatile raw material and an interesting alternative fuel that can be produced by the catalytic direct hydrogenation of CO2. Recently, this process has attracted the attention of the industry due to the environmental benefits of CO [...] Read more.
Dimethyl ether (DME) is a versatile raw material and an interesting alternative fuel that can be produced by the catalytic direct hydrogenation of CO2. Recently, this process has attracted the attention of the industry due to the environmental benefits of CO2 elimination from the atmosphere and its lower operating costs with respect to the classical, two-step synthesis of DME from syngas (CO + H2). However, due to kinetics and thermodynamic limits, the direct use of CO2 as raw material for DME production requires the development of more effective catalysts. In this context, the objective of this review is to present the latest progress achieved in the synthesis of bifunctional/hybrid catalytic systems for the CO2-to-DME process. For catalyst design, this process is challenging because it should combine metal and acid functionalities in the same catalyst, in a correct ratio and with controlled interaction. The metal catalyst is needed for the activation and transformation of the stable CO2 molecules into methanol, whereas the acid catalyst is needed to dehydrate the methanol into DME. Recent developments in the catalyst design have been discussed and analyzed in this review, presenting the different strategies employed for the preparation of novel bifunctional catalysts (physical/mechanical mixing) and hybrid catalysts (co-precipitation, impregnation, etc.) with improved efficiency toward DME formation. Finally, an outline of future prospects for the research and development of efficient bi-functional/hybrid catalytic systems will be presented. Full article
(This article belongs to the Special Issue Catalysts for Production and Conversion of Syngas)
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36 pages, 2112 KiB  
Review
An Overview of Lean Exhaust deNOx Aftertreatment Technologies and NOx Emission Regulations in the European Union
by Tommaso Selleri, Anastasios D. Melas, Ameya Joshi, Dario Manara, Adolfo Perujo and Ricardo Suarez-Bertoa
Catalysts 2021, 11(3), 404; https://doi.org/10.3390/catal11030404 - 23 Mar 2021
Cited by 62 | Viewed by 8771
Abstract
This paper reviews the recent advances in the management of nitrogen oxide (NOx) emissions from the internal combustion engine of light-duty and heavy-duty vehicles, addressing both technical and legal aspects. Particular focus is devoted to the often-virtuous interaction between new legislation imposing more [...] Read more.
This paper reviews the recent advances in the management of nitrogen oxide (NOx) emissions from the internal combustion engine of light-duty and heavy-duty vehicles, addressing both technical and legal aspects. Particular focus is devoted to the often-virtuous interaction between new legislation imposing more restrictions on the permitted pollutant emission levels and new technologies developed in order to meet these restrictions. The review begins first with the American and then European directives promulgated in the 1970s, aimed at limiting emissions of pollutants from road transport vehicles. Particular attention is paid to the introduction of the Euro standards in the European Union for light- and heavy-duty vehicles, used as a legal and time frame reference for the evolution of emission aftertreatment systems (ATSs). The paper also describes governmental approaches implemented for the control of pollutant emissions in circulating vehicles, such as market surveillance and in-service conformity. In parallel, it is explained how the gradual introduction of small-scale devices aimed at the NOx control, such as lean NOx traps (LNTs) systems, and, most of all, the selective catalytic reduction (SCR) of NOx, permitted the application to road-transport vehicles of this ATS, originally designed in larger sizes for industrial usage. The paper reviews chemical processes occurring in SCR systems and their advantages and drawbacks with respect to the pollutant emission limits imposed by the legislation. Their potential side effects are also addressed, such as the emission of extra, not-yet regulated pollutants such as, for example, NH3 and N2O. The NOx, N2O, and NH3 emission level evolution with the various Euro standards for both light- and heavy-duty vehicles are reported in the light of experimental data obtained at the European Commission’s Joint Research Centre. It is observed that the new technologies, boosted by increasingly stricter legal limits, have led in the last two decades to a clear decrease of over one order of magnitude of NOx emissions in Diesel light-duty vehicles, bringing them to the same level as Euro 6 gasoline vehicles (10 mg/km to 20 mg/km in average). On the other hand, an obvious increase in the emissions of both NH3 and N2O is observed in both Diesel and gasoline light-duty vehicles, whereby NH3 emissions in spark-ignition vehicles are mainly linked to two-reaction mechanisms occurring in three-way catalysts after the catalyst light-off and during engine rich-operation. NH3 emissions measured in recent Euro 6 light-duty vehicles amount to a few mg/km for both gasoline and Diesel engines, whereby N2O emissions exceeding a dozen mg/km have been observed in Diesel vehicles only. The present paper can be regarded as part of a general assessment in view of the next EU emission standards, and a discussion on the role the SCR technology may serve as a NOx emission control strategy from lean-burn vehicles. Full article
(This article belongs to the Special Issue Selective Catalytic Reduction of NOx by NH3)
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25 pages, 7449 KiB  
Article
Hydrogen Production via Pd-TiO2 Photocatalytic Water Splitting under Near-UV and Visible Light: Analysis of the Reaction Mechanism
by Bianca Rusinque, Salvador Escobedo and Hugo de Lasa
Catalysts 2021, 11(3), 405; https://doi.org/10.3390/catal11030405 - 23 Mar 2021
Cited by 35 | Viewed by 7541
Abstract
Photocatalytic hydrogen production via water splitting using a noble metal on a TiO2 is a technology that has developed rapidly over the past few years. Specifically, palladium doped TiO2 irradiated with near-UV or alternatively with visible light has shown promising results. [...] Read more.
Photocatalytic hydrogen production via water splitting using a noble metal on a TiO2 is a technology that has developed rapidly over the past few years. Specifically, palladium doped TiO2 irradiated with near-UV or alternatively with visible light has shown promising results. With this end in mind, strategically designed experiments were developed in the Photo-CREC Water-II (PCW-II) Reactor using a 0.25 wt.% Pd-TiO2 under near-UV and visible light, and ethanol as an organic scavenger. Acetaldehyde, carbon monoxide, carbon dioxide, methane, ethane, ethylene, and hydrogen peroxide together with hydrogen were the main chemical species observed. A Langmuir adsorption isotherm was also established for hydrogen peroxide. On this basis, it is shown that pH variations, hydrogen peroxide formation/adsorption, and the production of various redox chemical species provide an excellent carbon element balance, as well as OH• and H• radicals balances. Under near-UV irradiation, 113 cm3 STP of H2 is produced after 6 h, reaching an 99.8% elemental carbon balance and 99.2% OH• and H• and radical balance. It is also proven that a similar reaction network can be considered adequate for the photoreduced Pd-TiO2 photocatalyst yielding 29 cm3 STP of H2 with 95.4% carbon and the 97.5% OH•–H• radical balance closures. It is shown on this basis that a proposed “series-parallel” reaction network describes the water splitting reaction using the mesoporous Pd-TiO2 and ethanol as organic scavenger. Full article
(This article belongs to the Special Issue Commemorative Issue in Honor of Professor Hugo de Lasa)
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13 pages, 1735 KiB  
Article
Optical Management of CQD/AgNP@SiNW Arrays with Highly Efficient Capability of Dye Degradation
by Po-Hsuan Hsiao, Sasimontra Timjan, Kuan-Yi Kuo, Joon-Ching Juan and Chia-Yun Chen
Catalysts 2021, 11(3), 399; https://doi.org/10.3390/catal11030399 - 22 Mar 2021
Cited by 9 | Viewed by 2618
Abstract
The facile synthetic method for the preparation of incorporated carbon quantum dots (CQDs)/Ag nanoparticles (AgNPs) with well-aligned silicon nanowire (SiNW) arrays is demonstrated, offering the superior photodegradation capabilities covering UV to visible wavelength regions. By examining the morphology, microstructure, crystallinity, chemical feature, surface [...] Read more.
The facile synthetic method for the preparation of incorporated carbon quantum dots (CQDs)/Ag nanoparticles (AgNPs) with well-aligned silicon nanowire (SiNW) arrays is demonstrated, offering the superior photodegradation capabilities covering UV to visible wavelength regions. By examining the morphology, microstructure, crystallinity, chemical feature, surface groups, light-emitting, and reflection characteristics, these hybrid heterostructures are systematically identified. Moreover, the involving degradation kinetics, band diagram, cycling capability, and underlying mechanism of photodegradation are investigated, validating their remarkable and reliable photocatalytic performances contributed from the strongly reduced light reflectivity, superior capability of charge separation, and sound wettability with dye solutions. Full article
(This article belongs to the Special Issue Photocatalytic Removal of Dyes)
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17 pages, 10272 KiB  
Review
A Review of Hydrogen Purification Technologies for Fuel Cell Vehicles
by Zhemin Du, Congmin Liu, Junxiang Zhai, Xiuying Guo, Yalin Xiong, Wei Su and Guangli He
Catalysts 2021, 11(3), 393; https://doi.org/10.3390/catal11030393 - 19 Mar 2021
Cited by 143 | Viewed by 18806
Abstract
Nowadays, we face a series of global challenges, including the growing depletion of fossil energy, environmental pollution, and global warming. The replacement of coal, petroleum, and natural gas by secondary energy resources is vital for sustainable development. Hydrogen (H2) energy is [...] Read more.
Nowadays, we face a series of global challenges, including the growing depletion of fossil energy, environmental pollution, and global warming. The replacement of coal, petroleum, and natural gas by secondary energy resources is vital for sustainable development. Hydrogen (H2) energy is considered the ultimate energy in the 21st century because of its diverse sources, cleanliness, low carbon emission, flexibility, and high efficiency. H2 fuel cell vehicles are commonly the end-point application of H2 energy. Owing to their zero carbon emission, they are gradually replacing traditional vehicles powered by fossil fuel. As the H2 fuel cell vehicle industry rapidly develops, H2 fuel supply, especially H2 quality, attracts increasing attention. Compared with H2 for industrial use, the H2 purity requirements for fuel cells are not high. Still, the impurity content is strictly controlled since even a low amount of some impurities may irreversibly damage fuel cells’ performance and running life. This paper reviews different versions of current standards concerning H2 for fuel cell vehicles in China and abroad. Furthermore, we analyze the causes and developing trends for the changes in these standards in detail. On the other hand, according to characteristics of H2 for fuel cell vehicles, standard H2 purification technologies, such as pressure swing adsorption (PSA), membrane separation and metal hydride separation, were analyzed, and the latest research progress was reviewed. Full article
(This article belongs to the Special Issue Catalysts for Sustainable Hydrogen Production: Preparation, Applications and Process Integration)
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17 pages, 8454 KiB  
Article
Hexavalent Chromium Removal via Photoreduction by Sunlight on Titanium–Dioxide Nanotubes Formed by Anodization with a Fluorinated Glycerol–Water Electrolyte
by Siti Azlina Rosli, Nurhaswani Alias, Nurulhuda Bashirom, Syahriza Ismail, Wai Kian Tan, Go Kawamura, Atsunori Matsuda and Zainovia Lockman
Catalysts 2021, 11(3), 376; https://doi.org/10.3390/catal11030376 - 13 Mar 2021
Cited by 17 | Viewed by 2728
Abstract
In this paper, titanium–dioxide (TiO2) nanotubes (TNTs) are formed by anodic oxidation with a fluorinated glycerol–water (85% and 15%, respectively) electrolyte to examine the effect of fluoride ion concentration, time, and applied voltage on TNT morphologies and dimensions. For fluoride ion [...] Read more.
In this paper, titanium–dioxide (TiO2) nanotubes (TNTs) are formed by anodic oxidation with a fluorinated glycerol–water (85% and 15%, respectively) electrolyte to examine the effect of fluoride ion concentration, time, and applied voltage on TNT morphologies and dimensions. For fluoride ion concentration, the surface etching increases when the amount of ammonium fluoride added to the electrolyte solution increases, forming nanotube arrays with a clear pore structure. At a constant voltage of 20 V, TNTs with an average length of ~2 µm are obtained after anodization for 180 min. A prolonged anodization time only results in a marginal length increment. The TNT diameter is voltage dependent and increases from approximately 30 nm at 10 V to 310 nm at 60 V. At 80 V, the structure is destroyed. TNTs formed at 20 V for 180 min are annealed to induce the TiO2 anatase phase in either air or nitrogen. When ethylenediaminetetraacetic acid is added as a hole scavenger, 100% hexavalent chromium removal is obtained after 120 min of sunlight exposure for nitrogen-annealed TNTs. Full article
(This article belongs to the Special Issue Advances in Photocatalytic Wastewater Purification)
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13 pages, 4810 KiB  
Article
Green Synthesis of Silver and Gold Nanoparticles via Sargassum serratifolium Extract for Catalytic Reduction of Organic Dyes
by Beomjin Kim, Woo Chang Song, Sun Young Park and Geuntae Park
Catalysts 2021, 11(3), 347; https://doi.org/10.3390/catal11030347 - 08 Mar 2021
Cited by 47 | Viewed by 3585
Abstract
The green synthesis of inorganic nanoparticles (NPs) using bio-materials has attained enormous attention in recent years due to its simple, eco-friendly, low-cost and non-toxic nature. In this work, silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) were synthesized by the marine algae extract, Sargassum [...] Read more.
The green synthesis of inorganic nanoparticles (NPs) using bio-materials has attained enormous attention in recent years due to its simple, eco-friendly, low-cost and non-toxic nature. In this work, silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) were synthesized by the marine algae extract, Sargassum serratifolium (SS). The characteristic studies of bio-synthesized SS-AgNPs and SS-AuNPs were carried out by using ultraviolet–visible (UV–Vis) absorption spectroscopy, dynamic light scattering (DLS), high-resolution transmission electron microscope (HR-TEM), selected area electron diffraction (SAED), energy-dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Phytochemicals in the algae extract, such as meroterpenoids, acted as a capping agent for the NPs’ growth. The synthesized Ag and Au NPs were found to have important catalytic activity for the degradation of organic dyes, including methylene blue, rhodamine B and methyl orange. The reduction of dyes by SS-AgNPs and -AuNPs followed the pseudo-first order kinetics. Full article
(This article belongs to the Special Issue Innovative Catalytic and Photocatalytic Systems for Environmental Remediation)
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31 pages, 3219 KiB  
Review
Kinetics and Selectivity Study of Fischer–Tropsch Synthesis to C5+ Hydrocarbons: A Review
by Zahra Teimouri, Nicolas Abatzoglou and Ajay K. Dalai
Catalysts 2021, 11(3), 330; https://doi.org/10.3390/catal11030330 - 05 Mar 2021
Cited by 54 | Viewed by 8105
Abstract
Fischer–Tropsch synthesis (FTS) is considered as one of the non-oil-based alternatives for liquid fuel production. This gas-to-liquid (GTL) technology converts syngas to a wide range of hydrocarbons using metal (Fe and Co) unsupported and supported catalysts. Effective design of the catalyst plays a [...] Read more.
Fischer–Tropsch synthesis (FTS) is considered as one of the non-oil-based alternatives for liquid fuel production. This gas-to-liquid (GTL) technology converts syngas to a wide range of hydrocarbons using metal (Fe and Co) unsupported and supported catalysts. Effective design of the catalyst plays a significant role in enhancing syngas conversion, selectivity towards C5+ hydrocarbons, and decreasing selectivity towards methane. This work presents a review on catalyst design and the most employed support materials in FTS to synthesize heavier hydrocarbons. Furthermore, in this report, the recent achievements on mechanisms of this reaction will be discussed. Catalyst deactivation is one of the most important challenges during FTS, which will be covered in this work. The selectivity of FTS can be tuned by operational conditions, nature of the catalyst, support, and reactor configuration. The effects of all these parameters will be analyzed within this report. Moreover, zeolites can be employed as a support material of an FTS-based catalyst to direct synthesis of liquid fuels, and the specific character of zeolites will be elaborated further. Furthermore, this paper also includes a review of some of the most employed characterization techniques for Fe- and Co-based FTS catalysts. Kinetic study plays an important role in optimization and simulation of this industrial process. In this review, the recent developed reaction rate models are critically discussed. Full article
(This article belongs to the Special Issue Application of Metal-Based Nanocatalysts for Addressing Environmental Issues and Energy Demand)
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44 pages, 16182 KiB  
Review
TiO2 Photocatalysis for the Transformation of Aromatic Water Pollutants into Fuels
by Osama Al-Madanat, Yamen AlSalka, Wegdan Ramadan and Detlef W. Bahnemann
Catalysts 2021, 11(3), 317; https://doi.org/10.3390/catal11030317 - 28 Feb 2021
Cited by 34 | Viewed by 5004
Abstract
The growing world energy consumption, with reliance on conventional energy sources and the associated environmental pollution, are considered the most serious threats faced by mankind. Heterogeneous photocatalysis has become one of the most frequently investigated technologies, due to its dual functionality, i.e., environmental [...] Read more.
The growing world energy consumption, with reliance on conventional energy sources and the associated environmental pollution, are considered the most serious threats faced by mankind. Heterogeneous photocatalysis has become one of the most frequently investigated technologies, due to its dual functionality, i.e., environmental remediation and converting solar energy into chemical energy, especially molecular hydrogen. H2 burns cleanly and has the highest gravimetric gross calorific value among all fuels. However, the use of a suitable electron donor, in what so-called “photocatalytic reforming”, is required to achieve acceptable efficiency. This oxidation half-reaction can be exploited to oxidize the dissolved organic pollutants, thus, simultaneously improving the water quality. Such pollutants would replace other potentially costly electron donors, achieving the dual-functionality purpose. Since the aromatic compounds are widely spread in the environment, they are considered attractive targets to apply this technology. In this review, different aspects are highlighted, including the employing of different polymorphs of pristine titanium dioxide as photocatalysts in the photocatalytic processes, also improving the photocatalytic activity of TiO2 by loading different types of metal co-catalysts, especially platinum nanoparticles, and comparing the effect of various loading methods of such metal co-catalysts. Finally, the photocatalytic reforming of aromatic compounds employing TiO2-based semiconductors is presented. Full article
(This article belongs to the Special Issue Multifunctional Materials for Photocatalytic and Photoactivated Processes)
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51 pages, 12744 KiB  
Review
TiO2-Graphene Quantum Dots Nanocomposites for Photocatalysis in Energy and Biomedical Applications
by Anuja Bokare, Sowbaranigha Chinnusamy and Folarin Erogbogbo
Catalysts 2021, 11(3), 319; https://doi.org/10.3390/catal11030319 - 28 Feb 2021
Cited by 28 | Viewed by 6549
Abstract
The focus of current research in material science has shifted from “less efficient” single-component nanomaterials to the superior-performance, next-generation, multifunctional nanocomposites. TiO2 is a widely used benchmark photocatalyst with unique physicochemical properties. However, the large bandgap and massive recombination of photogenerated charge [...] Read more.
The focus of current research in material science has shifted from “less efficient” single-component nanomaterials to the superior-performance, next-generation, multifunctional nanocomposites. TiO2 is a widely used benchmark photocatalyst with unique physicochemical properties. However, the large bandgap and massive recombination of photogenerated charge carriers limit its overall photocatalytic efficiency. When TiO2 nanoparticles are modified with graphene quantum dots (GQDs), some significant improvements can be achieved in terms of (i) broadening the light absorption wavelengths, (ii) design of active reaction sites, and (iii) control of the electron-hole (e−-h+) recombination. Accordingly, TiO2-GQDs nanocomposites exhibit promising multifunctionalities in a wide range of fields including, but not limited to, energy, biomedical aids, electronics, and flexible wearable sensors. This review presents some important aspects of TiO2-GQDs nanocomposites as photocatalysts in energy and biomedical applications. These include: (1) structural formulations and synthesis methods of TiO2-GQDs nanocomposites; (2) discourse about the mechanism behind the overall higher photoactivities of these nanocomposites; (3) various characterization techniques which can be used to judge the photocatalytic performance of these nanocomposites, and (4) the application of these nanocomposites in biomedical and energy conversion devices. Although some objectives have been achieved, new challenges still exist and hinder the widespread application of these nanocomposites. These challenges are briefly discussed in the Future Scope section of this review. Full article
(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)
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26 pages, 1829 KiB  
Review
Advances in Valorization of Lignocellulosic Biomass towards Energy Generation
by Ikram ul Haq, Kinza Qaisar, Ali Nawaz, Fatima Akram, Hamid Mukhtar, Xin Zohu, Yong Xu, Muhammad Waseem Mumtaz, Umer Rashid, Wan Azlina Wan Ab Karim Ghani and Thomas Shean Yaw Choong
Catalysts 2021, 11(3), 309; https://doi.org/10.3390/catal11030309 - 26 Feb 2021
Cited by 68 | Viewed by 7599
Abstract
The booming demand for energy across the world, especially for petroleum-based fuels, has led to the search for a long-term solution as a perfect source of sustainable energy. Lignocellulosic biomass resolves this obstacle as it is a readily available, inexpensive, and renewable fuel [...] Read more.
The booming demand for energy across the world, especially for petroleum-based fuels, has led to the search for a long-term solution as a perfect source of sustainable energy. Lignocellulosic biomass resolves this obstacle as it is a readily available, inexpensive, and renewable fuel source that fulfills the criteria of sustainability. Valorization of lignocellulosic biomass and its components into value-added products maximizes the energy output and promotes the approach of lignocellulosic biorefinery. However, disruption of the recalcitrant structure of lignocellulosic biomass (LCB) via pretreatment technologies is costly and power-/heat-consuming. Therefore, devising an effective pretreatment method is a challenge. Likewise, the thermochemical and biological lignocellulosic conversion poses problems of efficiency, operational costs, and energy consumption. The advent of integrated technologies would probably resolve this problem. However, it is yet to be explored how to make it applicable at a commercial scale. This article will concisely review basic concepts of lignocellulosic composition and the routes opted by them to produce bioenergy. Moreover, it will also discuss the pros and cons of the pretreatment and conversion methods of lignocellulosic biomass. This critical analysis will bring to light the solutions for efficient and cost-effective conversion of lignocellulosic biomass that would pave the way for the development of sustainable energy systems. Full article
(This article belongs to the Special Issue New Trends in the Use of Catalysts for Biofuel and Bioproduct Generation)
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18 pages, 3448 KiB  
Article
The Efficacy of Silver Nitrate (AgNO3) as a Coating Agent to Protect Paper against High Deteriorating Microbes
by Amr Fouda, Gomaa Abdel-Maksoud, Hosam A. Saad, Adil A. Gobouri, Zuhair M. Mohammedsaleh and Mohamad Abdel-Haleem El-Sadany
Catalysts 2021, 11(3), 310; https://doi.org/10.3390/catal11030310 - 26 Feb 2021
Cited by 33 | Viewed by 5500
Abstract
This study focuses on the efficacy of silver nitrate (AgNO3) as a coating agent used to preserve papers against microbial deterioration. To this end, the in vitro cytotoxicity of AgNO3 was assessed against two normal cell lines, WI-38 and HFB-4, [...] Read more.
This study focuses on the efficacy of silver nitrate (AgNO3) as a coating agent used to preserve papers against microbial deterioration. To this end, the in vitro cytotoxicity of AgNO3 was assessed against two normal cell lines, WI-38 and HFB-4, to detect a safe dose that can be used as a coating agent, which was 80 µg mL−1. Bacillus subtilis B3 and Penicillium chrysogenum F9 were selected as high deteriorating microbes, previously isolated from a historical manuscript dating back to 1677 A.-D. The microbial growth inhibition, color change, mechanical properties, and cellulosic fibers of untreated/treated papers were evaluated. The data showed the efficacy of AgNO3 to inhibit the growth of B. subtilis with a percentage of 100% after 7 days, while it inhibits the growth of P. chrysogenum with a percentage of 85.9 ± 1.1% after 21 days. The color and mechanical properties of treated paper in the presence/absence of microbial inoculation were slightly changed, although they changed greatly due to microbial growth in the absence of AgNO3. The EDX analysis confirmed the successful adsorption of Ag-ion on papers, with a weight percentage of 1.9%. The cellulosic fibers of untreated paper in the presence of microbial growth were highly deteriorated as compared with treated and standard filter paper (shown by FT-IR and SEM). Full article
(This article belongs to the Special Issue Gold, Silver and Copper Catalysis)
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25 pages, 2218 KiB  
Review
Effective Strategies, Mechanisms, and Photocatalytic Efficiency of Semiconductor Nanomaterials Incorporating rGO for Environmental Contaminant Degradation
by Noor Haida Mohd Kaus, Ahmad Fadhil Rithwan, Rohana Adnan, Mohd Lokman Ibrahim, Sirikanjana Thongmee and Siti Fairus Mohd Yusoff
Catalysts 2021, 11(3), 302; https://doi.org/10.3390/catal11030302 - 25 Feb 2021
Cited by 28 | Viewed by 4373
Abstract
The water pollution problems severely affect the natural water resources due to the large disposal of dyes, heavy metals, antibiotics, and pesticides. Advanced oxidation processes (AOP) have been developed using semiconductor nanomaterials as photocatalysts for water treatment as an essential strategy to minimize [...] Read more.
The water pollution problems severely affect the natural water resources due to the large disposal of dyes, heavy metals, antibiotics, and pesticides. Advanced oxidation processes (AOP) have been developed using semiconductor nanomaterials as photocatalysts for water treatment as an essential strategy to minimize environmental pollution. Significant research efforts have been dedicated over the past few years to enhancing the photocatalytic efficiencies of semiconductor nanomaterials. Graphene-based composites created by integrating reduced graphene oxide (rGO) into various semiconductor nanomaterials enable the unique characteristics of graphene, such as the extended range of light absorption, the separation of charges, and the high capacity of adsorption of pollutants. Therefore, rGO-based composites improve the overall visible-light photocatalytic efficiency and lead to a new pathway for high-performance photocatalysts’ potential applications. This brief review illustrates the strategies of combining rGO with various semiconductor nanomaterials and focuses primarily on modification and efficiency towards environmental contaminants. Full article
(This article belongs to the Special Issue Photocatalysis: Activity of Nanomaterials)
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22 pages, 7449 KiB  
Review
Sonochemical and Sonoelectrochemical Production of Energy Materials
by Faranak Foroughi, Jacob J. Lamb, Odne S. Burheim and Bruno G. Pollet
Catalysts 2021, 11(2), 284; https://doi.org/10.3390/catal11020284 - 21 Feb 2021
Cited by 26 | Viewed by 5177
Abstract
Sonoelectrochemistry is the combination of ultrasound and electrochemistry which provides many advantages in electrochemistry, such as fast reaction rates, surface cleaning and activation, and increased mass transport at an electrode. Due to the advantages, some efforts have been made in order to benefit [...] Read more.
Sonoelectrochemistry is the combination of ultrasound and electrochemistry which provides many advantages in electrochemistry, such as fast reaction rates, surface cleaning and activation, and increased mass transport at an electrode. Due to the advantages, some efforts have been made in order to benefit sonoelectrochemistry in the field of energy and environmental engineering. This review paper highlights the developed progress of the application of sonoelectrochemistry in the production of hydrogen, electrocatalyst materials and electrodes for fuel cells and semiconductor photocatalyst materials. This review also provides the experimental methods that are utilized in several sonoelectrochemical techniques, such as different set-ups generally used for the synthesis of energy-related materials. Different key parameters in the operation of sonoelectrochemical synthesis including ultrasonication time, ultrasound frequency and operation current have been also discussed. There are not many research articles on the sonoelectrochemical production of materials for supercapacitors and water electrolyzers which play crucial roles in the renewable energy industry. Therefore, at the end of this review, some articles which have reported the use of ultrasound for the production of electrocatalysts for supercapacitors and electrolyzers have been reviewed. The current review might be helpful for scientists and engineers who are interested in and working on sonoelectrochemistry and electrocatalyst synthesis for energy storage and energy conversion. Full article
(This article belongs to the Special Issue Catalysis Under Ultrasonic Irradiation)
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23 pages, 5140 KiB  
Perspective
Metal-Organic Frameworks in Oxidation Catalysis with Hydrogen Peroxide
by Oxana Kholdeeva and Nataliya Maksimchuk
Catalysts 2021, 11(2), 283; https://doi.org/10.3390/catal11020283 - 21 Feb 2021
Cited by 34 | Viewed by 5308
Abstract
In recent years, metal–organic frameworks (MOFs) have received increasing attention as selective oxidation catalysts and supports for their construction. In this short review paper, we survey recent findings concerning use of MOFs in heterogeneous liquid-phase selective oxidation catalysis with the green oxidant–aqueous hydrogen [...] Read more.
In recent years, metal–organic frameworks (MOFs) have received increasing attention as selective oxidation catalysts and supports for their construction. In this short review paper, we survey recent findings concerning use of MOFs in heterogeneous liquid-phase selective oxidation catalysis with the green oxidant–aqueous hydrogen peroxide. MOFs having outstanding thermal and chemical stability, such as Cr(III)-based MIL-101, Ti(IV)-based MIL-125, Zr(IV)-based UiO-66(67), Zn(II)-based ZIF-8, and some others, will be in the main focus of this work. The effects of the metal nature and MOF structure on catalytic activity and oxidation selectivity are analyzed and the mechanisms of hydrogen peroxide activation are discussed. In some cases, we also make an attempt to analyze relationships between liquid-phase adsorption properties of MOFs and peculiarities of their catalytic performance. Attempts of using MOFs as supports for construction of single-site catalysts through their modification with heterometals will be also addressed in relation to the use of such catalysts for activation of H2O2. Special attention is given to the critical issues of catalyst stability and reusability. The scope and limitations of MOF catalysts in H2O2-based selective oxidation are discussed. Full article
(This article belongs to the Special Issue Heterogeneous Selective and Total Catalytic Oxidation)
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30 pages, 5825 KiB  
Review
Towards the Large-Scale Electrochemical Reduction of Carbon Dioxide
by Subin Park, Devina Thasia Wijaya, Jonggeol Na and Chan Woo Lee
Catalysts 2021, 11(2), 253; https://doi.org/10.3390/catal11020253 - 13 Feb 2021
Cited by 40 | Viewed by 7606
Abstract
The severe increase in the CO2 concentration is a causative factor of global warming, which accelerates the destruction of ecosystems. The massive utilization of CO2 for value-added chemical production is a key to commercialization to guarantee both economic feasibility and negative [...] Read more.
The severe increase in the CO2 concentration is a causative factor of global warming, which accelerates the destruction of ecosystems. The massive utilization of CO2 for value-added chemical production is a key to commercialization to guarantee both economic feasibility and negative carbon emission. Although the electrochemical reduction of CO2 is one of the most promising technologies, there are remaining challenges for large-scale production. Herein, an overview of these limitations is provided in terms of devices, processes, and catalysts. Further, the economic feasibility of the technology is described in terms of individual processes such as reactions and separation. Additionally, for the practical implementation of the electrochemical CO2 conversion technology, stable electrocatalytic performances need to be addressed in terms of current density, Faradaic efficiency, and overpotential. Hence, the present review also covers the known degradation behaviors and mechanisms of electrocatalysts and electrodes during electrolysis. Furthermore, strategic approaches for overcoming the stability issues are introduced based on recent reports from various research areas involved in the electrocatalytic conversion. Full article
(This article belongs to the Special Issue Recent Advances in Catalytic CO2 Conversion for Value-Added Chemical Production)
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18 pages, 4169 KiB  
Article
W-Doped ZnO Photocatalyst for the Degradation of Glyphosate in Aqueous Solution
by Mariaconcetta Russo, Giuseppina Iervolino and Vincenzo Vaiano
Catalysts 2021, 11(2), 234; https://doi.org/10.3390/catal11020234 - 09 Feb 2021
Cited by 26 | Viewed by 3393
Abstract
In this paper, the photocatalytic degradation of glyphosate by zinc oxide (ZnO) photocatalysts doped with tungsten (W) was investigated under solar simulated light. The photocatalysts were successfully synthesized through a simple precipitation method and subsequently characterized by different techniques: Raman spectroscopy, UV–Vis, N [...] Read more.
In this paper, the photocatalytic degradation of glyphosate by zinc oxide (ZnO) photocatalysts doped with tungsten (W) was investigated under solar simulated light. The photocatalysts were successfully synthesized through a simple precipitation method and subsequently characterized by different techniques: Raman spectroscopy, UV–Vis, N2 adsorption at −196 °C, X-ray diffraction, and SEM analysis. In particular, all the prepared catalysts were characterized by a crystallite size of about 28 nm and a hexagonal wurtzite structure. After the W doping, the bandgap energy decreased from 3.22 of pure ZnO to 3.19 for doped ZnO. This allowed us to obtain good results in terms of glyphosate degradation and simultaneous mineralization under solar simulated lamps, making the process environmentally friendly and with almost zero energy costs. In particular, the best photocatalytic performance was obtained with 100 W-ZnO (prepared with 1.5 mol% of W). With this catalyst, after 180 min of exposure to solar simulated light, the glyphosate degradation and mineralization was equal to 74% and 30%, respectively. Furthermore, it has been shown that the best catalyst dosage was equal to 1.5 g/L. The study on the influence of pH evidenced that the best photocatalytic performances are obtained at spontaneous (neutral) pH conditions. Finally, to determine the main reactive species in the glyphosate oxidation, the effects of different radical scavengers were tested. The results evidenced that the glyphosate oxidation mechanism seems to be related mainly to the O2•− generated under simulated solar light irradiation, but also in minor part to h+. Full article
(This article belongs to the Section Photocatalysis)
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15 pages, 21354 KiB  
Article
Tailoring Properties of Metal-Free Catalysts for the Highly Efficient Desulfurization of Sour Gases under Harsh Conditions
by Cuong Duong-Viet, Jean-Mario Nhut, Tri Truong-Huu, Giulia Tuci, Lam Nguyen-Dinh, Charlotte Pham, Giuliano Giambastiani and Cuong Pham-Huu
Catalysts 2021, 11(2), 226; https://doi.org/10.3390/catal11020226 - 09 Feb 2021
Cited by 6 | Viewed by 2368
Abstract
Carbon-based nanomaterials, particularly in the form of N-doped networks, are receiving the attention of the catalysis community as effective metal-free systems for a relatively wide range of industrially relevant transformations. Among them, they have drawn attention as highly valuable and durable catalysts for [...] Read more.
Carbon-based nanomaterials, particularly in the form of N-doped networks, are receiving the attention of the catalysis community as effective metal-free systems for a relatively wide range of industrially relevant transformations. Among them, they have drawn attention as highly valuable and durable catalysts for the selective hydrogen sulfide oxidation to elemental sulfur in the treatment of natural gas. In this contribution, we report the outstanding performance of N-C/SiC based composites obtained by the surface coating of a non-oxide ceramic with a mesoporous N-doped carbon phase, starting from commercially available and cheap food-grade components. Our study points out on the importance of controlling the chemical and morphological properties of the N-C phase to get more effective and robust catalysts suitable to operate H2S removal from sour (acid) gases under severe desulfurization conditions (high GHSVs and concentrations of aromatics as sour gas stream contaminants). We firstly discuss the optimization of the SiC impregnation/thermal treatment sequences for the N-C phase growth as well as on the role of aromatic contaminants in concentrations as high as 4 vol.% on the catalyst performance and its stability on run. A long-term desulfurization process (up to 720 h), in the presence of intermittent toluene rates (as aromatic contaminant) and variable operative temperatures, has been used to validate the excellent performance of our optimized N-C2/SiC catalyst as well as to rationalize its unique stability and coke-resistance on run. Full article
(This article belongs to the Special Issue Catalysts and Processes for H2S Conversion to Sulfur)
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18 pages, 12744 KiB  
Article
A Stereoselective, Multicomponent Catalytic Carbonylative Approach to a New Class of α,β-Unsaturated γ-Lactam Derivatives
by Raffaella Mancuso, Ida Ziccarelli, Matteo Brindisi, Cosimo D. Altomare, Luca Frattaruolo, Aurelia Falcicchio, Nicola Della Ca’, Anna Rita Cappello and Bartolo Gabriele
Catalysts 2021, 11(2), 227; https://doi.org/10.3390/catal11020227 - 09 Feb 2021
Cited by 13 | Viewed by 2570
Abstract
We report a stereoselective, multicomponent catalytic carbonylative approach to a new class of α,β-unsaturated γ-lactam derivatives with potential biological activity, that are, alkyl (Z)-2-(2-oxopyrrolidin-3-ylidene)acetates. Our method is based on the catalytic assembly of readily available building blocks, namely, homopropargylic amines, carbon [...] Read more.
We report a stereoselective, multicomponent catalytic carbonylative approach to a new class of α,β-unsaturated γ-lactam derivatives with potential biological activity, that are, alkyl (Z)-2-(2-oxopyrrolidin-3-ylidene)acetates. Our method is based on the catalytic assembly of readily available building blocks, namely, homopropargylic amines, carbon monoxide, an alcohol, and oxygen (from air). These simple substrates are efficiently activated in ordered sequence under the action of a very simple catalytic system, consisting of PdI2 in conjunction with KI to give the γ-lactam products in 47–85% yields. Carbonylation reactions are carried out at 100 °C for 2–5 h under 40 atm of a 4:1 mixture of CO‒air, with 0.5–5 mol% of PdI2 and 5–50 mol% of KI. Full article
(This article belongs to the Special Issue Polycyclic Heterocycles by Catalyzed Processes)
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11 pages, 1567 KiB  
Article
Biocatalytic Transformation of 5-Hydroxymethylfurfural into 2,5-di(hydroxymethyl)furan by a Newly Isolated Fusarium striatum Strain
by Alberto Millán, Núria Sala, Mercè Torres and Ramon Canela-Garayoa
Catalysts 2021, 11(2), 216; https://doi.org/10.3390/catal11020216 - 06 Feb 2021
Cited by 14 | Viewed by 2753
Abstract
The compound 2,5-di(hydroxymethyl)furan (DHMF) is a high-value chemical block that can be synthesized from 5-hydroxymethylfurfural (HMF), a platform chemical that results from the dehydration of biomass-derived carbohydrates. In this work, the HMF biotransformation capability of different Fusarium species was evaluated, and F. striatum [...] Read more.
The compound 2,5-di(hydroxymethyl)furan (DHMF) is a high-value chemical block that can be synthesized from 5-hydroxymethylfurfural (HMF), a platform chemical that results from the dehydration of biomass-derived carbohydrates. In this work, the HMF biotransformation capability of different Fusarium species was evaluated, and F. striatum was selected to produce DHMF. The effects of the inoculum size, glucose concentration and pH of the media over DHMF production were evaluated by a 23 factorial design. A substrate feeding approach was found suitable to overcome the toxicity effect of HMF towards the cells when added at high concentrations (>75 mM). The process was successfully scaled-up at bioreactor scale (1.3 L working volume) with excellent DHMF production yields (95%) and selectivity (98%). DHMF was purified from the reaction media with high recovery and purity by organic solvent extraction with ethyl acetate. Full article
(This article belongs to the Special Issue Biocatalysis and Whole-Cell Biotransformation in Biomanufacturing)
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43 pages, 6348 KiB  
Review
Electrocatalysis by Heme Enzymes—Applications in Biosensing
by Lidia Zuccarello, Catarina Barbosa, Smilja Todorovic and Célia M. Silveira
Catalysts 2021, 11(2), 218; https://doi.org/10.3390/catal11020218 - 06 Feb 2021
Cited by 25 | Viewed by 3794
Abstract
Heme proteins take part in a number of fundamental biological processes, including oxygen transport and storage, electron transfer, catalysis and signal transduction. The redox chemistry of the heme iron and the biochemical diversity of heme proteins have led to the development of a [...] Read more.
Heme proteins take part in a number of fundamental biological processes, including oxygen transport and storage, electron transfer, catalysis and signal transduction. The redox chemistry of the heme iron and the biochemical diversity of heme proteins have led to the development of a plethora of biotechnological applications. This work focuses on biosensing devices based on heme proteins, in which they are electronically coupled to an electrode and their activity is determined through the measurement of catalytic currents in the presence of substrate, i.e., the target analyte of the biosensor. After an overview of the main concepts of amperometric biosensors, we address transduction schemes, protein immobilization strategies, and the performance of devices that explore reactions of heme biocatalysts, including peroxidase, cytochrome P450, catalase, nitrite reductase, cytochrome c oxidase, cytochrome c and derived microperoxidases, hemoglobin, and myoglobin. We further discuss how structural information about immobilized heme proteins can lead to rational design of biosensing devices, ensuring insights into their efficiency and long-term stability. Full article
(This article belongs to the Special Issue Perspectives in Bioinorganic Catalysis)
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