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Volume 13
Issue 5
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Catalysts, Volume 13, Issue 5 (May 2023) – 129 articles

Cover Story (view full-size image): Catalytic total oxidation is important to control atmospheric emissions of VOCs. Iron–manganese mixed metal oxide catalysts with various Fe:Mn ratios were synthesized by coprecipitation using sodium carbonate. The most active catalyst was Fe0.50Mn0.50Ox. The impact of different precipitating agents on Fe0.50Mn0.50Ox catalysts was studied, with the use of (NH4)2CO3, K2CO3, NH4OH, KOH, and NaOH. The recorded activity for propane oxidation was generally higher than the Na2CO3-prepared catalyst, with hydroxide precipitated catalysts showing greater activity. The NH4OH catalyst performed the best due to its highly active mixed defect spinel structure. The feasibility of preparing efficient mixed metal oxide catalysts using abundant elements is highlighted, emphasizing the importance of composition, and selecting appropriate precipitating agents. View this paper
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10 pages, 11754 KiB  
Communication
Synthesis of a Series of Methyl Benzoates through Esterification with a Zr/Ti Solid Acid Catalyst
by Xiaofeng Yu, Chunjie Shi, Yueling Cheng, Yejing Zhu, Renyuan Song and Shengfei Hu
Catalysts 2023, 13(5), 915; https://doi.org/10.3390/catal13050915 - 22 May 2023
Viewed by 2020
Abstract
Methyl benzoate (MB) compounds are prepared by reacting various benzoic acids with methanol using an acidic catalyst. In this study, the solid acids of zirconium metal solids fixed with various substances were studied. We determined that zirconium metal catalysts with fixed Ti had [...] Read more.
Methyl benzoate (MB) compounds are prepared by reacting various benzoic acids with methanol using an acidic catalyst. In this study, the solid acids of zirconium metal solids fixed with various substances were studied. We determined that zirconium metal catalysts with fixed Ti had the best activity. The catalytic synthesis of a series of MB compounds using titanium zirconium solid acids was studied. The direct condensation of benzoic acid and methanol using a metallic Lewis acid without other auxiliary Bronsted acids is reported for the first time. Full article
(This article belongs to the Special Issue Applications of Heterogeneous Catalysts in Green Chemistry)
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12 pages, 4567 KiB  
Article
V6O13 Micro-Flower Arrays Grown In Situ on Ni Foam as Efficient Electrocatalysts for Hydrogen Evolution at Large Current Densities
by Yajie Xie, Jianfeng Huang, Yufei Wang, Liyun Cao, Yong Zhao, Koji Kajiyoshi, Yijun Liu and Liangliang Feng
Catalysts 2023, 13(5), 914; https://doi.org/10.3390/catal13050914 - 22 May 2023
Cited by 3 | Viewed by 1033
Abstract
Developing a high-activity, robust and economic electrocatalyst for large-scale green hydrogen production is still of great significance. Herein, a novel V6O13 nanosheets self-assembled micro-flower array self-supporting electrode is synthesized using a facile one-pot hydrothermal route. Owing to the large electrochemically [...] Read more.
Developing a high-activity, robust and economic electrocatalyst for large-scale green hydrogen production is still of great significance. Herein, a novel V6O13 nanosheets self-assembled micro-flower array self-supporting electrode is synthesized using a facile one-pot hydrothermal route. Owing to the large electrochemically active surface area of a unique hierarchical micro-flower and the stable all-in-one structure, the as-prepared V6O13/NF electrode delivers impressive HER activity with extremely low overpotentials of 125 and 298 mV at large current densities of 100 and 1000 mA cm−2, respectively, and a long-term durability for at least 90 h in an alkaline condition. This work extends the application of vanadium oxides to the realm of electrocatalytic hydrogen fuel production. Full article
(This article belongs to the Special Issue Tailored Nanosystems and Nanocatalysts for Electrocatalytic Applications)
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20 pages, 3107 KiB  
Article
Enzymatic-Based Hydrolysis of Digested Potato Peel Wastes by Amylase Producing Fungi to Improve Biogas Generation
by Mohammed S. Almuhayawi, Elhagag A. Hassan, Khalil K. Alkuwaity, Turki S. Abujamel, Jawahir A. Mokhtar, Hatoon A. Niyazi, Saad B. Almasaudi, Turki A. Alamri, Azhar A. Najjar, Nidal M. Zabermawi, Essam I. Azhar, Rania M. Makki, Hanouf A. Niyazi and Steve M. Harakeh
Catalysts 2023, 13(5), 913; https://doi.org/10.3390/catal13050913 - 22 May 2023
Cited by 2 | Viewed by 1865
Abstract
Potato peel wastes are generated in high quantities from potato processing industries. They are pollutants to the environment, and they release greenhouse gases into the atmosphere. The present study assessed the potentiality of hydrolyzing potato wastes by amylase-producing fungi to improve biogas generation [...] Read more.
Potato peel wastes are generated in high quantities from potato processing industries. They are pollutants to the environment, and they release greenhouse gases into the atmosphere. The present study assessed the potentiality of hydrolyzing potato wastes by amylase-producing fungi to improve biogas generation from potato peels through the anaerobic digestion process. Different fungal isolates were screened for amylase production on potato wastes, and the highest amylase producer was selected for optimizing the efficacy of producing amylases in high quantities to efficiently allow the conversion of potato organic matter into fermentable sugars that are utilized for the anaerobic digestion process. The best amylase producers were those derived from Rhizopus stolonifer (32.61 ± 0.89 U/mL). The highest cumulative methane yield from hydrolyzed potato peel was 65.23 ± 3.9 mL CH4/g and the methane production rate was 0.39 mL CH4/h, whereas the highest biogas yield from unhydrolyzed potato wastes was 41.32 ± 2.15 mL CH4/g and the biogas production rate was 0.25 mL CH4/h. Furthermore, it was found that the two combined sequential stages of anaerobic digestion (biogas production) followed by biodiesel production (enzymatic esterification) were the most effective, recording 72.36 ± 1.85 mL CH4/g and 64.82% biodiesel of the total analytes. However, one-pot fermentation revealed that biogas yield was 22.83 ± 2.8 mL CH4/g and the biodiesel extracted was 23.67% of the total analytes. The insights of the current paper may increase the feasibility of potato peel-based biorefinery through the biological hydrolysis strategy of potato wastes using eco-friendly enzymes. Full article
(This article belongs to the Special Issue Catalysis for Bitumen/Heavy Oil Upgrading and Petroleum Refining)
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12 pages, 2554 KiB  
Article
Synthesis of Cationic [4], [5], and [6]Azahelicenes with Extended π-Conjugated Systems
by Samuel Hrubý, Jan Ulč, Ivana Císařová and Martin Kotora
Catalysts 2023, 13(5), 912; https://doi.org/10.3390/catal13050912 - 22 May 2023
Viewed by 1267
Abstract
The scope of Rh-catalyzed C–C bond cleavage/annulation of biphenylene with various aromatic nitriles was studied. The subsequent Rh- and Ir-catalyzed C–H bond activation/annulation sequence of the formed 9-arylphenanthridines with alkynes gave rise to cationic [4], [5], [6] helical quinolizinium salts. The scope of [...] Read more.
The scope of Rh-catalyzed C–C bond cleavage/annulation of biphenylene with various aromatic nitriles was studied. The subsequent Rh- and Ir-catalyzed C–H bond activation/annulation sequence of the formed 9-arylphenanthridines with alkynes gave rise to cationic [4], [5], [6] helical quinolizinium salts. The scope of the reaction with respect to the structural features of the starting 9-arylphenanthridines and alkynes was studied. Their helical arrangement was confirmed through single-crystal X-ray analyses of selected compounds. Most of the prepared quinolizinium salts exhibited fluorescence emission maxima in the region of 525–623 nm with absolute quantum yields up to 25%. Full article
(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members and Topical Advisory Panel Members of Catalysts in Section "Catalysis in Organic and Polymer Chemistry")
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14 pages, 2586 KiB  
Article
New Platinum Complexes from Salen- and Hydroxy-Substituted Salpn-Naphthalene Ligands with CO2 Reduction Activity
by Javier O. Rivera-Reyes, Joesene Soto-Pérez, Miguel Sepulveda-Pagán, Linguo Lu, Justin Borrero-Negrón, Alanys V. Luna-Ramírez, Pedro Trinidad-Pérez, Yomaira Pagán-Torres, Zhongfang Chen, Carlos R. Cabrera, William C. West, John-Paul Jones and Dalice M. Piñero Cruz
Catalysts 2023, 13(5), 911; https://doi.org/10.3390/catal13050911 - 22 May 2023
Viewed by 1948
Abstract
The electrocatalytic reduction of carbon dioxide (CO2) into added-value products is a promising alternative to completing the cycle of atmospheric CO2. We report two new platinum complexes—a salen-like naphthalene (PtL1) and a hydroxy-substituted salpn naphthalene (PtL2 [...] Read more.
The electrocatalytic reduction of carbon dioxide (CO2) into added-value products is a promising alternative to completing the cycle of atmospheric CO2. We report two new platinum complexes—a salen-like naphthalene (PtL1) and a hydroxy-substituted salpn naphthalene (PtL2)—that are capable of activating CO2 to produce carbon monoxide (CO). The predominant keto tautomer of the non-innocent ligands was determined using DFT calculations and UV-Vis spectroscopy. The PtL2 complex has a CO Faradaic efficiency >40% in the presence of water as a sacrificial proton source at −2.5 V vs. Fc/Fc+. The addition of the hydroxy group in combination with water as a proton source decreased the reduction potential and increased the CO formation tenfold when compared to PtL1. Full article
(This article belongs to the Section Electrocatalysis)
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14 pages, 2370 KiB  
Article
Effects of ZSM-5 Morphology and Fe Promoter for Dimethyl Ether Conversion to Gasoline-Range Hydrocarbons
by Mansoor Ali, Jong Jin Kim, Faisal Zafar, Dongming Shen, Xu Wang and Jong Wook Bae
Catalysts 2023, 13(5), 910; https://doi.org/10.3390/catal13050910 - 21 May 2023
Viewed by 1477
Abstract
The synthesis of gasoline-range hydrocarbons by gas-phase dimethyl ether (DME) conversion was investigated on various ZSM-5 zeolites with different morphologies and Fe contents. The different morphologies of ZSM-5 significantly altered the distributions of the acidic sites, which showed different selectivities to gasoline-range hydrocarbons. [...] Read more.
The synthesis of gasoline-range hydrocarbons by gas-phase dimethyl ether (DME) conversion was investigated on various ZSM-5 zeolites with different morphologies and Fe contents. The different morphologies of ZSM-5 significantly altered the distributions of the acidic sites, which showed different selectivities to gasoline-range hydrocarbons. Nanostructured ZSM-5 (N-ZSM-5) revealed the highest C5+ selectivity of 41.7% with an aromatics selectivity of 23.6% at ~100% DME conversion. The superior catalytic activity of N-ZSM-5 was attributed to the largest strong Brønsted acidic sites and smaller crystallite sizes, which were beneficial for the faster removal rate of heavy hydrocarbons due to its shorter diffusion pathlength compared to conventional ZSM-5 (C-ZSM-5). In addition, 10 wt% Fe-impregnated N-ZSM-5 revealed an enhanced C5+ selectivity of 60.6% with a smaller C1–C4 selectivity of 21.9%, which were attributed to the adjusted acidic sites by suppressing the cracking reactions of the surface intermediates, which are responsible for the selective formation of smaller light hydrocarbons. However, the excess amount of Fe on N-ZSM-5 showed a lower DME conversion of 83.5% with a lower C5+ selectivity of 38.5% due to the blockages of the active acidic sites. Nanostructured N-ZSM-5 possessing a larger amount of strong Brønsted acid sites with 10 wt% Fe modification clearly showed a higher formation rate of gasoline-range hydrocarbons due to an enhanced secondary oligomerization of surface intermediates to form heavier aromatic hydrocarbons. Full article
(This article belongs to the Special Issue Advanced Catalysis for Green Fuel Synthesis and Energy Conversion)
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15 pages, 2344 KiB  
Article
Electrochemical Characterisation of the Photoanode Containing TiO2 and SnS2 in the Presence of Various Pharmaceuticals
by Gabrijela Radić, Klara Perović, Tayebeh Sharifi, Hrvoje Kušić, Marin Kovačić and Marijana Kraljić Roković
Catalysts 2023, 13(5), 909; https://doi.org/10.3390/catal13050909 - 20 May 2023
Cited by 3 | Viewed by 1389
Abstract
In this work, the behaviour of photoanodes made of TiO2, SnS2 and TiO2/SnS2 was examined in the presence and absence of pharmaceuticals diclofenac (DCF), memantine hydrochloride (MEM) and salicylic acid (SA). The focus of the current research [...] Read more.
In this work, the behaviour of photoanodes made of TiO2, SnS2 and TiO2/SnS2 was examined in the presence and absence of pharmaceuticals diclofenac (DCF), memantine hydrochloride (MEM) and salicylic acid (SA). The focus of the current research is on the following photoelectrochemical (PEC) characterisation methods: linear polarisation, electrochemical impedance spectroscopy (EIS), and open circuit potential (OCP) monitoring. Linear polarisation and EIS provided useful information about the interaction between the pharmaceuticals and the photocatalytic materials. The presence of the selected pharmaceuticals affects the OCP value, mainly due to the pH change. The results obtained by PEC characterisation were compared to the photocatalytic (PC) efficiency of pharmaceutical degradation. In addition to the photocurrent response, the linear voltammogram indicates the electrochemical oxidation of DCF and SA. Geometry optimizations using density functional theory (DFT) showed that the HOMO orbitals’ position of DCF and SA are above the position of the TiO2 HOMO level and below the position of the SnS2 HOMO level. Due to this, the characteristic current peak for DCF and SA was registered, but only for TiO2 and TiO2/SnS2 photoanodes. The oxidation current peak was not registered for MEM, although h+ scavenging properties were noticed for TiO2 in the presence of MEM. Apparently, this is an interplay between the protonated and non-protonated forms of MEM and the differences in their HOMO positions. Full article
(This article belongs to the Special Issue Advances in Photocatalytic Wastewater Purification, 2nd Edition)
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20 pages, 11135 KiB  
Article
Synthesis, and Anticancer Evaluation of 4-[(Indol-3-yl)-arylmethyl]-1-phenyl-3-methyl-5-pyrazolone Derivatives via a Magnetic Aminated Starch Biocatalyst
by Ali Ramshini, Shefa Mirani Nezhad, Seied Ali Pourmousavi, Ehsan Nazarzadeh Zare, Mona Pourjafar and Esmaeel Sharifi
Catalysts 2023, 13(5), 908; https://doi.org/10.3390/catal13050908 - 20 May 2023
Viewed by 1457
Abstract
An eco-friendly biocatalyst was constructed in three steps. In the first step, the tosylated starch (TsST) was synthesized by using a 4-toluenesulfonyl chloride. In the second step, the aminated starch was synthesized via the reaction of TsST with para-phenylenediamine. In the third step, [...] Read more.
An eco-friendly biocatalyst was constructed in three steps. In the first step, the tosylated starch (TsST) was synthesized by using a 4-toluenesulfonyl chloride. In the second step, the aminated starch was synthesized via the reaction of TsST with para-phenylenediamine. In the third step, the magnetic biocatalyst was fabricated by an in situ coprecipitation process from ferric and ferrous salts in the existence of aminated starch (AST). The biocatalyst was characterized by 1H NMR, EDX, FESEM, FTIR, VSM, and TGA analyses. The magnetic aminated starch (MAST) was used as a biocatalyst for the synthesis of 4-[(indol-3-yl)-arylmethyl]-1-phenyl-3-methyl-5-pyrazolone derivatives. The various products were prepared in noteworthy yields (85–93%) in fast reaction times (35–80 min) without laborious work-up procedures. The anticancer evaluation of some 4-[(indol-3-yl)-arylmethyl]-1-phenyl-3-methyl-5-pyrazolones derivatives was studied on the survival rate of breast cancer cell lines (MCF-7) and human fibroblast cells by using an MTT assay. Additionally, recovery of the biocatalyst was studied, and results showed that the MAST was easily isolated from the reaction flask and could be recycled for up to six consecutive cycles without meaningfully falling in its efficiency. Full article
(This article belongs to the Special Issue Advances in Polymer-Supported and Polymer-Immobilized Catalysts)
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14 pages, 4161 KiB  
Article
Exceptional Photocatalytic Performance of the LaFeO3/g-C3N4 Z-Scheme Heterojunction for Water Splitting and Organic Dyes Degradation
by Muhammad Humayun, Ayesha Bahadur, Abbas Khan and Mohamed Bououdina
Catalysts 2023, 13(5), 907; https://doi.org/10.3390/catal13050907 - 20 May 2023
Cited by 12 | Viewed by 1521
Abstract
To simulate natural photosynthesis, scientists have developed an artificial Z-scheme system that splits water into hydrogen and oxygen using two different semiconductors. Researchers are striving to improve the performance of Z-scheme systems by improving light absorption, developing redox couples with high stability, and [...] Read more.
To simulate natural photosynthesis, scientists have developed an artificial Z-scheme system that splits water into hydrogen and oxygen using two different semiconductors. Researchers are striving to improve the performance of Z-scheme systems by improving light absorption, developing redox couples with high stability, and finding new cocatalysts. Here, we report the synthesis and utilization of LaFeO3/g-C3N4 as a Z-scheme system for water reduction to produce hydrogen and organic dye degradation under visible light irradiation. The as-fabricated photocatalyst revealed exceptional activity for H2 production (i.e., 351 µmol h−1g−1), which is 14.6 times higher compared to that of the single-component g-C3N4 (i.e., 24 µmol h−1g−1). In addition, the composite photocatalyst degraded 87% of Methylene Blue (MB) and 94% of Rhodamine B (RhB) in 2 h. Various experimental analyses confirmed that the exceptional performance of the LaFeO3/g-C3N4 Z-scheme catalyst is due to remarkably enhanced charge carrier separation and improved light absorption. The development of this highly effective Z-scheme heterostructure photocatalyst will pave the way for the sustainable development of newly designed Z-scheme scheme systems that will tackle energy and environmental crises. Full article
(This article belongs to the Special Issue Advances in Heterojunction Photocatalysts)
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15 pages, 6244 KiB  
Article
Properties of CrOx/MCM-41 and Its Catalytic Activity in the Reaction of Propane Dehydrogenation in the Presence of CO2
by Maria Igonina, Marina Tedeeva, Konstantin Kalmykov, Gennadiy Kapustin, Vera Nissenbaum, Igor Mishin, Petr Pribytkov, Sergey Dunaev, Leonid Kustov and Alexander Kustov
Catalysts 2023, 13(5), 906; https://doi.org/10.3390/catal13050906 - 19 May 2023
Cited by 3 | Viewed by 1436
Abstract
Propylene is an important raw material for the production of many valuable compounds, especially polypropylene, the consumption of which continues to grow every year. The reaction of oxidative dehydrogenation of propane, where carbon dioxide is used as a mild oxidant, is a promising [...] Read more.
Propylene is an important raw material for the production of many valuable compounds, especially polypropylene, the consumption of which continues to grow every year. The reaction of oxidative dehydrogenation of propane, where carbon dioxide is used as a mild oxidant, is a promising method for producing propylene. At the same time, the problem of utilization of greenhouse gas CO2 is partially solved. The synthesis and analysis of the physicochemical properties of mesoporous silicate MCM-41 and supported catalysts CrOx/MCM-41 prepared on its basis were carried out. These catalysts were prepared using incipient wetness impregnation. The support and catalysts were characterized by the methods of low-temperature nitrogen adsorption, TG-DTA, XRD, SEM, TPR-H2, UV/Vis diffuse reflectance spectroscopy, and small-angle X-ray scattering. It is shown that chromium is present in the samples simultaneously in the form of Cr3+ and Cr6+. The catalytic tests were performed in the range of 550–700 °C. The highest selectivity for propylene was observed for the 5%Cr/MCM-41 catalyst and was 76% at a temperature of 650 °C with a propane conversion of 20%. The deposited catalysts Cr/MCM-41 and Cr/SiO2 (Acros) were compared. The propylene selectivity for the MCM-41-supported catalyst was ~1.5 times higher than that for the SiO2-supported catalyst. Full article
(This article belongs to the Special Issue Heterogeneous Catalysts for Petrochemical Synthesis and Oil Refining, 2nd Edition)
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24 pages, 7391 KiB  
Article
A Comprehensive Study of Electrocatalytic Degradation of M-Tolylhydrazine with Binary Metal Oxide (Er2O3@NiO) Nanocomposite Modified Glassy Carbon Electrode
by Tahir Ali Sheikh, Abdullah M. Asiri, Amna Siddique, Hadi M. Marwani, Md. Rezaur Rahman, Muhammad Nadeem Akhtar and Mohammed M. Rahman
Catalysts 2023, 13(5), 905; https://doi.org/10.3390/catal13050905 - 19 May 2023
Cited by 1 | Viewed by 1544
Abstract
Generally, our ecosystem is continuously contaminated as a result of anthropogenic activities that form the basis of our comfort in our routine life. Thus, most scientists are engaged in the development of new technologies that can be used in environmental remediation. Herein, highly [...] Read more.
Generally, our ecosystem is continuously contaminated as a result of anthropogenic activities that form the basis of our comfort in our routine life. Thus, most scientists are engaged in the development of new technologies that can be used in environmental remediation. Herein, highly calcined binary metal oxide (Er2O3@NiO) semiconductor nanocomposite (NC) was synthesized using a classical wet chemical process with the intention to both detect and degrade the toxic chemicals in an aqueous medium using a novel electrochemical current–potential (I–V) approach for the first time. Optical, morphological, and structural properties of the newly synthesized semiconductor NC were also studied in detail using FT-IR, UV/Vis., FESEM-EDS, XPS, BET, EIS, and XRD techniques. Then, a modified glassy carbon electrode (GCE) based on the newly synthesized semiconductor nanocomposite (Er2O3@NiO-NC/Nafion/GCE) as a selective electrochemical sensor was fabricated with the help of 5% ethanolic-Nafion as the conducting polymer binder in order to both detect and electro-hydrolyze toxic chemicals in an aqueous medium. Comparative study showed that this newly developed Er2O3@NiO-NC/Nafion/GCE was found to be very selective against m-tolyl hydrazine (m-Tolyl HDZN) and to have good affinity in the presence of other interfering toxic chemicals. Analytical parameters were also studied in this approach to optimize the newly designed Er2O3@NiO-NC/Nafion/GCE as an efficient and selective m-Tolyl HDZN sensor. Its limit of detection (LOD) at an SNR of 3 was calculated as 0.066 pM over the linear dynamic range (LDR) of our target analyte concentration (0.1 pM–0.1 mM). The limit of quantification (LOQ) and sensitivity were also calculated as 0.22 pM and 14.50 µAµM−1cm−2, respectively. m-Tolyl HDZN is among the toxic chemicals in our ecosystem that have lethal effects in living beings. Therefore, this newly designed electrochemical sensor based on semiconductor nanostructure material offers, for the first time, a cost-effective technique, in addition to long-term stability, that can be used as an alternative for efficiently probing other toxic chemicals in real samples. Full article
(This article belongs to the Special Issue Electro/Photocatalyst for Degradation of Emerging Water Pollutants and Water Splitting)
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16 pages, 3982 KiB  
Article
Nitrogen Self-Doped Metal Free Catalysts Derived from Chitin via One Step Method for Efficient Electrocatalytic CO2 Reduction to CO
by Peixu Sun, Xiaoxiao Wang, Mingjian Zhu, Naveed Ahmad, Kai Zhang and Xia Xu
Catalysts 2023, 13(5), 904; https://doi.org/10.3390/catal13050904 - 18 May 2023
Viewed by 1298
Abstract
In this study, a facile one-step method via pyrolysis was used to prepare nitrogen self-doped metal free catalysts derived from inexpensive biomass-chitin for an electrochemical CO2 reduction reaction (CO2RR). The microstructure, surface area, defect and N type in the catalysts [...] Read more.
In this study, a facile one-step method via pyrolysis was used to prepare nitrogen self-doped metal free catalysts derived from inexpensive biomass-chitin for an electrochemical CO2 reduction reaction (CO2RR). The microstructure, surface area, defect and N type in the catalysts were analyzed by BET, Raman, XPS, SEM and TEM. The sustainable chitin-based electrocatalyst prepared under optimized conditions has a surface area of 1972 m2/g and can convert CO2 into CO with FECO of ~90% at a potential of −0.59 V (vs. RHE). This good CO2RR performance results from plentiful active sites due to a high surface area, rich ultra-micropores that are beneficial to CO2 adsorption, abundant mesopores for CO2 transport improvement, a high content of pyridinic and graphitic nitrogen that is favorable for a CO2 reduction reaction and a low interfacial charge transfer resistance leading to a rapid electron transfer rate from the catalyst to CO2. This study shows the feasibility of N self-doped biomass-derived catalysts for CO2RR with the potential for large-scale industrial applications. Full article
(This article belongs to the Section Electrocatalysis)
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17 pages, 7726 KiB  
Article
CO2 Electroreduction to Formate—Comparative Study Regarding the Electrocatalytic Performance of SnO2 Nanoparticles
by Henning Weinrich, Bastian Rutjens, Shibabrata Basak, Bernhard Schmid, Osmane Camara, Ansgar Kretzschmar, Hans Kungl, Hermann Tempel and Rüdiger-A. Eichel
Catalysts 2023, 13(5), 903; https://doi.org/10.3390/catal13050903 - 18 May 2023
Cited by 3 | Viewed by 1431
Abstract
SnO2 nanoparticles have frequently been reported as effective electrocatalysts for CO2 electroreduction to formate. However, in the literature, there is little knowledge of SnO2 nanoparticles that guarantee superior electrocatalytic performance. Hence, in this study, several SnO2 nanoparticles are compared [...] Read more.
SnO2 nanoparticles have frequently been reported as effective electrocatalysts for CO2 electroreduction to formate. However, in the literature, there is little knowledge of SnO2 nanoparticles that guarantee superior electrocatalytic performance. Hence, in this study, several SnO2 nanoparticles are compared with respect to their material properties, and correlations to the electrocatalytic performance are established. For comparison, three custom-made SnO2-electrocatalysts were prepared, reproducing frequently cited procedures in literature. Based on the comparison, it is found that hydrothermal, sol-gel, and solid-state synthesis provide quite different electrocatalysts, particularly in terms of the particle size and crystal lattice defect structure. Desirably small nanoparticles with a comparatively high number of lattice defects are found for the nanoparticles prepared by hydrothermal synthesis, which also provide the best electrocatalytic performance in terms of Faradaic efficiency for the electroreduction of CO2 to formate. However, despite the considerably smaller surface area, the commercial reference also provides significant electrocatalytic performance, e.g., in terms of the overall produced amount of formate, which suggests a surprisingly high surface area-specific activity for this material that is low on defects. Thus, defects do not appear to be the preferred reaction site for the CO2 electroreduction to formate on SnO2 in this case. Full article
(This article belongs to the Special Issue CO2 Catalytic Conversion and Utilization)
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45 pages, 1448 KiB  
Review
Sustainable Biorefineries Based on Catalytic Biomass Conversion: A Review
by Juan Camilo Solarte-Toro, Mariana Ortiz-Sanchez, Pablo-José Inocencio-García and Carlos Ariel Cardona Alzate
Catalysts 2023, 13(5), 902; https://doi.org/10.3390/catal13050902 - 17 May 2023
Cited by 3 | Viewed by 2102
Abstract
Biorefineries have been profiled as potential alternatives to increase biomass use at the industrial level. However, more efforts are required to improve the sustainability of these facilities through process improvement and product portfolio increase. The catalytic conversion of biomass to chemicals and energy [...] Read more.
Biorefineries have been profiled as potential alternatives to increase biomass use at the industrial level. However, more efforts are required to improve the sustainability of these facilities through process improvement and product portfolio increase. The catalytic conversion of biomass to chemicals and energy vectors is one of the most studied research lines today. The open literature has described catalytic pathways for producing biofuels and platform molecules using this renewable resource. Nevertheless, few literature reviews have aimed to analyze the role of the catalytic conversion of biomass in biorefineries while considering the following items: (i) biocatalysis, (ii) carbon dioxide conversion, (iii) design based on catalytic biomass upgrading, and (iv) sustainability metrics. This paper reviews several processes where catalysis has been applied to improve yields and conversion to elucidate the potential of this research field to boost biomass implementation in different productive sectors. This paper provides an overview of the catalytic conversion of biomass into a series of biofuels and high-value-added products, involving key topics related to catalyst performance, use, applications, and recent trends. In addition, several research gaps and ideas are highlighted based on previous studies. In conclusion, the catalytic conversion of biomass has the potential to increase biorefineries’ sustainability. Nevertheless, more studies focused on (i) the production of new catalysts using renewable resources, (ii) the techno-economic and environmental assessment of processes involving catalysis, and (iii) the influence of involving biomass valorization via heterogeneous catalysis in existing facilities are required to obtain a real understanding of catalytic upgrades’ benefits. Full article
(This article belongs to the Special Issue Catalytic Conversion of Biomass to Biofuels)
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19 pages, 4572 KiB  
Article
Influence of Y Doping on Catalytic Activity of CeO2, MnOx, and CeMnOx Catalysts for Selective Catalytic Reduction of NO by NH3
by Eleonora La Greca, Tamara S. Kharlamova, Maria V. Grabchenko, Valery A. Svetlichnyi, Giuseppe Pantaleo, Luca Consentino, Olga A. Stonkus, Olga V. Vodyankina and Leonarda Francesca Liotta
Catalysts 2023, 13(5), 901; https://doi.org/10.3390/catal13050901 - 17 May 2023
Cited by 1 | Viewed by 1265
Abstract
Novel yttrium-doped CeO2, MnOx, and CeMnOx composites are investigated as catalysts for low-temperature NH3-SCR. The study involves the preparation of unmodified oxide supports using a citrate method followed by modification with Y (2 wt.%) using two [...] Read more.
Novel yttrium-doped CeO2, MnOx, and CeMnOx composites are investigated as catalysts for low-temperature NH3-SCR. The study involves the preparation of unmodified oxide supports using a citrate method followed by modification with Y (2 wt.%) using two approaches, including the one-pot citrate method and incipient wetness impregnation of undoped oxides. The NH3-SCR reaction is studied in a fixed-bed quartz reactor to test the ability of the prepared catalysts in NO reduction. The gas reaction mixture consists of 800 ppm NO, 800 ppm NH3, 10 vol.% O2, and He as a balance gas at a WHSV of 25,000 mL g−1 h−1. The results indicate that undoped CeMnOx mixed oxide exhibits significantly higher deNOx performance compared with undoped and Y-doped MnOx and CeO2 catalysts. Indeed, yttrium presence in CeMnOx promotes the competitive NH3-SCO reaction, reducing the amount of NH3 available for NO reduction and lowering the catalyst activity. Furthermore, the physical-chemical properties of the prepared catalysts are studied using nitrogen adsorption/desorption, XRD, Raman spectroscopy, temperature-programmed reduction with hydrogen, and temperature-programmed desorption of ammonia. This study presents a promising approach to enhancing the performance of NH3-SCR catalysts at low temperatures that can have significant implications for reducing NO emissions. Full article
(This article belongs to the Special Issue Heterogeneous Catalysis and Advanced Oxidation Processes (AOP) for Environmental Protection (VOCs Oxidation, Air and Water Purification), 2nd Edition)
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23 pages, 5537 KiB  
Article
Novel Laser-Assisted Chemical Bath Synthesis of Pure and Silver-Doped Zinc Oxide Nanoparticles with Improved Antimicrobial and Photocatalytic Properties
by Samer H. Zyoud, Samer O. Alalalmeh, Omar E. Hegazi, Ibrahim S. Yahia, Heba Y. Zahran, Hamed Abu Sara, Samir Haj Bloukh, Moyad Shahwan, Ahed H. Zyoud, Nageeb Hassan, Akram Ashames, Malek G. Daher, Ghaseb N. Makhadmeh, Ammar Jairoun, Naser Qamhieh and Mohamed Sh. Abdel-wahab
Catalysts 2023, 13(5), 900; https://doi.org/10.3390/catal13050900 - 17 May 2023
Cited by 5 | Viewed by 2098
Abstract
Antimicrobial resistance poses a significant threat to global health, amplified by factors such as water scarcity and suboptimal hygienic practices. Addressing AMR effectively necessitates a comprehensive strategy encompassing enhanced access to potable water, developing innovative antibiotics, and exploring alternative treatment modalities, such as [...] Read more.
Antimicrobial resistance poses a significant threat to global health, amplified by factors such as water scarcity and suboptimal hygienic practices. Addressing AMR effectively necessitates a comprehensive strategy encompassing enhanced access to potable water, developing innovative antibiotics, and exploring alternative treatment modalities, such as harnessing solar photocatalysis with zinc oxide nanoparticles for water purification and antimicrobial applications. The Laser-Assisted Chemical Bath Synthesis (LACBS) technique facilitates the fabrication of pure ZnO nanostructures, providing a potentially efficacious solution for mitigating pathogen proliferation and managing wastewater. The photocatalytic degradation of MB and MO dyes was investigated using blue laser light at 445 nm, and degradation rates were determined accordingly. Ag-doped ZnO nanostructures were characterized through X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and Fourier-transform infrared spectroscopy. The antimicrobial efficacy of LACBS-synthesized ZnO nanoparticles was assessed against C. albicans, S. aureus, B. subtilis, E. coli, and K. pneumoniae using the disc diffusion method, revealing 40 mm, 37 mm, 21 mm, 27 mm, and 45 mm inhibition zones at the highest concentration of doped-Ag (4.5%), respectively. These inhibition zones were measured in accordance with the guidelines established by the Clinical and Laboratory Standards Institute. X-ray diffraction patterns for ZnO, ZnOAg(1.5%), ZnO:Ag(3%), and ZnO:Ag(4.5%) samples revealed variations in intensity and crystallinity. Scanning electron microscopy exposed morphological disparities among the nanostructures, while energy-dispersive X-ray spectroscopy verified their elemental compositions. UV-Vis absorption analyses inspected the optical band gaps, and Fourier-transform infrared spectra identified the stretching mode of metal-oxygen bonds. Under blue laser irradiation, Ag-doped ZnO exhibited enhanced photocatalytic activity during the photocatalytic degradation. These nanoparticles, synthesized via the cost-effective and straightforward LACBS method, benefit from silver doping that augments their electron-trapping properties and photocatalytic activity, thereby enabling efficient dye degradation. Consequently, Ag-doped ZnO nanoparticles hold promise as a potent solution for counteracting drug-resistant microorganisms and as an effective disinfectant. Full article
(This article belongs to the Special Issue Composites Photocatalysts for Sustainable Solar Energy Conversion)
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17 pages, 6683 KiB  
Article
Evaluation of Heterogeneous Catalytic Ozonation Process for the Removal of Micropollutants from Water/Wastewater: Application of a Novel Pilot-Scale Continuous Flow System
by Efthimia Kaprara, Charalampos Belesakos, Konstantinos Kollis, Savvina Psaltou, Anastasios Zouboulis and Manassis Mitrakas
Catalysts 2023, 13(5), 899; https://doi.org/10.3390/catal13050899 - 17 May 2023
Cited by 1 | Viewed by 1234
Abstract
The present study evaluates the removal of micropollutants from water/wastewater contaminated sources through the application of a heterogeneous catalytic ozonation process, using a pilot-scale continuous operation unit, composed of a membrane module for the diffusion and effective dilution of ozone into the liquid [...] Read more.
The present study evaluates the removal of micropollutants from water/wastewater contaminated sources through the application of a heterogeneous catalytic ozonation process, using a pilot-scale continuous operation unit, composed of a membrane module for the diffusion and effective dilution of ozone into the liquid phase to be treated and a plug flow reactor/continuous stirred tank reactor (PFR/CSTR) contact reactor system in series, where the catalyst is recirculated in dispersion mode. The solid materials tested as catalysts are natural and calcined zeolite, Bayoxide and alumina, whereas the examined micropollutants, used in this case as probe compounds, are p-chlorobenzoic acid (p-CBA), atrazine, benzotriazole and carbamazepine. A high-performance liquid chromatography system was used to determine the removal of micropollutants. In the case of p-CBA, an ozone-resistant compound, the addition of catalyst was found to significantly enhance its degradation rate, leading to >99% removal under the optimum defined conditions, i.e., in terms of catalyst concentration, pH, temperature, and process time. On the other hand, in the case of atrazine, a different ozone-resistant compound, the introduction of examined catalysts in the ozonation process was found to reduce the degradation of micropollutant, when compared with the application of single ozonation, indicating the importance of specific affinity between the pollutant and the solid material used as catalyst. Benzotriazole, a moderately ozone-reactive compound was degraded by more than 95% under all experimental conditions and catalysts tested in the pilot unit, while carbamazepine, a highly ozone-reactive compound, was completely removed even during the first stage of treatment process (i.e., at the membrane contactor). When increasing the pH value (in the range 6–8) and the contact time, the performance of catalytic ozonation process also improved. Full article
(This article belongs to the Special Issue Transition Metal Complexes as Catalysts)
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13 pages, 6364 KiB  
Article
Immobilization of TiO2 Photocatalysts for Water Treatment in Geopolymer Based Coatings
by Lukas Dufner, Felix Ott, Nikolai Otto, Tom Lembcke and Frank Kern
Catalysts 2023, 13(5), 898; https://doi.org/10.3390/catal13050898 - 16 May 2023
Cited by 4 | Viewed by 1309
Abstract
This study presents a simple and sustainable coating technology for the deposition of photocatalytic coatings based on titanium dioxide and geopolymers, which requires no thermal post-treatment. Titania powder P25, potassium silicate and a calcium aluminate-based hardener were dispersed in water and applied to [...] Read more.
This study presents a simple and sustainable coating technology for the deposition of photocatalytic coatings based on titanium dioxide and geopolymers, which requires no thermal post-treatment. Titania powder P25, potassium silicate and a calcium aluminate-based hardener were dispersed in water and applied to aluminum substrates using a paintbrush, a roller and a spray gun. The coatings were air-dried for 12 h. The photocatalytic activities were tested via degradation of an aqueous methylene blue solution in a batch reactor under artificial UV-A light. The roller and the spray gun-based coatings yielded well-adhering coatings with high photocatalytic activity. Brushed coatings were inhomogeneous and unstable. The presented method of producing photocatalytic coatings is very simple to apply and does not require complex technologies or energy-intensive thermal treatments. Full article
(This article belongs to the Special Issue Heterogeneous Photocatalysis: A Solution for a Greener Earth II)
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19 pages, 4320 KiB  
Article
Novel Control System Strategy for the Catalytic Oxidation of VOCs with Heat Recovery
by Angel Federico Miranda, María Laura Rodríguez, Federico Martin Serra and Daniel Oscar Borio
Catalysts 2023, 13(5), 897; https://doi.org/10.3390/catal13050897 - 16 May 2023
Cited by 1 | Viewed by 1024
Abstract
A theoretical study of the dynamic closed-loop behaviour of a reactor/feed-effluent heat exchanger (FEHE)/furnace system for the catalytic combustion of volatile organic compounds (VOCs) is presented. A 1D pseudohomogeneous plug-flow model is proposed to simulate the non-steady-state operation of the monolith reactor and [...] Read more.
A theoretical study of the dynamic closed-loop behaviour of a reactor/feed-effluent heat exchanger (FEHE)/furnace system for the catalytic combustion of volatile organic compounds (VOCs) is presented. A 1D pseudohomogeneous plug-flow model is proposed to simulate the non-steady-state operation of the monolith reactor and the FEHE, while the furnace behaviour is described by means of a heterogeneous model of lumped parameters. Positive energy feedback is a source of instability that leads to strong thermal oscillations (limit cycles) and may cause damage to the equipment and sintering of the catalyst. The design of a robust and flexible control system and an efficient control strategy are, therefore, required to ensure safe and stable operation. The response of the system under three different control strategies to the most frequent disturbance variables—the feed flowrate (FV0) and feed concentration of VOCs (C0Et)—was evaluated. One of the control strategies consisted of a single-loop feedback system with servomechanism changes in the reactor inlet temperature (T0) that manipulated the bypass valve and, sequentially, the natural gas flowrate in the furnace (FNG). This approach made it possible to meet the control objective (reducing VOCs) without losing controllability and while minimizing the use of external fuel. Full article
(This article belongs to the Special Issue Catalysts for Air Pollution Control: Present and Future)
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12 pages, 3002 KiB  
Article
Support Effect of Ga-Based Catalysts in the CO2-Assisted Oxidative Dehydrogenation of Propane
by Wei Zhou, Yulin Jiang, Zhiguo Sun, Shiqi Zhou, Erpai Xing, Yang Hai, Guanghao Chen and Yuetong Zhao
Catalysts 2023, 13(5), 896; https://doi.org/10.3390/catal13050896 - 16 May 2023
Cited by 2 | Viewed by 1608
Abstract
Carbon dioxide (CO2) assisted oxidative dehydrogenation of propane over Ga-modified catalysts is highly sensitive to the identity of support, but the underlying cause of support effects has not been well established. In this article, SSZ-13, SSZ-39, ZSM-5, silica and γ-Al2 [...] Read more.
Carbon dioxide (CO2) assisted oxidative dehydrogenation of propane over Ga-modified catalysts is highly sensitive to the identity of support, but the underlying cause of support effects has not been well established. In this article, SSZ-13, SSZ-39, ZSM-5, silica and γ-Al2O3 were used to load Ga species by incipient wet impregnation. The structure, textural properties, acidity of the Ga-based catalysts and the process of CO2-assisted oxidative dehydrogenation of propane were examined by X-ray diffraction (XRD), nitrogen physisorption (N2 physisorption), ammonia temperature-programmed desorption (NH3-TPD), pyridine chemisorbed Fourier transform infrared spectra (Py-FTIR), OH-FTIR and in situ FTIR. Evaluation of the catalytic performance combined with detailed catalyst characterization suggests that their dehydrogenation activity is positively associated with the number of acid sites in middle strength, confirming that the Lewis acid sites generated by Ga cations are the active species in the reaction. Ga/Na-SSZ-39(9) also has feasible acidic strength and a unique channel structure, which is conducive to the dissociative adsorption of propane and desorption of olefins. The Ga/Na-SSZ-39(9) catalysts showed superior olefins selectivity and catalytic stability at 600 ℃ compared to any other catalysts. This approach to quantifying support acid strength, and channel structure and applying it as a key catalytic descriptor of support effects is a useful tool to enable the rational design of next-generation CO2-assisted oxidative dehydrogenation catalysts. Full article
(This article belongs to the Special Issue Heterogeneous Catalysis for Clean Energy Production and Carbon Dioxide Utilization)
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12 pages, 1462 KiB  
Article
Ordered Mesoporous TiO2: The Effect of Structure, Residual Template and Metal Doping on Photocatalytic Activity
by Ahmed M. Mohammed, Ahmet E. Becerikli, Simon Ristig, Norbert Steinfeldt and Jennifer Strunk
Catalysts 2023, 13(5), 895; https://doi.org/10.3390/catal13050895 - 16 May 2023
Cited by 2 | Viewed by 1099
Abstract
Using a series of ordered mesoporous TiO2 (om-TiO2) with and without Ce or Cu doping, the effects of structure, metal doping and residual template species in the structure are systematically evaluated in terms of products formed during a CO2 [...] Read more.
Using a series of ordered mesoporous TiO2 (om-TiO2) with and without Ce or Cu doping, the effects of structure, metal doping and residual template species in the structure are systematically evaluated in terms of products formed during a CO2 photoreduction process. It is found that the ordered mesoporous structure contributes significantly in the hydrogen evolution reaction from the splitting of gaseous water. No cocatalyst was needed to achieve high hydrogen yields. While carbon-containing products are also observed, the presence of remainders of the organic template used in the synthesis process does not allow an unambiguous identification of the source of products. Small amounts of metal doping do not majorly influence the hydrogen evolution, thus the mesoporous structure can eventually be identified as the main cause for the improved performance. Full article
(This article belongs to the Special Issue Environmental Remediation via Metal-Oxides-Mediated Heterogeneous Photocatalysis)
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16 pages, 3261 KiB  
Article
NO Oxidation on Lanthanum-Doped Ceria Nanoparticles with Controlled Morphology
by Susana Fernández-García, Miguel Tinoco, Ana Belén Hungría, Xiaowei Chen, José Juan Calvino, Juan Carlos Martínez-Munuera, Javier Giménez-Mañogil and Avelina García-García
Catalysts 2023, 13(5), 894; https://doi.org/10.3390/catal13050894 - 15 May 2023
Cited by 2 | Viewed by 1304
Abstract
The present work aims to assess the impact of morphology and reducibility on lanthanum-doped ceria nanocatalysts with controlled morphology on the NO oxidation reaction. Specifically, samples were prepared using a hydrothermal method incorporating lanthanum at varying molar concentrations (0, 5, 10, and 15 [...] Read more.
The present work aims to assess the impact of morphology and reducibility on lanthanum-doped ceria nanocatalysts with controlled morphology on the NO oxidation reaction. Specifically, samples were prepared using a hydrothermal method incorporating lanthanum at varying molar concentrations (0, 5, 10, and 15 mol.%) into ceria with a controlled morphology (nanocubes and nanorods). The structural, compositional, and redox characterization of these catalysts has been performed via scanning transmission electron microscopy (STEM), X-ray diffraction (XRD), X-ray energy dispersive spectroscopy (X-EDS), inductively coupled plasma (ICP), hydrogen temperature-programmed reduction (H2-TPR), and oxygen storage capacity (OSC). NO oxidation catalytic tests were conducted, and the results were compared with estimated curves (obtained by considering the proportions of the corresponding components), which revealed the presence of a synergistic effect between lanthanum and ceria. The degree of enhancement was found to depend on both the morphology and the amount of lanthanum incorporated into CeO2. These findings may facilitate the optimization of features concerning ceria-based nanocatalysts for the removal of NOx emissions from exhaust gases. Full article
(This article belongs to the Special Issue Catalytic Materials: State-of-the-Art and Perspectives in Spain)
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17 pages, 6503 KiB  
Article
Hydrothermally Derived Mg-Doped TiO2 Nanostructures for Enhanced H2 Evolution Using Photo- and Electro-Catalytic Water Splitting
by Mohd Fazil, Saad M. Alshehri, Yuanbing Mao and Tokeer Ahmad
Catalysts 2023, 13(5), 893; https://doi.org/10.3390/catal13050893 - 15 May 2023
Cited by 7 | Viewed by 2419
Abstract
Mg-doped TiO2 nano-structures in different compositions (1, 2.5 and 5%) were successfully synthesized by low-temperature hydrothermal route. X-ray diffraction and electron microscopic studies were used to investigate the crystal structure, surface morphology and particle size of the as-synthesized materials. Raman studies were [...] Read more.
Mg-doped TiO2 nano-structures in different compositions (1, 2.5 and 5%) were successfully synthesized by low-temperature hydrothermal route. X-ray diffraction and electron microscopic studies were used to investigate the crystal structure, surface morphology and particle size of the as-synthesized materials. Raman studies were carried out to elucidate the phase identification and the modes of vibrations to determine the impact of dopant ion on the crystal structures. The band gap was estimated using UV-DRS studies whereas, BET surface area analysis revealed an increase in the surface area of increasing Mg2+ ions concentration in TiO2 nanostructures. Among the synthesized various composition of nano-structures, 5% Mg-doped TiO2 photocatalyst showed maximum hydrogen evolution activity (38.96 mmol gcat−1) in an 8-h analysis cycle. Moreover, the 2.5% Mg-doped TiO2 nanocatalyst with tafel slopes of 123.5 and 126.7 mV/dec showed strong activity for both HER in 0.5 N H2SO4 and 0.1 N KOH, with an onset potential of 0.96 V (at 10 mA/cm2) and −1.38 V (at 1 mA/cm2) for HER, respectively. Experimental investigations deduced that the incorporation of Mg2+ ions in the TiO2 resulted in the increase of hydrogen generation catalytic activity of titanium dioxide owing to the synergistic effect provided by the remarkable surface area and the presence of defects introduced by doping. Full article
(This article belongs to the Special Issue Advanced Nanostructured Materials for Modern Catalysis Applications)
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16 pages, 6222 KiB  
Article
PtCu Nanoparticle Catalyst for Electrocatalytic Glycerol Oxidation: How Does the PtCu Affect to Glycerol Oxidation Reaction Performance by Changing pH Conditions?
by Lee Seul Oh, Jeonghyun Han, Eunho Lim, Won Bae Kim and Hyung Ju Kim
Catalysts 2023, 13(5), 892; https://doi.org/10.3390/catal13050892 - 15 May 2023
Cited by 3 | Viewed by 1743
Abstract
In this work, we show that finding and controlling optimum pH environments with Pt-based alloy catalysts can create high catalytic performances for electrocatalytic glycerol oxidation reaction (EGOR). Compared to a Pt/C catalyst, the PtCu/C alloy catalyst has higher reaction rate and turnover frequency [...] Read more.
In this work, we show that finding and controlling optimum pH environments with Pt-based alloy catalysts can create high catalytic performances for electrocatalytic glycerol oxidation reaction (EGOR). Compared to a Pt/C catalyst, the PtCu/C alloy catalyst has higher reaction rate and turnover frequency (TOF) values by increasing the pH. Specifically, the reaction rate and TOF of the PtCu/C catalyst at pH 13 were 2.93 and 6.65 times higher than those of Pt/C, respectively. The PtCu/C catalyst also showed lower onset potential value and higher mass and specific activities than the Pt/C by increasing the pH. This indicates that the Cu in the PtCu alloy improves the catalytic activity for the EGOR in an OH− group-rich environment. In the case of the PtCu/C catalyst at a high pH condition, the selectivities of tartronic acid and oxalic acid tended to increase as the selectivity of lactic acid decreased. This result means that the PtCu alloy follows primary alcohol oxidation pathways, which are more favorable in an OH− group-rich environment than with only Pt. This study proposes that it is critical to optimize and control the reaction conditions for developing efficient EGOR catalysts. Full article
(This article belongs to the Special Issue Theme Issue in Honor of Prof. Dr. Jae Sung Lee)
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19 pages, 5830 KiB  
Article
Bio-Fabrication of Cu/Ag/Zn Nanoparticles and Their Antioxidant and Dye Degradation Activities
by Srijal Kunwar, Arpita Roy, Utsav Bhusal, Amel Gacem, Mahmood M. S. Abdullah, Promila Sharma, Krishna Kumar Yadav, Sarvesh Rustagi, Nidhi Chatterjee, Vishal Kumar Deshwal, Hyun-Kyung Park and Byong-Hun Jeon
Catalysts 2023, 13(5), 891; https://doi.org/10.3390/catal13050891 - 15 May 2023
Cited by 8 | Viewed by 1827
Abstract
The biological synthesis of nanoparticles with copper, silver, and zinc (Cu, Ag, Zn) is reported in this study, adopting a greener, safe, reliable, and eco-friendly approach by using an aqueous leaf extract of Catharanthus roseus. The synthesised trimetallic nanoparticles were characterised using [...] Read more.
The biological synthesis of nanoparticles with copper, silver, and zinc (Cu, Ag, Zn) is reported in this study, adopting a greener, safe, reliable, and eco-friendly approach by using an aqueous leaf extract of Catharanthus roseus. The synthesised trimetallic nanoparticles were characterised using different characterisation techniques. The UV–visible spectroscopic technique was initially used to assess nanoparticle formation, in which absorption bands were observed at 220, 270, and 370 nm for Cu, Zn, and Ag nanocomposites, respectively. XRD revealed that the average crystalline size of the nanocomposites was 34.67 nm. The roles of reducing and capping/stabilising agents in the synthesis of Cu/Ag/Zn nanoparticles were confirmed by FTIR analysis, and the successful biosynthesis of the same was also confirmed by X-ray energy-dispersive spectroscopy (EDX) analysis. Potential applications of these synthesised trimetallic nanoparticles were evaluated by assessing their antioxidant and catalytic dye degradation activities. The antioxidant activity of the synthesised nanomaterial was studied using the DPPH assay. The catalytic breakdown of the harmful dyes phenol red and eosin yellow was examined using NaBH4 as a reducing agent. The results showed that the nanomaterial’s radical scavenging capacity at 1000 ug/mL was 75.76% and the degradation of these dyes was up to 78% in the presence of NaBH4. Furthermore, the biogenic trimetallic nanomaterial exhibited effective catalytic degradation activity against methyl red and phenol red dyes. Full article
(This article belongs to the Special Issue Recent Advances on Nano-Catalysts for Biological Processes II)
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14 pages, 7143 KiB  
Article
Tailoring CoNi Alloy-Embedded Carbon Nanofibers by Coaxial Electrospinning for an Enhanced Oxygen Reduction Reaction
by Haibo Ouyang, Leer Bao, Jinfan Liu, Cuiyan Li and Ru Gao
Catalysts 2023, 13(5), 890; https://doi.org/10.3390/catal13050890 - 15 May 2023
Viewed by 1237
Abstract
A flexible CoNi@CNF electrochemical catalyst was developed using coaxial electrostatic spinning technology. The distribution and content of CoNi alloy nanoparticles on the surface of carbon fibers were adjusted by regulating the feed speed ratio of the outer and inner axes of coaxial electrostatic [...] Read more.
A flexible CoNi@CNF electrochemical catalyst was developed using coaxial electrostatic spinning technology. The distribution and content of CoNi alloy nanoparticles on the surface of carbon fibers were adjusted by regulating the feed speed ratio of the outer and inner axes of coaxial electrostatic spinning. The results indicate that the content of the CoNi alloy distributed on the carbon fiber surface increased from 26.7 wt.% to 38.4 wt.% with an increase in the feed speed of the inner axis. However, the excessive precipitation of the CoNi alloy on the carbon fiber surface leads to the segregation of the internal CoNi alloy, which is unfavorable for the exposure of active sites during the electrolytic reaction. The best electrocatalytic performance of the composite was achieved when the rate of the outer axis feed speed was constant (3 mm/h) and the rate of the inner axis was 1.5 mm/h. The initial oxygen reduction potential and half-slope potential were 0.99 V and 0.92 V (VS RHE), respectively. The diffusion-limited current density was 6.31 mA/cm−2 and the current strength retention was 95.2% after the 20,000 s timed current test. Full article
(This article belongs to the Special Issue Tailored Nanosystems and Nanocatalysts for Electrocatalytic Applications)
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19 pages, 2463 KiB  
Article
Revisiting Isothermal Effectiveness Factor Equations for Reversible Reactions
by William Q. Rios, Bruno Antunes, Alírio E. Rodrigues, Inês Portugal and Carlos M. Silva
Catalysts 2023, 13(5), 889; https://doi.org/10.3390/catal13050889 - 15 May 2023
Viewed by 1260
Abstract
Ion exchange resins have many industrial applications, namely as sorbents and catalysts. In solid-catalyzed reactions, intraparticle reaction-diffusion competition is generally described by effectiveness factors calculated numerically or analytically in the case of isothermal particles and simple rate laws. Although robust, numerical calculations can [...] Read more.
Ion exchange resins have many industrial applications, namely as sorbents and catalysts. In solid-catalyzed reactions, intraparticle reaction-diffusion competition is generally described by effectiveness factors calculated numerically or analytically in the case of isothermal particles and simple rate laws. Although robust, numerical calculations can be time-consuming, and convergence is not always guaranteed and lacks the flexibility of user-friendly equations. In this work, analytical equations for effectiveness factors of reversible reactions derived from the general scheme A+B⇌C+D are developed and numerically validated. These effectiveness factors are analytically expressed in terms of an irreversible nth order Thiele modulus (specifically written for the  nth order forward reaction), the thermodynamic equilibrium constant, the ratios of effective diffusivities, and the ratios of surface concentrations. The application of such analytical equations is illustrated for two liquid phase reactions catalyzed by Amberlyst-15, specifically the synthesis of ethyl acetate and acetaldehyde dimethyl acetal. For both reactions, the prediction of the concentration profiles in isothermal batch reactors achieved errors between 1.13% and 3.38% for six distinct experimental conditions. Finally, the impact of non-ideal behavior upon the multicomponent effective diffusivities, subsequently conveyed to the effectiveness factors, is enlightened. Full article
(This article belongs to the Special Issue Advances in the Catalytic Behavior of Ion-Exchange Resins)
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25 pages, 841 KiB  
Review
Advances in Green Synthesis of Metal Oxide Nanoparticles by Marine Algae for Wastewater Treatment by Adsorption and Photocatalysis Techniques
by Ahmed E. Alprol, Abdallah Tageldein Mansour, Abdelwahab M. Abdelwahab and Mohamed Ashour
Catalysts 2023, 13(5), 888; https://doi.org/10.3390/catal13050888 - 15 May 2023
Cited by 13 | Viewed by 2789
Abstract
The use of algae-based green synthesis of metal oxide nanoparticles (MONPs) for bioremediation is an environmentally friendly and cost-effective alternative to conventional approaches. Algal-mediated synthesis offers several benefits over other biogenic processes, such as plants, bacteria, and fungi, including ease of synthesis, scalability, [...] Read more.
The use of algae-based green synthesis of metal oxide nanoparticles (MONPs) for bioremediation is an environmentally friendly and cost-effective alternative to conventional approaches. Algal-mediated synthesis offers several benefits over other biogenic processes, such as plants, bacteria, and fungi, including ease of synthesis, scalability, and rapid synthesis. Algae are readily available in nature, nontoxic, and can produce various types of metal oxide nanoparticles. This approach could significantly accelerate the development of novel algae-nanomaterials with improved properties and performance, leading to more efficient and cost-effective bioremediation of pollutants from water solutions, seawater, and industrial effluent. This review focuses on the biogenic fabrication of metal oxide nanoparticles based on aquatic plants (microalgae and seaweeds) due to their many advantages and attractive applications in pollutant remediation from aqueous solutions. Additionally, photocatalysis is highlighted as a promising tool for the remediation of industrial effluents due to its efficacy, ease of use, quick oxidation, cost-effectiveness, and reduced synthesis of harmful byproducts. Full article
(This article belongs to the Special Issue Advances in the Synthesis and Applications of Transition/Noble Metal Oxide Photocatalysts, 2nd Edition)
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16 pages, 1516 KiB  
Article
The Studies of Sepharose-Immobilized Lipases: Combining Techniques for the Enhancement of Activity and Thermal Stability
by Tomasz Siódmiak, Jacek Dulęba, Gudmundur G. Haraldsson, Joanna Siódmiak and Michał Piotr Marszałł
Catalysts 2023, 13(5), 887; https://doi.org/10.3390/catal13050887 - 15 May 2023
Viewed by 1434
Abstract
Thermal stability is one of the essential parameters characterizing biocatalysts with potential applications in the chemical and pharmaceutical industries. Therefore, it is extremely important to develop standardized procedures for enzyme stability studies. The paper attempts to assess the thermal stability of immobilized lipases [...] Read more.
Thermal stability is one of the essential parameters characterizing biocatalysts with potential applications in the chemical and pharmaceutical industries. Therefore, it is extremely important to develop standardized procedures for enzyme stability studies. The paper attempts to assess the thermal stability of immobilized lipases in aqueous buffers: lipase B from Candida antarctica (CALB) and lipase from Candida rugosa (CRL-OF) immobilized on the Octyl-Sepharose CL-4B carrier. As part of the optimization conditions of the immobilization, the influence of time on the catalytic activity and lipase loading, as well as the effect of temperature on lipase activity (optimal incubation—14 h at 4 °C), was determined. The thermal stability test procedure was carried out for 7 days using a climatic chamber (65 °C) and a refrigerator (4 °C). The studies of immobilized lipases included the assessment of the impact of various solvents (water, citrate buffer, 1,2-dichloropropane—DCP), temperature, light in the visible spectral range (400–800 nm), and additions of calcium ions. The highest value of residual activity (564.5 ± 21.6%) was received by storing the immobilized CALB in citrate buffer (pH 4.0, 500 mM) with the addition of calcium ions (Ca2+). On the other hand, residual activity values for immobilized CRL-OF after storage in the climatic chamber were lower than 5%. A combining of techniques: immobilization onto the support in high ionic strength and low pH, with a technique of extremally high-temperature applied in a climatic chamber, with the addition of Ca2+ allowed to achieve of excellent thermal stability of the immobilized CALB, with increasing of catalytic activity more than five-fold. Additionally, performing studies on the thermal stability of the tested lipases using a climatic chamber seems to be particularly promising in the context of unifying and standardizing storage guidelines, enabling the comparison of results between different laboratories, as well as enhancing catalytic activity. Full article
(This article belongs to the Special Issue Supported Biocatalysts for Sustainable Chemistry)
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15 pages, 7350 KiB  
Article
Highly Active Carbon Material Derived from Carica papaya Fruit Juice: Access to Efficient Photocatalytic Degradation of Methylene Blue in Aqueous Solution under the Illumination of Ultraviolet Light
by Muhammad Ali Bhatti, Elmuez Dawi, Aneela Tahira, Khalida Faryal Almani, Shymaa S. Medany, Ayman Nafady, Zulifqar Ali Solangi, Umair Aftab and Zaffar Hussain Ibhupoto
Catalysts 2023, 13(5), 886; https://doi.org/10.3390/catal13050886 - 14 May 2023
Viewed by 1586
Abstract
Herein, we describe a cost-effective, efficient, sustainable, and environmentally friendly pyrolytic method for the synthesis of highly active carbon materials from Carica papaya fruit juice for the photodegradation of various pollutants, such as methylene blue (MB), in aqueous solutions using ultraviolet (UV) light. [...] Read more.
Herein, we describe a cost-effective, efficient, sustainable, and environmentally friendly pyrolytic method for the synthesis of highly active carbon materials from Carica papaya fruit juice for the photodegradation of various pollutants, such as methylene blue (MB), in aqueous solutions using ultraviolet (UV) light. Various analytical techniques were used to examine the morphology, crystal quality, functional group chemistry, particle size distribution, and optical properties of the materials. For evaluating the performance of the newly prepared carbon material, various photocatalyst parameters were investigated, including initial dye concentration, catalyst dose, pH of dye solution, cyclic stability, and scavenger studies. The obtained findings attest that the optimal degradation efficiency of carbon material for high MB concentrations (2.3 × 10−5 M) is around 98.08%, whereas at low concentrations of MB (1.5 × 10−5 M) it reaches 99.67%. Degradation kinetics indicate that MB degrades in a first-order manner. Importantly, as the pH of the dye solution was adjusted to ~11, the degradation rate increased significantly. The scavenger study indicated that hydroxyl radicals were the predominant species involved in the degradation of MB. In addition, active surface site exposure and charge transfer were strongly associated with efficient MB degradation. On the basis of its performance, this newly developed carbon material may prove to be an excellent alternative and promising photocatalyst for wastewater treatment. Furthermore, the synthetic approach used to produce carbon material from Carica papaya fruit juice may prove useful for the development of a new generation of photoactive materials for environmentally friendly applications, as well as for the production of hydrogen from solar energy. Full article
(This article belongs to the Special Issue UV/Vis/NIR Photocatalysis and Optical Properties)
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