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20 pages, 28759 KiB

Open AccessArticle

The Effect of Composition on the Properties and Application of CuO-NiO Nanocomposites Synthesized Using a Saponin-Green/Microwave-Assisted Hydrothermal Method

by Amnah Al-Yunus, Wafa Al-Arjan, Hassan Traboulsi and Manal Hessien

Int. J. Mol. Sci. 2024, 25(7), 4119; https://doi.org/10.3390/ijms25074119 - 8 Apr 2024

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Abstract

In this study, we explored the formation of CuO nanoparticles, NiO nanoflakes, and CuO-NiO nanocomposites using saponin extract and a microwave-assisted hydrothermal method. Five green synthetic samples were prepared using aqueous saponin extract and a microwave-assisted hydrothermal procedure at 200 °C for 30 [...] Read more.

In this study, we explored the formation of CuO nanoparticles, NiO nanoflakes, and CuO-NiO nanocomposites using saponin extract and a microwave-assisted hydrothermal method. Five green synthetic samples were prepared using aqueous saponin extract and a microwave-assisted hydrothermal procedure at 200 °C for 30 min. The samples were pristine copper oxide (100C), 75% copper oxide–25% nickel oxide (75C25N), 50% copper oxide–50% nickel oxide (50C50N), 25% copper oxide–75% nickel oxide (25C75N), and pristine nickel oxide (100N). The samples were characterized using FT-IR, XRD, XPS, SEM, and TEM. The XRD results showed that copper oxide and nickel oxide formed monoclinic and cubic phases, respectively. The morphology of the samples was useful and consisted of copper oxide nanoparticles and nickel oxide nanoflakes. XPS confirmed the +2 oxidation state of both the copper and nickel ions. Moreover, the optical bandgaps of copper oxide and nickel oxide were determined to be in the range of 1.29–1.6 eV and 3.36–3.63 eV, respectively, and the magnetic property studies showed that the synthesized samples exhibited ferromagnetic and superparamagnetic properties. In addition, the catalytic activity was tested against para-nitrophenol, demonstrating that the catalyst efficiency gradually improved in the presence of CuO. The highest rate constants were obtained for the 100C and 75C25N samples, with catalytic efficiencies of 98.7% and 78.2%, respectively, after 45 min. Full article

(This article belongs to the Special Issue Advanced Catalytic Materials)

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18 pages, 3076 KiB

Open AccessArticle

The Effect of Water Co-Feeding on the Catalytic Performance of Zn/HZSM-5 in Ethylene Aromatization Reactions

by Jiabei Shao, Pengcheng Feng, Baichao Li, Jie Gao, Yanyan Chen, Mei Dong, Zhangfeng Qin, Weibin Fan and Jianguo Wang

Int. J. Mol. Sci. 2024, 25(4), 2387; https://doi.org/10.3390/ijms25042387 - 17 Feb 2024

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Abstract

During the methanol-to-aromatics (MTA) process, a large amount of water is generated, while the influence and mechanism of water on the activity and selectivity of the light olefin aromatization reaction are still unclear. Therefore, a study was conducted to systematically investigate the effects [...] Read more.

During the methanol-to-aromatics (MTA) process, a large amount of water is generated, while the influence and mechanism of water on the activity and selectivity of the light olefin aromatization reaction are still unclear. Therefore, a study was conducted to systematically investigate the effects of water on the reactivity and the product distribution in ethylene aromatization using infrared spectroscopy (IR), intelligent gravitation analyzer (IGA), and X-ray absorption fine structure (XAFS) characterizations. The results demonstrated that the presence of water reduced ethylene conversion and aromatic selectivity while increasing hydrogen selectivity at the same contact time. This indicated that water had an effect on the reaction pathway by promoting the dehydrogenation reaction and suppressing the hydrogen transfer reaction. A detailed analysis using linear combination fitting (LCF) of Zn K-edge X-ray absorption near-edge spectroscopy (XANES) on Zn/HZSM-5 catalysts showed significant variations in the state of existence and the distribution of Zn species on the deactivated catalysts, depending on different reaction atmospheres and water contents. The presence of water strongly hindered the conversion of ZnOH⁺ species, which served as the active centers for the dehydrogenation reaction, to ZnO on the catalyst. As a result, the dehydrogenation activity remained high in the presence of water. This study using IR and IGA techniques revealed that water on the Zn/HZSM-5 catalyst inhibited the adsorption of ethylene on the zeolite, resulting in a noticeable decrease in ethylene conversion and a decrease in aromatic selectivity. These findings contribute to a deeper understanding of the aromatization reaction process and provide data support for the design of efficient aromatization catalysts. Full article

(This article belongs to the Special Issue Advanced Catalytic Materials)

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16 pages, 5234 KiB

Open AccessArticle

Construction of a g-C₃N₄/Bi(OH)₃ Heterojunction for the Enhancement of Visible Light Photocatalytic Antibacterial Activity

by Jian Feng, Li Wang, Bo Xiao, Xia Ran, Caiying Wang, Jinming Zhu, Zuoji Liu, Chaozhong Li, Xinai Cui, Rong Li, Guangwei Feng and Zeqin Dai

Int. J. Mol. Sci. 2024, 25(3), 1872; https://doi.org/10.3390/ijms25031872 - 3 Feb 2024

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Abstract

Photocatalytic technology has been recently conducted to remove microbial contamination due to its unique features of nontoxic by-products, low cost, negligible microbial resistance and broad-spectrum elimination capacity. Herein, a novel two dimensional (2D) g-C₃N₄/Bi(OH)₃ (CNB) heterojunction was fabricated [...] Read more.

Photocatalytic technology has been recently conducted to remove microbial contamination due to its unique features of nontoxic by-products, low cost, negligible microbial resistance and broad-spectrum elimination capacity. Herein, a novel two dimensional (2D) g-C₃N₄/Bi(OH)₃ (CNB) heterojunction was fabricated byincorporating Bi(OH)₃ (BOH) nanoparticles with g-C₃N₄ (CN) nanosheets. This CNB heterojunction exhibited high photocatalytic antibacterial efficiency (99.3%) against Escherichia coli (E. coli) under visible light irradiation, which was 4.3 and 3.4 times that of BOH (23.0%) and CN (28.0%), respectively. The increase in specific surface area, ultra-thin layered structure, construction of a heterojunction and enhancement of visible light absorption were conducive to facilitating the separation and transfer of photoinduced charge carriers. Live/dead cell staining, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) assays and scanning electron microscopy (SEM) have been implemented to investigate the damage to the cell membrane and the leakage of the intracellular protein in the photocatalytic antibacterial process. The e⁻, h⁺ and O₂^•− were the active species involved in this process. This study proposed an appropriate photocatalyst for efficient treatment of bacterial contamination. Full article

(This article belongs to the Special Issue Advanced Catalytic Materials)

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13 pages, 2425 KiB

Open AccessArticle

Nanoparticulated WO₃/NiWO₄ Using Cellulose as a Template and Its Application as an Auxiliary Co-Catalyst to Pt for Ethanol and Glycerol Electro-Oxidation

by Munique G. Guimarães, Julio L. Macedo, José J. Linares and Grace F. Ghesti

Int. J. Mol. Sci. 2024, 25(2), 685; https://doi.org/10.3390/ijms25020685 - 5 Jan 2024

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Abstract

This work reports the use of cellulose as a template to prepare nanosized WO₃ or NiWO₄ and its application as a co-catalyst in the electro-oxidation of ethanol and glycerol. Microcrystalline cellulose was hydrolyzed with phosphotungstic acid (H₃PW₁₂O [...] Read more.

This work reports the use of cellulose as a template to prepare nanosized WO₃ or NiWO₄ and its application as a co-catalyst in the electro-oxidation of ethanol and glycerol. Microcrystalline cellulose was hydrolyzed with phosphotungstic acid (H₃PW₁₂O₄₀) to prepare the nanocrystalline cellulose template. The latter was air-calcinated to remove the template and obtain nanometric WO₃. Tungsten oxide was impregnated with Ni(NO₃)₂, which was subsequently air-calcinated to obtain the nanometric NiWO₄. Elemental analysis confirmed the coexistence of nickel and tungsten, whereas thermal analysis evidenced a high thermal stability for these materials. The X-ray diffractograms displayed crystal facets of WO₃ and, when Ni(II) was added, NiWO₄. The transmission electron micrographs corroborated the formation of nanosized particles with average particle sizes in the range of 30 to 50 nm. Finally, to apply this material, Pt/WO₃-C and Pt/WO₃-NiWO₄-C were prepared and used in ethanol and glycerol electro-oxidation in an alkaline medium, observing a promotional effect of the oxide and tungstate by reducing the onset potential and increasing the current density. These materials show great potential to produce clean electricity or green hydrogen, contributing to energetic transition. Full article

(This article belongs to the Special Issue Advanced Catalytic Materials)

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13 pages, 2368 KiB

Open AccessArticle

The Facile Synthesis of a Re-Complex Heterogeneous Catalysis System for Enhancing CO₂ Photoreduction Activity

by Bo Li, Hang Li, Shiyan Liang, Jiaao Cheng, Xin Zhong, Yifan Chen and Yujie Song

Int. J. Mol. Sci. 2023, 24(13), 11106; https://doi.org/10.3390/ijms241311106 - 5 Jul 2023

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Abstract

fac-Re(2,2’-bipyridine)(CO)₃Cl] (denoted as ReCC) is an efficient molecule-catalyst with high selectivity in the photoreduction of CO₂ to CO in a homogeneous system. However, the two major drawbacks of Re(I) complexes in the homogeneous system, easy degradation and difficult separation, [...] Read more.

fac-Re(2,2’-bipyridine)(CO)₃Cl] (denoted as ReCC) is an efficient molecule-catalyst with high selectivity in the photoreduction of CO₂ to CO in a homogeneous system. However, the two major drawbacks of Re(I) complexes in the homogeneous system, easy degradation and difficult separation, seriously hinder its development in the field of industrial applications. In this paper, we designed and prepared two different Re-complex fixation systems (denoted as ReCC@TiO₂-5 wt% and ReCC-TiO₂-5 wt%) based on TiO₂ gel via the sensitization method and sol–gel method, respectively. Compared with a pure ReCC complex, both of them exhibited excellent photocatalytic reduction activity. In particular, the sol–gel hybrid system (ReCC-TiO₂-5 wt%) displayed outstanding positive synergistic effects on the photocatalytic activity and the long durability of the photocatalytic process. A series of characterizations were carried out to explore the probable photocatalytic reduction process mechanism, which provides the theoretical basis and technical support for the Re complex fixation method. Full article

(This article belongs to the Special Issue Advanced Catalytic Materials)

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16 pages, 5494 KiB

Open AccessArticle

Boosting the Photocatalysis of Plasmonic Au-Cu Nanocatalyst by AuCu-TiO₂ Interface Derived from O₂ Plasma Treatment

by Bin Zhu, Xue Li, Yecheng Li, Jinglin Liu and Xiaomin Zhang

Int. J. Mol. Sci. 2023, 24(13), 10487; https://doi.org/10.3390/ijms241310487 - 22 Jun 2023

Cited by 3 | Viewed by 895

Abstract

Plasmonic gold (Au) and Au-based nanocatalysts have received significant attention over the past few decades due to their unique visible light (VL) photocatalytic features for a wide variety of chemical reactions in the fields of environmental protection. However, improving their VL photocatalytic activity [...] Read more.

Plasmonic gold (Au) and Au-based nanocatalysts have received significant attention over the past few decades due to their unique visible light (VL) photocatalytic features for a wide variety of chemical reactions in the fields of environmental protection. However, improving their VL photocatalytic activity via a rational design is prevalently regarded as a grand challenge. Herein we boosted the VL photocatalysis of the TiO₂-supported Au-Cu nanocatalyst by applying O₂ plasma to treat this bimetallic plasmonic nanocatalyst. We found that O₂ plasma treatment led to a strong interaction between the Au and Cu species compared with conventional calcination treatment. This interaction controlled the size of plasmonic metallic nanoparticles and also contributed to the construction of AuCu-TiO₂ interfacial sites by forming AuCu alloy nanoparticles, which, thus, enabled the plasmonic Au-Cu nanocatalyst to reduce the Schottky barrier height and create numbers of highly active interfacial sites. The catalyst’s characterizations and density functional theory (DFT) calculations demonstrated that boosted VL photocatalytic activity over O₂ plasma treated Au-Cu/TiO₂ nanocatalyst arose from the favorable transfer of hot electrons and a low barrier for the reaction between CO and O with the construction of large numbers of AuCu-TiO₂ interfacial sites. This work provides an efficient approach for the rational design and development of highly active plasmonic Au and Au-based nanocatalysts and deepens our understanding of their role in VL photocatalytic reactions. Full article

(This article belongs to the Special Issue Advanced Catalytic Materials)

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12 pages, 2472 KiB

Open AccessArticle

Thermally Stable and Reusable Silica and Nano-Fructosome Encapsulated CalB Enzyme Particles for Rapid Enzymatic Hydrolysis and Acylation

by Woo Young Jang, Jung Hoon Sohn and Jeong Ho Chang

Int. J. Mol. Sci. 2023, 24(12), 9838; https://doi.org/10.3390/ijms24129838 - 7 Jun 2023

Cited by 2 | Viewed by 997

Abstract

This study reports the preparation of silica-coated and nano-fructosome encapsulated Candida antarctica lipase B particles (CalB@NF@SiO₂) and a demonstration of their enzymatic hydrolysis and acylation. CalB@NF@SiO₂ particles were prepared as a function of TEOS concentration (3–100 mM). Their mean particle [...] Read more.

This study reports the preparation of silica-coated and nano-fructosome encapsulated Candida antarctica lipase B particles (CalB@NF@SiO₂) and a demonstration of their enzymatic hydrolysis and acylation. CalB@NF@SiO₂ particles were prepared as a function of TEOS concentration (3–100 mM). Their mean particle size was 185 nm by TEM. Enzymatic hydrolysis was performed to compare catalytic efficiencies of CalB@NF and CalB@NF@SiO₂. The catalytic constants (K_m, V_max, and K_cat) of CalB@NF and CalB@NF@SiO₂ were calculated using the Michaelis–Menten equation and Lineweaver–Burk plot. Optimal stability of CalB@NF@SiO₂ was found at pH 8 and a temperature of 35 °C. Moreover, CalB@NF@SiO₂ particles were reused for seven cycles to evaluate their reusability. In addition, enzymatic synthesis of benzyl benzoate was demonstrated via an acylation reaction with benzoic anhydride. The efficiency of CalB@NF@SiO₂ for converting benzoic anhydride to benzyl benzoate by the acylation reaction was 97%, indicating that benzoic anhydride was almost completely converted to benzyl benzoate. Consequently, CalB@NF@SiO₂ particles are better than CalB@NF particles for enzymatic synthesis. In addition, they are reusable with high stability at optimal pH and temperature. Full article

(This article belongs to the Special Issue Advanced Catalytic Materials)

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15 pages, 8939 KiB

Open AccessArticle

Application of RSM Method for Optimization of Geraniol Transformation Process in the Presence of Garnet

by Anna Fajdek-Bieda, Andrzej Perec and Aleksandra Radomska-Zalas

Int. J. Mol. Sci. 2023, 24(3), 2689; https://doi.org/10.3390/ijms24032689 - 31 Jan 2023

Cited by 2 | Viewed by 1126

Abstract

This paper presents the results of tests obtained for the transformation of geraniol in the presence of garnet as a catalyst by the response surface method (RSM). The method analyzed the influence of the following parameters: a temperature of 50–150 °C, a catalyst [...] Read more.

This paper presents the results of tests obtained for the transformation of geraniol in the presence of garnet as a catalyst by the response surface method (RSM). The method analyzed the influence of the following parameters: a temperature of 50–150 °C, a catalyst concentration (garnet) of 1.0–10.0 wt% and a reaction time of 0.25–24 h. Response functions included the conversion of geraniol (GA), selectivity for conversion to neral (NE) and selectivity for conversion to citronellol (CL). In addition, the influence of all control parameters on each of the response parameters is presented in the form of second-order polynomials. The optimal parameters of the geraniol transformation process were a temperature of 55 °C, a catalyst concentration of 5 wt% and a reaction time of 2 h, for which high values of the GA conversion function and the selectivity of conversion to NE and CL were obtained. For the GA conversion, the optimum was obtained at 94 mol% at 60 °C, a catalyst concentration of 5.0 wt% and a reaction time of 2 h. For NE selectivity, the optimum value was reached at 49 mol% at 60 °C, a catalyst concentration equal to 2.5 (5.0) wt% mole and a reaction time of almost 2 h. For CL selectivity, the optimum value of 49 mol% was obtained for control factors: a temperature equal to 20 °C, a catalyst concentration equal to 5.0 wt% and a response time equal to 2 h. The optimal set of control factors for all power factors is characterized by a temperature of 55 °C, a catalyst concentration of 5 wt% and a reaction time of 2 h. Full article

(This article belongs to the Special Issue Advanced Catalytic Materials)

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9 pages, 1923 KiB

Open AccessArticle

Influence of Lanthanum Precursor on the Activity of Nickel Catalysts in the Mixed-Methane Reforming Process

by Mateusz Zakrzewski, Oleksandr Shtyka, Jacek Rogowski, Radoslaw Ciesielski, Adam Kedziora and Tomasz Maniecki

Int. J. Mol. Sci. 2023, 24(2), 975; https://doi.org/10.3390/ijms24020975 - 4 Jan 2023

Cited by 1 | Viewed by 1229

Abstract

This work investigated the influence of the catalytic support precursor on the activity of nickel catalysts 20%Ni/5%La₂O₃–95%Al₂O₃ in the mixed methane reforming process. The activity tests were carried out at a temperature of 750 °C. The [...] Read more.

This work investigated the influence of the catalytic support precursor on the activity of nickel catalysts 20%Ni/5%La₂O₃–95%Al₂O₃ in the mixed methane reforming process. The activity tests were carried out at a temperature of 750 °C. The research showed that the catalyst prepared from the precursor containing chloride exhibited very low conversions of methane and carbon dioxide. The poisoned catalyst system before and after the calcination process was subjected to Temperature Programmed Surface Reaction tests to determine whether the thermal treatment causes a decrease in the amount of chlorine in the system. To determine the decomposition temperature of the LaCl₃ precursor and the nickel chloride NiCl₂ compound, the samples were analyzed by Thermogravimetry. Finally, the catalytic samples were tested by Time-of-Flight Secondary Ion Mass Spectrometry analysis to confirm the presence of nickel–chlorine bonds on the surface of the catalytic system. Full article

(This article belongs to the Special Issue Advanced Catalytic Materials)

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