Nanomaterials

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16 pages, 4046 KiB

Open AccessFeature PaperArticle

Kinetic Analysis of 4-Nitrophenol Reduction by “Water-Soluble” Palladium Nanoparticles

by Anas Iben Ayad, Denis Luart, Aissa Ould Dris and Erwann Guénin

Nanomaterials 2020, 10(6), 1169; https://doi.org/10.3390/nano10061169 - 15 Jun 2020

Cited by 79 | Viewed by 4823

The most important model catalytic reaction to test the catalytic activity of metal nanoparticles is the reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride as it can be precisely monitored by UV–vis spectroscopy with high accuracy. This work presents the catalytic reduction of [...] Read more.

The most important model catalytic reaction to test the catalytic activity of metal nanoparticles is the reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride as it can be precisely monitored by UV–vis spectroscopy with high accuracy. This work presents the catalytic reduction of 4-nitrophenol (4-Nip) to 4-aminophenol (4-Amp) in the presence of Pd nanoparticles and sodium borohydride as reductants in water. We first evaluate the kinetics using classical pseudo first-order kinetics. We report the effects of different initial 4-Nip and NaBH₄ concentrations, reaction temperatures, and mass of Pd nanoparticles used for catalytic reduction. The thermodynamic parameters (activation energy, enthalpy, and entropy) were also determined. Results show that the kinetics are highly dependent on the reactant ratio and that pseudo first-order simplification is not always fit to describe the kinetics of the reaction. Assuming that all steps of this reaction proceed only on the surface of Pd nanoparticles, we applied a Langmuir−Hinshelwood model to describe the kinetics of the reaction. Experimental data of the decay rate of 4-nitrophenol were successfully fitted to the theoretical values obtained from the Langmuir–Hinshelwood model and all thermodynamic parameters, the true rate constant k, as well as the adsorption constants of 4-Nip, and BH₄⁻ (K_4-Nip and K_BH4−) were determined for each temperature. Full article

(This article belongs to the Special Issue Nanocatalysts in Chemistry: Synthesis and Applications)

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11 pages, 3864 KiB

Open AccessArticle

Facile Preparation and Highly Efficient Catalytic Performances of Pd-Cu Bimetallic Catalyst Synthesized via Seed-Mediated Method

by Fangke Zhan, Juanjuan Yin, Jingxin Zhou, Tifeng Jiao, Lexin Zhang, Meirong Xia, Zhenhua Bai and Qiuming Peng

Nanomaterials 2020, 10(1), 6; https://doi.org/10.3390/nano10010006 - 18 Dec 2019

Cited by 34 | Viewed by 3803

Abstract

With the rapid development of industry, the problem of environmental pollution has become increasingly prominent. Exploring and preparing green, efficient, and low cost catalysts has become the key challenge for scientists. However, some conventional preparation methods are limited by conditions, such as cumbersome [...] Read more.

With the rapid development of industry, the problem of environmental pollution has become increasingly prominent. Exploring and preparing green, efficient, and low cost catalysts has become the key challenge for scientists. However, some conventional preparation methods are limited by conditions, such as cumbersome operation, high energy consumption, and high pollution. Here, a simple and efficient seed-mediated method was designed and proposed to synthesize a highly efficient bimetallic catalyst for catalyzing nitro compounds. A Pd-Cu bimetallic composite (BCM) can be prepared by synthesizing the original seed crystal of precious metal palladium, then growing the mature nanocrystalline palladium and supporting the transition metal copper. Importantly, after eight consecutive catalytic cycles, the conversion of the catalyzed 2-NA was 84%, while the conversion of the catalyzed 4-NP was still 72%. And the catalytic first order rates of 2-NA and 4-NP constants were 0.015 s⁻¹, and 0.069 s⁻¹, respectively. Therefore, current research of nanocomposites catalyst showed great significance for serious environmental pollution problems and the protection of living environment, providing a new idea for the preparation of new bimetallic catalytic materials. Full article

(This article belongs to the Special Issue Nanocatalysts in Chemistry: Synthesis and Applications)

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11 pages, 2946 KiB

Open AccessArticle

Preparation of a Pd/Al₂O₃ Catalyst with Microwave-Induced Plasma Jet Irradiation under Atmospheric Pressure

by Jai Young Chung, Satoshi Kodama and Hidetoshi Sekiguchi

Nanomaterials 2019, 9(12), 1734; https://doi.org/10.3390/nano9121734 - 5 Dec 2019

Cited by 10 | Viewed by 3372

Abstract

Microwave-induced plasma under atmospheric pressure is an effective technique for catalyst preparation. A Pd/Al₂O₃ catalyst was prepared using a fixed bed with microwave plasma irradiation. The activity of the catalyst was compared with that of catalysts made using the plasma [...] Read more.

Microwave-induced plasma under atmospheric pressure is an effective technique for catalyst preparation. A Pd/Al₂O₃ catalyst was prepared using a fixed bed with microwave plasma irradiation. The activity of the catalyst was compared with that of catalysts made using the plasma spouted bed and the conventional furnace. From the results of X-ray powder diffraction (XRD) spectra and transmission electron microscopy (TEM) images, plasma treatment induced a rapid reduction process (PdO→Pd). Moreover, the plasma treatment derived the growth of a different facet from Pd (111) to Pd (100). A different kind of phase transition behavior was observed with plasma-treated alumina. H₂ chemisorption analysis confirmed that the plasma treatment had a positive effect on the dispersion of Pd metal on the support. These improvements to the properties of the catalyst resulted in excellent performance in hydrogenation of acetylene. Full article

(This article belongs to the Special Issue Nanocatalysts in Chemistry: Synthesis and Applications)

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12 pages, 3846 KiB

Open AccessArticle

Reusable Surface-Modified Bacterial Cellulose Based on Atom Transfer Radical Polymerization Technology with Excellent Catalytic Properties

by Xin Li, Quan Feng, Dawei Li, Narh Christopher, Huizhen Ke and Qufu Wei

Nanomaterials 2019, 9(10), 1443; https://doi.org/10.3390/nano9101443 - 11 Oct 2019

Cited by 3 | Viewed by 2738

Abstract

The high catalytic activity of membrane-binding gold nanoparticles (AuNPs) makes its application in oxidation or reduction an attractive challenge. Herein, surface-functionalized bacterial cellulose (BC-poly(HEMA)) was successfully prepared with 2-hydroxyethyl methacrylate (HEMA) as monomers via the atom transfer radical polymerization (ATRP) method. BC-poly(HEMA) was [...] Read more.

The high catalytic activity of membrane-binding gold nanoparticles (AuNPs) makes its application in oxidation or reduction an attractive challenge. Herein, surface-functionalized bacterial cellulose (BC-poly(HEMA)) was successfully prepared with 2-hydroxyethyl methacrylate (HEMA) as monomers via the atom transfer radical polymerization (ATRP) method. BC-poly(HEMA) was further utilized as not only reducing agent but also carrier for uniform distribution of the AuNPs in the diameter of about 8 nm on the membrane surface during the synthesis stage. The synthesized AuNPs/BC-poly(HEMA) exhibited excellent catalytic activity and reusability for reducing 4-nitrophenol (4-NP) from NaBH₄. The results proved that the catalytic performance of AuNPs/BC-poly(HEMA) was affected by the surrounding temperature and pH, and AuNPs/BC-poly(HEMA) maintained the extremely high catalytic activity of AuNPs/BC-poly(HEMA) even after 10 reuses. In addition, no 4-NP was detected in the degradation solution after being stored for 45 days. The reusable catalyst prepared by this work shows a potential industrial application prospect. Full article

(This article belongs to the Special Issue Nanocatalysts in Chemistry: Synthesis and Applications)

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11 pages, 2193 KiB

Open AccessArticle

Preparation of Pd/C by Atmospheric-Pressure Ethanol Cold Plasma and Its Preparation Mechanism

by Zhuang Li, Jingsen Zhang, Hongyang Wang, Zhihui Li, Xiuling Zhang and Lanbo Di

Nanomaterials 2019, 9(10), 1437; https://doi.org/10.3390/nano9101437 - 10 Oct 2019

Cited by 5 | Viewed by 2906

Abstract

Treatment with atmospheric-pressure (AP) hydrogen cold plasma is an effective method for preparing highly active supported metal catalytic materials. However, this technique typically uses H₂ as working gas, which is explosive and difficult to transport. This study proposes the use of PdCl [...] Read more.

Treatment with atmospheric-pressure (AP) hydrogen cold plasma is an effective method for preparing highly active supported metal catalytic materials. However, this technique typically uses H₂ as working gas, which is explosive and difficult to transport. This study proposes the use of PdCl₂ as a Pd precursor and activated carbon as the support to fabricate Pd/C catalytic materials (Pd/C-EP-Ar) by using ethanol—which is renewable, easily stored, and safe—combined with AP cold plasma (AP ethanol cold plasma) followed by calcination in Ar gas at 550 °C for 2 h. Both Pd/C-EP and Pd/C-HP fabricated using AP ethanol and hydrogen cold plasma (without calcination in Ar gas) respectively, exhibit low CO oxidation reactivity. The activity of Pd/C-EP is lower than Pd/C-HP, which is mainly ascribed to the carbon layer formed by ethanol decomposition during plasma treatment. However, the 100% CO conversion temperature (T₁₀₀) of Pd/C-EP-Ar is 140 °C, which is similar to that of Pd/C-HP-Ar fabricated using AP hydrogen cold plasma (calcined in Ar gas at 550 °C for 2 h). The characterization results of X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy indicated that the carbon layer formed by ethanol decomposition enhanced the interaction of metal nanoparticles to the support, and a high Pd/C atomic ratio was obtained. This was beneficial to the high CO oxidation performance. This work provides a safe method for synthesizing high-performance Pd/C catalytic materials avoiding the use of H₂, which is explosive and difficult to transport. Full article

(This article belongs to the Special Issue Nanocatalysts in Chemistry: Synthesis and Applications)

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11 pages, 3632 KiB

Open AccessArticle

Short-Time Hydrothermal Synthesis of CuBi₂O₄ Nanocolumn Arrays for Efficient Visible-Light Photocatalysis

by Yi Wang, Fang Cai, Pengran Guo, Yongqian Lei, Qiaoyue Xi and Fuxian Wang

Nanomaterials 2019, 9(9), 1257; https://doi.org/10.3390/nano9091257 - 5 Sep 2019

Cited by 27 | Viewed by 9914

Abstract

In this article, a short-time hydrothermal method is developed to prepare CuBi₂O₄ nanocolumn arrays. By using Bi(NO₃)₃·5H₂O in acetic acid and Cu(NO₃)₂·3H₂O in ethanol as precursor solutions, tetragonal [...] Read more.

In this article, a short-time hydrothermal method is developed to prepare CuBi₂O₄ nanocolumn arrays. By using Bi(NO₃)₃·5H₂O in acetic acid and Cu(NO₃)₂·3H₂O in ethanol as precursor solutions, tetragonal CuBi₂O₄ with good visible light absorption can be fabricated within 0.5 h at 120 °C. Tetragonal structured CuBi₂O₄ can be formed after 15 min hydrothermal treatment, however it possesses poor visible light absorption and low photocatalytic activity. Extending the hydrothermal treatment duration to 0.5 h results in a significant improvement invisible light absorption of the tetragonal CuBi₂O₄. The CuBi₂O₄ obtained through 0.5 h hydrothermal synthesis shows a band gap of 1.75 eV and exhibits the highest photocatalytic performance among the CuBi₂O₄ prepared with various hydrothermal time. The removal rate of methylene blue by the 0.5 h CuBi₂O₄ reaches 91% under visible light irradiation for 0.5 h. This study proposes a novel strategy to prepare photoactive CuBi₂O₄ nanocolumn arrays within 0.5 h at a moderate temperature of 120 °C. The hydrothermal method provides a facile strategy for the fast synthesis of metal-oxide-based photocatalysts at mild reaction conditions. Full article

(This article belongs to the Special Issue Nanocatalysts in Chemistry: Synthesis and Applications)

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10 pages, 3658 KiB

Open AccessArticle

Facile Synthesis of Pd Nanocubes with Assistant of Iodide and Investigation of Their Electrocatalytic Performances Towards Formic Acid Oxidation

by Xuan Liu, Zichao Li, Kuankuan Wang, Luming Zhou, Xihui Zhao, Wenhai Jiang, Qun Li and Yujia Deng

Nanomaterials 2019, 9(3), 375; https://doi.org/10.3390/nano9030375 - 5 Mar 2019

Cited by 11 | Viewed by 4663

Abstract

This article presents a facile, one-pot method using the aqueous phase for the synthesis of high-quality Pd nanocubes. In this study, Pd chloride was used as the precursor, sodium iodide as capping agent, and poly(vinylpyrrolidone) as surfactant and reducing agent. The effects of [...] Read more.

This article presents a facile, one-pot method using the aqueous phase for the synthesis of high-quality Pd nanocubes. In this study, Pd chloride was used as the precursor, sodium iodide as capping agent, and poly(vinylpyrrolidone) as surfactant and reducing agent. The effects of different halogens on the morphology of Pd nanocrystals were investigated. The results showed that, in this synthesis system, the selection and proper amount of sodium iodide was essential to the preparation of high-quality Pd nanocubes. When iodide was replaced by other halogens (such as bromide and chloride), Pd nanocrystals with cubic morphology could not be obtained. In addition, we have found that NaBH₄ can be used to efficiently remove inorganic covers, such as iodide, from the surface of Pd nanoparticles as synthesized. The Pd nanoparticles obtained were employed as electro-catalysts for formic acid oxidation, and they exhibited excellent catalytic activity and good stability towards this reaction. Full article

(This article belongs to the Special Issue Nanocatalysts in Chemistry: Synthesis and Applications)

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7 pages, 3671 KiB

Open AccessArticle

A Simple and Fast Method to Synthesize Cubic Iridium Nanoparticles with Clean Surface Free from Surfactants

by Rongrong Zhang, Xuan Liu, Litong Shi, Xin Jin, Yanchao Dong, Kang Li, Xihui Zhao, Qun Li and Yujia Deng

Nanomaterials 2019, 9(1), 76; https://doi.org/10.3390/nano9010076 - 8 Jan 2019

Cited by 14 | Viewed by 4767

Abstract

Cubic Iridium nanoparticles without any surfactants on the surface have been synthesized successfully in this work. The process of synthesis was quite simple by just injecting one drop of 400 µL solution containing Iridium precursor onto Cu foil (1 cm × 1 cm), [...] Read more.

Cubic Iridium nanoparticles without any surfactants on the surface have been synthesized successfully in this work. The process of synthesis was quite simple by just injecting one drop of 400 µL solution containing Iridium precursor onto Cu foil (1 cm × 1 cm), and through galvanic reaction between the Ir precursor and Cu foil, the cubic Iridium nanoparticle could be obtained quite quickly (<30 s). The Cu foil played the roles of both reducing agent and substrate. This method could also be employed to synthesize cubic nanoparticles of other Pt-group metals such as Rh. By employing this method, cubic metal nanoparticles with surfactant-free surfaces could be produced economically and efficiently, and as a result, a realistic relationship between structure and catalytic activity could be established. Full article

(This article belongs to the Special Issue Nanocatalysts in Chemistry: Synthesis and Applications)

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11 pages, 4441 KiB

Open AccessArticle

Controllable Synthesis and Catalytic Performance of Gold Nanoparticles with Cucurbit[n]urils (n = 5–8)

by Liangfeng Zhang, Simin Liu, Yuhua Wang, Haijun Zhang and Feng Liang

Nanomaterials 2018, 8(12), 1015; https://doi.org/10.3390/nano8121015 - 6 Dec 2018

Cited by 21 | Viewed by 4306

Abstract

A series of gold nanoparticles (AuNPs) was prepared in situ with different cucurbit[n]urils (CB[n]s) in an alkaline aqueous solution. The nanoparticle sizes can be well controlled by CB[n]s (n = 5, 6, 7, [...] Read more.

A series of gold nanoparticles (AuNPs) was prepared in situ with different cucurbit[n]urils (CB[n]s) in an alkaline aqueous solution. The nanoparticle sizes can be well controlled by CB[n]s (n = 5, 6, 7, 8) with different ring sizes. The packing densities of CB[5–8] and free surface area on AuNPs were determined. A direct relationship was found between the ring size and packing density of CB[n]s with respect to the AuNP-catalyzed reduction of 4-nitrophenol in the presence of NaBH₄. The larger particle size and higher surface coverage of bigger CB[n]-capped AuNPs significantly decreased the catalytic activity. Furthermore, this work could lead to new applications that utilize AuNPs under an overlayer of CB[n]s for catalysis, sensing, and drug delivery. Full article

(This article belongs to the Special Issue Nanocatalysts in Chemistry: Synthesis and Applications)

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