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Catalysts, Volume 1, Issue 1 (December 2011), Pages 1-190

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Editorial

Jump to: Research, Review

Open AccessEditorial Welcome to Catalysts––A New Open Access Journal for a Growing Scientific Community
Catalysts 2011, 1(1), 1-2; doi:10.3390/catal1010001
Received: 27 April 2011 / Published: 9 May 2011
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Abstract
There is something intrinsically fascinating about catalysts. The thought that a material can speed up a reaction by hundreds or thousands of times without being consumed is truly amazing. I frequently have the pleasure of teaching undergraduate and graduate chemical reaction engineering [...] Read more.
There is something intrinsically fascinating about catalysts. The thought that a material can speed up a reaction by hundreds or thousands of times without being consumed is truly amazing. I frequently have the pleasure of teaching undergraduate and graduate chemical reaction engineering courses that include sections on catalysts. I have found that students take an immediate interest in catalysts and are fascinated by how they work. I certainly have been captivated with catalysts myself, as I have devoted my entire academic career to studying their properties. [...] Full article

Research

Jump to: Editorial, Review

Open AccessArticle Role of the Support Effects on the Catalytic Activity of Gold Clusters: A Density Functional Theory Study
Catalysts 2011, 1(1), 18-39; doi:10.3390/catal1010018
Received: 6 October 2011 / Revised: 31 October 2011 / Accepted: 16 November 2011 / Published: 17 November 2011
Cited by 20 | PDF Full-text (4231 KB) | HTML Full-text | XML Full-text
Abstract
It is demonstrated that the support effects play a crucial role in the gold nanocatalysis. Two types of support are considered—the “inert” support of hexagonal boron nitride (h-BN) with the N and B vacancy defects and the “active” support of rutile TiO [...] Read more.
It is demonstrated that the support effects play a crucial role in the gold nanocatalysis. Two types of support are considered—the “inert” support of hexagonal boron nitride (h-BN) with the N and B vacancy defects and the “active” support of rutile TiO2(110). It is demonstrated that Au and Au2 can be trapped effectively by the vacancy defects in h-BN. In that case, the strong adsorption on the surface defects is accompanied by the charge transfer to/from the adsorbate. The excess of the positive or negative charge on the supported gold clusters can considerably promote their catalytic activity. Therefore gold clusters supported on the defected h-BN surface can not be considered as pseudo-free clusters. We also demonstrate that the rutile TiO2(110) support energetically promotes H2 dissociation on gold clusters. We show that the formation of the OH group near the supported gold cluster is an important condition for H2 dissociation. We demonstrate that the active sites towards H2 dissociation on the supported Aun are located at corners and edges of the gold cluster in the vicinity of the low coordinated oxygen atoms on TiO2(110). Thus catalytic activity of a gold nanoparticle supported on the rutile TiO2(110) surface is proportional to the length of the perimeter interface between the nanoparticle and the support. Full article
(This article belongs to the Special Issue Gold Catalysts)
Open AccessArticle Gold Functionalized Supported Ionic Liquids Catalyst for CO Oxidation
Catalysts 2011, 1(1), 52-68; doi:10.3390/catal1010052
Received: 21 September 2011 / Revised: 17 October 2011 / Accepted: 17 November 2011 / Published: 25 November 2011
Cited by 2 | PDF Full-text (755 KB) | HTML Full-text | XML Full-text
Abstract
The present study tries to give an insight to the combination of the homogeneous and heterogeneous catalytic properties in a new class of materials. Well dispersed gold nanoparticles on an ionic liquid layer supported on a mineral carrier have been prepared. This [...] Read more.
The present study tries to give an insight to the combination of the homogeneous and heterogeneous catalytic properties in a new class of materials. Well dispersed gold nanoparticles on an ionic liquid layer supported on a mineral carrier have been prepared. This work is concentrated on the characterizations and understanding of the interactions between all the components of the catalytic system. The application of the materials in the reaction of oxidation of carbon monoxide shows rather unexpected results—a good catalytic activity completely independent of the temperature. Full article
(This article belongs to the Special Issue Gold Catalysts)
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Open AccessArticle In Situ Synthesis of Bimetallic Hybrid Nanocatalysts on a Paper-Structured Matrix for Catalytic Applications
Catalysts 2011, 1(1), 69-82; doi:10.3390/catal1010069
Received: 25 September 2011 / Revised: 14 November 2011 / Accepted: 18 November 2011 / Published: 25 November 2011
Cited by 9 | PDF Full-text (1236 KB) | HTML Full-text | XML Full-text
Abstract
Bimetallic nanoparticles have attracted significant attention as their electrochemical and catalytic properties being superior to those of the individual component nanoparticles. In this study, gold-silver hybrid nanoparticles (AuAgNPs) with an Aucore-Agshell nanostructure were successfully synthesized on zinc oxide (ZnO) [...] Read more.
Bimetallic nanoparticles have attracted significant attention as their electrochemical and catalytic properties being superior to those of the individual component nanoparticles. In this study, gold-silver hybrid nanoparticles (AuAgNPs) with an Aucore-Agshell nanostructure were successfully synthesized on zinc oxide (ZnO) whiskers. The as-prepared nanocatalyst, denoted AuAgNPs@ZnO whisker, exhibits an excellent catalytic efficiency in the aqueous reduction of 4-nitrophenol to 4-aminophenol; the turnover frequency was up to 40 times higher than that of each component nanoparticle. Their unique features were attributed to the electronic ligand effect at the bimetallic interface. In addition, the AuAgNPs were synthesized on a ZnO whisker-containing paper with a fiber-network microstructure, which was prepared via a papermaking technique. The paper-structured AuAgNPs composite possessed both a paper-like practical utility and a good catalytic performance. Furthermore, the on-paper synthesis process for these bimetallic nanocatalysts is facile. These easy-to-handle nanocatalyst hybrid composites are expected to find a wide range of applications in various chemical and catalytic processes. Full article
(This article belongs to the Special Issue Gold Catalysts)
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Open AccessArticle Synthesis and Catalytic Features of Hybrid Metal Nanoparticles Supported on Cellulose Nanofibers
Catalysts 2011, 1(1), 83-96; doi:10.3390/catal1010083
Received: 6 October 2011 / Revised: 15 November 2011 / Accepted: 18 November 2011 / Published: 25 November 2011
Cited by 27 | PDF Full-text (1124 KB) | HTML Full-text | XML Full-text
Abstract
The structural and functional design of metal nanoparticles has recently allowed remarkable progress in the development of high-performance catalysts. Gold nanoparticles (AuNPs) are among the most innovative catalysts, despite bulk Au metal being regarded as stable and inactive. The hybridization of metal [...] Read more.
The structural and functional design of metal nanoparticles has recently allowed remarkable progress in the development of high-performance catalysts. Gold nanoparticles (AuNPs) are among the most innovative catalysts, despite bulk Au metal being regarded as stable and inactive. The hybridization of metal NPs has attracted major interest in the field of advanced nanocatalysts, due to electro-mediated ligand effects. In practical terms, metal NPs need to be supported on a suitable matrix to avoid any undesirable aggregation; many researchers have reported the potential of polymer-supported AuNPs. However, the use of conventional polymer matrices make it difficult to take full advantage of the inherent properties of the metal NPs, since most of active NPs are imbedded inside the polymer support. This results in poor accessibility for the reactants. Herein, we report the topochemical synthesis of Au and palladium (Pd) bimetallic NPs over the surfaces of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibers (TOCNs), and their exceptional catalytic performance. Highly-dispersed AuPdNPs were successfully synthesized in situ on the crystal surfaces of TOCNs with a very high density of carboxylate groups. The AuPdNPs@TOCN nanocomposites exhibit excellent catalytic efficiencies in the aqueous reduction of 4-nitrophenol to 4-aminophenol, depending on the molar ratios of Au and Pd. Full article
(This article belongs to the Special Issue Gold Catalysts)
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Open AccessArticle Nano-Scale Au Supported on Carbon Materials for the Low Temperature Water Gas Shift (WGS) Reaction
Catalysts 2011, 1(1), 155-174; doi:10.3390/catal1010155
Received: 11 October 2011 / Revised: 4 November 2011 / Accepted: 29 November 2011 / Published: 9 December 2011
Cited by 3 | PDF Full-text (6721 KB) | HTML Full-text | XML Full-text
Abstract
Au-based catalysts supported on carbon materials with different structures such as graphite (G) and fishbone type carbon nanofibers (CNF-F) were prepared using two different methods (impregnation and gold-sol) to be tested in the water gas shift (WGS) reaction. Atomic absorption spectrometry, transmission [...] Read more.
Au-based catalysts supported on carbon materials with different structures such as graphite (G) and fishbone type carbon nanofibers (CNF-F) were prepared using two different methods (impregnation and gold-sol) to be tested in the water gas shift (WGS) reaction. Atomic absorption spectrometry, transmission electron microscopy (TEM), temperature-programmed oxidation (TPO), X-ray diffraction (XRD), Raman spectroscopy, elemental analyses (CNH), N2 adsorption-desorption analysis, temperature-programmed reduction (TPR) and temperature-programmed decomposition were employed to characterize both the supports and catalysts. Both the crystalline nature of the carbon supports and the method of gold incorporation had a strong influence on the way in which Au particles were deposited on the carbon surface. The higher crystallinity and the smaller and well dispersed Au particle size were, the higher activity of the catalysts in the WGS reaction was noted. Finally, catalytic activity showed an important dependence on the reaction temperature and steam-to-CO molar ratio. Full article
(This article belongs to the Special Issue Gold Catalysts)
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Open AccessArticle Pre-Reduction of Au/Iron Oxide Catalyst for Low-Temperature Water-Gas Shift Reaction Below 150 °C
Catalysts 2011, 1(1), 175-190; doi:10.3390/catal1010175
Received: 6 October 2011 / Revised: 14 November 2011 / Accepted: 29 November 2011 / Published: 9 December 2011
Cited by 6 | PDF Full-text (907 KB) | HTML Full-text | XML Full-text
Abstract
Low-temperature water-gas shift reaction (WGS) using gold catalyst is expected to be an attractive technique to realize an efficient on-site hydrogen production process. In this paper, Au/Fe3O4 catalysts for promoting the WGS below 150 °C were developed by a [...] Read more.
Low-temperature water-gas shift reaction (WGS) using gold catalyst is expected to be an attractive technique to realize an efficient on-site hydrogen production process. In this paper, Au/Fe3O4 catalysts for promoting the WGS below 150 °C were developed by a preliminary reduction of Au/iron oxide (Fe3+) catalyst utilizing high reactivity of Au nano-particles. The reduction was conducted under a CO, H2, or CO/H2O stream at either 140 or 200 °C, and the effect of reduction conditions on the characteristics of the Au/Fe3O4 catalyst and on the catalytic activity in WGS at 80 °C was investigated. The reaction progress during the pre-reduction treatment was qualitatively analyzed, and it was found that the iron oxide in Au/Fe2O3 calcined at 200 °C was easily reduced to Fe3O4 phase in all reduction conditions. The reduction conditions affected the characteristics of both Au and iron oxide, but all of the reduced catalysts had small Fe3O4 particles of less than 20 nm with Au particles on the surface. The surface area and content of cationic Au were high in the order of CO, H2, CO/H2O, and 140, 200 °C. In the WGS test at 80 °C using the developed catalysts, the activities of the catalysts pre-reduced by CO at 140 or 200 °C and by H2 at 140 °C were very high with 100% CO conversion even at such a low temperature. These results indicated that factors such as higher surface area, crystallized Fe3O4, and cationic Au content contributed to the catalytic activity. Full article
(This article belongs to the Special Issue Gold Catalysts)
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Review

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Open AccessReview Atomically Monodisperse Gold Nanoclusters Catalysts with Precise Core-Shell Structure
Catalysts 2011, 1(1), 3-17; doi:10.3390/catal1010003
Received: 26 July 2011 / Revised: 26 August 2011 / Accepted: 29 August 2011 / Published: 7 September 2011
Cited by 17 | PDF Full-text (1206 KB) | HTML Full-text | XML Full-text
Abstract
The emphasis of this review is atomically monodisperse Aun nanoclusters catalysts (n = number of metal atom in cluster) that are ideally composed of an exact number of metal atoms. Aun which range in size from a dozen to [...] Read more.
The emphasis of this review is atomically monodisperse Aun nanoclusters catalysts (n = number of metal atom in cluster) that are ideally composed of an exact number of metal atoms. Aun which range in size from a dozen to a few hundred atoms are particularly promising for nanocatalysis due to their unique core-shell structure and non-metallic electronic properties. Aun nanoclusters catalysts have been demonstrated to exhibit excellent catalytic activity in hydrogenation and oxidation processes. Such unique properties of Aun significantly promote molecule activation by enhancing adsorption energy of reactant molecules on catalyst surface. The structural determination of Aun nanoclusters allows for a precise correlation of particle structure with catalytic properties and also permits the identification of catalytically active sites on the gold particle at an atomic level. By learning these fundamental principles, one would ultimately be able to design new types of highly active and highly selective gold nanocluster catalysts for a variety of catalytic processes. Full article
(This article belongs to the Special Issue Gold Catalysts)
Open AccessReview Catalytic Reactions on Model Gold Surfaces: Effect of Surface Steps and of Surface Doping
Catalysts 2011, 1(1), 40-51; doi:10.3390/catal1010040
Received: 6 October 2011 / Revised: 11 November 2011 / Accepted: 15 November 2011 / Published: 21 November 2011
Cited by 4 | PDF Full-text (443 KB) | HTML Full-text | XML Full-text
Abstract
The adsorption energies and the activation energy barriers for a series of reactions catalyzed by gold surfaces and obtained theoretically through density functional theory (DFT) based calculations were considered to clarify the role of the low coordinated gold atoms and the role [...] Read more.
The adsorption energies and the activation energy barriers for a series of reactions catalyzed by gold surfaces and obtained theoretically through density functional theory (DFT) based calculations were considered to clarify the role of the low coordinated gold atoms and the role of doping in the catalytic activity of gold. The effect of the surface steps was introduced by comparison of the activation energy barriers and of the adsorption energies on flat gold surfaces such as the Au(111) surface with those on stepped surfaces such as the Au(321) or the Au(110) surfaces. It is concluded that the presence of low coordinated atoms on the latter surfaces increases the adsorption energies of the reactants and decreases the activation energy barriers. Furthermore, the increasing of the adsorption energy of the reaction products can lead to lower overall reaction rates in the presence of low gold coordinated atoms due to desorption limitations. On the other hand, the effect of doping gold surfaces with other transition metal atoms was analyzed using the dissociation reaction of molecular oxygen as a test case. The calculations showed that increasing the silver content in some gold surfaces was related to a considerable increment of the reactivity of bimetallic systems toward the oxygen dissociation. Importantly, that increment in the reactivity was enhanced by the presence of low coordinated atoms in the catalytic surface models considered. Full article
(This article belongs to the Special Issue Gold Catalysts)
Open AccessReview Synthesis of Gold Catalysts Supported on Mesoporous Silica Materials: Recent Developments
Catalysts 2011, 1(1), 97-154; doi:10.3390/catal1010097
Received: 13 October 2011 / Revised: 24 November 2011 / Accepted: 25 November 2011 / Published: 2 December 2011
Cited by 37 | PDF Full-text (1316 KB) | HTML Full-text | XML Full-text
Abstract
Mesoporous silica materials (MSM) with ordered and controllable porous structure, high surface area, pore volume and thermal stability are very suitable catalyst supports, because they provide high dispersion of metal nanoparticles and facilitate the access of the substrates to the active sites. [...] Read more.
Mesoporous silica materials (MSM) with ordered and controllable porous structure, high surface area, pore volume and thermal stability are very suitable catalyst supports, because they provide high dispersion of metal nanoparticles and facilitate the access of the substrates to the active sites. Since the conventional wet-impregnation and deposition-precipitation methods are not appropriate for the incorporation of gold nanoparticles (AuNPs) into MSM, considerable efforts have been made to develop suitable methods to synthesize Au/MSM catalysts, because the incorporation of AuNPs into the channel system can prevent their agglomeration and leaching. In this review, we summarize the main methods to synthesize active gold catalysts supported on MSM. Examples and details of the preparative methods, as well as selected applications are provided. We expect this article to be interesting to researchers due to the wide variety of chemical reactions that can be catalyzed by gold supported catalysts. Full article
(This article belongs to the Special Issue Gold Catalysts)
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