Metal species with different size (single atoms, nanoclusters, and nanoparticles) show different catalytic behavior for various heterogeneous catalytic reactions. It has been shown in the literature that many factors including the particle size, shape, chemical composition, metal–support interaction, and metal–reactant/solvent interaction can have significant influences on the catalytic properties of metal catalysts. The recent developments of well-controlled synthesis methodologies and advanced characterization tools allow one to correlate the relationships at the molecular level. In this Review, the electronic and geometric structures of single atoms, nanoclusters, and nanoparticles will be discussed. Furthermore, we will summarize the catalytic applications of single atoms, nanoclusters, and nanoparticles for different types of reactions, including CO oxidation, selective oxidation, selective hydrogenation, organic reactions, electrocatalytic, and photocatalytic reactions. We will compare the results o...

Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles.

The applications of copper (Cu) and Cu-based nanoparticles, which are based on the earth-abundant and inexpensive copper metal, have generated a great deal of interest in recent years, especially in the field of catalysis. The possible modification of the chemical and physical properties of these nanoparticles using different synthetic strategies and conditions and/or via postsynthetic chemical treatments has been largely responsible for the rapid growth of interest in these nanomaterials and their applications in catalysis. In addition, the design and development of novel support and/or multimetallic systems (e.g., alloys, etc.) has also made significant contributions to the field. In this comprehensive review, we report different synthetic approaches to Cu and Cu-based nanoparticles (metallic copper, copper oxides, and hybrid copper nanostructures) and copper nanoparticles immobilized into or supported on various support materials (SiO2, magnetic support materials, etc.), along with their applications i...

http://pubs.acs.org/doi/pdfplus/10.1021/acs.chemrev.5b00482

Cu and Cu-Based Nanoparticles: Synthesis and Applications in Catalysis.

Note: Times Cited: 875 Reference EPFL-ARTICLE-206025doi:10.1021/cr0501846View record in Web of Science URL: ://WOS:000249839900009 Record created on 2015-03-03, modified on 2017-05-12

Complex Hydrides for Hydrogen Storage

CO2 conversion covers a wide range of possible application areas from fuels to bulk and commodity chemicals and even to specialty products with biological activity such as pharmaceuticals. In the present review, we discuss selected examples in these areas in a combined analysis of the state-of-the-art of synthetic methodologies and processes with their life cycle assessment. Thereby, we attempted to assess the potential to reduce the environmental footprint in these application fields relative to the current petrochemical value chain. This analysis and discussion differs significantly from a viewpoint on CO2 utilization as a measure for global CO2 mitigation. Whereas the latter focuses on reducing the end-of-pipe problem “CO2 emissions” from todays’ industries, the approach taken here tries to identify opportunities by exploiting a novel feedstock that avoids the utilization of fossil resource in transition toward more sustainable future production. Thus, the motivation to develop CO2-based chemistry does...

Sustainable Conversion of Carbon Dioxide: An Integrated Review of Catalysis and Life Cycle Assessment

The Golden Age of Transfer Hydrogenation

http://www.surfcat.fudan.edu.cn/_upload/tpl/02/05/517/template517/publications/2009/13.pdf

Dry citrate-precursor synthesized nanocrystalline cobalt oxide as highly active catalyst for total oxidation of propane

Catalytic properties of Au nanoclusters deposited on a one-dimensional CeO2 (1-D) nanorod and CeO2-nanoparticles have been investigated during CO oxidation at ambient temperatures. The kinetic data showed that the activity of Au catalysts could be remarkably improved by using CeO2-nanorods as support compared to the CeO2-nanoparticles. The measured specific rate and apparent activation energy (Ea) at 278 K were 4.02 molCO gAu−1 h−1 and 15.9 kJ mol−1, respectively, for the Au/CeO2-nanorods (Au-CR) catalyst, while those for the Au/CeO2-nanoparticles (Au-CP) catalyst were 0.15 molCO gAu−1 h−1 and 28.4 kJ mol−1, respectively. Characterization by X-ray diffraction (XRD), transmission electron microscopy (TEM), hydrogen temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), diffuse reflectance UV–Vis spectroscopy (DR UV–Vis) and in situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) of CO adsorption reveal that the predominantly exposed {1 0 0}/{1 1 0}-dominated surface structures of ceria nanorods show great superiority for anchoring and dispersing of gold nanoclusters, which in turn leads to a higher reducibility and activity of the Au-CeO2 surface for CO oxidation. It is also confirmed that, arising from the strong metal–support interaction (SMSI), the presence of gold nanoclusters has a strong influence on the electronic state of the CeO2 substrates.

http://www.surfcat.fudan.edu.cn/_upload/tpl/02/05/517/template517/publications/2009/12.pdf

Morphology effects of nanoscale ceria on the activity of Au/CeO2 catalysts for low-temperature CO oxidation

Bimetallic, nanostructured materials hold promise for improving catalyst activity and selectivity, yet little is known about the dynamic compositional and structural changes that these systems undergo during pretreatment that leads to efficient catalyst function. Here we use ozone-activated silver-gold alloys in the form of nanoporous gold as a case study to demonstrate the dynamic behaviour of bimetallic systems during activation to produce a functioning catalyst. We show that it is these dynamic changes that give rise to the observed catalytic activity. Advanced in situ electron microscopy and X-ray photoelectron spectroscopy are used to demonstrate that major restructuring and compositional changes occur along the path to catalytic function for selective alcohol oxidation. Transient kinetic measurements correlate the restructuring to three types of oxygen on the surface. The direct influence of changes in surface silver concentration and restructuring at the nanoscale on oxidation activity is demonstrated. Our results demonstrate that characterization of these dynamic changes is necessary to unlock the full potential of bimetallic catalytic materials.

/pdf/dynamic-restructuring-drives-catalytic-activity-on-5zrxeem2cq.pdf

Dynamic restructuring drives catalytic activity on nanoporous gold-silver alloy catalysts

The selective oxidation of alcohols is one of the most challenging reactions in green chemistry. Although a number of methods have been developed, the search for new, facile, cost-effective, and environmentally benign procedures that avoid the use of a large excess of toxic and expensive stoichiometric metal oxidants has attracted substantial interest. An attractive method is the direct oxidation of alcohols—promoted by reusable heterogeneous catalysts—using air or molecular oxygen (O2) under solventfree conditions or (in the case of solid alcohols) in green organic solvents. Ideally, the reaction should also be performed under mild conditions (preferably at room temperature) for the synthesis of complex, thermolabile compounds, which are typical in fine chemistry. Satisfactory results were attained in only very few cases, in which a large excess of base additives was required, and this was usually achieved at the expense of selectivity. Therefore, the development of excellent reusable catalysts for liquid-phase aerobic oxidation of alcohols under mild conditions would constitute a breakthrough in both green chemistry and organic synthesis. Recently, supported gold nanoparticles have attracted considerable attention because of their extraordinarily high activity and selectivity. The outstanding catalytic ability of gold is related to the size and shape of the nanoparticles, the degree of coordinative unsaturation of the gold atoms, and the interactions between gold and the oxide support. Although several gold systems have been reported for the catalysis of alcohol oxidation reactions, in most cases they have been applied at temperatures above 100 8C. Dehydrogenation is known to be the rate-limiting step in the oxidation of alcohols on various noble metals. Therefore, the combination of gold nanoparticles with a suitable support (characterized by an exceptional alcohol-dehydrogenation activity) may allow the fabrication of new, versatile gold catalysts that could be used for liquid-phase organic synthesis under mild conditions. Herein, we demonstrate for the first time that mesostructured Ga–Al mixed-oxide solid solutions are highly promising supports for the fabrication of exceptionally effective gold catalysts for aerobic alcohol oxidation under mild conditions. A series of binary mesostructured Ga–Al mixed-oxide supports (denoted as GaxAl6 xO9; x= 2, 3, 4), along with unitary oxides of g-Ga2O3 and g-Al2O3, was prepared through an alcoholic sol–gel pathway. The X-ray diffraction (XRD) patterns of all as-synthesized binary substrates are characteristic of g-Ga2O3/Al2O3 solid solutions with a spinel-type structure. When gold nanoparticles were deposited onto these high-surface-area materials, no gold diffraction line was detected, and the pattern showed no significant differences relative to that of the support, thus indicating that the structure of the catalyst was maintained. A representative transmission electron microscopy (TEM) image of the Au/ GaxAl6 xO9 sample confirms that the gold particles were evenly deposited on the Ga–Al mixed-oxide support, with most particles being smaller than about 6 nm (see the Supporting Information for TEM and XRD data). To check the possible alcohol-dehydrogenation capability of the Au/GaxAl6 xO9 materials, we adsorbed 2-propanol on their surface and performed temperature-programmed surface reaction (TPSR) measurements of the desorbed H2 molecules (see the Supporting Information). Ga-containing mixed-oxide supports were found to be indispensable for attaining highly active alcohol-dehydrogenation materials (Figure 1A). Furthermore, the dehydrogenation activity of the catalysts was observed to be strongly dependent on the composition of these supports. A strongly enhanced hydrogen signal was identified in the case of a Ga3Al3O9 solid solution containing a Ga/Al molar ratio of 1:1—in sharp contrast to what was observed for the reference gold catalysts Au/TiO2 and Au/Fe2O3 (provided by the World Gold Council), where no H2 species were detected. These results can be rationalized by assuming that the formation of Ga–Al mixed-oxide solid solutions may favor the creation of specific dehydrogenation sites as a consequence of the presence of Ga atoms at the surface atomic sites (Td and Oh) of Al2O3 and highly dispersed GaO4 tetrahedra in the surface spinels. [16] These sites are responsible for the considerably enhanced dehydrogenation activity observed for the Ga–Al mixed-oxide-supported Au catalysts. Our initial aerobic-oxidation studies focused on the case of benzyl alcohol (Figure 1B), with the aim to understand the effect of the composition of the support on the catalytic performance of the gold catalysts. The reactions were performed in a magnetically stirred glass batch reactor in the presence of a solvent (at 90 8C) under O2 and at [*] F. Z. Su, Dr. Y. M. Liu, L. C. Wang, Prof. Y. Cao, Prof. H. Y. He, Prof. K. N. Fan Department of Chemistry and Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials Fudan University, Shanghai 200433 (P. R. China) Fax: (+86)21-6564-2978 E-mail: yongcao@fudan.edu.cn

Ga–Al Mixed‐Oxide‐Supported Gold Nanoparticles with Enhanced Activity for Aerobic Alcohol Oxidation

The selective reduction of nitro compounds to the corresponding amines is one of the most important transformations in synthetic organic chemistry. Although a number of methods have been developed, the search for new facile, chemoselective, cost-effective, and environmentally friendly procedures that avoid the use of expensive and hazardous stoichiometric reducing agents in large excess has attracted substantial interest. An attractive alternative is the catalytic reduction of nitro compounds with cheap and readily available CO and H2O as the hydrogen source. In particular, the specific reduction of a nitro group under mild conditions in the presence of other functionalities is desirable. As opposed to commonly used catalytic hydrogenation, which involves H2 as the reductant, [3] the use of CO and H2O as the hydrogen source leads to remarkable chemoselectivity and is of great industrial potential, especially when an efficient and reusable catalytic system can be employed. However, relevant studies have largely focused on various rutheniumor rhodium-based homogeneous systems, which are not practically useful because of their low turnover numbers (TONs) and turnover frequencies (TOFs), and the requirement of organic and/or inorganic bases in large excess as cocatalysts. Despite tremendous efforts in the last two decades, few examples of heterogeneous catalyst systems for the reduction of a nitro compounds with CO/H2O as the reductant have appeared, and these systems have often suffered from low efficiency as well as limited substrate scope and catalyst reusability. Supported gold nanoparticles have emerged as active and extremely selective catalysts for a broad array of organic reactions owing to their unique catalytic properties under mild conditions. Whereas the potential of gold-catalyzed selective oxidation reactions for atom-economical and sustainable organic synthesis is widely recognized, the possibilities offered by catalytic reduction with supported gold nanoparticles have remained largely unexplored. Recently, Corma and Serna reported that the chemoselective reduction of a nitro group in the presence of other reducible functionalities is possible with supported gold nanoparticles. One critical limitation associated with the current gold-catalyzed processes for the reduction of nitro compounds, however, is that the hydrogen-delivery rate is too low for practical applications. 11] Herein, we describe a highly effective gold-catalyzed, CO/H2O-mediated reduction that circumvents inconvenient H2 activation to enable the rapid, efficient, and chemoselective reduction of a wide range of organic nitro compounds under mild conditions. The reaction is general and proceeds efficiently under an atmosphere of CO at room temperature. To the best of our knowledge, this gold-based catalytic system is the most efficient, simple, and environmentally friendly catalytic system for the selective reduction of nitro compounds that has been developed to date. Initially, nitrobenzene was used as a model substrate in investigations of the catalytic activity of different solid catalysts under a CO atmosphere at room temperature. The Pt, Pd, and Ru catalysts tested were not active for this reaction. Of the various gold catalysts tested, very small Au nanoparticles (with a diameter of about 1.9 nm) supported on TiO2 showed the highest activity (this catalyst system is denoted as Au/TiO2-VS; see details in the Supporting Information). As observed for other gold-catalyzed processes, both the nature of the support and the particle size had a strong influence on the activity of the Au nanoparticles. Thus, at 25 8C under 1 atm of CO, aniline was produced exclusively with an average TOF in the range of 0.9–33 h 1 (Table 1, entries 1–4). No trace of azo or azoxy compounds, byproducts frequently formed under homogeneous CO/H2O catalysis, was observed. Of particular note is that the reaction proceeded efficiently at a pressure of only 1 atm, which enables the use of common glass reactors. There are very few catalysts that are effective under such mild conditions, the most active of which is a homogeneous [Rh(CO)2(acac)] complex in the presence of a large excess of NaOH. However, the TOF of Au/TiO2-VS is 97 times greater than that of [Rh(CO)2(acac)] under base-free reaction conditions (Table 1, entry 9). The high activity of Au/TiO2-VS under ambient conditions significantly improves the economical and environmental impact of this gold-catalyzed reduction process. Next, the reaction conditions were optimized for the reduction of nitrobenzene through variation of the pressure and solvent. First, the effect of the pressure of CO (PCO) was investigated. The reaction rate increased dramatically as PCO was raised from 1 to 5 atm (Table 1, entries 1, 10, and 11) but leveled off at 5–15 atm (Table 1, entries 12 and 13). These [*] L. He, Dr. L. C. Wang, H. Sun, J. Ni, Prof. Y. Cao, Prof. H. Y. He, Prof. K. N. Fan Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials Department of Chemistry, Fudan University Shanghai 200433 (China) Fax: (+ 86)21-6564-3774 E-mail: yongcao@fudan.edu.cn

Lu-Cun Wang

Papers

Dry citrate-precursor synthesized nanocrystalline cobalt oxide as highly active catalyst for total oxidation of propane

Morphology effects of nanoscale ceria on the activity of Au/CeO2 catalysts for low-temperature CO oxidation

Dynamic restructuring drives catalytic activity on nanoporous gold-silver alloy catalysts

Ga–Al Mixed‐Oxide‐Supported Gold Nanoparticles with Enhanced Activity for Aerobic Alcohol Oxidation

Efficient and selective room-temperature gold-catalyzed reduction of nitro compounds with CO and H(2)O as the hydrogen source.