Activation of atom-precise clusters for catalysis

Sudheeshkumar, V.; Sulaiman, Kazeem O.; Scott, Robert W. J.

doi:10.1039/c9na00549h

Cited by 55 publications

(78 citation statements)

References 130 publications

(172 reference statements)

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“…Au atoms can be prepared and Au 25 (SC 2 H 4 Ph) 18 , Au 38 (SC 2 H 4 Ph) 24 and Au 144 (SC 2 H 4 Ph) 60 are exemplarily mentioned here. [ 27,99,175,235–238 ] The number and configuration/type of ligands/staples typically varies, enabling to tune the physical properties and catalytic performance of the clusters. Once a pure solution of monodisperse Au x (SR) y clusters has been obtained, it can be used for standard impregnation of supporting oxides (e.g., CeO 2 , TiO 2 , Al 2 O 3, SiO 2 ).…”

Section: Resultsmentioning

confidence: 99%

Operando Surface Spectroscopy and Microscopy during Catalytic Reactions: From Clusters via Nanoparticles to Meso‐Scale Aggregates

Rupprechter

2021

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described as metal dispersion (number of metal surface atoms relative to the total number of metal atoms in the catalyst), whereas the support is characterized by the specific surface area (m 2 g −1). For hemispherical metal particles of ≈1.5, 2, 5, and 10 nm diameter, the dispersion is about 0.8, 0.6, 0.3, and 0.1, respectively, illustrating why the nanoscale is required not to waste precious metal inside the particles. The ultimate dispersion is, of course, provided by single metal atoms and this concept is followed in "single atom catalysis" or "single site catalysis". [10-17] However, the adsorption and reaction steps of a catalytic reaction do typically not occur on isolated single atoms, but also involve neighboring sites, for example, of the oxide support [18] or of a metal matrix (for bimetallic nanoparticles, active metal atoms may be embedded in an inert or less-active metal matrix [11,19-23]). The so-called site isolation of active atoms may prevent CC bond cleavage (coking), which requires at least two neighboring active metals. In any case, the stability of the single atoms is the key challenge, as atoms may diffuse and sinter. Furthermore, for example, Pt, Pd, Cu, or Au atoms are mobilized by CO, [24-28] forming CO-M 1 units that may eventually sinter into larger clusters. Herein, we define metal clusters as entities with less than ≈100 atoms, characterizing the so-called "non-scalable" regime (Figure 1a). [29] Their atomic and electronic structure is significantly different from that of bulk metals, for example, with respect to atom positions (icosahedral vs face centered cubic fcc), distances (lattice contraction or expansion), and band structure (semiconductor vs metal). Clearly, these properties are size-dependent ("each atom counts" [30,31]), with pronounced impact on adsorption and reaction properties. [5,32] Accordingly, nanoparticles with more than ≈100 atoms are in the "scalableregime" and start to have or exhibit bulk atomic and electronic structure. [6,32-34] Nevertheless, the relative contributions of corner, edge, step, terrace and phase boundary sites on the surface of a nanoparticle (Figure 1b,c) are still size-dependent. [35,36] Meso-scale ("black") powders of metals are clearly bulk-like and have very low dispersion (Figure 1d), but the µm-sized aggregates still consist of adjoining nanocrystals with structured surfaces, comparable to that of true nanoparticles. Operando characterization of working catalysts, requiring per definitionem the simultaneous measurement of catalytic performance, is crucial to identify the relevant catalyst structure, composition and adsorbed species. Frequently applied operando techniques are discussed, including X-ray absorption spectroscopy, near ambient pressure X-ray photoelectron spectroscopy and infrared spectroscopy. In contrast to these area-averaging spectroscopies, operando surface microscopy by photoemission electron microscopy delivers spatially-resolved data, directly visualizing catalyst heterogeneity. For thorough interpretation, the exper...

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Section: Resultsmentioning

confidence: 99%

Operando Surface Spectroscopy and Microscopy during Catalytic Reactions: From Clusters via Nanoparticles to Meso‐Scale Aggregates

Rupprechter

2021

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“…Therefore, it was assumed that decoration of CNTs with Ag NPs for catalytic applications is an excellent concept via simple one-step method of PLAL technique as a fast and eco-friendly method. It almost certainly performs better in catalytic reduction against different hazardous organic compounds [ 31 , 32 ].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Ag Nanoparticles-Decorated CNTs via Laser Ablation Method for the Enhancement the Photocatalytic Removal of Naphthalene from Water

et al. 2021

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Silver nanoparticles (Ag NPs) were decorated with different amounts on the exterior walls of carbon nanotubes (CNTs) by a laser ablation assisted method, especially in liquid media to be applied as a good adsorption material against naphthalene. The laser ablation time was controlled the amount of decoration Ag NPs on CNTs. The prepared nanocomposite was analyzed via different analytical techniques. Ag NPs with a small size distribution of 29 nm are uniformly decorated with spherical shape on CNTs walls. The disorder degree of tubular structure and shifting of the vibrational characteristic peaks increase with the increase in the decoration of Ag NPs. After that, the prepared samples were investigated for the removal of naphthalene. These studies of loading Ag NPs with different amounts on the surface of CNTs act as a promising material for water treatment.

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“…As such, they possess unique properties that open new scientific horizons. Indeed, the physical [ 1 , 2 ], biological [ 3 , 4 ], and chemical [ 5 , 6 ] characteristics of gold and silver nanoparticles (AuNPs and AgNPs, respectively) confer on them wide applicability [ 7 ] in medicine [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ], agriculture [ 22 , 23 , 24 , 25 , 26 ], photonics [ 12 , 18 , 20 , 27 , 28 , 29 , 30 ], microelectronics [ 31 , 32 , 33 ], and catalysis [ 30 , 34 , 35 , 36 , 37 , 38 , 39 ]. The plasmonic properties of Au and Ag thus stimulate a wide range of research in nanoscale optics, photonics and sensors [ 40 ].…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Producing Metallic Nanoparticles, with an Emphasis on Silver and Gold Nanoparticles, Using Bottom-Up Methods

Karimadom

Kornweitz

2021

Molecules

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Bottom-up nanoparticle (NP) formation is assumed to begin with the reduction of the precursor metallic ions to form zero-valent atoms. Studies in which this assumption was made are reviewed. The standard reduction potential for the formation of aqueous metallic atoms—E0(Mn+aq/M0aq)—is significantly lower than the usual standard reduction potential for reducing metallic ions Mn+ in aqueous solution to a metal in solid state. E0(Mn+aq/M0solid). E0(Mn+aq/M0aq) values are negative for many typical metals, including Ag and Au, for which E0(Mn+aq/M0solid) is positive. Therefore, many common moderate reduction agents that do not have significantly high negative reduction standard potentials (e.g., hydrogen, carbon monoxide, citrate, hydroxylamine, formaldehyde, ascorbate, squartic acid, and BH4−), and cannot reduce the metallic cations to zero-valent atoms, indicating that the mechanism of NP production should be reconsidered. Both AgNP and AuNP formations were found to be multi-step processes that begin with the formation of clusters constructed from a skeleton of M+-M+ (M = Ag or Au) bonds that is followed by the reduction of a cation M+ in the cluster to M0, to form Mn0 via the formation of NPs. The plausibility of M+-M+ formation is reviewed. Studies that suggest a revised mechanism for the formation of AgNPs and AuNPs are also reviewed.

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Activation of atom-precise clusters for catalysis

Abstract: This review details methods used to activate Au and Ag clusters for catalysis and routes that have been effective in mitigating sintering.

Cited by 55 publications

References 130 publications

Operando Surface Spectroscopy and Microscopy during Catalytic Reactions: From Clusters via Nanoparticles to Meso‐Scale Aggregates

Operando Surface Spectroscopy and Microscopy during Catalytic Reactions: From Clusters via Nanoparticles to Meso‐Scale Aggregates

Synthesis of Ag Nanoparticles-Decorated CNTs via Laser Ablation Method for the Enhancement the Photocatalytic Removal of Naphthalene from Water

Mechanism of Producing Metallic Nanoparticles, with an Emphasis on Silver and Gold Nanoparticles, Using Bottom-Up Methods

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