Preparation and characterisation of a highly active bimetallic (Pd–Ru) nanoparticle heterogeneous catalyst†

Hermans, Sophie; Shephard, Douglas S.; Johnson, Brian F. G.; Raja, Robert; Sankar, Gopinathan; Bromley, Stefan T.; Thomas, John Meurig

doi:10.1039/a901263j

Cited by 136 publications

(102 citation statements)

References 14 publications

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“…In fact, studies involving cluster-based nanoparticle catalysts even highlighted the integral importance of site-15 isolation as well as particle size in enhancing efficiency of catalytic oxidations and hydrogenations. [20][21][22][23][24][25] The nature of support materials has ranged from metal oxides 26 and carbonaceous materials, 27 to microporous alternatives such as zeolites 28,29 or metal-organic frameworks 20 (MOFs), 30,31 and mesoporous silica-derived hosts 32 such as MCM-41 or SBA-15. Nanoporous materials have been extensively explored for their intrinsic catalytic properties, 33 however isolated single-sites in the form of doped frameworks [34][35][36] or supported nanoparticles have proved to be 25 superior.…”

Section: Figurementioning

confidence: 99%

Elucidating Structure–Property Relationships in the Design of Metal Nanoparticle Catalysts for the Activation of Molecular Oxygen

et al. 2015

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A novel synthetic strategy for the design of metal nanoparticles by extrusion of anionic chloride precursors from a porous copper chlorophosphate framework has been devised for the sustainable aerobic oxidation of vanillyl alcohol (4-hydroxy-3-methoxybenzyl alcohol) to vanillin (4-hydroxy-3-methoxybenzaldehyde) using a one-step, base-free method. The precise nature of the Au, Pt and Pd species has been elucidated for the as-synthesized and thermallyactivated analogues, which exhibit fascinating catalytic properties when subjected to diverse activation environments. By 20 employing a combination of structural and spectroscopic characterization tools, it has been shown that analogous heat treatments have differing effects on extrusion of a particular metal species. The most active catalyst in this series of materials were the extruded Pt nanoparticles that were generated by reduction in H2, which exhibit enhanced catalytic behavior, when compared to its Au or Pd counterparts, for industrially-significant, aerobic oxidation reactions.

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Section: Figurementioning

confidence: 99%

Elucidating Structure–Property Relationships in the Design of Metal Nanoparticle Catalysts for the Activation of Molecular Oxygen

et al. 2015

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“…For example, organometallic cluster precursors containing two different metals have been used to prepare supported bimetallic catalysts, but continuous variation of the elemental composition of the resulting particles requires large precursor libraries. [14][15][16] Most other methods for preparing supported bimetallic nanoparticles in the <5-nm size range lead to phase segregation of the two metals and thus poor control over the composition of individual particles, 17 although limited success has been achieved using surfactant-stabilized nanoparticles. 18 We prepared DENs consisting of PdAu alloys within fourthgeneration, amine-terminated poly(amidoamine) (PAMAM) dendrimers (G4-NH 2 (Pd n Au 55-n )) by co-complexation of the two corresponding metal salts followed by chemical reduction of the dendrimer/metal-ion composite.…”

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confidence: 99%

Titania-Supported PdAu Bimetallic Catalysts Prepared from Dendrimer-Encapsulated Nanoparticle Precursors

et al. 2005

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In this communication, we report the synthesis and characterization of TiO 2 -supported PdAu bimetallic nanoparticle catalysts prepared using dendrimer-encapsulated nanoparticles (DENs). 1 The key result is that the compositional fidelity of the original bimetallic DENs, and to some extent their size, is retained in the supported catalyst after removal of the dendrimer template by calcination at 500°C. Additionally, the gas-phase catalytic activity for CO oxidation is higher for the bimetallic catalysts than that for the corresponding Pd-only and Au-only monometallics. 2,3 It has previously been shown that 1-3-nm diameter alloy and core-shell bimetallic PdPt, 4,5 PdAu, 6 PdRh, 7 and AuAg 8 nanoparticles can be synthesized within dendrimer templates. 1 The resulting materials are characterized by a high degree of uniformity in size, structure, and elemental composition, and in some cases they have enhanced solution-phase catalytic activities compared to the analogous monometallic materials. [4][5][6][7] There are also a few examples of dendrimer/nanoparticle composites of various sorts being used to prepare supported Pt, 9 Pd, 10 Au, 10 CuO, 11 and Fe 2 O 3 nanoparticles. 12 In some cases, these were shown to be catalytically active. 9,12 To the best of our knowledge, however, there is only one very recent example of a heterogeneous catalyst prepared from a bimetallic DEN precursor. 13 The DEN approach to bimetallic nanoparticles is potentially simpler than many alternative methods. For example, organometallic cluster precursors containing two different metals have been used to prepare supported bimetallic catalysts, but continuous variation of the elemental composition of the resulting particles requires large precursor libraries. [14][15][16] Most other methods for preparing supported bimetallic nanoparticles in the <5-nm size range lead to phase segregation of the two metals and thus poor control over the composition of individual particles, 17 although limited success has been achieved using surfactant-stabilized nanoparticles. 18 We prepared DENs consisting of PdAu alloys within fourthgeneration, amine-terminated poly(amidoamine) (PAMAM) dendrimers (G4-NH 2 (Pd n Au 55-n )) by co-complexation of the two corresponding metal salts followed by chemical reduction of the dendrimer/metal-ion composite. 6 The synthesis was carried out in a 99% methanol solution using a procedure we previously reported for preparing DENs within amine-terminated dendrimers. 10 For example, G4-NH 2 (Pd 27.5 Au 27.5 ) was synthesized as follows: 0.0924 g of a 14.2 wt % solution of G4-NH 2 in MeOH and 20 µL of 0.3 M HCl were added to 1 L of 99% MeOH, followed by 255 µL of a 0.10 M K 2 PdCl 4 solution. The HCl was added to prevent crosslinking of the G4-NH 2 dendrimer by Pd 2+ (Pd 2+ is used to designate PdCl 4 2-and all its hydrolysis products). 19 After being stirred for 10 min, 255 µL of a 0.10 M HAuCl 4 solution was added. After being stirred for an additional 2 min, 1 mL of a 1.0 M NaBH 4 solution was added (20× molar excess). The s...

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“…Along with our colleagues, Johnson et al [47][48][49][50] we have shown that monodisperse mixed-metal cluster carbonylates may be uniformly incorporated inside mesoporous silica and gently decarbonylated to yield the naked clusters, which are anchored securely to the underlying silica ( Figure 12). The key point in this case is to recognize that the method of preparation produces 1) clusters that are of the same stoi- 2À is readily sequestered within the mesopores of silica in the presence of the molecular cation PPN + (bis(triphenylphosphine)iminium).…”

Section: Individual Isolated Bimetallic Clusters As Single-site Hetmentioning

confidence: 88%

“…Turnover frequencies associated with {Pd 6 Ru 6 } nanoclusters in the hydrogenation of a typical alkene exceed by an order of magnitude those for monoelemental palladium or ruthenium clusters. [48] The structures of these nanoparticle bimetallic clusters are determined (usually under in situ catalytic conditions) by X-ray absorption spectroscopy. Two examples are shown in Figure 14.…”

Section: Individual Isolated Bimetallic Clusters As Single-site Hetmentioning

confidence: 99%

Single‐Site Heterogeneous Catalysts

2005

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Intellectually, the advantages that flow from the availability of single-site heterogeneous catalysts (SSHC) are many. They facilitate the determination of the kinetics and mechanism of catalytic turnover-both experimentally and computationally-and make accessible the energetics of various intermediates (including short-lived transition states). These facts in turn offer a rational strategic principle for the design of new catalysts and the improvement of existing ones. It is generally possible to prepare soluble molecular fragments that circumscribe the single-site, thus enabling a direct comparison to be made, experimentally, between the catalytic performance of the same active site when functioning as a heterogeneous (continuous solid) as well as a homogeneous (dispersed molecular) catalyst. This approach also makes it possible to modify the immediate atomic environment as well as the central atomic structure of the active site. From the practical standpoint, SSHC exhibit very high selectivities leading to the production of sharply defined molecular products, just as do their homogeneous analogues. Given that mesoporous silicas with very large internal surface areas are ideal supports for SSHC, and that more than a quarter of the elements of the Periodic Table may be grafted as active sites onto such silicas, there is abundant scope for creating new catalytic opportunities.

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Preparation and characterisation of a highly active bimetallic (Pd–Ru) nanoparticle heterogeneous catalyst†

Cited by 136 publications

References 14 publications

Elucidating Structure–Property Relationships in the Design of Metal Nanoparticle Catalysts for the Activation of Molecular Oxygen

Elucidating Structure–Property Relationships in the Design of Metal Nanoparticle Catalysts for the Activation of Molecular Oxygen

Titania-Supported PdAu Bimetallic Catalysts Prepared from Dendrimer-Encapsulated Nanoparticle Precursors

Single‐Site Heterogeneous Catalysts

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