Application of the xenon-adsorption method for the study of metal cluster formation and growth on Y zeolite

Ryoo, Ryong; Cho, Sung June; Pak, Chanho; Kim, Jeong Guk; Ihm, Son Ki; Lee, Jun Young

doi:10.1021/ja00027a011

Cited by 77 publications

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“…Thus, the observed shift of iso ϭ 1,032 ppm here must then originate to a large extent from the Knight shift alone. This compares reasonably well with the 800 ppm reported from supported catalyst work of xenon on iridium clusters (30). The latter results are room-temperature measurements of the chemical shift at very low pressure.…”

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confidence: 79%

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¹²⁹Xe on Ir(111): NMR study of xenon on a metal single crystal surface

Jänsch

Gerhard

Koch

2004

Proc. Natl. Acad. Sci. U.S.A.

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NMR experiments of 129 Xe adsorbed on an iridium single crystal surface are reported. Very high nuclear polarization (P z Ϸ 0.7) makes the experiment possible. A coverage of less then one monolayer is investigated on the Ir(111) surface with an area of 0.8 cm 2 . The observed resonance line shifts are very large and highly anisotropic. We find iso ‫؍‬ 1,032 ؎ 11 ppm and an ‫؍‬ 291 ؎ 33 ppm, which are far above the typical range of physisorption. The highly ordered substrate leads to homogeneous conditions for the xenon atoms, as seen in the narrow linewidth of 20 ppm. Chemical shifts under physisorption conditions are not large enough to totally explain the results. Knight shift can clearly be identified as the cause of the findings. This shift shows the presence of conduction electrons of the metallic substrate at the xenon nucleus and thus the mixing of metallic and atomic states at the Fermi level. Such mixing is in accordance with recent Hartree-Fock and density functional calculations of similar van der Waals adsorption systems. Quantitative comparisons, however, fail completely. The size and ratio of an and iso are pure ground-state properties in a structurally simple system. They are accessible to theory and provide detailed local information that can serve as a benchmark for theory.

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confidence: 79%

“…The linewidth observed is Ͻ20 ppm. When nanometer size particles are prepared, the shift goes up to 800 ppm (30). The difference between small and large clusters is essentially the occurrence of free electrons and an established Fermi level, so that paramagnetic metallic behavior occurs.…”

mentioning

confidence: 99%

¹²⁹Xe on Ir(111): NMR study of xenon on a metal single crystal surface

Jänsch

Gerhard

Koch

2004

Proc. Natl. Acad. Sci. U.S.A.

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“…The sample was sealed in the NMR tube after adsorption of =5 Xe atoms per Pt particle, as determined from the xenon adsorption isotherm and from the average size of the metal particles. As shown by Ryoo et al [20], particles interact with each Pt cluster through the 0.74 nm apertures of the NaY zeolite supercages. The narrow component of the spectrum at =250 ppm corresponds to xenon adsorbed on the zeolite support and can be attributed to xenon in excess of that needed for monolayer coverage of the exposed metal atoms.…”

mentioning

confidence: 89%

“…Because of the high adsorption energy of xenon on the metal particle surfaces (45 kJ/mol [20]), the sticking time of Xe atoms adsorbed on Pt clusters at such low temperatures becomes long enough to prevent motional narrowing caused by exchange between metal and support.…”

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confidence: 99%

Surface Study of Supported Metal Particles by129XeNMR

et al. 1995

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The surfaces of platinum clusters in the supercages of NaY zeolite have been studied by ' Xe NMR over the temperature range 80 -293 K. The sensitivity of this weakly perturbing technique makes it possible to reveal the heterogeneity of the electronic structure of the particle surface. The temperature dependence of the ' Xe spin-lattice relaxation indicates that the surface sites with the highest adsorption energy possess metallic character.

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“…Faujasite zeolites, including X-and Y-type zeolites, have ordered void volumes known as supercages in their unit cell that make them as desirable hosts for the preparation of metal nanoparticles such as Pd, Pt, Rh, Au, Ag and Cu [21][22][23][24][25][26][27][28]. Moreover, exploitation of faujasite zeolites as catalytic supports is very widespread because of their desirable properties such as high thermal stability and mechanical strength.…”

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confidence: 99%

Novel Utilization of Zeolited Fly Ash Hosting Cobalt Nanoparticles as a Catalyst Applied to the Fischer–Tropsch Synthesis

2008

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In order to produce an inexpensive catalyst for the Fischer-Tropsch synthesis (FTS), zeolitized high silicon fly ash utilized as a catalytic support for cobalt nanoparticles. The ability of this new support in proper hosting of nanoparticles studied through various characterization methods such as X-ray diffraction, nitrogen sorption, transmission electron microscopy, energy-dispersive spectroscopic and temperature-programmed reduction. In addition, the catalytic properties for the FTS evaluated at 523 K and 20 MPa. The obtained results show remarkable influence of utilized support specifications upon the formation and catalytic behavior of cobalt nanoparticles in the FTS.

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Application of the xenon-adsorption method for the study of metal cluster formation and growth on Y zeolite

Cited by 77 publications

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¹²⁹Xe on Ir(111): NMR study of xenon on a metal single crystal surface

¹²⁹Xe on Ir(111): NMR study of xenon on a metal single crystal surface

Surface Study of Supported Metal Particles by129XeNMR

Novel Utilization of Zeolited Fly Ash Hosting Cobalt Nanoparticles as a Catalyst Applied to the Fischer–Tropsch Synthesis

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Application of the xenon-adsorption method for the study of metal cluster formation and growth on Y zeolite

Cited by 77 publications

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129Xe on Ir(111): NMR study of xenon on a metal single crystal surface

129Xe on Ir(111): NMR study of xenon on a metal single crystal surface

Surface Study of Supported Metal Particles by129XeNMR

Novel Utilization of Zeolited Fly Ash Hosting Cobalt Nanoparticles as a Catalyst Applied to the Fischer–Tropsch Synthesis

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¹²⁹Xe on Ir(111): NMR study of xenon on a metal single crystal surface

¹²⁹Xe on Ir(111): NMR study of xenon on a metal single crystal surface