Structures of metal nanoparticles adsorbed on MgO(001). II. Pt and Pd

Goniakowski, Jacek; Jelea, A.; Mottet, C.; Barcaro, Giovanni; Fortunelli, Alessandro; Kuntová, Z.; Nita, Florin; Levi, A.C.; Rossi, Giulia; Ferrando, Riccardo

doi:10.1063/1.3121307

Cited by 49 publications

(38 citation statements)

References 37 publications

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“…Apart from the cube-on-cube epitaxy -referred to as [ [57][58][59][60][61][62][63][64][65] . Here we make use of the same notation for the different particle epitaxies as employed in 57 .…”

Section: Methodsmentioning

confidence: 99%

In Situ Oxidation Study of Pt Nanoparticles on MgO(001)

et al. 2013

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Noble metal nanoparticles supported by oxide carriers are widely employed in heterogeneous catalysis. In order to improve catalyst efficiency it is important to understand oxidation processes on the atomic scale. Here we studied oxygen-induced shape changes of Pt nanoparticles on MgO(001) by means of in-situ surface x-ray diffraction (SXRD) and x-ray reflectivity measurements (XRR). The x-ray results on the particle morphology were complemented by transmission electron microscopy (TEM) studies. The samples were prepared by means of physical vapor deposition and differed in average particle size and lateral particle size distribution. The oxygen-induced particle shape changes were found to be independent of particle size * To whom correspondence should be addressed † Max-Planck-Institut für Intelligente Systeme (former Max-Planck-Institut für Metallforschung), Heisenbergstr. and were characterized by the emergence of higher indexed facets. We propose a particle sizedependent oxidation behavior with a kinetically hindered bulk oxide formation. The formed bulk oxide structures were concluded to be (110)-oriented Pt 3 O 4 and a modified structure of (0001)-oriented α-PtO 2 . CO exposure of the oxidized particles did not lead to a shape change reversibility.

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“…Apart from the cube-on-cube epitaxy -referred to as [ [57][58][59][60][61][62][63][64][65] . Here we make use of the same notation for the different particle epitaxies as employed in 57 .…”

Section: Methodsmentioning

confidence: 99%

In Situ Oxidation Study of Pt Nanoparticles on MgO(001)

et al. 2013

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“…This cutout was then halfembedded in a matrix of randomly distributed atoms (2240 Si, 1904 C, and 2140 N) in a box of 5.4 ⇥ 5.6 ⇥ 2.6 nm, leading to a total of 6870 atoms in the simulation box. We have chosen to adsorb the Pd NP onto the SiCN substrate via the 111 facet, which is in agreement with the preferred epitaxy reported for other Pdsupported systems 56 .…”

Section: Molecular-dynamics Simulationsmentioning

confidence: 60%

“…One strategy for obtaining the structure of a Pd particle on a SiCN support would be to use global optimization methods or schemes like the Wulff-Kaischew construction 55,56 to find low energy geometries. However, for a system as large as the one that we consider here, global optimization techniques would be computationally overwhelming and would most likely lead to a very large number of local minima.…”

Section: Molecular-dynamics Simulationsmentioning

confidence: 99%

Investigating the electronic structure of a supported metal nanoparticle: Pd in SiCN

Schmidt

Albuquerque

Kempe

et al. 2016

Phys. Chem. Chem. Phys.

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We investigate the electronic structure of a Palladium nanoparticle that is partially embedded in a matrix of silicon carbonitride. From classical molecular dynamics simulations we first obtain a representative atomic structure. This geometry then serves as input to density-functional theory calculations that allow us to access the electronic structure of the combined system of particle and matrix. In order to make the computations feasible, we devise a subsystem strategy for calculating the relevant electronic properties. We analyze the Kohn-Sham density of states and pay particular attention to d-states which are prone to be affected by electronic self-interaction. We find that the density of states close to the Fermi level is dominated by states that originate from the Palladium nanoparticle. The matrix has little direct effect on the electronic structure of the metal. Our results contribute to explaining why silicon carbonitride does not have detrimental effects on the catalytic properties of palladium particles and can serve positively as a stabilizing mechanical support. MotivationFirst-principles electronic-structure theory 1-13 allows to gain unbiased insights into the microscopic, quantum-mechanical effects that are at the heart of modern nanotechnology [14][15][16][17][18][19][20][21][22][23][24] . However, often full ab-initio studies on systems of experimental relevance remain challenging since the computational effort grows immensely with system size 25 . For instance, in many experiments metal nanoparticles that have a diameter of several nm and contain several hundreds or thousands of atoms are used. For such systems, tens of thousands of electrons have to be taken into account for first-principles studies. Even with modern computers using massive parallelization, geometry optimizations and detailed investigations of the electronic structure of systems of that size are out of reach. Therefore, strategies have to be devised how insights can be gained into large systems despite of these computational limitations. In this work, we take a first step in this direction and investigate a palladium nanoparticle which is partially embedded in a matrix of silicon carbonitride (SiCN).This system is of practical relevance because noble-metal nanoparticles, in particular nanoparticles containing Pd, are effective catalysts for a wide range of chemical reactions [26][27][28][29][30] . In comparison to bulk metals, nanoparticles exhibit a high surface-

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“…Larger versions of such nanoparticles have been observed by STM for Pd supported on Al 2 O 3. 11 Theoretical basin‐hopping global optimizations predict similar structures for various noble metals of up to 200 atoms on MgO(001) surfaces 12. Recently, Vajda et al 13.…”

Section: Adsorption Energies (Eads) Of Isolated Carbon Atoms[a]mentioning

confidence: 93%

Template‐Assisted Formation of Fullerenes from Short‐Chain Hydrocarbons by Supported Platinum Nanoparticles

Viñes¹,

Görling²

2011

Angew Chem Int Ed

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Since the discovery of C 60 fullerenes, [1] research on the respective family of carbon allotropes has grown enormously, [2] mainly motivated by potential technological applications. Fullerenes are of interest in molecular electronics and for nonlinear optical devices.[3] Metal-insulator transitions of alkali-intercalated fullerenes [4] and superconductivity of alkali-doped fullerene compounds have attracted considerable scientific attention; [5] the great interest in fullerenebased materials has boosted the search for a rational design of fullerenes by new synthesis strategies. [6] Fullerenes usually are obtained by vaporization methods, [6] but can also be synthesized from polyarene precursor C 60 H 30 (1). Scott and co-workers have reported fullerene formation in the gas phase either through a series of cyclodehydrogenation steps [7] on 1 or through cyclization of a trichloroderivative, C 60 H 27 Cl 3 . [6,8] These methods, however, lead to yields below 1 %. Recently, Otero and co-workers showed that a Pt(111) single crystal surface-mediated process can achieve almost a 100 % yield, [9,10] using 1 and the precursor C 60 H 27 N 3 (2) to eventually obtain, after annealing over 750 K, fullerene and triazafullerene species. Nevertheless, the yield for the synthesis of the precursors from commercial chemicals is still only 33 % for 1 and 56 % for 2.The great improvement of the latter studies is to employ organic compounds, whose inherent geometric structure (exhibiting several interconnected C 6 and C 5 rings) and electronic structure (strong aromaticity) favor the formation of fullerenes. Inspired by this idea the following question arises: Is it possible to synthesize fullerenes from simple and abundant precursors with the help of templates, whose specific geometric and electronic structures enable a natural formation of fullerenes? This means that the formation of fullerenes is induced by specific properties of a template which acts, in addition, as a catalyst during the synthesis process. In the ideal case, the use of pertinent templates would favor the formation of specific fullerenes and, by mixing small heteroatom-containing molecules with the precursors, of heterofullerenes.Herein we show the possibility of using supported nanoparticles as templates and catalysts for the fullerene synthesis from simple precursor molecules, considering as a proof of principle, the synthesis of a simple fullerene, C 60 , from methane or ethylene by nanometer-sized platinum nanoparticles on an oxide support. By means of state-of-the-art ab initio calculations based on DFT we give arguments for the effectiveness of this set-up. For a successful fullerene synthesis sketched here, several conditions have to be fulfilled: 1) the precursor molecules have to be completely dehydrogenated at the Pt nanoparticles, releasing the hydrogen atoms as gaseous hydrogen (H 2 (g)) at working temperature, 2) C atoms or intermediate carbon compounds have to remain at the Pt nanoparticle and must not migrate to the support, and 3) the formation of...

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Structures of metal nanoparticles adsorbed on MgO(001). II. Pt and Pd

Cited by 49 publications

References 37 publications

In Situ Oxidation Study of Pt Nanoparticles on MgO(001)

In Situ Oxidation Study of Pt Nanoparticles on MgO(001)

Investigating the electronic structure of a supported metal nanoparticle: Pd in SiCN

Template‐Assisted Formation of Fullerenes from Short‐Chain Hydrocarbons by Supported Platinum Nanoparticles

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