Microscopic Insights into Methane Activation and Related Processes on Pt/Ceria Model Catalysts

Lykhach, Yaroslava; Staudt, Thorsten; Lorenz, Michael; Streber, Regine; Bayer, Andreas; Steinrück, Hans‐Peter; Libuda, Jörg

doi:10.1002/cphc.200900673

Cited by 60 publications

(100 citation statements)

References 55 publications

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“…The initially slow rate of CH formation suggests that CH is formed from CH 3 in a sequential reaction after thermalization. At higher CH 3 exposures (> 200 L), the CH formation rate increases, resembling the dominant contribution of the CH species in C 1s spectra observed previously [53] (note that CH 3 exposure for the period of 1400 s results in a total dose of about 140 L). This is in contrast with CH 3 formation, which saturates faster and most probably reflects a scenario in which a monolayer of methyl species is also formed at the interior of nanoparticle facets.…”

supporting

confidence: 61%

“…In previous SSMB/XPS experiments using laboratory light sources, we have found the first indications that after initial methane activation and formation of CH 3 , dehydrogenation of these species proceeds spontaneously to CH and C, even at temperatures as low as 130 K. [53] On the contrary, these reactions required significantly higher temperatures on both PtA C H T U N G T R E N N U N G (111) [56] and on stepped Pt single-crystal surfaces. [62,75] To further verify this observation, HR-PES experiments were performed by using synchrotron radiation, providing both better spectral and temporal resolution than what could be obtained in the previous experiments.…”

mentioning

confidence: 95%

“…[54,55,74] We have also investigated the growth of Pt nanoparticles on the film by means of scanning tunneling microscopy (STM). [53] It was found that Pt grows in the form of three-dimensional islands with a nucleation density of around 5 10 12 cm À2 under the conditions applied. Based on this value, it was estimated that the Pt nanoparticles contain, on average, around 600 Pt atoms, corresponding to an average particle size of around 3.3 nm.…”

mentioning

confidence: 99%

“…The samples were prepared by the deposition of a Pt layer with a nominal thickness of 0.5 nm onto a wellordered 2.5 nm thick CeO 2 A C H T U N G T R E N N U N G (111)/CuA C H T U N G T R E N N U N G (111) film at 300 K. Details of the sample preparation and treatment procedure can be found in the literature. [53][54][55] The Pt/CeO 2 /CuA C H T U N G T R E N N U N G (111) samples were exposed to a collimated supersonic molecular beam (SSMB) of CH 4 at a sample temperature of 100 K. The SSMB was generated from a resistively heated 100 mm molybdenum nozzle at a seeding ratio of 1:10 in a He environment. Previously, the kinetic energy (KE) of CH 4 was determined to be 68 kJ mol…”

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confidence: 99%

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Methane Activation by Platinum: Critical Role of Edge and Corner Sites of Metal Nanoparticles

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Staudt

et al. 2010

Chemistry A European J

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Complete dehydrogenation of methane is studied on model Pt catalysts by means of state-of-the-art DFT methods and by a combination of supersonic molecular beams with high-resolution photoelectron spectroscopy. The DFT results predict that intermediate species like CH(3) and CH(2) are specially stabilized at sites located at particles edges and corners by an amount of 50-80 kJ mol(-1). This stabilization is caused by an enhanced activity of low-coordinated sites accompanied by their special flexibility to accommodate adsorbates. The kinetics of the complete dehydrogenation of methane is substantially modified according to the reaction energy profiles when switching from Pt(111) extended surfaces to Pt nanoparticles. The CH(3) and CH(2) formation steps are endothermic on Pt(111) but markedly exothermic on Pt(79). An important decrease of the reaction barriers is observed in the latter case with values of approximately 60 kJ mol(-1) for first C-H bond scission and 40 kJ mol(-1) for methyl decomposition. DFT predictions are experimentally confirmed by methane decomposition on Pt nanoparticles supported on an ordered CeO(2) film on Cu(111). It is shown that CH(3) generated on the Pt nanoparticles undergoes spontaneous dehydrogenation at 100 K. This is in sharp contrast to previous results on Pt single-crystal surfaces in which CH(3) was stable up to much higher temperatures. This result underlines the critical role of particle edge sites in methane activation and dehydrogenation.

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confidence: 61%

mentioning

confidence: 95%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Methane Activation by Platinum: Critical Role of Edge and Corner Sites of Metal Nanoparticles

Viñes

Lykhach

Staudt

et al. 2010

Chemistry A European J

Self Cite

133

107

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“…$Ce 4? redox chemistry [173,[184][185][186][187][188]. Sacrificial reduction of the ceria supports by reactively formed hydrogen liberated during the oxidative dehydrogenation of alcohols could mitigate in situ reduction of oxidised palladium, and hence maintain selox activity and catalyst lifetime, with Ce 4?…”

Section: Establishing Support Effectsmentioning

confidence: 99%

Catalysing sustainable fuel and chemical synthesis

Lee

2014

Appl Petrochem Res

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Concerns over the economics of proven fossil fuel reserves, in concert with government and public acceptance of the anthropogenic origin of rising CO 2 emissions and associated climate change from such combustible carbon, are driving academic and commercial research into new sustainable routes to fuel and chemicals. The quest for such sustainable resources to meet the demands of a rapidly rising global population represents one of this century's grand challenges. Here, we discuss catalytic solutions to the clean synthesis of biodiesel, the most readily implemented and low cost, alternative source of transportation fuels, and oxygenated organic molecules for the manufacture of fine and speciality chemicals to meet future societal demands.

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

Viñes

Görling

2011

Angewandte Chemie

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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 o...

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Microscopic Insights into Methane Activation and Related Processes on Pt/Ceria Model Catalysts

Cited by 60 publications

References 55 publications

Methane Activation by Platinum: Critical Role of Edge and Corner Sites of Metal Nanoparticles

Methane Activation by Platinum: Critical Role of Edge and Corner Sites of Metal Nanoparticles

Catalysing sustainable fuel and chemical synthesis

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

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