Surface Science Approach to Heterogeneous Catalysis

Rupprechter, Günther

doi:10.1002/9783527680573.ch39

Cited by 12 publications

(10 citation statements)

References 313 publications

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“…It is noted that studies on model catalysts comprising carbon supports are relatively rare compared to oxides. [1313][1314][1315] In this review article, we were interested in compiling and discussing the most significant experimental and theoretical results allowing a better understanding of key phenomena in catalysis as: i) the anchoring of the metal; ii) the metal-support interactions (geometric effects, charge transfer); iii) confinement; iv) spillover; or v) surface functional group effects.…”

Section: Discussionmentioning

confidence: 99%

A Theory/Experience Description of Support Effects in Carbon-Supported Catalysts

2019

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Fermi level in vii) are shown in purple in ii)-vi) with an iso-value of ±0.003 a.u. Reprinted with permission from ref 57 . Copyright 2014 from the Royal Society of Chemistry; b) Molecular model of a corannulene-like element functionalized with three carboxylic groups from two different perspectives in the cpk representation (on the left). The final structure (190 elements in a cubic cell of 60 Å in size) obtained from random packing of the individual elements (on the right). Cyan: carbon, red: oxygen, white: hydrogen. Reprinted with permission from ref 59 Copyright 2017 from Elsevier; c) Side-views of Ru13 adsorbed on Gr-DV-2COOH site before (on left panel) and after a proton jump (right panel). C atoms are in black, O in red, H in with white and Ru in mocha. Reprinted with permission from ref 60 Copyright 2014 from Elsevier; and d) Spin-density projection in µB/a.u. 2 on the graphene plane around i) the hydrogen chemisorption defect (∆) and ii) the vacancy defect in the a sublattice. Carbon atoms corresponding to the a sublattice (o) and to the b sublattice (•) are distinguished. Simulated STM images of the defects are shown in iii) and iv), respectively. Reprinted with permission from ref 61 .

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Section: Discussionmentioning

confidence: 99%

A Theory/Experience Description of Support Effects in Carbon-Supported Catalysts

2019

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“…Simpler models have been used to better be able to address the fundamental chemistry involved, following a so-called modern surface science approach. Well-defined surfaces, single crystal or polycrystalline disks of the main metal in this case, are placed in well-controlled environments, namely, ultrahigh vacuum (UHV) conditions, to be able to use a battery of surface-sensitive techniques such as X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), − scanning tunneling microscopy (STM), ,,, temperature-programmed desorption (TPD), ,,, and reflection–absorption infrared absorption spectroscopy (RAIRS), ,,− to extract molecular details on the adsorption and reactivity of the reactants and modifiers. ,, This approach has provided much insight into the surface chiral chemistry involved, but is limited by the simplicity of the systems used, which do not include the solvent present under catalytic conditions (a fact referred to as the “pressure gap”), − and ignores the characteristics of realistic catalysts, where the metal is present as small nanoparticles (NPs) dispersed on a high-surface-area support, typically an oxide such as silica or alumina (the “materials gap”). ,− …”

Section: Introductionmentioning

confidence: 99%

Adsorption of Chiral Modifiers from Solution onto Supported Platinum Catalysts: The Effect of the Solvent, Other Coadsorbates, and the Support

Wang

Lee

et al. 2020

J. Phys. Chem. C

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The adsorption from a solution of s-1-(1-naphthyl)ethylamine (s-NEA), cinchonidine, and cinchonine on Pt/SiO2, Pt/Al2O3, and a Pt disk was probed in situ by infrared absorption spectroscopy. Adsorption on the supported catalysts shows similar behavior to that seen on flat polycrystalline Pt surfaces, with the adsorption geometry transitioning from the aromatic ring lying close to parallel to the metal surface at low coverages to a more tilted geometry at monolayer saturation. The extent of the adsorption of the chiral modifiers and its degree of irreversibility both vary with the nature of the liquid (CCl4, toluene, ethanol), tracking solubility. Carbon monoxide can be coadsorbed with s-NEA, a coadsorption that leads to a compression and an increase in ordering of the s-NEA layer (aided by exposing the surface to H2). In contrast, s-NEA adsorption dominates when competing with quinoline. Finally, a few small differences were seen in the IR spectra of the chiral modifiers adsorbed on Pt/SiO2 (compared to the other solids) because of the smaller size of the Pt nanoparticles associated with that catalyst. In general, it is crucial to characterize the adsorption of chiral modifiers in situ in the presence of the liquid phase, but the contribution from the catalyst support appears to be minor.

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“…For many years, the surface science approach to heterogeneous catalysis was restricted to gas pressures of 10 −6 mbar and below, giving rise to the well-known “pressure gap” problem [ 1 – 3 ]. This limitation was overcome when surface-sensitive methods (or modes thereof) were developed that could be operated at least in the mbar pressure range.…”

Section: Introductionmentioning

confidence: 99%

Polarization-Dependent SFG Spectroscopy of Near Ambient Pressure CO Adsorption on Pt(111) and Pd(111) Revisited

Roiaz

Pramhaas

et al. 2018

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Polarization-dependent sum frequency generation (SFG) vibrational spectroscopy was employed to examine CO overlayers on Pt(111) and Pd(111) single crystal surfaces at room temperature. Utilizing different polarization combinations (SSP and PPP) of the visible and SFG light allows to determine the molecular orientation (tilt angle) of interface molecules but the analysis of the measured is involved and requires a proper optical interface model. For CO/Pt(111), the hyperpolarizability ratio is not exactly known and varying R in the range 0.1–0.5 yields tilt angles of 40°–0°, respectively. Based on the known perpendicular adsorption of CO on Pt, an exact R-value of 0.49 was determined. Polarization-dependent SFG spectra in the pressure range 10−4 to 36 mbar did not indicate any change of the tilt angle of adsorbed CO. Modeling also indicated a strong dependence of on the incidence angles of visible and IR laser beams. Complementing previous low temperature/low pressure data, room temperature CO adsorption on Pd(111) was examined from 10−6 to 250 mbar. The absolute PPP and SSP spectral intensities on Pt and Pd were simulated, as well as the expected ratios. Although CO on Pt and Pd should exhibit similar intensities (at high CO coverage), the higher ratio for Pd (48 vs. 27 on Pt) renders the detection of adsorbed CO in SSP spectra difficult. The presence or absence of CO species in SSP spectra can thus not simply be correlated to tilted or perpendicular CO molecules, respectively. Careful modeling, including not only molecular and interface properties, but also the experimental configuration (incidence angles), is certainly required even for seemingly simple adsorbate–substrate systems.

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Surface Science Approach to Heterogeneous Catalysis

Cited by 12 publications

References 313 publications

A Theory/Experience Description of Support Effects in Carbon-Supported Catalysts

A Theory/Experience Description of Support Effects in Carbon-Supported Catalysts

Adsorption of Chiral Modifiers from Solution onto Supported Platinum Catalysts: The Effect of the Solvent, Other Coadsorbates, and the Support

Polarization-Dependent SFG Spectroscopy of Near Ambient Pressure CO Adsorption on Pt(111) and Pd(111) Revisited

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