Abstraction of D chemisorbed on graphite (0001) with gaseous H atoms

Zecho, Thomas; Güttler, A.; Sha, Xuejun; Lemoine, Didier; Jackson, Bret; Küppers, J.

doi:10.1016/s0009-2614(02)01573-7

Cited by 77 publications

(104 citation statements)

References 20 publications

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“…Since this panel presents the results with the dimer Eley-Rideal mechanism, this maximum indicates the time at which a maximum of D containing dimers is formed. This behavior contradicts the experiments [28] where the [HD] signal decreases over time and is therefore not likely to be the primary mechanism involved in the abstraction. …”

Section: Mechanism Iii: Dimer Eley-ridealcontrasting

confidence: 85%

“…The initial signal depends linearly on the deuterium coverage, which agrees with Figure 3c in [28]. Figure 7 also displays the total HD yield.…”

Section: Mechanism I: Direct Eley-ridealsupporting

confidence: 79%

“…Several simulation runs were performed using a similar set of pre-exposures as used by Zecho et al [28]. The H and D fluxes were 4.8 × 10…”

Section: Resultsmentioning

confidence: 99%

“…Figure 7 plots, among other quantities, the cross section which indeed shows some coverage dependence. It is however much less than seen in the experiments [28]. The cross section and the value of the initial signal is obtained by fitting the curves shown in Figure 6-I to Eq.…”

Section: Mechanism I: Direct Eley-ridealmentioning

confidence: 88%

“…For the derivation of this equation, we refer to [28]. The expression is obtained assuming only direct Eley-Rideal.…”

Section: Comparison With Experimentsmentioning

confidence: 99%

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Kinetic Monte Carlo studies of hydrogen abstraction from graphite

Cuppen

Hornekær

2008

The Journal of Chemical Physics

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We present Monte Carlo simulations on Eley-Rideal abstraction reactions of atomic hydrogen chemisorbed on graphite. The results are obtained via a hybrid approach using energy barriers derived from DFT calculations as input to Monte Carlo simulations. By comparing with experimental data we discriminate between contributions from different Eley-Rideal mechanisms. A combination of two different mechanisms yields, good quantitative and qualitative agreement between the experimentally derived and the simulated Eley-Rideal abstraction cross sections and surface configurations. These two mechanisms include a direct Eley-Rideal reaction with fast diffusing H atoms and a dimer mediated Eley-Rideal mechanism with increased cross section at low coverage. Such a dimer mediated Eley-Rideal mechanism has not previously been proposed and serves as an alternative explanation to the steering behavior often given as the cause of the coverage dependence observed in Eley-Rideal reaction cross sections.

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Section: Mechanism Iii: Dimer Eley-ridealcontrasting

confidence: 85%

“…The initial signal depends linearly on the deuterium coverage, which agrees with Figure 3c in [28]. Figure 7 also displays the total HD yield.…”

Section: Mechanism I: Direct Eley-ridealsupporting

confidence: 79%

“…Several simulation runs were performed using a similar set of pre-exposures as used by Zecho et al [28]. The H and D fluxes were 4.8 × 10…”

Section: Resultsmentioning

confidence: 99%

Section: Mechanism I: Direct Eley-ridealmentioning

confidence: 88%

“…For the derivation of this equation, we refer to [28]. The expression is obtained assuming only direct Eley-Rideal.…”

Section: Comparison With Experimentsmentioning

confidence: 99%

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Kinetic Monte Carlo studies of hydrogen abstraction from graphite

Cuppen

Hornekær

2008

The Journal of Chemical Physics

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Dynamics of Surface Reactions

Ertl

2008

Handbook of Heterogeneous Catalysis

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Catalysis concerns the rate of a chemical reaction which is usually expressed as a function of the concentrations of the species involved in the reaction and a set of rate constants k i which depend on temperature T. Within the framework of transition state theory (TST) [1], which forms the basis of chemical kinetics, the latter are given bywhereby E* is the activation energy (= the height of the energy barrier along the 'reaction coordinate', i.e. the path with minimum energy with respect to all other degrees of freedom for nuclear motion). The term ΔS *The basic idea of TST consists in the assumption that at all stages along the reaction coordinate thermal equilibrium is established, so that the temperature (T) is the only essential (macroscopic) parameter. This requires that energy exchange between the various degrees of freedom of the particle interacting with the surface and the heat bath of the solid occur much faster than the process of chemical transformation. This chapter will discuss effects, for which this condition is not fulfilled and hence the observed phenomena are governed by dynamics rather than by kinetics. Energy exchange between adsorbate and solidAn estimate of the typical energy relaxation time of a chemisorbed particle, t relax , can be obtained from ob-

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Kinetic Isotope Effect in the Hydrogenation and Deuteration of Graphene

Paris¹,

Verbitskiy

Nefedov

et al. 2012

Adv Funct Materials

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Summary We have observed a strong kinetic isotope effect (KIE) for the hydrogenation/deuteration reaction on quasi-free-standing monolayer graphene leading to substantially higher saturation coverage of D as compared to H. The unique geometry of the experiment and the relatively low flux of H/D atoms allowed us to study the surface chemistry of graphene during hydrogenation/deuteration monitoring the whole reaction in situ and in real time by photoemission spectroscopy. The experimental results for hydrogenation/deuteration are well described using a phenomenological kinetic model with terms for chemisorption, associative desorption and reflection of H/D atoms. The observed significant difference in the reaction involving H and D with graphene is relevant for isotope specific chemical reactivity in functional carbon materials and is important for the intensive research regarding atomic control of chemical reactivity at the nanoscale. The deuterium-doped graphene develops a band-gap similar to that observed for hydrogen [Haberer et al, Nano Letters 6, (2010), 3360] and consequently that the electronic isotope effect is weak. Electronic isotope effect MotivationKinetic isotope effects (KIEs), i.e. a different reaction constant for isotopes, are important phenomena in physical chemistry. They have been studied for a long time in their relation to the activation and rate of chemical reactions. A significant contribution to KIE are vibrational zero-point energy (ZPE) effects that upshift the energy of a chemical bond by half the phonon frequency of its constituents. Hence, KIEs are easy to observe in the hydrogen isotopes (deuterium and tritium) due to their large relative mass difference and were studied, even at the single-molecule level for hydrogen transfer in organic reactions including acid and base catalysis, enzyme reactions and catalytic decomposition. Most of these reactions were carried out with H and D in a molecular configuration and it was found that the reaction constant for the D compounds is lower than for the corresponding H compounds. These results are explained by the larger ZPE for H bonds, which results in a lower potential energy barrier to be overcome for Hbonds breaking as compared to D bonds. As a result, the bond-breaking reaction proceeds faster for the H compound than for the D compound. There have been very few reports on experiments carried out with one reactant being atomic H or D such as the H-D exchange reactions or reactions of H(D) with oxygen, where it was found that the oxygen-H(D) reaction proceeds equally fast for D and H. This was attributed to the absence of vibrational zero-point energy effects for the atomic species. Much less is known about the kinetics of these reactions in functional carbon materials based on hydrogenated graphene, such as novel 2D polymers.Here we present a novel inverse kinetic isotope effect involving the reaction of H/D radicals with the carbon atoms of epitaxial graphene. The advantages of graphene include a flat, well ordered large area surfa...

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Abstraction of D chemisorbed on graphite (0001) with gaseous H atoms

Cited by 77 publications

References 20 publications

Kinetic Monte Carlo studies of hydrogen abstraction from graphite

Kinetic Monte Carlo studies of hydrogen abstraction from graphite

Dynamics of Surface Reactions

Kinetic Isotope Effect in the Hydrogenation and Deuteration of Graphene

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