Quantum-chemical calculation of a spillover model on a graphite support

Borisov, Yu. А.; Zolotarev, Yu. A.; Laskatelev, E. V.; Myasoedov, N. F.

doi:10.1007/bf02495386

Cited by 13 publications

(13 citation statements)

References 8 publications

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“…The activation energies were 33.8 and 13.08 kcal/mol, respectively. In contrast to [4], we obtained a negative enthalpy of attachment of atomic hydrogen to the central atoms of the cluster, which amounted to -11.2 kcal/mol and ∆G= -3.37 kcal/mol, which shows that the reaction is favorable. For comparison, the energy of hydrogen detachment from a similar position from [5] is equal to 42 kcal/mol.…”

Section: Migration Of Charged Particlescontrasting

confidence: 60%

“…Two variants of the hydrogen spillover over a carbon surface are proposed in literature, confirmed by quantum-chemical modeling: migration of a charged [4] and neutral bounded particle [5]. The choice is made in favor of the migration of a charged particle, since the activation energy of this process is close to the experimental.…”

Section: Problem Statementmentioning

confidence: 93%

“…In [3] two variants of a hydrogen spillover over a graphite surface were proposed for the first time. Since it is difficult to compare the results of quantum-chemical calculations performed by different approaches, here various spillover mechanisms over carbon surfaces are compared within a single quantum-chemical approach: mechanisms with the migration of charged particles over the surface [4], a mechanism of hydrogen atom migration along the edge and the surface of graphite [5], the "relay" mechanism between hydrogen radicals and hydrogen molecules [3], the transfer of a carbon radical center and the new generation of a hydrogen radical [3]. Like any chain process, the last two mechanisms include a non-linear stage, when one act of atomic hydrogen generation leads to many acts of substitution in the product.…”

Section: Problem Statementmentioning

confidence: 99%

“…Similarly to [4], the process of transfer of a hydrogen atom between neighboring carbon atoms and the same process for a charged system was considered, Fig. 2.…”

Section: Migration Of Charged Particlesmentioning

confidence: 99%

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Hydrogen Spillover Mechanisms over a Graphite Surface

Leshchev

2019

EPJ Web Conf.

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Four different mechanisms of hydrogen spillower over carbon surface are considered in the framework of a single quantum-chemical approach. Two of them, described in the literature, are the physical migration of a bonded hydrogen atom along the surface and the edge of the graphene. One of the mechanisms proposed by the author does not include the migration of atomic hydrogen, but is realized via a transfer of carbon radical over a carbon sheet and generation of H atom in another place. Calculated activation energies of all four mechanisms are compared.

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Section: Migration Of Charged Particlescontrasting

confidence: 60%

Section: Problem Statementmentioning

confidence: 93%

Section: Problem Statementmentioning

confidence: 99%

“…Similarly to [4], the process of transfer of a hydrogen atom between neighboring carbon atoms and the same process for a charged system was considered, Fig. 2.…”

Section: Migration Of Charged Particlesmentioning

confidence: 99%

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Hydrogen Spillover Mechanisms over a Graphite Surface

Leshchev

2019

EPJ Web Conf.

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“…Borisov et al [21] performed ab initio Hartree-Fock (HF/6-31G*) calculations of a model compound, coronene (C 24 H 12 ), having planar graphite-like framework, of a complex of this compound with proton, and of the transition state in proton migration over the model surface [21]. It has been found that the proton affinity of C 24 H 12 is 779 kJ mol -1 and the activation energy of proton transfer between the adjacent carbon atoms of C 24 H 12 is 42 kJ mol -1 , which is very close to the experimentally determined value of 65 kJ mol -1 for the activation energy Е а of hydrogen spillover on the graphite surface [21].…”

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confidence: 98%

Efficiency of isotope exchange between sodium 4-phenylbenzoate and activated tritium

et al. 2015

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The efficiency of the protium-tritium isotope exchange in the sodium 4-phenylbenzoate (PBNa) molecule on activating the reaction on a tungsten filament at 1940 K (target temperature 77 and 295 K) and on heating the substrate supported on 5% Pd/C in the presence of gaseous tritium is compared. It is shown that the reaction mechanism is laregly determined by the properties of the material on which this reaction occurs and not only by the method of generation of activated tritium species. In the reaction of tritium atom with PBNa deposited on glass walls of the reaction vessel, the isotope substitution of tritium for protium occurred by the radical mechanism, leading to the formation of [ 3 H]PBNa and hydrogenation products. It is assumed that the spillover of tritium atom over the support (carbon) surface is accompanied by polarization of the electronic shell and formation of the cluster ( 3 H + )(ē), which leads to changes in the composition of the reaction products. The combined treatment of PBNa on 5% Pd/C allows estimation of the concentration of clusters on the carbon surface, which reaches 10.9 particles per 100 nm 2 (9.2 nm 2 per cluster).Hydrogen spillover on various materials is being actively studied today, because this phenomenon underlies many catalytic reactions and can favor the development of efficient methods for hydrogen storage [1][2][3][4][5][6][7]. Interaction of hydrogen molecules with platinum group metals leads to the formation of activated hydrogen species capable of migration from the catalyst on the support. The spillover mechanism and the reactivity of the migrating species are determined by the nature of the surface over which the hydrogen activated on the catalyst migrates. Although ample experimental data [1-6] demonstrate the possibility of hydrogen spillover on various supports, the calculations made in [7] show that hydrogen spillover is efficient only on the surface of materials on which redox reactions can occur, e.g., on the surface of transition metal oxides. In this case, a proton interacting with oxygen anions migrates over the surface, which is accompanied by the electron transfer from the reduced M (n-1)+ cation to the adjacent M n+ cation [8,9]. The spillover intensity is determined by the activation energy of the proton and electron migration in the matrix. Adsorbed water plays an important role in such migration, which was demonstrated by the calculations adequately describing the hydrogen migration over the WO 3 surface [10]: The О-Н bond dissociation energy is compensated by the simultaneous formation of a new О-Н bond. Similar mechanism was suggested for the hydrogen spillover over the MoO 3 surface [11]. The hydrogen spillover on materials incapable of reversible redox reactions is attributed to the presence of defects or impurity atoms on the support surface [12].In adsorption of hydrogen atoms on materials characterized by the charge distribution on the surface or by high dipole moments, the electronic shell of the atom undergoes deformation polarization up to the f...

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The efficiency of solvent‐free catalyst systems in the synthesis of tritium‐labelled biologically active compounds

Shevchenko

Nagaev

Myasoedov

2010

Labelled Comp Radiopharmac

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Modern theories about the processes that take place inside solvent‐free catalyst systems are considered and the various factors that have an effect on the successful introduction of tritium into organic compounds are summarized. Obtaining labelled compounds using solvent‐free catalyst systems, liquid‐phase methods, and isotopic exchange with tritiated water are all regarded as various manifestations of the same set of occurrences in the presence of tritium, a substrate and a catalyst. The use of various isotopic exchange methods has made possible the introduction of tritium into practically any type of biologically active compound. This will enable scientists to carry out more detailed studies of the processes inside living organisms. Copyright © 2010 John Wiley & Sons, Ltd.

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Quantum-chemical calculation of a spillover model on a graphite support

Cited by 13 publications

References 8 publications

Hydrogen Spillover Mechanisms over a Graphite Surface

Hydrogen Spillover Mechanisms over a Graphite Surface

Efficiency of isotope exchange between sodium 4-phenylbenzoate and activated tritium

The efficiency of solvent‐free catalyst systems in the synthesis of tritium‐labelled biologically active compounds

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