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Author |
Shirazi, M.; Bogaerts, A.; Neyts, E.C. |
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Title |
A DFT study of H-dissolution into the bulk of a crystalline Ni(111) surface: a chemical identifier for the reaction kinetics |
Type |
A1 Journal article |
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Year  |
2017 |
Publication |
Physical chemistry, chemical physics |
Abbreviated Journal |
Phys Chem Chem Phys |
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Volume |
19 |
Issue |
19 |
Pages |
19150-19158 |
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Keywords |
A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT) |
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Abstract |
In this study, we investigated the diffusion of H-atoms to the subsurface and their further diffusion into the bulk of a Ni(111) crystal by means of density functional theory calculations in the context of thermal and plasma-assisted catalysis. The H-atoms at the surface can originate from the dissociative adsorption of H2 or CH4 molecules, determining the surface H-coverage. When a threshold H-coverage is passed, corresponding to 1.00 ML for the crystalline Ni(111) surface, the surface-bound H-atoms start to diffuse to the subsurface. A similar threshold coverage is observed for the interstitial H-coverage. Once the interstitial sites are filled up with a coverage above 1.00 ML of H, dissolution of interstitial H-atoms to the layer below the interstitial sites will be initiated. Hence, by applying a high pressure or inducing a reactive plasma and high temperature, increasing the H-flux to the surface, a large amount of hydrogen can diffuse in a crystalline metal like Ni and can be absorbed. The formation of metal hydride may modify the entire reaction kinetics of the system. Equivalently, the H-atoms in the bulk can easily go back to the surface and release a large amount of heat. In a plasma process, H-atoms are formed in the plasma, and therefore the energy barrier for dissociative adsorption is dismissed, thus allowing achievement of the threshold coverage without applying a high pressure as in a thermal process. As a result, depending on the crystal plane and type of metal, a large number of H-atoms can be dissolved (absorbed) in the metal catalyst, explaining the high efficiency of plasma-assisted catalytic reactions. Here, the mechanism of H-dissolution is established as a chemical identifier for the investigation of the reaction kinetics of a chemical process. |
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Wos |
000406334300034 |
Publication Date |
2017-06-22 |
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Edition |
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ISSN |
1463-9076 |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
4.123 |
Times cited |
10 |
Open Access |
OpenAccess |
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Notes |
Financial support from the Reactive Atmospheric Plasma processIng – eDucation (RAPID) network, through the EU 7th Framework Programme (grant agreement no. 606889), is gratefully acknowledged. The calculations were performed using the Turing HPC infrastructure at the CalcUA core facility of the Universiteit Antwerpen, a division of the Flemish Supercomputer Center VSC, funded by the Hercules Foundation, the Flemish Government department (EWI) and the Universiteit Antwerpen. |
Approved |
Most recent IF: 4.123 |
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Call Number |
PLASMANT @ plasmant @ c:irua:144794 |
Serial |
4633 |
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Author |
Shirazi, M.; Neyts, E.C.; Bogaerts, A. |
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Title |
DFT study of Ni-catalyzed plasma dry reforming of methane |
Type |
A1 Journal article |
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Year |
2017 |
Publication |
Applied catalysis : B : environmental |
Abbreviated Journal |
Appl Catal B-Environ |
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Volume |
205 |
Issue |
205 |
Pages |
605-614 |
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Keywords |
A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT) |
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Abstract |
tWe investigated the plasma-assisted catalytic reactions for the production of value-added chemicalsfrom Ni-catalyzed plasma dry reforming of methane by means of density functional theory (DFT). Weinspected many activation barriers, from the early stage of adsorption of the major chemical fragmentsderived fromCH4andCO2molecules up to the formation of value-added chemicals at the surface, focusingon the formation of methanol, as well as the hydrogenation of C1and C2hydrocarbon fragments. Theactivation barrier calculations show that the presence of surface-bound H atoms and in some cases alsoremaining chemical fragments at the surface facilitates the formation of products. This implies that thehydrogenation of a chemical fragment on the hydrogenated crystalline surface is energetically favouredcompared to the simple hydrogenation of the chemical fragment at the bare Ni(111) surface. Indeed, thepresence of hydrogen modifies the electronic structure of the surface and the course of the reactions.We therefore conclude that surface-bound H atoms, and to some extent also the remaining chemicalfragments at the crystalline surface, induce the following effects: they facilitate associative desorption ofmethanol and ethane by increasing the rate of H-transfer to the adsorbed fragments while they impedehydrogenation of ethylene to ethane, thus promoting again the desorption of ethylene. Overall, they thusfacilitate the catalytic conversion of the formed fragments from CH4and CO2, into value-added chemicals.Finally, we believe that the retention of methane fragments, especially CH3, in the presence of surface-boundHatoms (as observed here for Ni) can be regarded as an identifier for the proper choice of a catalystfor the production of value-added chemicals. |
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Wos |
000393931000063 |
Publication Date |
2017-01-05 |
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ISSN |
0926-3373 |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
9.446 |
Times cited |
26 |
Open Access |
OpenAccess |
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Notes |
Financial support from the Reactive Atmospheric Plasmaprocessing –eDucation network (RAPID), through the EU 7thFramework Programme (grant agreement no. 606889) is grate-fully acknowledged. The calculations were performed using theTuring HPC infrastructure at the CalcUA core facility of the Univer-siteit Antwerpen, a division of the Flemish Supercomputer CenterVSC, funded by the Hercules Foundation, the Flemish |
Approved |
Most recent IF: 9.446 |
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Call Number |
PLASMANT @ plasmant @ c:irua:139514 |
Serial |
4343 |
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