Dissociation of hydrogen on metal surfaces

Harris, Justin

doi:10.1021/la00059a022

Cited by 24 publications

(15 citation statements)

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“…This assumption of equality between adsorption and desorption energies should be valid here, since H 2 dissociation barriers on most transition metal surfaces are small or zero. 69 TDS experiments for high coverages of hydrogen on W(001) observed a desorption peak corresponding to 1.40 eV. 26 Our values are higher, but they reflect ¼ ML coverage where H-H repulsions are much smaller.…”

Section: Hydrogen On Tungsten Surfacesmentioning

confidence: 69%

Hydrogen in tungsten: Absorption, diffusion, vacancy trapping, and decohesion

2010

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Understanding the interaction between atomic hydrogen and solid tungsten is important for the development of fusion reactors in which proposed tungsten walls would be bombarded with high energy particles including hydrogen isotopes. Here, we report results from periodic density-functional theory calculations for three crucial aspects of this interaction: surface-to-subsurface diffusion of H into W, trapping of H at vacancies, and H-enhanced decohesion, with a view to assess the likely extent of hydrogen isotope incorporation into tungsten reactor walls. We find energy barriers of (at least) 2.08 eV and 1.77 eV for H uptake (inward diffusion) into W(001) and W(110) surfaces, respectively, along with very small barriers for the reverse process (outward diffusion). Although H dissolution in defect-free bulk W is predicted to be endothermic, vacancies in bulk W are predicted to exothermically trap multiple H atoms. Furthermore, adsorbed hydrogen is predicted to greatly stabilize W surfaces such that decohesion (fracture) may result from high local H concentrations.

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Section: Hydrogen On Tungsten Surfacesmentioning

confidence: 69%

Hydrogen in tungsten: Absorption, diffusion, vacancy trapping, and decohesion

2010

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“…At low coverage, Θ ads ≪, and with the activity of vacant sites close to unity, the surface coverage is approximated by, The equilibrium constant, K ads , contains parameters such as the sticking coefficient, s 0 , which is related to the catalytic activity of the metal surface. The catalytic activity of a metal surface has direct implications on the dynamics of the H 2 -metal interaction, and has been attributed to geometric factors such as crystallographic orientation and surface inhomogeneities, as well as to electronic factors such as defect induced potentials, work functions and the density of states at the Fermi level [92][93][94][95][96].…”

Section: Mass Transfer: Adsorption Dissociation and Diffusionmentioning

confidence: 99%

Comparison of Cu and Pt point-contact electrodes on proton conducting BaZr0.7Ce0.2Y0.1O3−

2017

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“…14 This will increase the Pauli repulsion between the surface s electrons and the approaching close-shelled H 2 , which should pile up the reaction barrier at the entrance channel. 31 These experimental and theoretical works explain the H and H desorption behaviors in the present work. Previous work indicated that H species arise from the decomposition of surface hydroxyls on hardly reducible iron oxides.…”

Section: H 2 -Tprmentioning

confidence: 54%

Alkalis in iron‐based Fischer–Tropsch synthesis catalysts: distribution, migration and promotion

Cheng

Zhang

et al. 2016

J of Chemical Tech & Biotech

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BACKGROUND Alkali metals are considered important chemical promoters used in Fischer–Tropsch synthesis (FTS) iron‐based catalysts. The purpose of this study is to distinguish the relative effects of alkali metals on iron based FTS catalysts. RESULTS It is found that Li and Na promoters can easily diffuse into/out the bulk of catalysts while K, Rb and Cs mostly concentrate on the catalyst surface. Alkalis also inhibited H2 adsorption, improved CO adsorption and dissociation, and suppressed the hydrogenation of carbon species on the surfaces of iron or iron carbides. Li and Na decreased the FTS activity while K, Rb and Cs largely increased the FTS activity of iron catalysts. The selectivities to methane and alkane were decreased while those to olefin and heavier hydrocarbons were increased by alkalis. Among these alkalis, potassium showed an optimal promotional effect on FTS performances. CONCLUSION The distributions of alkalis in catalysts were quite different owing to their atomic radii. The majority of Li and Na promoters diffused into the bulk of catalysts while K, Rb and Cs mostly concentrated on the catalyst surface. The selectivity of methane exhibits a parabola‐like trend with increasing atomic number of alkalis and reaches a minimum at KFeSi catalyst. © 2016 Society of Chemical Industry

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Dissociation of hydrogen on metal surfaces

Cited by 24 publications

References 0 publications

Hydrogen in tungsten: Absorption, diffusion, vacancy trapping, and decohesion

Hydrogen in tungsten: Absorption, diffusion, vacancy trapping, and decohesion

Comparison of Cu and Pt point-contact electrodes on proton conducting BaZr0.7Ce0.2Y0.1O3−

Alkalis in iron‐based Fischer–Tropsch synthesis catalysts: distribution, migration and promotion

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