Energy disposal during desorption of D2 from the surface and subsurface region of Ni(111)

Wright, S. L.; Skelly, J.; Hodgson, A.

doi:10.1039/b004010j

Cited by 22 publications

(18 citation statements)

References 34 publications

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“…Indeed, on the noncatalytic Ti substrate, the onset temperatures for hydrogen desorption significantly differed (by 50 • C) as particle size increased and the surface area decreased accordingly (Figure 5b), in agreement with previous reports [15]. The initial desorption of hydrogen at 210 • C is also consistent with reported thermal desorption spectra of molecular hydrogen adsorbed at Ni surfaces [31][32][33]. It can thus be concluded that the shift in desorption temperature observed on the Ni catalytic substrate from 290 to 390 • C as particle size increased from 68 ± 11 to 421 ± 70 nm is related to rate-limiting steps other than hydrogen recombination at the magnesium surface.…”

Section: Hydrogen Sorption Propertiessupporting

confidence: 81%

Electrodeposited Magnesium Nanoparticles Linking Particle Size to Activation Energy

Shen

Aguey‐Zinsou

2016

Energies

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Abstract:The kinetics of hydrogen absorption/desorption can be improved by decreasing particle size down to a few nanometres. However, the associated evolution of activation energy remains unclear. In an attempt to clarify such an evolution with respect to particle size, we electrochemically deposited Mg nanoparticles on a catalytic nickel and noncatalytic titanium substrate. At a short deposition time of 1 h, magnesium particles with a size of 68 ± 11 nm could be formed on the nickel substrate, whereas longer deposition times led to much larger particles of 421 ± 70 nm. Evaluation of the hydrogen desorption properties of the deposited magnesium nanoparticles confirmed the effectiveness of the nickel substrate in facilitating the recombination of hydrogen, but also a significant decrease in activation energy from 56.1 to 37.8 kJ·mol −1 H 2 as particle size decreased from 421 ± 70 to 68 ± 11 nm. Hence, the activation energy was found to be intrinsically linked to magnesium particle size. Such a reduction in activation energy was associated with the decrease of path lengths for hydrogen diffusion at the desorbing MgH 2 /Mg interface. Further reduction in particle size to a few nanometres to remove any barrier for hydrogen diffusion would then leave the single nucleation and growth of the magnesium phase as the only remaining rate-limiting step, assuming that the magnesium surface can effectively catalyse the dissociation/recombination of hydrogen.

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Section: Hydrogen Sorption Propertiessupporting

confidence: 81%

Electrodeposited Magnesium Nanoparticles Linking Particle Size to Activation Energy

Shen

Aguey‐Zinsou

2016

Energies

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“…In both reports it was pointed out that the activation energy barrier for the process starting from surface H and CH 3 is considerably lower in energy, and the increased reactivity when the Ni catalyst is prepared with subsurface H atoms is not due to a new reaction pathway but rather the additional energy given to the initial state of the desorption process by driving the H atoms into subsurface sites. 7,8 The reactivity of subsurface deuterium on Ni͑111͒ has been studied by Wright et al 9,10 Temperature-programmed desorption experiments of D in both subsurface and surface sites show enhanced D 2 associative desorption on Ni͑111͒ at 180 K, as compared to a thermal base line. The angular distribution of desorbing molecules is consistent with subsurface D atoms surfacing at vacant sites and diffusing on the surface before combining to form D 2 .…”

Section: Introductionmentioning

confidence: 98%

Theoretical calculations of CH4 and H2 associative desorption from Ni(111): Could subsurface hydrogen play an important role?

Henkelman

Arnaldsson

Jónsson

2006

The Journal of Chemical Physics

167

140

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The results of theoretical calculations of associative desorption of CH(4) and H(2) from the Ni(111) surface are presented. Both minimum-energy paths and classical dynamics trajectories were generated using density-functional theory to estimate the energy and atomic forces. In particular, the recombination of a subsurface H atom with adsorbed CH(3) (methyl) or H at the surface was studied. The calculations do not show any evidence for enhanced CH(4) formation as the H atom emerges from the subsurface site. In fact, there is no minimum-energy path for such a concerted process on the energy surface. Dynamical trajectories started at the transition state for the H-atom hop from subsurface to surface site also did not lead to direct formation of a methane molecule but rather led to the formation of a thermally excited H atom and CH(3) group bound to the surface. The formation (as well as rupture) of the H-H and C-H bonds only occurs on the exposed side of a surface Ni atom. The transition states are quite similar for the two molecules, except that in the case of the C-H bond, the underlying Ni atom rises out of the surface plane by 0.25 A. Classical dynamics trajectories started at the transition state for desorption of CH(4) show that 15% of the barrier energy, 0.8 eV, is taken up by Ni atom vibrations, while about 60% goes into translation and 20% into vibration of a desorbing CH(4) molecule. The most important vibrational modes, accounting for 90% of the vibrational energy, are the four high-frequency CH(4) stretches. By time reversibility of the classical trajectories, this means that translational energy is most effective for dissociative adsorption at low-energy characteristic of thermal excitations but energy in stretching modes is also important. Quantum-mechanical tunneling in CH(4) dissociative adsorption and associative desorption is estimated to be important below 200 K and is, therefore, not expected to play an important role under typical conditions. An unexpected mechanism for the rotation of the adsorbed methyl group was discovered and illustrated a strong three-center C-H-Ni contribution to the methyl-surface bonding.

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“…Lin et al 25 reported the direct imaging of subsurface hydrogen atoms in Pd nanoparticles. Wright et al 26 examined the reaction between subsurface and surface D atoms on Ni(111). The detected product translational excitation suggested that the recombination was direct at low temperatures, whereas the indirect channel started to work at high temperatures due to the decrease in the energy release.…”

Section: Introductionmentioning

confidence: 99%

H Resurface and Hot H Promoted H₂ Recombination on Ni(111): Effects of Arrangement, Surface Coverage, and Lattice Motion

Ying

2021

J. Phys. Chem. C

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Subsurface H can affect catalytic reactivity and selectivity. H resurface and H2 recombination with a subsurface H on Ni(111) were investigated by the quantum instanton method, and the arrangement, surface coverage, lattice motion, and hot H effects were explored. The arrangement effect of a surface H and a subsurface H varied the H resurfacing rate constant by 57 times at 300 K. From the clean Ni(111) to two H adsorbed Ni(111), the increase of surface coverage suppressed the H resurfacing rate constant by four orders of magnitude at 300 K, whereas it increased the H penetration rate constant by about 10 times. The lattice motion effect was extremely remarkable for H resurface, H penetration, and direct H2 recombination, which enhanced the corresponding rate constants by about 10, 14, and 9 orders of magnitude, respectively, at 300 K. The hot resurfacing H could speed up H2 recombination by 140 times at 300 K. For the H2 recombination of a surface H and a subsurface H, the two-step process was much faster than the direct process. In the two-step process, H resurface was the rate-limiting step at extremely low temperatures due to the frozen lattice, while the recombination of two surface H atoms became the rate-limiting step as the lattice was relaxed with increasing temperature.

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Energy disposal during desorption of D2 from the surface and subsurface region of Ni(111)

Cited by 22 publications

References 34 publications

Electrodeposited Magnesium Nanoparticles Linking Particle Size to Activation Energy

Electrodeposited Magnesium Nanoparticles Linking Particle Size to Activation Energy

Theoretical calculations of CH4 and H2 associative desorption from Ni(111): Could subsurface hydrogen play an important role?

H Resurface and Hot H Promoted H₂ Recombination on Ni(111): Effects of Arrangement, Surface Coverage, and Lattice Motion

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Energy disposal during desorption of D2 from the surface and subsurface region of Ni(111)

Cited by 22 publications

References 34 publications

Electrodeposited Magnesium Nanoparticles Linking Particle Size to Activation Energy

Electrodeposited Magnesium Nanoparticles Linking Particle Size to Activation Energy

Theoretical calculations of CH4 and H2 associative desorption from Ni(111): Could subsurface hydrogen play an important role?

H Resurface and Hot H Promoted H2 Recombination on Ni(111): Effects of Arrangement, Surface Coverage, and Lattice Motion

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H Resurface and Hot H Promoted H₂ Recombination on Ni(111): Effects of Arrangement, Surface Coverage, and Lattice Motion