Atomic Iodine Desorption from Single Crystal Nickel Surfaces

Myli, K. B.; Grassian, Vicki H.

doi:10.1021/la00003a028

Cited by 4 publications

(8 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The standard enthalpy of formation of atomic iodine on Ni(111) was previously determined with temperature-programmed desorption (TPD) measurements of the desorption rate of iodine adatoms to make iodine gas atoms . However, this paper assumed a pre-exponential factor of desorption of 1.0 × 10 10 s –1 , which is inconsistent with those determined experimentally for closely related systems. , To improve this value, we will use two methods to estimate the pre-exponential factor for desorption of this system.…”

Section: Discussionmentioning

confidence: 97%

“…Second, we estimate the prefactor by the method of Campbell et al, using the reported entropy of gas-phase iodine atoms. We use for this the entropy of I(g) at 990 K, which is the temperature that iodine adatoms at 0.04 ML coverage reach their maximum desorption rate in that TPD experiment . This gives the pre-exponential factor of desorption to be 3.9 × 10 14 s –1 .…”

Section: Discussionmentioning

confidence: 99%

“…Averaging these two values results in a desorption activation energy ( E des ) of 286 ± 9 kJ/mol, which we will use for the analysis below. (For comparison, the paper with the TPD experiment reported a desorption energy of 214 kJ/mol in the limit of low coverage based on a much lower prefactor resulting in an adsorption enthalpy of −291 kJ/mol.…”

Section: Discussionmentioning

confidence: 99%

“…3 The heat released during this reaction is measured directly using single-crystal adsorption calorimetry (SCAC). Since the energy of the adsorbed iodine atoms has been determined previously with TPD studies, 4 we can extract from this heat the enthalpy of formation of adsorbed methyl.…”

Section: ■ Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Energetics of Adsorbed Methyl and Methyl Iodide on Ni(111) by Calorimetry: Comparison to Pt(111) and Implications for Catalysis

et al. 2017

View full text Add to dashboard Cite

The heat of adsorption and sticking probability of methyl iodide were measured on Ni(111) at 100 and 160 K using single-crystal adsorption calorimetry (SCAC). At 100 K, methyl iodide adsorbs molecularly with a heat of 102 kJ/mol on terrace sites in the low-coverage limit, giving a standard enthalpy of formation (ΔH f °) of CH 3 I(ad) of −87 kJ/mol. A heat of 122 kJ/mol is also measured on defect sites, probably step edges. Calorimetry of the dissociative adsorption of methyl iodide on Ni( 111) at 160 K yielded an integral heat of adsorption of −270 kJ/mol at 0.04 ML, providing the energetics of adsorbed methyl, with ΔH f °[CH 3 (ad)] = −71 kJ/mol and a CH 3 −Ni(111) bond enthalpy of 218 kJ/mol. This is 22 kJ/mol stronger than the reported value for H 3 C−Pt(111) bonds, explaining the greater activity of Ni catalysts for hydrogenolysis in comparison to Pt. The measured energetics for methyl were compared to density functional theory (DFT) calculations from previous literature, showing that these methods systematically underestimate the bond energy of methyl to Ni(111).

show abstract

Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Energetics of Adsorbed Methyl and Methyl Iodide on Ni(111) by Calorimetry: Comparison to Pt(111) and Implications for Catalysis

et al. 2017

View full text Add to dashboard Cite

show abstract

“…Iodine adsorption on the nickel surface was mainly studied on the (100) plane by the Jones and Woodruff group − and recently on the (111) plane by Komarov et al It is noteworthy that the thermodesorption experiments performed by Myli and Grassian , showed that iodine desorbs from the Ni(100) and Ni(111) surfaces in the atomic form. To our knowledge, there is no published work concerning the adsorption/desorption of iodine on the (110) face of nickel.…”

Section: Introductionmentioning

confidence: 99%

Iodine Adsorption on Ni(110): 2D-Phase Transitions and NiI₂ Growth

2019

View full text Add to dashboard Cite

Scanning tunneling microscopy, low-energy electron diffraction, Auger electron spectroscopy, and density functional theory calculations have been used to investigate I2 adsorption on the Ni(110) surface. Dissociative adsorption takes place rapidly to form a c(2 × 2) layer at an iodine coverage of 0.5 ML. DFT calculations show that hollow sites are energetically preferable for iodine adsorption on the Ni(110) surface. Increase of iodine coverage above 0.5 ML leads to the commensurate–incommensurate phase transition via nucleation of loops of domain walls and to their subsequent ordering into the striped superstructure. At saturation, a striped domain-wall phase degenerates into the uniaxially compressed quasi-hexagonal phase. Further iodine dosing leads to the nucleation and growth of 2D nickel iodide islands.

show abstract