The calorimetric heats of adsorption of hydrogen on platinum films

Černý, S.; Smutek, M.; Bůzek, František

doi:10.1016/0021-9517(75)90085-8

Cited by 39 publications

(6 citation statements)

References 23 publications

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“…These results are in agreement with results from previous calorimetric measurements performed on polycrystalline Pt catalysts (for example 28,38,42 ). Moreover, these results are in agreement with results reported by various groups for the dependence of the heat versus coverage for hydrogen adsorption on Pt films, filaments and supported Pt materials. − , …”

Section: Resultssupporting

confidence: 92%

“…DFT calculations of the energies for the hydrogen atom adsorption at atop-, bridge-bonded and 3-fold sites (reactions 4−6 in Table ) gave values of −261, −262, and −263 kJ/mol, respectively. These numbers correspond to values of −85, −87, and −89 kJ/mol, respectively, for the energy changes of dissociative adsorption of H 2 on these sites; and these values are in agreement with experimental initial heats of −75 to −95 kJ/mol for the dissociative adsorption of H 2 on a variety of Pt surfaces. ,,− In addition, the calculated values for the Pt−H binding energies and the prediction that these values are insensitive to the site coordination on Pt(111) are in agreement with results from recent theoretical studies. − Analogous to ethylidyne adsorption, the 3-fold hcp site was found to be energetically similar to the fcc site.…”

Section: Resultssupporting

confidence: 86%

“…Comparisons of the energetics of hydrogen adsorption on Pt(111) terrace sites and on step/edge sites (e.g., a (997) plane) showed that the step/edge sites have heats that are stronger by 12−15 kJ/mol. ,, In agreement with these results, the initial heats for adsorption of hydrogen on polycrystalline films, filaments and supported Pt materials, which are expected to have a measurable number of step/edge sites, were found to be about −95 kJ/mol. − The integral heat of adsorption was reported to be independent of the dispersion for supported Pt . Moreover, the dependence of the differential heat versus coverage was the same on samples with different metal particle sizes .…”

Section: Introductionmentioning

confidence: 67%

“…Moreover, the dependence of the differential heat versus coverage was the same on samples with different metal particle sizes . Furthermore, this dependence is similar for a wide variety of Pt surfaces. ,, To explain the apparent invariance of the heats of adsorption with surface structure, Masel et al performed theoretical calculations for sites with different coordination numbers on several Pt crystal planes . They found that although a stronger heat of adsorption can be expected for coordinatively unsaturated sites, this effect can be negated by surface relaxations and reconstructions, leading to similar heats of adsorption on different types of sites.…”

Section: Introductionmentioning

confidence: 97%

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DFT Calculations and Monte Carlo Simulations of the Co-Adsorption of Hydrogen Atoms and Ethylidyne Species on Pt(111)

et al. 2001

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A grandcanonical Monte Carlo (MC) simulation is described for calculating surface coverages of adsorbed hydrogen atoms and ethylidyne species on Pt(111) as a function of temperature and partial pressures of ethane and hydrogen. The MC simulation is based on self-consistent, gradient-corrected density functional theory (DFT) calculations of the energies of adsorption of H atoms and ethylidyne species at various positions on a periodic Pt(111) slab. DFT calculations of lateral interaction energies between pairs of adsorbates at various distances of separation on the Pt(111) slab are reported. The MC simulation results are in agreement with results from microcalorimetric measurements at 300 K and 573−673 K of the heats of hydrogen adsorption versus adsorbate coverage on two silica-supported Pt samples and on Pt powder. The MC simulation results for the coadsorption of H atoms and ethylidyne species on Pt(111) are used to develop analytical expressions that describe the surface coverages by these species over a wide range of temperatures and pressures (i.e., hydrogen pressures from 1 to 101 kPa, ethane pressures from 0.1 to 10 kPa, and temperatures from 550 to 750 K). The application of these results is discussed for modeling the kinetics of ethane hydrogenolysis over Pt catalysts.

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Section: Resultssupporting

confidence: 92%

Section: Resultssupporting

confidence: 86%

Section: Introductionmentioning

confidence: 67%

Section: Introductionmentioning

confidence: 97%

See 2 more Smart Citations

DFT Calculations and Monte Carlo Simulations of the Co-Adsorption of Hydrogen Atoms and Ethylidyne Species on Pt(111)

et al. 2001

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“…Comparisons of the energetics of hydrogen adsorption on Pt(111) terrace sites and on step/edge sites (e.g., a (997) plane) showed that the step/edge sites have heats that are stronger by 12−15 kJ/mol. ,, In agreement with these results, the initial heats for adsorption of hydrogen on polycrystalline films, filaments, and supported Pt materials, which are expected to have a measurable number of step/edge sites, were found to be about −95 kJ/mol. − The integral heat of adsorption was reported to be independent of the dispersion for supported Pt .…”

Section: Introductionmentioning

confidence: 70%

Monte Carlo Simulations of Reaction Kinetics for Ethane Hydrogenolysis over Pt

et al. 2002

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A Monte Carlo (MC) molecular model, with parameters derived from density functional theory calculations, is used to describe experimental data for the rate of ethane hydrogenolysis for a Pt/SiO 2 catalyst over a wide range of conditions. The surface concentrations of the most abundant stable species (hydrogen atoms, ethylidyne species, and di-σ-bonded ethylene) are simulated with a MC grandcanonical ensemble, and the rate of ethane hydrogenolysis is calculated by simulating surface concentrations for three types of transition state complexes for C-C bond cleavage. The simulation shows that larger repulsive interactions between adsorbed C 2 H x and H species lead to more negative reaction orders with respect to the hydrogen pressure. The results of the MC simulation indicate that the reaction proceeds primarily through C-C bond cleavage in adsorbed C 2 H 5 species, with smaller contributions from adsorbed CHCH 3 and CHCH 2 species. The MC results suggest that although the most abundant surface hydrocarbon species has a stoichiometry of C 2 H 3 , the reaction proceeds through more highly hydrogenated C 2 H 5 species. The state of the surface is predicted to change from being primarily hydrogen-covered at most experimental conditions to being highly hydrocarbon-covered at low hydrogen partial pressures.

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