The adsorption, desorption, and exchange reactions of oxygen, hydrogen, and water on platinum surfaces. III. Water adsorption and exchange with oxygen and hydrogen

1977 ◽  
Vol 55 (10) ◽  
pp. 1658-1666 ◽  
Author(s):  
Y. K. Peng ◽  
P. T. Dawson
Keyword(s):  
Exchange Reaction ◽  
Hydrogen Adsorption ◽  
High Vacuum ◽  
Adsorbed Water ◽  
Ultra High Vacuum ◽  
Exchange Reactions ◽  
Adsorption Of Water ◽  
Apparent Activation Energies ◽  
Distribution Studies ◽  
Adsorption Desorption

Ultra-high vacuum thermal desorption experiments have been carried out on the adsorption of water, and the D2O/H and D216O/18O exchange reactions on platinum previously characterized by oxygen and hydrogen adsorption studies. Water is weakly adsorbed and only at T < 150 K, an observation confirmed by using H2 adsorption as a chemical probe for the presence of adsorbed water. The thickness of the adsorbed D2O layers was determined by a novel method involving monitoring the power output of the temperature programmer. Exchange occurs between adsorbed H and a D2O overlayer and the extent of exchange increases with the thickness of the overlayer. Isotope distribution studies show that the surface is heterogeneous and the exchange reaction does not occur at uniform rate. Exchange occurs between adsorbed 18O and a D216O overlayer. The extent of exchange is constant up to T ∼ 300 K showing that D2O is more strongly bound on O-covered Pt presumably as a result of H bonding. Heterogeneity also is apparent in the O-exchange reaction. The apparent activation energies for exchange are 1.8 and 2.9 kcal mol−1 for the half- and fully-covered surfaces, respectively.

The Adsorption, Desorption, and Exchange Reactions of Oxygen, Hydrogen, and Water on Platinum Surfaces. II. Hydrogen Adsorption, Exchange, and Equilibration

1975 ◽  
Vol 53 (2) ◽  
pp. 298-306 ◽  
Author(s):  
Y. K. Peng ◽  
P. T. Dawson
Keyword(s):  
Hydrogen Adsorption ◽  
Surface Composition ◽  
Co Adsorption ◽  
Exchange Reactions ◽  
Platinum Surface ◽  
Polycrystalline Platinum ◽  
Platinum Surfaces ◽  
Exponential Factors ◽  
Apparent Activation Energies ◽  
Adsorption Desorption

The adsorption, desorption, exchange, and equilibration reactions of hydrogen and deuterium on a platinum filament have been investigated by thermal desorption mass spectrometry. A surface saturated with hydrogen at 120 °K has a coverage 4.2 × 1014 molecules cm−2 and gives desorption spectra with four distinct peaks: β1,(165 °K), β2(220 °K), β3(280 °K), and β4(350 °K). Apparent activation energies and pre-exponential factors were determined for the β2-, β3-, and β4-peaks. For both co-adsorption and sequential adsorption of H2 and D2 the mass 2, 3, and 4 desorption spectra have identical shapes and the gas desorbs at equilibrium throughout. It is concluded that hydrogen adsorbs dissociatively. Exchange and equilibration were studied at 120, 210, and 285 °K by determining the surface composition and isotope distribution after varying fractions of preadsorbed H had been replaced. Following exchange at 120 °K the desorption spectra show a higher D content and a lack of equilibrium in the desorbing gas at low temperature. In most other experiments the mass 2,3, and 4 desorption spectra had identical shapes and the gas desorbed at equilibrium. The results are interpreted by a model which requires that the polycrystalline platinum surface is intrinsically heterogeneous. It appears that different mechanisms are unnecessary to interpret the differences in kinetics observed for exchange and equilibration at low temperatures.

scholarly journals Effect of H Adsorption on the Magnetic Properties of an Fe Island on a W(110) Surface

2019 ◽  
Author(s):  
Marko Melander ◽  
Hannes Jonsson
Keyword(s):  
Magnetic Properties ◽  
Data Storage ◽  
Density Functional ◽  
Hydrogen Adsorption ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Low Dimensional ◽  
Low Dimensional Materials

<p>Low-dimensional materials, such as ultrathin films, nanoislands and wires, are actively being researched due to their interesting magnetic properties and possible technological applications for example in high density data storage. Results of calculations of an Fe nanoisland on a W(110) support are presented here with particular focus on the effect of hydrogen adsorption on its magnetic properties. This is an important consideration since hydrogen is present even under ultra-high vacuum conditions. The calculations are based on density functional theory within the generalized gradient approximation. The adsorption of H atoms is found to strongly decrease the magnetic moment of the Fe atoms they are bound to, down to less than a half in some cases as compared with the clean Fe island. The results show that it may be important to take the presence of hydrogen into account in measurements of magnetic properties of nanoislands.</p>

scholarly journals Hydrogen Nanometrology in Advanced Carbon Nanomaterial Electrodes

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1079
Author(s):  
Rui Lobo ◽  
Noe Alvarez ◽  
Vesselin Shanov
Keyword(s):  
Carbon Nanotube ◽  
Hydrogen Storage ◽  
Hydrogen Adsorption ◽  
Accurate Determination ◽  
High Vacuum ◽  
Hydrogen Uptake ◽  
Ultra High Vacuum ◽  
3D Graphene ◽  
Hydrogen Mass ◽  
Carbon Nanotube Networks

A comparative experimental study between advanced carbon nanostructured electrodes, in similar hydrogen uptake/desorption conditions, is investigated making use of the recent molecular beam-thermal desorption spectrometry. This technique is used for monitoring hydrogen uptake and release from different carbon electrocatalysts: 3D-graphene, single-walled carbon nanotube networks, multi-walled carbon nanotube networks, and carbon nanotube thread. It allows an accurate determination of the hydrogen mass absorbed in electrodes made from these materials, with significant enhancement in the signal-to-noise ratio for trace hydrogen avoiding recourse to ultra-high vacuum procedures. The hydrogen mass spectra account for the enhanced surface capability for hydrogen adsorption in the different types of electrode in similar uptake conditions, and confirm their enhanced hydrogen storage capacity, pointing to a great potential of carbon nanotube threads in replacing the heavier metals or metal alloys as hydrogen storage media.

scholarly journals Effect of H Adsorption on the Magnetic Properties of an Fe Island on a W(110) Surface

2019 ◽  
Author(s):  
Marko Melander ◽  
Hannes Jonsson
Keyword(s):  
Magnetic Properties ◽  
Data Storage ◽  
Density Functional ◽  
Hydrogen Adsorption ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Low Dimensional ◽  
Low Dimensional Materials

<p>Low-dimensional materials, such as ultrathin films, nanoislands and wires, are actively being researched due to their interesting magnetic properties and possible technological applications for example in high density data storage. Results of calculations of an Fe nanoisland on a W(110) support are presented here with particular focus on the effect of hydrogen adsorption on its magnetic properties. This is an important consideration since hydrogen is present even under ultra-high vacuum conditions. The calculations are based on density functional theory within the generalized gradient approximation. The adsorption of H atoms is found to strongly decrease the magnetic moment of the Fe atoms they are bound to, down to less than a half in some cases as compared with the clean Fe island. The results show that it may be important to take the presence of hydrogen into account in measurements of magnetic properties of nanoislands.</p>

scholarly journals Water vapor adsorption/desorption on granulated binder-free low-module zeolites

2021 ◽  
Vol 266 ◽  
pp. 02007
Author(s):  
T.N. Borisova ◽  
N.E. Gordina ◽  
V.Yu. Prokof’ev ◽  
E.E. Afanas’eva ◽  
A.V. Afineevskii
Keyword(s):  
Water Vapor ◽  
Coherent Scattering ◽  
Coherent Scattering Region ◽  
Water Vapor Adsorption ◽  
Dew Point ◽  
Static Tests ◽  
Lta Zeolite ◽  
Adsorption Of Water ◽  
Apparent Activation Energies ◽  
Adsorption Desorption

A characteristic of granulated LTA and SOD zeolites is given. It was determined that LTA zeolite particles have a cube shape with a size of ~2 μm; SOD particles have an irregular shape with a size of 0.5–1 μm. The dimension of the coherent scattering region was calculated to be 760 nm for LTA and 453 nm for SOD. The specific surface area of LTA is 115 m2·g–1 and SOD is 141 m2·g–1. Static tests of granulated zeolite showed that the maximum quantity of absorbed water vapor for LTA was ~30 wt.%, and for SOD ~20 wt.%. It was found LTA zeolite to provide adsorption of water from the gas to a dew point of –50 °C, and SOD zeolite of –9 °C. The apparent activation energies for the desorption of water on zeolites were calculated using isoconversional analysis of Friedman, Ozawa–Flynn–Wall, and Kissinger–Akahira–Sunose.

Restoration of Porous Silicon Luminescence in Water Vapour

1995 ◽  
Vol 405 ◽  
Author(s):  
M. S. Brodin ◽  
V. N. Bykov ◽  
D. B. Dan'ko ◽  
R. D. Fedorovich ◽  
A. A. Kipen' ◽  
...  
Keyword(s):  
Water Vapour ◽  
High Vacuum ◽  
Sample Surface ◽  
Ultra High Vacuum ◽  
Porous Si ◽  
Two Factors ◽  
Adsorption Of Water ◽  
Wave Region ◽  
Red Luminescence

AbstractInfluence of different adsorbates on recovery of porous Si luminescence was in situ investigated for samples preheated under ultra-high vacuum conditions. Exposure to simple adsorbates (O2, H2, N2 up to a pressure of 10-3 to 10-1 Torr), long exposure to air at the atmosphere pressure, or immersion into distilled water fail to recover the red luminescence. On the other hand, we found that the red luminescence can be recovered by adsorption of water vapour onto the sample surface.The red luminescence of as-prepared porous Si can be caused by water molecules (together with possible impurities) adsorbed in the pores. The immense surface of the pores provides a large number of emitting sites. The porous Si layer can filter for the emitted light, cutting off the wave region shorter than yellow. The combination of these two factors (emission and filtering) can result in the visible red-orange luminescence of porous Si.

Adsorption of water on graphene/Ru(0001)—an experimental ultra-high vacuum study

2014 ◽  
Vol 50 (57) ◽  
pp. 7698-7701 ◽  
Author(s):  
A. Chakradhar ◽  
U. Burghaus
Keyword(s):  
High Vacuum ◽  
Ultra High Vacuum ◽  
Wetting Properties ◽  
Adsorption Of Water

The intrinsic wetting properties of graphene/Ru(0001) were characterized at ultra-high vacuum conditions.

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