Hydrogen physisorption

Optimal Texture for Hydrogen Physisorption and Electrosorption in Nanoporous Carbons... 

This is very likely due to their very high reactivity, making deposition difficult and unwanted side reactions probable. Because the walls have uniform thickness (<1 nm), zeolites have been used as a template for the synthesis of ordered micro porous carbon materials [127-130] and they are tested for hydrogen physisorption [131]. 

Darkrim, F., Vermesse, J., Malbmnot, P., and Levesque, D. (1999). Monte Carlo simulations of nitrogen and hydrogen physisorption at high pressures and room temperature. Comparison with experiments. J. Chem. Phys., 110, 4020-7. 

I. Cabria, M.J. Lopez and J.A. Alonso, Enhancement of hydrogen physisorption on graphene and carbon nanotubes by Li doping . The Journal of Chemical Physics, 123, 204721 (2005). 

Hydrogen physisorption on pure carbon materials will not meet DOE targets, owing to the thermodynamic enthalpy of hydrogen adsorption on carbon. For instance, our previous work on SWNTs yielded a value of 38 milli-electron volt [1] or 3.6 kilojoule per mole (kJ/mole), values consistent with adsorption on a graphene surface [2]. Our work for... 

Coupling to a mineral surface requires the presence of active hydroxyls on the substrate. The coupling reaction is a multi-step process that proceeds from a state of physisorption through hydrogen bond formation to actual covalent bond formation through condensation of surface hydroxyls with silanols ... 

The first step of the grafting process is probably the physisorption of Bu4Sn on the surface of the support (higher surface area), which then migrates from the support to the metal surface. Then, when the physisorbed complex interacts with the surface Pt atoms covered by hydrogen atoms (Pts-H ), there is... 

It is most convenient to explain catalysis using an example. We have chosen a hydrogenation catalysed by nickel in the metallic state. According to the schematic of Fig. 3.1 the first step in the actual catalysis is adsorption . It is useful to distinguish physisorption and chemisorption . In the former case weak, physical forces and in the latter case relatively strong, chemical forces play a role. When the molecules adsorb at an active site physisorption or chemisorption can occur. In catalysis often physisorption followed by chemisorption is the start of the catalytic cycle. This can be understood from Fig. 3.2, which illustrates the adsorption of hydrogen on a nickel surface. 

Titrations of carbon monoxide and hydrogen sulfide up to 800 torr were performed at 30°C each volumetric titration was composed of two adsorption isotherms the first isotherm was a combination of chemisorption and physisorption. 

Fast adsorption/desorption kinetics and relatively small (<10 kj/mol) adsorption enthalpies are observed for hydrogen adsorption on many porous materials, which indicates that physisorption on porous materials is suitable for fast recharging with hydrogen [81,82], The narrowest pores make the biggest contribution to hydrogen-adsorption capacity, whereas mesopores contribute to total pore volume, but little to hydrogen capacity, and are detrimental for the overall volumetric capacity. Hence, porous materials with very narrow pores or pore-size distributions are required for enhanced hydrogen capacity at low pressures. 

Benard, P, R. Chahine, Storage of hydrogen by physisorption on carbon and nanostructured materials. Scr. Mater. 56,803-808,2007. 

Okamoto, Y., Y. Miyamoto, Ab initio investigation of physisorption of molecular hydrogen on planar and curved graphene, /. Phys. Chem. B 105, 3470, 2001. 

The interaction between drug compounds and excipients, as these influence drug dissolution, can be successfully studied by means of reflectance spectroscopy. In one study concerning probucol and indomethacin, it was deduced that hydrogen bonding and van der Waals forces determined the physisorption between the active and the excipients in several model formulations [36]. Chemisorption forces were found to play only minor roles in these interactions. These studies indicated that surface catalytic effects could be important during the selection of formulation excipients. 

There is a wide range of adsorption enthalpies AH(adsi, ranging from effectively zero to as much a 600 kJ per mole of adsorbate. The adsorptive interaction cannot truly be said to be a bond if the enthalpy is small the interaction will probably be more akin to van der Waals forces, or maybe hydrogen bonds if the substrate bears a surface layer of oxide. We call this type of adsorption physical adsorption, which is often abbreviated to physisorption. At the other extreme are adsorption processes for which A//(ads) is so large that real chemical bond(s) form between the substrate and adsorbate. We call this type of adsorption chemical adsorption, although we might abbreviate this to chemisorption. 

Physisorption (i.e., adsorption of hydrogen) of molecular hydrogen by weak van der Waals forces to the inner surface of a highly porous material. Adsorption has been studied on various nanomaterials, e.g., nanocarbons, metal organic frameworks and polymers. 

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