Hydrogen adsorption capacity studies

Hydrogen adsorption has been studied for a wide range of porous carbons,silicas, ° aluminas, zeolites, porous 

The amounts of hydrogen adsorbed under high pressure at 77 and 298 K and corresponding surface areas and pore volumes have been investigated 

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To date, Ref. [65] provides probably the most reliable data on a series of chemically activated carbons and also on other types of carbon materials, such as activated carbon fibers, CNTs, and CNFs. The best values measured for adsorption capacity at 298 K were 1.2 and 2.7 wt% at 20 and 50MPa, respectively. At 77K, the hydrogen adsorption capacity reached 5.6wt% at 4MPa. Such values demonstrate that nanoporous carbons are not worst than other kinds of materials studied at the moment for hydrogen storage. 

The co-existence of at least two modes of ethylene adsorption has been clearly demonstrated in studies of 14C-ethylene adsorption on nickel films [62] and various alumina- and silica-supported metals [53,63—65] at ambient temperature and above. When 14C-ethylene is adsorbed on to alumina-supported palladium, platinum, ruthenium, rhodium, nickel and iridium catalysts [63], it is observed that only a fraction of the initially adsorbed ethylene can be removed by molecular exchange with non-radioactive ethylene, by evacuation or during the subsequent hydrogenation of ethylene—hydrogen mixtures (Fig. 6). While the adsorptive capacity of the catalysts decreases in the order Ni > Rh > Ru > Ir > Pt > Pd, the percentage of the initially adsorbed ethylene retained by the surface which was the same for each of the processes, decreased in the order... 

A remarkable adsorption capacity on high surface area ACs under a hydrogen pressure has been reported for the first time at the beginning of the 1980s [55,56], Whereas hydrogen is absorbed in the interstitial sites of metallic alloys, the main storage mechanism in carbon materials is the adsorption in micropores [57,58], Depending on the authors, theoretical studies found that the optimum pore... 

To conclude this section, it is necessary to state that experimental hydrogen adsorption studies on zeolites at room temperature are scarce. It has been reported that zeolites can store only very small amounts of hydrogen (<0.5 wt % at 60 bar) at room temperature [151]. In this regard, LSX zeolites, as well, fully exchanged with alkali-metal cations, that is, Li+, Na+, and K+, to get samples Li-LSX, Na-LSX, and K-LSX, were tested for their hydrogen storage capacities at 298 K and 10 MPa, and the measured H2 capacity was 0.6 wt % [38],... 

The SWNT systems chosen in the present studies include 3 armchair nanotubes and 3 zigzag nanotubes with diameters ranging from 4 A to 12 A, and 1 chiral nanotube with a diameter of 8.28 A. The nanotubes were carefully chosen to address the fundamental issues of curvature and chirality and the effect of each on the adsorption capacity. First, to understand the curvature effect on hydrogen uptake, we selected nanotubes with diameters varying from about 4 A to 12 A. Next, to investigate the effect of nanotube chirality, we intentionally chose the nanotubes of different chiral architectures with similar diameters. Finally, to study the capacity of a given nanotube, we included three different H2 loadings at 0.4 wt. %, 3.0 wt. % and 6.5 wt. %, respectively, in our MD simulations. 

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