Influence of milling conditions on hydrogen storage capacities of activated carbon mechanically milled in an H2 atmosphere

Carbon Nanomaterials, Relevance to Solving the Hydrogen Storage Problem

“…( 14) and ( 15) suggest that the equilibrium (local) concentration of adsorbed hydrogen molecules in the intergranular nanoregions in GNFs and nanostructured graphite at 300 K and a hydrogen pressure 1-10 MPa is close in the order of magnitude to the carbohydride value (H 2 /C def }) Iim  0.5. In other words, the hydrogen content in the material may approach the target value [3][4][5] of 2010 that makes such materials suitable for use as adsorbents for hydrogendriven vehicles; this agrees with the results in [10,18] of processing the sorption data in [12,14,[54][55][56]. At the same time, for process II (as well as for processes III and IV), the rate of diffusion discharge of chemisorbed hydrogen from the material at room temperature is low (basically because of the high value of Q II ), which does not meet the technical requirements [3][4][5] for hydrogen-driven vehicles.…”

“…[3][4][5] as the lower limit of 2010 of the sorption capacity of adsorbent materials suitable for storing hydrogen in vehicles. The given estimate is confirmed by the analysis in [10,18] of the sorption data in [12,14,[54][55][56]; the results are discussed below.…”

“…Regarding the results in [89], we must note that two to three TPD peaks (see Fig. 5) were observed in nanostructured graphite in [14,[53][54][55][56], which, according to the analysis in Refs. [10,18] (Section 3, Table 1), correspond to chemisorption processes II, III, and/or IV.…”

“…3 and 5a, TPD peak III) and related carbon nanostructures with sp 2 hybridization, including graphite nanofibers (GNF) (Fig. 4, TPD peak  (III)) and nanostructured graphite [14,[52][53][54][55][56] (Figs. 5b and c, TPD peak III).…”

“…[95] (in the form of strands, microcrystalline films, and `rugs' with a polycrystalline structure), i.e., the presence in the single-wall nanotube samples used in [94,95] of graphite multilayer nanostructures typical of the GNF samples used in [94], in which the sorption process  may run; (6) the appearance (studied in [95]) in the mass spectra of the gases released in the course of a multistage prolonged (many-hour) heating up to 673 K in a vacuum of deuterated single-wall nanotube samples, the prevailing contribution of hydrocarbons, and, at higher temperatures of the multistage heating process (773 K for 3 hours and 823 K for three hours), the appearance of the prevailing contribution of deuterium and HD molecules; and (7) (a) the manifestation of only one C-H peak in the IR spectrum of nanostructured graphite studied in [89] (see Section 5.2), which basically corresponds to the C-H 2 configuration comparable to model H in Fig. 6 for chemisorption process II; (b) manifestation in such a material of two to three high-temperature TPD peaks [14,[53][54][55][56]96] (chemisorption processes II, III, and/or IV, Table 1 and Fig. 5), two peaks in the NMR spectrum (of the Gaussian and Lorentzian types) [14,65], and two peaks corresponding to C-H bonds, 0.11 and 0.18 nm long, in the spectrum of the neutrondiffraction radial distribution [14]; (c) the manifestation of two high-temperature TPD peaks diffusion characteristics of chemisorption process IV, as we did in the analytical study in Ref.…”