On Thermodynamic Stability of Hydrogenated Graphene Layers, Relevance to the Hydrogen on-board Storage

Abstract

The present analytical study using thermodynamic methods for analysis of data from a number of theoretical and experimental works, devoted to the current problem of thermodynamic stability and related thermodynamic characteristics of the following graphene layers systems: 1) double-side hydrogenated graphene of composition CH -theoretical graphane (Sofo et al. 2007) and experimental graphane (Elias et al. 2009); 2) theoretical single-side hydrogenated graphene of composition CH; 3) theoretical single-side hydrogenated graphene of composition C 2 H -graphone; 4) experimental hydrogenated epitaxial graphene, bilayer graphene and a few layers of graphene on SiO 2 or other substrates; 5) experimental and theoretical single-external side hydrogenated single-walled carbon nanotubes, and experimental hydrofullerene C 60 H 36 ; 6) experimental single-internal side hydrogenated (up to C 2 H or CH composition) graphene nanoblisters with intercalated high pressure H 2 gas inside them, formed on a surface of highly oriented pyrolytic graphite or epitaxial graphene under the atomic hydrogen treatment; and 7) experimental hydrogenated graphite (multigraphene) nanofibers with intercalated solid H 2 nano-regions inside them. The main target of the present study is to show a possible breakthrough in solving the problem of hydrogen on-board storage in fuel cell powered vehicles (Nechaev -2012.

Fundamental Open Questions on Engineering of “Super” Hydrogen Sorption in Graphite Nanofibers: Relevance for Clean Energy Applications

“…[53] (1999) in [20]) reported very low hydrogen storage capacity at 303 K, comparable to activated carbon, for graphite nanofibers (GNFs) prepared by catalytic decomposition of ethylene over nickel, iron, copper/nickel and alumina/magnesia catalysts and concluded that they were unlikely storage materials for hydrogen. However, they left the door open by stating that subtle processing effect might convert inactive materials into effective hydrogen sorbents (as has been recently shown in analytical studies [2] [3], and is considered in the present analytical study). As was also noted in [20], the announcement at the MRS meeting did not escape the automakers and Daimler-Chrysler began an evaluation study with the NU group of these "super" hydrogen storage materials.…”

“…In the present paper are considered, in the light of a constructive critical analysis [2] [3] of a number of data [4]- [12] [20]- [22], some fundamental aspects-open questions, relevant to developing, may be, within several years time frame, of a key breakthrough technology of a compact and energy efficient hydrogen storage in hydrogenated graphite nanofibers (GNFs).…”

“…The known data on volumetric (volume) and gravimetric (mass) energy densities for different energy carriers [1] are shown in Figure 1. The additional symbol (the red circle) corresponds to the analytical data [2] [3] on the molecular solid hydrogen intercalated into the hydrogenated graphite nanofibers (GNFs); those are related to the extraordinary data [4]- [12] (being under consideration in this paper). As is noted in a number of studies, for instance in the recent review [13] [14], hydrogen-based fuel cells are promising solutions for the efficient and clean delivery of electricity.…”

“…Nevertheless, none of the proposed systems, with the exception of the nobody reproduced extraordinary experimental data [4]- [12] and the related analytical data [2] [3], are currently offering the required performances for the on-board hydrogen storage in fuel-cell-powered electrical vehicles [15] [16]. The performances are usually formulated in terms of hydrogen storage gravimetric (mass) and volumetric (volume) capacities (Figure 2, [17]) and control of adsorption/desorption processes, particularly, relevance to so called "reversibility" of the stored hydrogen.…”

“…These values are higher than the targets established by the E.U and/or Japan. The additional symbol (the large red circle) corresponds to the analytical data [2] [3] on the molecular solid hydrogen intercalated into the hydrogenated graphite nanofibers (GNFs); those are related to the extraordinary data [4]- [12] (being under consideration in this paper). The 2017 targets [16] are of 5.5 mass% H 2 (of the system mass) and 40 kg (H 2 )/m 3 (system).…”