Combined Hydrogen Production and Storage with Subsequent Carbon Crystallization

Abstract

We provide evidence of low-temperature hydrogen evolution and possible hydrogen trapping in an anthracite coal derivative, formed via reactive ball milling with cyclohexene. No molecular hydrogen is added to the process. Raman-active molecular hydrogen vibrations are apparent in samples at atmospheric conditions (300 K, 1 bar) for samples prepared 1 year previously and stored in ambient air. Hydrogen evolves slowly at room temperature and is accelerated upon sample heating, with a first increase in hydrogen evolution occurring at approximately 60 degrees C. Subsequent chemical modification leads to the observation of crystalline carbons, including nanocrystalline diamond surrounded by graphene ribbons, other sp2-sp3 transition regions, purely graphitic regions, and a previously unidentified crystalline carbon form surrounded by amorphous carbon. The combined evidence for hydrogen trapping and carbon crystallization suggests hydrogen-induced crystallization of the amorphous carbon materials, as metastable hydrogenated carbons formed via the high-energy milling process rearrange into more thermodynamically stable carbon forms and molecular hydrogen.

Development of Doped Nanoporous Carbons for Hydrogen Storage

“…In conjunction with ambient temperature hydrogen evolution reported elsewhere, 7 the Raman spectroscopy provided supporting evidence for an unusual hydrogen interaction within the material. Molecular hydrogen has a characteristic strong Raman vibron centered at 4160 cm -1 (Figure 14a), one of several Q branch lines (Q 1 (J) (Δν=1; ΔJ=0; J=0, 1, 2, 3).…”

“…Synthesis of RBMAs is described elsewhere. 7 In brief, ball milling was done on a Fritsch Planetary Mono Mill Pulverisette 6 LC -106A with a 250 ml stainless steel (Fe-Cr-Ni) vessel and a set of twenty 10mm diameter stainless steel balls. The samples were generally milled for 80 hours at 400 rpm in ultra-high purity (99.99999%) grade argon atmosphere to prevent oxidation and minimize air exposure.…”

“…RBMA Studies. RBMAs were used to establish characterization procedures for hydrogenated tetrahedral amorphous carbons, as RBMAs were previously shown 7 to have regions of suspected sp 2 -sp 3 phase transition. Therefore these materials provided a means to establish methods to study the carbon transitions that may occur during interaction with hydrogen.…”

Ab initio studies of staggered Li adatoms on graphene

“…Hydrogen is the most obvious choice of dopant, and hydrogenated graphene, which is more commonly referred to as graphane [7,8], has been studied very extensively [9]. From previous work, the main results for our purposes are two fold: firstly, the energetically most favoured site for a single isolated hydrogen adatom on graphene is the on-top site and, secondly, 100% coverage at the on-top sites results in insulating behaviour, with the lowest energy configuration corresponding to hydrogen adatoms attaching alternately above and below the graphene layer.…”

A preliminary report on the formation of graphite from sub-bituminous coal during oxidation in H<SUB align="right">2O<SUB align="right">2/HCOOH: a new forecast

“…by value additions (World Coal Association, 2013). Coal-based carbon materials, such as activated carbon, carbon blocks, carbon electrodes, and carbon nano-tubes have been produced and utilised worldwide for a long time (Balsamo et al, 2013;Yua et al, 2003;He et al, 2012;Xiao et al, 2010;Lueking et al, 2006). However, no attention or attempt has been made for the chemical conversion of coal into graphite as per our best of literature survey.…”