title: 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.
authors.affiliation: The Pennsylvania State University, 120 Hosler, University Park, Pennsylvania 16802-5000, USA. adl11@psu.edu
authors.forename: Angela D
authors.initials: AD
authors.lastname: Lueking
authors.forename: Humberto R
authors.initials: HR
authors.lastname: Gutierrez
authors.forename: Dania A
authors.initials: DA
authors.lastname: Fonseca
authors.forename: Deepa L
authors.initials: DL
authors.lastname: Narayanan
authors.forename: Dirk
authors.initials: D
authors.lastname: Van Essendelft
authors.forename: Puja
authors.initials: P
authors.lastname: Jain
authors.forename: Caroline E B
authors.initials: CE
authors.lastname: Clifford