Near-Stoichiometric Bulk Graphane from Halogenated Graphenes (X = Cl/Br/I) by the Birch Reduction for High Density Energy Storage
Hydrogen is a clean fuel with high specific energy and its handling and storage are important toward fuel cell research. Particularly, high-density hydrogen storage is crucial for the viability of future hydrogen-powered devices. This leads to the search for suitable methods; one such option is chemical storage in light materials with large surface areas, such as graphene. Here, the bulk production of graphane by Birch reduction of halogenated (Cl/Br/I) graphene precursors is reported as a potentially scalable procedure. Prior treatment with strong hydrohalic acids is used to remove oxygen-groups and to substitute these with halogens, resulting in effective hydrogenation. An unprecedented level of hydrogen storage is obtained from the iodinated-graphene starting material at 7.44 wt%, far above the U.S. Department of Energy's 2020 system target of 5.5 wt% and close to its ultimate 7.5 wt% goal. As the stored hydrogen is chemisorbed on the graphane scaffold it is stable at both room temperature and on atmospheric exposure, where neither temperature control nor pressure regulation is required. Hydrogen may then be desorbed at elevated temperatures above 400 degrees C.