few-layer graphene_PNAS2011.pdf

Chemical storage of hydrogen in few-layer graphene K. S. Subrahmanyam a, Prashant Kumar a, Urmimala Maitra a, A. Govindaraj a, K. P. S. S. Hembram b , Umesh V. Waghmare b, and C. N. R. Rao a,1 Chemistry and Physics of Materials Unit, and Theoretical Science Unit and International Centre for Materials Science, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur ., Bangalore-560 064, India Contributed by C. N. R. Rao, December 28, 2010 (sent for review December 14, 2010) Birch reduction of few-layer graphene samples gives rise to hydrogenated samples containing up to 5 wt % of hydrogen. Spectroscopic studies reveal the presence of sp 3C-H bonds in the hydrogenated graphenes. They, however, pose readily on heating to 500 °C or on irradiation with UV or laser radiation releasing all the hydrogen, thereby demonstrating the possible use of few-layer graphene for chemical storage of hydrogen. First-principles calculations throw light on the mechanism of dehy- drogenation that appears to involve a significant reconstruction and relaxation of the lattice. hydrogen storage ∣reversible hydrogenation S torage of hydrogen in a suitable solid matrix is a major chal- lenge facing the munity (1). Some time ago car- bon nanotubes were suggested to be useful for storing hydrogen, but only ～ 3 wt % storage has since been achieved (2 –4). It has been shown that reaction of sin