Abstract
Carbon is an attractive material for hydrogen adsorption due to its light weight, variety of structures, and ability to both physisorb and chemisorb hydrogen. Recently, fully hydrogenated graphene layers (“graphane”) have been predicted to exist [J. O. Sofo et al., Phys. Rev. B 75, 15340 (2007)], and experimentally observed [D. C. Elias et al., Science 323, 610 (2009)]. In this work, we examine analogs of graphane, in particular and . Unlike graphene, these materials have a band gap without hydrogenation. Our results indicate that the hydrogenation product of BN is metastable: the fully hydrogenated compound is higher in energy than hexagonal BN sheets plus molecules, in sharp contrast with graphane. We find that is energetically very close to hexagonal molecules. Furthermore, our examination of the relative binding strengths of rows of symmetry related hydrogen atoms on shows that this compound is marginally higher in energy than plus an molecule, with the hydrogen atoms in absorbed on the carbon sites. These remaining hydrogen atoms are not as strongly bound as in graphane, indicating that the average hydrogen chemisorption energy is controllable by changing the carbon content in the B-C-N layer.
- Received 19 August 2009
DOI:https://doi.org/10.1103/PhysRevB.80.195411
©2009 American Physical Society