We performed first-principles calculations to investigate the hydrogen storage characteristics of carbon-based 3-D solid structures, called covalently bonded graphenes (CBGs). Using the density functional method and the Møller-Plesset perturbation method, we show that H2 molecular binding in the CBGs is stronger than that on an isolated graphene with an increase of 20 to approximately 150% in binding energy, which is very promising for storage at ambient conditions. We also suggest that the CBGs of appropriate size can effectively work as frameworks for transition metal dispersion. The adsorption properties of hydrogen on the metal atoms dispersed inside the CBGs are also presented.

We studied catalytic performance, particularly tolerance against CO poisoning and particle migration, of Pt nanoparticles dispersed on graphene using ab initio calculations. It was shown that the binding of Pt nanoparticles to graphene and the molecular adsorption on Pt can be controlled by introducing defects on graphene. Pt d-band center is a key parameter that is tailored by such defect formation. It is observed that the binding energy difference between H(2) and CO is well correlated with the d-band center, whereas individual H(2) and CO binding energies are not. Relative occupation ratio of H(2) on Pt in a CO environment showed that Pt nanoparticles can tolerate CO more than does bulk Pt when the particles are deposited on nitrogen-doped graphene.

The noncovalent hydrogen binding on transition-metal atoms dispersed on carbon clusters and graphene is studied with the use of the pseudopotential density-functional method. It is found that the presence of acceptorlike states in the absorbents is essential for enhancing the metal adsorption strength and for increasing the number of hydrogen molecules attached to the metal atoms. Particular configurations of boron substitutional doping are found to be very efficient for providing such states and thus enhancing storage capacity. Optimal doping conditions are suggested based on our calculations for the binding energy and ratio between metal and hydrogen molecules.