Hydrogen interaction with fullerenes: From C${}_{20}$ to graphene

The paper presents a systematic study of the trends in the interaction of hydrogen with carbon fullerenes versus their curvature, where graphene is taken as the limit of zero curvature. The efficiency of hydrogen incapsulation in fullerenes, penetration into them, and adsorption on their surface are analyzed and discussed. The effects on magnetism are also considered; in particular, it is shown that hydrogen adsorption to some fullerenes induces magnetism to initially nonmagnetic systems. In addition, highly hydrogen-saturated fullerenes are examined and the suitability of fullerenes for hydrogen storage is discussed.

Figure 1

(a) Schematic energy diagram of the interaction energy between hydrogen atom and fullerene cage. (b) Hydrogen atom at the center of the fullerene and (c) chemisorbed from the inside. (d) Hydrogen atom chemisorbed outside the fullerene. (e) Schematic energy diagram for H atom adsorbed to the inner wall and H located at the center of the fullerene.

Figure 2

(a) Interaction energy of the H atom confined at the center of a fullerene C${}_m$ and (b) magnetic moment of the fullerene C${}_m$ and C${}_m$H system, where $m$ is the number of carbon atoms.

Figure 3

Penetration barrier for the hydrogen atom entering the C${}_{60}$ fullerene. Both facets are situated $\approx$3.3 Å from the center of the fullerene.

Figure 4

Adsorption energy for hydrogen atom chemisorbed to the surface of different fullerene molecules. Adsorption data for each fullerene is listed in Table .

Figure 5

Spin-density isosurface for (a) C${}_{28}$ at 0.20 $e/$Å${}^3$, (b) C${}_{32}$ at 0.16 $e/$Å${}^3$, and (c) C${}_{36}$ at 0.10 $e/$Å${}^3$.

Figure 6

Spin-density isosurface for (a) C${}_{28}$ with two hydrogen atoms on surface ($2\times \mathrm{site}$ s1) at 0.15 $e/$Å${}^3$ and (b) C${}_{28}$ with three hydrogen atoms on surface ($3\times \mathrm{site}$ s1) at 0.10 $e/$Å${}^3$.

Figure 7

Hydrogen molecule dissociation and adsorption above C-C bond (a) and above hexagonal facet (b) on the fullerene and graphene outer surfaces.

Figure 8

Configurations of H saturated fullerene and graphene surfaces: (a) C${}_{20}$, (b) C${}_{20}$H, (c) C${}_{20}$H${}_2$, (d) C${}_{20}$H${}_8$, (e) C${}_{20}$H${}_{12}$, (f) C${}_{20}$H${}_{20}$, (g) Graphene 1 ML, (h) Graphene 1/2 ML, (i) Graphene 1/6 ML, (j) C${}_{60}$H${}_2$, (k) C${}_{60}$H${}_{36}$, and (l) C${}_{60}$H${}_{60}$. In graphene pictures, dashed circles represents hydrogen atoms on the other side of graphene sheet and polygon represents supercell used in calculations.