Hydrogenation of Single-Walled Carbon Nanotubes

Towards the development of a useful mechanism for hydrogen storage, we have studied the hydrogenation of single-walled carbon nanotubes with atomic hydrogen using core-level photoelectron spectroscopy and x-ray absorption spectroscopy. We find that atomic hydrogen creates C-H bonds with the carbon atoms in the nanotube walls, and such C-H bonds can be completely broken by heating to 600 °C. We demonstrate approximately $65\pm 15\mathrm{at}\%$ hydrogenation of carbon atoms in the single-walled carbon nanotubes, which is equivalent to $5.1\pm 1.2\mathrm{\text{wt}}\%$ hydrogen capacity. We also show that the hydrogenation is a reversible process.

Figure 1

C1s XPS spectra of (a) clean SWCN film and (b) SWCN film after hydrogenation. Spectra are normalized to the area of the C1s peak. Inset: Raman spectrum of a clean SWCN film.

Figure 2

Carbon $K$-edge XAS spectra of (a) clean SWCN film and (b) SWCN film after hydrogenation.

Figure 3

Decomposition C1s XPS spectrum [plot (b), Fig. 1] into peak (1) (unaffected carbon atoms) and peak (2) (hydrogenated carbon atoms). The inset indicates the calculated C1s binding energies (BE) for hydrogenated nanotubes in different diameters (D) which are shown as vertical lines.

Figure 4

C1s XPS spectra of SWCN film exposed to the two cycles of hydrogenation and dehydrogenation: (a) clean SWCN film, (b) hydrogenated SWCN film, (c) SWCN annealed at 600 °C, (d) hydrogenated SWCN film, and (e) SWCN annealed at 600 °C. Spectra are normalized to the area of the C1s peak. Inset: Raman spectrum of SWCN film after two cycles of hydrogenation or dehydrogenation.