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 600o C. We demonstrate approximately 65 ± 15 at % hydrogenation of carbon atoms in the single-walled carbon nanotubes which is equivalent to 5.1 ± 1.2 weight % hydrogen capacity. We also show that the hydrogenation is a reversible process.

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The kinetics of the adsorption system CO/Pt(111) has been studied by time-resolved high-resolution x-ray photoelectron spectroscopy using third generation synchrotron radiation at BESSY II. CO is dosed by a supersonic molecular beam device which allows for a high sample pressure (here up to 10−6 mbar) and a fast switching of the pressure. The site-specific occupation of CO adsorbed on on-top and bridge sites is determined quantitatively from C 1s spectra, which can be taken with a minimum collection time of 1.5 s per spectrum. Based on the observation of thermal equilibrium between the two sites, we perform a phenomenological analysis of the data, assuming a constant binding energy difference ΔE. From the on-top/bridge occupation ratio as a function of coverage obtained by uptake measurements we extract a value of ΔE=41 meV. With the same ansatz, ΔE is calculated from temperature-dependent measurements at a constant coverage. Finally, determination of the coverage during isothermal desorption is used to obtain the total binding energy of CO on Pt(111). Differences between our evaluation methods and literature reports are discussed.

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