Adsorption and Desorption of Weakly Bonded Adsorbates from Single-Wall Carbon Nanotube Bundles

Tobias Hertel¹, Jennah Kriebel² , Gunnar Moos¹ and Roman Fasel³

¹Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
²Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford St, Cambridge Ma, 02138, USA
³EMPA Dübendorf, Abt. 124, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland

We present an investigation of the kinetics of adsorption and desorption of some weakly bonded gases from single wall carbon nanotube bundles and - for comparison - from graphite. Thermal desorption spectra from CH₄, Xe and SF₆ as well as those of MeOH, EtOH and H₂O can be used to obtain adsorbate binding energies. The observed trends in the binding energies of gases with different van der Waals radii suggest that so-called groove sites on the external bundle surface are the preferred low coverage adsorption sites due to their higher binding energy. These results shed new light on the wetting properties of SWNT bundles. In addition we find that measured sticking coefficients can be related to the diffusion kinetics of adsorbates into the bulk of the nanotube samples.