X-ray absorption near edge spectroscopy of the electronic structure of potassium adsorbed single walled carbon nanotubes

Abstract

Carbon nanotubes (CNTs) show exceptional properties which make them extremely attractive for many applications. The electronic structure of potassium adsorbed single-walled carbon nanotubes (SWCNTs) is investigated by x-ray near edge structure (XANES) spectroscopy. Gas molecules (H2O, O2, CO2, CO) and potassium (K) adsorbates showed non negligible sensitivity to the geometry, thermal annealing treatment, and hybridization. The SWCNT type is shown by transmission electron microscopy (TEM) whereas an aleatory arrangement of SWCNTs and the spherical iron particles along carbon nanotubes are observed by scanning electron microscopy (SEM). XANES shows that the charge transfer effect in K-doping SWCNTs increases the conductivity to 62.7%. The adsorption study demonstrates that the adsorption mechanism to remove potassium from aqueous solutions using SWCNTs is assimilated to the ion exchange process. The functional groups OH−, C=O and C≡C are involved in the adsorption process. They are correlated to the assignment of the adsorbates given by XANES.