129Xe NMR investigation of catalytic filamentous carbon

Abstract

A series of catalytic filamentous carbons (CFC) obtained from gas phase reaction on iron subgroup metal catalysts was studied by 129Xe NMR. A connection between 129Xe NMR parameters and structural, textural and paramagnetic properties of CFC was discussed. The chemical shift ( δ) was shown to depend on the structure of the CFC surface formed by edge, basal or both (edge and basal) graphite faces. This dependence follows a general trend of the chemical shift to increase with adsorption potential of a surface. The term describing Xe–Xe interaction ( δ Xe–Xe) in confined space decreased with the average pore size of CFC granule. For hollow multi-wall carbon nanotubes two 129Xe NMR signals were attributed to voids inside nanotubes and to interstices between the interlaced nanotubes. However, analysis of experimental data is complicated due to the presence of paramagnetic metal particles necessary to the filament growth. Therefore, ESR data are given and correlated with 129Xe NMR results.