Electrochemical sorption of hydrogen in single-wall carbon nanotubes encapsulated in palladium

The distribution of hydrogen in the palladium matrix and single-wall carbon nanotubes (SWCNs) in Pd-SWCN nanocomposite upon electrochemical hydrogenation is quantitatively studied in situ using voltammetry and chronoammetry. The high mobility of hydrogen in nanotubes is discovered and reflected in the low H-SWCN bond energy, which equals 0.073 ± 0.05 eV/H-atom and is close to the hydrogen activation energy (ɛH = 0.072–0.08 eV/H-atom) obtained using vacuum thermal desorption [7]. The presence of SWCN is shown to increase the hydrogen capacity of the Pd-SWCN composite compared to individual palladium by nearly 25%. The hydrogen storage capacity of nanotubes (CH) in Pd-SWCN composite increases with an increase in the Pd-to-SWCN volume ratio (V(Pd)/V(SWCN)). CH reaches the maximum limiting value of 12 wt % at V(Pd)/V(SWCN) > 12.