Hydrogen in potassium-doped carbon nanotubes studied by positron annihilation

Abstract The positron lifetime for potassium-doped carbon nanotubes (K-NTs) ascribed to positrons in trapping centers is shortened upon exposure of the K-NTs to hydrogen. Thermal desorption of hydrogen from hydrogenated K-NTs shows a peak around 510 K, where a hydrogenated potassium-graphite intercalation compound (K-GIC) shows a peak. The absorbed hydrogen is bonded with K-NTs in the same manner as found in hydrogenated K-GIC, and their positron-trapping centers are located in a more negatively charged region, such as a two-dimensional structure of hydride ions.