Effect of surface characteristics and catalyst loaded amount on hydrogen storage in carbon nanotubes

Hydrogen spillover effect on hydrogen storage in catalyst loaded carbon nanotubes (CNTs) with different surface characteristics was investigated in the present study. Three diameter ranges of pristine CNTs were employed. Physical structure of CNTs surface was modified by KOH activation at different temperatures. Various cobalt contents were deposited onto the pristine/activated CNTs by wet impregnation method. The experimental results revealed that hydrogen storage in CNTs was strongly affected by the physical surface structure and by the catalyst loading. Higher hydrogen storage capacity was obtained while larger specific surface area of CNTs and higher catalyst content onto CNTs. Moreover, it was found that the relationship between the surface concentration of spilt-over H atoms (QH, mmol-H/m2) and the specific Co content (CCo, mmol-Co/m2) is approximately linear. The correlated slopes (QH/CCo) of the activated CNTs with defect feature and of the pristine CNTs are 8.6 and 2.4, respectively. Hydrogen spillover effect is much more significant for the activated CNTs with defect feature than for the pristine CNTs.