Enhancement of hydrogen spillover onto carbon nanotubes with defect feature

Hydrogen spillover is one of potential ways to enhance hydrogen storage in carbon nanotubes (CNTs). In this study, hydrogen spillover effect on hydrogen storage in cobalt (Co) metal loaded CNTs with different structural characteristics was investigated. The surface structure of CNTs was modified by KOH activation at temperature range from 873 K to 1073 K, in order to produce different defects of CNTs. The experimental results revealed that the specific surface area of the CNTs increased along with activation temperature from 467 m2/g (at 873 K) to 859 m2/g (at 1073 K). The higher surface area of CNTs was obtained by activating the higher temperature. Hydrogen storage capacity in the CNTs was determined by a dynamic thermogravimetric method with heating/cooling cycles between 303 K and 673 K under one atmosphere. Measurements showed the weight change during the heating/cooling cycles for the activated CNT samples was larger than the as-prepared ones. The enhancement of hydrogen storage in the activated CNTs was attributed to hydrogen spillover effect. The defective structure of the CNTs after activation is a significant factor to promote hydrogen spillover.