Electrochemical hydrogen storage in singlewalled carbon nanotubes

Abstract

The singlewalled carbon nanotubes with a different amount of transition metals of 20 wt% and 5 wt% are synthesized by arc discharge. These samples are pre-annealed at 300 °C in air for five hours for the purpose of removing amorphous carbons, which exist in the samples, and again heated at 900 °C as many hours in Ar gas in order to improve their crystallinities. The discharge storage capacity of 210 mAh/g (0.74 Hwt%) is obtained at cutoff voltage of 0.8 V. We observed that the plateau region in the voltage scan is maintained during the constant-current discharge mode. It is very important for practical applications. The CV measurement also shows redox reaction peak near 1 V during discharge, in good agreement with the charge-discharge experiment.