Hydrogen storage in sonicated carbon materials

The hydrogen storage in purified single-wall carbon nanotubes (SWNTs). grap hite and diamond powder was investigated at room temperature and ambient pr essure. The samples were sonicated in 5 M HNO3 for various periods of rime using an ultrasonic probe of the alloy Ti-6Al-4V. The goal of this treatmen t was to open the carbon nanotubes. The maximum value of overall hydrogen s torage was found to be 1.5 wt %. as determined by thermal desorption spectr oscopy. The storage capacity increases with sonication time. The sonication treatment introduces particles of the Ti alloy into the samples, as shown by X-ray diffraction, transmission electron microscopy, and chemical analys is. All of the hydrogen uptake can be explained by the assumption that the hydrogen is only stored in the Ti-alloy particles. The presence of Ti-alloy particles does not allow the determination of whether a small amount of hy drogen possibly is stored in the SWNTs them selves, and the fraction of nan otubes opened by the sonication treatment is unknown.