Hydrogen storage in single-walled carbon nanotubes

'Full text:' The issue of hydrogen storage in single-walled carbon nanotubes (SWNT) is surrounded by high expectations, but also major controversies. Existing experimental data show large lab-to-lab and sample-to-sample variation. The irreproducibility of hydrogen uptake is believed to result from use of material of varying purity, poor characterization of as-grown and processed samples, and, sometimes, a sloppy experimental procedure. To conclusively resolve the problem we undertook a systematic investigation of gas adsorption on SWNT by volumetric, gravimetric, X-ray, neutron, and other analytical methods. The SWNT grown at NRC using an in-house optimized process are between those of highest quality available in research quantities in the world. The growing technology allows for high sample quality as well as long-term quality consistency. A simple, but efficient method for controlled opening of carbon nanotubes has been developed. As-grown (close-ended) and processed (open-ended) SWNT have been thoroughly characterized by Ar, Kr, and N2 isothermal adsorption at 77 and 87 K. Binding energies at various adsorption sites have been determined. Gas condensation inside open nanotubes has been observed. Presently, isothermal gas adsorption, X-ray scattering and neutron scattering experiments to determine H2 adsorption sites and corresponding binding energies in both close-ended and open-ended SWNT are underway. (author)