Hydrogen storage capacity of some carbon nanotubes and filaments

We have studied the sorption of hydrogen by 8 different carbon materials at pressures up to 11 MPa (1600 psi) and temperatures from -80oC to +500oC. Our samples include graphite flakes, Aldrich activated carbon, graphitized PYROGRAF vapor-grown carbon fibers (VGCF), etched PYROGRAF fibers, Showa-Denko VGCF, filaments grown from a FeNiCu alloy, and nanotubes from MER Corp. and Rice University. The results so far have been remarkably similar: very little hydrogen sorption. In fact, the sorption is so small that we must pay careful attention to calibration to get reliable answers. The largest sorption observed is less than 0.1 weight percent hydrogen at room temperature and 3.5 MPa. Furthermore, our efforts to activate these materials by reduction at high temperatures and pressures were also futile. These results cast serious doubts on any claims for large hydrogen sorption in carbon materials. (author)