Hydrogen in carbon nanostructures

The non-dissociative hydrogen uptake for two types of carbon-based materials was explored. The maximum measured differential hydrogen uptake capacities at hydrogen pressures of 10 MPa were experimentally determined with the volumetric Sieverts method to 2.9 (300 K), and 4.1 wt% (77 K) for MWNB (multi-walled nanobarrels) and 2.6 (300 K), and 3.3 (77 K) wt%, for ANPC (amorphous nanoporous carbon). The total hydrogen uptake was calculated to be 3.2 (300 K) and 6.2 (77 K) wt% for MWNB at a hydrogen pressure of 10 MPa, and 2.8 (300 K) and 4.2 (77 K), respectively, for ANPC. The adsorption energies were determined to be 7.2 and 4.2 (KJ/mol) for ANPC and MWNB, respectively, at the lowest coverage. At higher coverage (concentration), a multi-site model is required to describe the coverage dependence, consistent with large heterogeneity of the adsorption sites. (C) 2002 Elsevier Science B.V. All rights reserved.