We are using nano-structured materials to address the limitations of hydrogen storage materials: in particular their kinetics of adsorption and desorption as well as the enthalpy of adsorption. In materials that bind hydrogen through chemisorptions, stability is too high (>50kJ/mol) requiring high temperatures to drive off the hydrogen; whereas materials that store hydrogen through physisorption have binding energies that are too low (<10kJ/mol), requiring the use of cryogenic temperatures [1]. The challenge is to bridge this energy gap to obtain binding energies in the range (10-60kJ/mol) [1]. In this study we attempt to fill this energy gap as well as improve uptake and reaction kinetics by synthesising nano-structured composite materials that adsorb hydrogen through physisorption and possibly chemisorption. We report on the preliminary results of functionilising graphite nano-fibres (GNFs) by doping them with charge donor species that increase charge on graphite sheets to improve the H₂ physisorption enthalpy and uptake [2]. GNFs with diameters of tens of nanometres (50-150nm) and large surface areas have been obtained via the heat treatment of polymer fibres (T>2500°C) produced through the electrospinning process. We have determined how the low literature value of storage of H₂ in graphite has been improved by nano-structuring and doping. We show that elecrospinning can potentially be used to produce composite hydride-carbon fibres to improve the sorption kinetics and enthalpy as enabled by nano-structuring [1].

[1] Vincent Berube, Gregg Radtke, Mildred Dresselhaus and Gang Chen, Int. J. Energy Res. 31 (2007) 6637-663
[2] A. Lovell, PhD Thesis, UCL 2007