chapter  40
30 Pages

Molecular Hydrogen in Carbon Nanostructures

Nanostructured materials have opened up new possibilities for solving the storage problem. ™eir high porosities make them promising candidates for reaching the required storage capacities, and the small dimensions involved reduce the time taken for the hydrogen molecules to travel from their resident site to the

40.1 Introduction: ™e Hydrogen Storage Challenge ...............................................................40-1 40.2Fundamentals.........................................................................................................................40-2

40.4 Outlook ................................................................................................................................. 40-25 Acknowledgments.......................................................................................................................... 40-26 References........................................................................................................................................ 40-26

surface. Owing to their light weight and high porosities, carbonbased nanostructured materials have been intensively investigated as potential hydrogen storage media over the past two decades. Several update reports and reviews already exist in the literature [3-18], where the emphasis has been placed on a detailed account of the ultimate hydrogen-storage performance of a vast range of substrates and synthesis protocols, to the detriment of building a consistent and robust microscopic picture of how molecular hydrogen interacts with these materials. ™is tutorial review is intended to šll the above gap by shi¥ing the focus to the hydrogen molecule. As such, the intent is to be illustrative rather than exhaustive in our exposition of the state of the art in the šeld. To this end, Section 40.2 discusses in detail both the molecular and bulk properties of hydrogen and the various ways it interacts with solid-state media. Both experimental and theoretical tools are also introduced in some detail, particularly those that can o£er novel insight into the hydrogen-storage problem. ™ese topics are illustrated in detail by working out specišc examples of direct relevance to the use of carbon-based nanomaterials. Section 40.3 makes extensive use of the fundamental principles introduced earlier on. First, it explores the topological consequences of rolling and bending graphite the basis of constructing novel forms of carbon. ™e e£ects of topology and chemical doping are then treated in detail by presenting two case studies taken from our recent work. Section 40.4 concludes this tutorial by providing an assessment of where we stand at the present time, the lessons learnt, and the challenges ahead.