Thermal decomposition of the non-interstitial hydrides for the storage and production of hydrogen.

Hydrogen is nature’s simplest, lightest atom, consisting of a single proton and a single electron.2 Paradoxically, this “simplicity” in electronic structure leads to unique consequences for the chemical and physical properties of the element and its atomic, cationic, and anionic siblings. In its desire to possess either a totally empty or a totally filled 1s electron shell, hydrogen exhibits three common oxidation states: +1, 0, and -1 (reflecting a 1s0, 1s1, or 1s2 electronic configuration, respectively). The relative change in the number of electrons surrounding the nucleus associated with the transformations H0 f H-I and H0 f H+I ((1e, (100%) is thus the largest among the chemical elements of the Periodic Table; so are the relative changes of many key chemical and physical properties of these three unitary species (see section 3). Hydrogen dominates the 15-billion-year tale of our universe (see, e.g., ref 1). It is by far-and-away the most abundant element in the cosmos, of which it makes up 88.6% of the composition by weight. The chemical evolution of the stars depends crucially upon the advance of hydrogen fusion. Bewildering amounts of life-giving solar rays provide energy for our own hospitable planet in the form of heat and light to our plant world via the remarkable photosynthetic cycle. Hydrogen as water is pivotal to life and is present also in the overwhelming majority of organic compounds. But hydrogen is also one of the most important elements in the chemistry of the energy-giving materials, such as hydrocarbons (mineral oil and methane gas). The inevitable socio-economic impact of recurring fuel crises, the threat of the early end of the fossil fuels era in the coming 50 years,3 the increasing pollution of our environment, and the problem of anthropogenic-induced climate changeswidely, if not universally accepted4shave been the catalysts for the utilization of clean5 and renewable energy resources. Hydrogen is undoubtedly one of the key alternatives * Address correspondence to Prof. Peter P. Edwards, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK, E-mail [email protected], telephone +44-(0)-1865-272-652, fax +44-(0)-1865-272-690, or to Dr. Wojciech Grochala, The Department of Chemistry, The University of Warsaw, Pasteur 1, 02093 Warsaw Poland, E-mail wg22@ cornell.edu, telephone +48-22-822-0211 ext. 276, fax +44-22-8222309. † The University of Birmingham. ‡ The University of Warsaw. § University of Oxford. 1283 Chem. Rev. 2004, 104, 1283−1315