This Thesis considers the use of solid-state metal ammines as ammonia storage materials and endeavours to understand these materials on a fundamental chemical level. The ammines of LiBH₄, MgCl₂, MgBr₂, MgI₂ and Mg(BH₄)₂, are investigated. The structures of lithium borohydride ammines, Li(NH₃)_nBH₄ with n = 1, 2, 3 and 4 are solved using X-ray and neutron diffraction, vibrational spectroscopy, nuclear magnetic resonance, and first-principles calculations. The reversibility, bonding and ammonia storage properties of this system are discussed, and investigated using gravimetric analysis and vibrational spectroscopy. The ammines of magnesium halides are investigated using X-ray and neutron powder diffraction, gravimetric techniques, nuclear magnetic resonance, first-principles calculations and vibrational spectroscopy. Their disordered structures, bonding, and decomposition are discussed, and the trends in their properties are used to interpret the properties of other ammines. The ammines of magnesium borohydride are investigated using X-ray and neutron powder diffraction, gravimetric techniques, first-principles calculations and vibrational spectroscopy. The structure, decomposition and reversibility of Mg(NH₃)₆(BH₄)₂ as an ammonia store are presented. Throughout the Thesis and at the end of each Chapter the possibility of using these ammines as solid-state ammonia stores is discussed.

In comparison with the high-pressure adsorption at room temperature, hydrogen adsorption at cryogenic temperatures can be significantly improved at low pressures, which has great potential for prospective mobile applications. In this study, a differential pressure based manometry system was designed and constructed for fast analysing hydrogen adsorption uptakes of sorbents up to a maximum of 10 wt% at 77 K and up to 11 bar. The safety design of the system in compliance with European ATEX directives (Zone 2) for explosive atmospheres was discussed in detail, together with additional pneumatic systems for remote control of the experiments. A thorough error analysis of related experimental tests was also performed. Common carbon sorbents, including several Norit branded activated carbons and graphene nanoplatelets (GNPs) with various surface areas, were characterised for their pore structures. The structural differences among GPNs of different surface areas were also studied. The hydrogen adsorption isotherms of these sorbents, examined in the newly-built manometry system, were further analysed and discussed with reference to the assessed microstructural properties. The carbonisation processes of plasma carbons from the microwave splitting of methane, and biochars from the pyrolysis of Miscanthus, were intensively studied primarily based on Raman spectroscopy, in conjunction with other characterisation techniques such as XRD, FTIR and XPS, for exploring the formation of graphitic structures and crystallinity under various conditions. Two selected types of carbons, the activated carbon AC Norit GSX with a specific surface areas of 875 m2/g and the graphene nanoplates with a specific surface area of 700 m2/g, were decorated with palladium nanoparticles in different compositions. The growth and distribution of doped palladium particles in the carbon substrates were studied, and their effects on porous properties and microstructures of the sorbents were also reviewed. Hydrogen adsorption tests of the decorated carbons were further conducted and discussed, to explore the potential effects of Pd contents on the adsorption kinetics and hydrogen absolute uptakes.