In search for a lightweight hydrogen storage material attention has focused on the Na-Al-H system, which allows, if doped with Ti, reversible uptake/release of > 4 wt.% H2. Still problematic is the reaction speed, which is too slow for practical applications. In an attempt to identify the kinetic bottlenecks we explore the basic atomistic processes with a combination of first-principles calculations and surface-analytical experiments. First ion scattering measurements confirm the presence of Ti at the surface. Calculations predict that the Ti-catalyst acts by reducing the energy barrier for hydrogen dissociation and recombination. A possible rate-limiting step in solid-state reactions is the mass transport between the phases. Thermal-desorption spectra of NaAlH4 –samples show volatile AlHx-species (alanes) suggesting that long-range mass transport occurs via migration of these very mobile species. We are seeking ways to tune these basic steps and thereby improve the performance of the material.