Reactivity of hydride-forming systems, the role of dissociation and nucleation stages

This paper reviews some recent results on the interaction of gaseous hydrogen with solid substrates of metals to form hydrides. A first part refers to theoretical and experimental aspects of the chemical process at the metal surface; the surface can be crystalline, ordered or desordered, clean or precovered with C, S, CO or oxidised. The second part is concerned with the main steps of the chemical reaction which are the nucleation and growth of the hydride phases