Particular active sites, M-x-M-y' (where x and y are the number of unsaturations, i.e. anionic vacancies, on each cation M and M') involving reactive hydrogen are created during the activation of non-metallic catalytic materials. The anionic vacancies created in bulk and at the surface of the solid, by the loss of H2O or H2S, are able to receive hydrogen in a hydridic form according to a heterolytic dissociation ((X2-Mn)+square + H-2 -> (XH-Mn)+H- with X = O or S). The non-metallic catalytic materials become catalytic hydrogen reservoirs. Besides a high reactivity, the hydrogen species, stored in the solid, present marked diffusion properties leading to a dynamic behavior of the solid and active sites. (c) 2005 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.