The solar thermal energy could be stored and reused at the desired locations and conditions. The requirement is to develop a suitable medium which could be able to store the solar thermal energy reversibly. Metal-metal hydride system may be one of the options. The high hydrogen storage capacity and fast hydrogenation-dehydrogenation kinetics are the desirable conditions for the practical applications. In this regard, magnesium magnesium hydride (Mg-MgH2) system has been considered as a potential candidate. The prerequisite is to fine tune the hydrogenation-dehydrogenation kinetics by a suitable additive. Niobium pentoxide (Nb2O5) has been recognized as a suitable additive to improve the hydrogenation-dehydrogenation kinetics. The Nb2O5 is found in various morphological forms, however; all of them are not suitable to enhance the hydrogenation dehydrogenation kinetics of Mg-MgH2 system. In the current study, it has been found that the mesoporous amorphous Nb2O5 has shown remarkable catalytic property on the Mg-MgH2 system as compared to crystalline Nb2O5 under the similar experimental conditions. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.