This study focused on hydrogen sorption properties of 15 mu m thick Mg-based films with Al, Fe and Ti as alloying elements The binary alloys are used to establish as baseline case for the ternary Mg-Al-Ti, Mg-Fe-Ti and Mg-Al-Fe compositions We show that the ternary alloys in particular display remarkable sorption behavior at 200 degrees C the films are capable of absorbing 4-6 wt% hydrogen in seconds, and desorbing in minutes Furthermore, this sorption behavior is stable over cycling for the Mg-Al-Ti and Mg-Fe-Ti alloys Even after 100 absorption/desorption cycles, no degradation in capacity or kinetics is observed. For Mg-Al-Fe, the properties are clearly worse compared to the other ternary combinations These differences are explained by considering the properties of all the different phases present during cycling in terms of their hydrogen affinity and catalytic activity Based on these considerations, some general design principles for Mg-based hydrogen storage alloys are suggested (C) 2009 Professor T Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved