The Mg50Co50 and Mg50Pd5Co45 alloys with nano-crystalline body-centered cubic (BCC) structure were confirmed by means of XRD and TEM/SAED analyses. They are available in the anode of Ni-MH battery system, which can be reversibly charged and discharged with maximum capacity of 458 mAh g(-1). They exhibit greatly enhanced reversible hydrogen storage, differing from their tough dehydrogenation performances in solid gas system [Y. Zhang et al., Journal of Alloys and Compounds 393 (2005) 147-153]. This phenomenon can be ascribed to the structural stability of Mg50Co50-based binary and ternary BCC alloys in the electrochemical reactions, and also the electro-catalysis activity. Introducing Pd into Mg50Co50 alloy lifts not only the initial discharge capacity, but also the high-rate dischargeability. The exchange current density and hydrogen diffusion mobility can also be improved by the Pd additive in the ternary electrode alloys. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.