Hydrogen storage and electrochemical properties of the Ti0.32Cr0.43-x-yV0.25FexMny (x=0-0.055, y=0-0.080) alloys and their composites with MmNi3.99Al0.29Mn0.3Co0.6 alloy

In this paper, we investigated the hydrogen storage and electrochemical characteristics of the bcc type Ti(0.3)2Cr(0.43-x-y)V(0.25)Fe(x)Mn(y) (x = 0,0.03,0.055; y = 0,0.03,0.055,0.080) alloys and their composites with the AB 5 type MmNi(3.99)Al(0.29)Mn(0.3)Co(0.6) (Mm: misch-metal) alloy. The maximum hydrogen capacities of the bcc alloys were proportional to the lattice parameters of the alloys. The increased substitution of Fe/Mn for Cr in the bcc alloys increased the plateau pressure in the respective pressure-composition isotherms. In particular, the plateau pressure was more sensitive to Fe substitution than Mn substitution. Electrochemically, the Ti0.32Cr0.345V0.25Fe0.03Mn0.055 composite alloy electrode showed the optimum discharge capacity and cyclability because it had the beneficial effects of both Fe and Mn substitutions. Furthermore, among the other composite alloy electrodes, the Ti0.32Cr0.345V0.25Fe0.03Mn0.055 composite alloy electrode showed the smallest charge transfer resistance, which allowed its easy activation and, higher rate capability. (C) 2013 Elsevier B. V. All rights reserved.