Hydrogen storage properties of ZrVxNi3.5-x (x=0.0-0.9) metal hydride alloys

The structure, gaseous storage, and electrochemical properties of a series of ZrVxNi3.5-x (x = 0.0-0.9) metal hydride alloys were studied for this report. Several trends were observed as the V-content in the alloy was increased. First, the main Zr2Ni7 phase shifted from a monoclinic structure to a cubic one, and the abundance of secondary phases (ZrNi3 and ZrNi5) decreased. Secondly, the equilibrium pressure in the gaseous phase increased, and the hydrogen storage first decreased and then increased. Lastly, electrochemical testing showed that the discharge capacity increased and then decreased, and both the high-rate dischargeability and the bulk diffusion constant increased. Compared with other metal hydride systems, the alloys in the current study showed better bulk reaction kinetics but worse surface reaction kinetics. The electrochemical discharge capacity was higher than the gaseous phase capacity, which can be explained by a synergetic effect of the secondary phases. (C) 2013 Elsevier B.V. All rights reserved.