Effect of molybdenum content on structural, gaseous storage, and electrochemical properties of C14-predominant AB2 metal hydride alloys

Abstract

The structure, gaseous storage, and electrochemical properties of Mo-modified C14-predominant AB2 metal hydride alloys were studied. The addition of Mo expands the unit cell volume and stabilizes the metal hydride. This increased metal-to-hydrogen bond strength reduces the equilibrium plateau pressure, reversible hydrogen storage, and the high-rate dischargeability in the flooded cell configuration, but not the high-rate dischargeability in the sealed cell configuration. The low-temperature performance was improved by the addition of Mo through increases in bulk diffusion rate, surface area, and surface catalytic ability. The increase in bulk diffusion is the result of smaller crystallites and larger AB2–AB2 grain boundary densities. The increase in surface area is due to the high solubility of Mo in alkaline solution. Even with a higher leaching rate, the Mo-containing alloys still have strong corrosion resistance which contributes positively to both the charge retention and the cycle life performances. As the Mo-content in the alloy increases, the low temperature performance improves at the expense of a lower capacity.