Increase in the Surface Catalytic Ability by Addition of Palladium in C14 Metal Hydride Alloy

Abstract

A combination of analytic tools and electrochemical testing was employed to study the contributions of Palladium (Pd) in a Zr-based AB2 metal hydride alloy (Ti12Zr22.8V10 Cr7.5Mn8.1Co7Ni32.2Al0.4). Pd enters the A-site of both the C14 and C15 Laves phases and shrinks the unit cell volumes, which results in a decrease of both gaseous phase and electrochemical hydrogen storage capacities. On the other hand, the addition of Pd benefits both the bulk transport of hydrogen and the surface electrochemical reaction. Improvements in high-rate dischargeability and low-temperature performances are solely due to an increase in surface catalytic ability. Addition of Pd also decreases the surface reactive area, but such properties can be mediated through incorporation of additional modifications with rare earth elements. A review of Pd-addition to other hydrogen storage materials is also included.

Keywords

• metal hydride
• nickel metal hydride battery
• Laves phase alloy
• palladium
• electrochemistry
• pressure concentration isotherm