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.
Highlights
Zr-based AB2 metal hydride (MH) alloy is an important research subject since it provides a possible improvement to the relatively low gravimetric energy density of nickel/metal hydride batteries [1,2]
The major results accomplished by incorporating Pd in MH alloys are summarized in Table 1, and consist mainly of improvements in gaseous hydrogen absorption and desorption kinetics, electrochemical discharge capacity, high-rate dischargeability (HRD), activation, and cycle life performance in several MH alloy systems, including
X‐ray diffraction (XRD) analysis results show that Pd2 occupies the A‐site for both the C14 and C15 structures, studied
Summary
Zr-based AB2 metal hydride (MH) alloy is an important research subject since it provides a possible improvement to the relatively low gravimetric energy density of nickel/metal hydride batteries [1,2]. Work regarding substitution of C14 Laves phase MH alloys started at the first row of transition metals [3,4,5,6] and proceeded to several non-transition metals (for example, Mg [7], La [8], Ce [9], and Nd [10]). Pd’s ability to absorb a large volume of hydrogen was first reported more than 150 years ago by Thomas Graham in 1866 [13], which built the foundation for modern MH research work [14,15,16]. The major results accomplished by incorporating Pd in MH alloys are summarized in Table 1, and consist mainly of improvements in gaseous hydrogen absorption and desorption kinetics, electrochemical discharge capacity, high-rate dischargeability (HRD), activation, and cycle life performance in several MH alloy systems, including
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