Hydrogen absorption behavior of Zr-based getter materials with Pd[sbnd]Ag coating against gaseous impurities

In this work, Pd[sbnd]Ag coating has been deposited on different Zr-based Lave phase alloys, including ZrV₂, Zr_0.9Ti_0.1V₂ and Zr₅₇V₃₆Fe₇, by the electroless plating technique. It is attempted to illustrate the role of Pd[sbnd]Ag coating on hydrogenation performance of Zr-based alloys against gaseous impurities. X-ray diffraction and scanning electron microscope (SEM) observations along with energy disperse spectroscopy (EDS) give evidences that the Pd[sbnd]Ag coating has been uniformly deposited on the surface of experimental alloys. Activation behavior and hydrogenation kinetics in pure H₂ and mixture gases (H₂ containing 1 vol.% air) are evaluated by using a Sieverts-type apparatus. The Pd[sbnd]Ag coating accelerates the hydrogenation kinetics and slightly decreases the hydrogen storage capacity of experimental Zr-based AB₂ alloys. The poisoning effect of air gaseous impurities mainly deteriorates the hydrogen absorption capacity of experimental Zr-based alloys with Pd[sbnd]Ag coating at room temperature. The Pd[sbnd]Ag coated Zr_0.9Ti_0.1V₂ preserves the fastest hydriding reaction rate at 303 K and 673 K among three experimental alloys. The slope value in the rapid absorbing stage (k_a1) in mixture gases at each temperature of Pd[sbnd]Ag coated Zr-based AB₂ alloys is quite higher than that of the corresponding bare alloy which indicates the uniform Pd[sbnd]Ag coating evidently improves the poison resistance capability of alloys in a wide temperature range. The Pd[sbnd]Ag coating does not fall off significantly from the surface after 6 times hydrogenation/dehydrogenation cycles.