Positive impacts of tuning lattice on cyclic performance in ZrCo-based hydrogen isotope storage alloys

Effects of V doping on microstructure, kinetic, and thermodynamic characteristics of Zr 50‐ x V x Co 50 ( x = 0, 2.5, 3.5, and 5.0) hydrogen storage alloys

“…The occurrence of cracks can be explained in two manners. First, the hydrogen atoms are stored in/released from the grain boundary or tetrahedral/octahedral interstitial position within the unit cell, resulting in expansion/contraction of the cell volume during the hydrogenation/dehydrogenation cycle, which destroys the internal structure of the alloy involving the fracture of the metal bond and lattice distortion 16,30 . Second, the emergence of a brittle Laves phase (ZrCo 2 and ZrV 0.24 Co 1.76 ) in Zr 47.5 V 2.5 Co 50 promotes the appearance of cracks.…”

“…The final hydrogenation amount could reach ~1.93 wt% for ZrCo under 4‐bar H 2 at 348 K 15 . Generally, the disproportionation reaction occurs rapidly under high hydrogen pressure and temperature (>653 K) or repeated hydrogen absorption/desorption cycles, 16 forming the nonhydrogen‐absorbing ZrCo 2 and stable ZrH 2 14 . The hydriding/dehydriding disproportionation reactions are and , which are the prime reason deteriorating the hydrogen storage properties of samples.…”

“…In addition, element doping alters the microstructure inside the crystal including cell expansion/contraction, lattice distortion, and atom occupancy 16,30‐34 . Theoretically, H atoms tend to occupy the intertetrahedron space in ZrCoH 3 because the intertetrahedron space is larger than the interoctahedron space and the bond strength of Co‐H(T) is higher than that of Co‐H(O) 35 .…”

“…Nevertheless, the increase in plateau pressure during dehydrogenation decreases the stability of hydride, thus reducing its dehydrogenation temperature, which effectively prevents disproportionation owing to the high temperature 26,27,37,38 . Lattice alteration via element doping can be applied to improve the cycling properties of the ZrCo alloy 16 . Hence, it is of significance to choose the replacement element to optimize the properties of the ZrCo alloy.…”

“…7 The initial activation of a ZrCo granule with a particle size of 2 to 4 mm at 573 K lasts more than 3 hours to reach the saturated hydrogen absorption capacity. 14 The final hydrogenation amount could reach $1.93 wt% for ZrCo under 4-bar H 2 at 348 K. 15 Generally, the disproportionation reaction occurs rapidly under high hydrogen pressure and temperature (>653 K) or repeated hydrogen absorption/ desorption cycles, 16 forming the nonhydrogen-absorbing ZrCo 2 and stable ZrH 2 . 14 The hydriding/dehydriding disproportionation reactions are 2ZrCo þ H 2 !…”