Structural evolution and electrochemical hydrogenation behavior of Ti2Ni alloy

Electrochemical hydrogen storage properties of a non-equilibrium Ti2Ni alloy

“…When the electrolyte temperature was 313 K, the non-equilibrium electrode showed a high discharge capacity of 336 mAh g 21 at the first cycle, which was evidently higher than those of the Ti 2 Ni alloys reported in the literature 7-10,12-15 and 310 mAh g 21 of the commercial LaNi 5 -based alloys. 16,17 This is quite different from the discharge properties of the crystalline Ti 2 Ni alloy, which showed a significant decrease of discharge capacity when the electrolyte temperature was increased, 13 as shown in Fig. 2.…”

“…The XRD pattern of the alloy after discharging on the tenth cycle indicated that this volume expansion by hydrogen absorption disappeared, in spite of the drastic decay of the discharge capacity. The non-equilibrium Ti 2 Ni alloy, quite different from the crystalline alloy, 9,13 showed a reversible change of the bulk structure during cycling. Fig.…”

“…11,12 However, the irreversible formation of metal hydride during hydrogen absorption of the alloy suppressed its hydrogen desorption, meaning in that the alloy had a low maximum discharge capacity, less than 250 mAh g 21 . 9,13 This severely limited the application of Ti 2 Ni-based alloys, which were almost removed from the list of hydrogen storage alloys.…”

“…A crystalline Ti 2 Ni alloy fabricated by an induction melting method 13 was crushed into powders below a 200 mesh, and then mechanically milled in a stainless steel vial containing stainless steel balls (10 and 6 mm) at 1400 rpm for 10 h under an argon atmosphere to form an amorphous Ti 2 Ni alloy (see ESI, Fig. S1{), which was subsequently heat treated at 693 K under an argon atmosphere with a purity of 99.99%, leading to the formation of a non-equilibrium Ti 2 Ni alloy containing amorphous and nanocrystalline phases.…”

“…The structural change during cycling has been carried out by XRD. 13 Hydrogen absorption led to a non-elastic lattice expansion of the crystalline alloy. The charge and discharge curves of the non-equilibrium electrode at 313 K were also shown in Fig.…”