Hydrogen storage and cyclic properties of (VFe)60(TiCrCo)40-xZrx (0 ≤ x ≤ 2) alloys

Hydrogen storage and cyclic properties of (VFe)60(TiCrCo)40-xZrx (0 ≤ x ≤ 2) alloys had been investigated systematically. The results showed that the alloys when x = 0 and 0.5 consist of BCC main phase, C14 Laves phase and CeO2 phase, while Zr-based FCC phase appears in the alloys when x = 1 and 2, and the contents of the Laves phase and the Zr-based FCC phase increase with the increment of Zr substitution for Ti. Zr substituted compositions were found to have better hydrogen absorption kinetics but the hydrogen storage capacities decrease as the substitution amounts increase. Owing to that Zr element can reduce the micro-strain accumulation in the crystal lattice during the hydrogen absorption-desorption cycles, the cyclic properties of the (VFe)60(TiCrCo)40-xZrx alloys are improved. As Zr content increases, the desorption capacity fading rate of (VFe)60(TiCrCo)40-xZrx decreases and the best cyclic property was obtained when x = 2 with only 4.5% capacity decay after 10 cycles in this work.