Hydrogen storage in Mo substituted low-V alloys treated by melt-spin process

Abstract

Vanadium (V)-based body-centered cubic (BCC) alloys with a high theoretical storage capacity are considered a promising material for hydrogen storage. Nonetheless, the high-price raw material of pure V confines their application. Herein, a low-V BCC alloy (Ti41Cr50V5Mo4) with an excellent dehydriding capacity (2.4 wt% H) is successfully developed via Mo partial substitution and coupling with the melt-spin process. The alloys' crystal structures, micromorphology, and de-/hydrogenation mechanisms are investigated systematically. It is found that the Mo-substitution and the melt-spin process can keep and extend the BCC zone in the low-V portion of Ti-Cr-V phase diagram, and Mo atom is uniformly distributed in the BCC alloy. The dehydrogenation mechanism of the low-V BCC alloy was determined to follow a diffusion-controlled model with an activation energy of 52.38 kJ/mol. The dehydrogenation enthalpy ΔH of the hydriding low-V alloy was −40.8 kJ/mol by the van’t Hoff equation, which is consistent with V-based alloys. The cycle test also proves that the synergistic effect of Mo substitution and melt spin improved the durability of the low-V alloy. The retention rate of hydrogen capacity can achieve 94 % after 15 cycles. These findings might guide the design of reversible metal hydrides with low cost and excellent hydrogen storage performances.