Optimizing hydrogen storage in TiFe-V alloys: Influence of sample purity and heat treatment

Abstract

This study investigates the hydrogen storage properties of titanium-iron (TiFe) alloys with vanadium (V) addition, using industrial-grade materials. The research aims to optimize TiFe-V alloys for practical hydrogen storage applications by improving activation kinetics, maximizing useable capacity, and enhancing long-term stability. Three compositions-Ti48Fe47V5 (V5), Ti47Fe47V6 (V6) and Ti46Fe47.5V6.5 (V6.5)-were examined to assess their response to heat treatment and purity of raw materials. The addition of 3 wt% Ce to low-purity alloys effectively prevents the formation of the Ti4Fe2Ox phase, increasing the B2 phase proportion and improving hydrogen storage capacity. Mischmetal (Mm) addition similarly reduced the Ti4Fe2Ox phase and enhanced activation kinetics, offering a cost-effective alternative to Ce. Short-term heat treatments (4-8 h) at 1000 degrees C were found to dissolve 60-80 % of the C14 phase into the B2 matrix, enabling efficient production without the need for prolonged homogenization. The Mm-added V6.5 alloy, after 8 h of heat treatment, demonstrated fast hydrogen absorption at 40 degrees C and achieved a useable capacity of approximately 1.44 wt%. These results indicate that Ce and Mm additions, combined with optimized heat treatment, can facilitate the scalable production of TiFe alloys with high hydrogen storage performance.