Effect of Nb, Zr, V, Ni and Cr incorporation on the microstructure, kinetics and hydrogen storage capacity of an AB-type TiFe alloy

Solid-state hydrogen storage is regarded as a promising technology for future hydrogen energy systems due to its high safety, high volumetric hydrogen density, and reversible hydrogen storage capability. Nevertheless, improving the activation behavior of TiFe-based alloys remains a major challenge for their practical application. In this context, TiFe and Ti 46 Fe 46 Nb 2.5 Zr 2.5 V 2 Cr 0.5 Ni 0.5 AB alloys were developed by dynamic vacuum induction melting and evaluated in terms of their microstructure, chemical composition, and crystalline phases using field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy, and X-ray diffraction (XRD) techniques. The performance of the alloys obtained was evaluated in solid-state hydrogen storage using Sieverts-type equipment, where absorption kinetics, pressure and composition isotherms, and absorption cycles were evaluated. The TiFe alloy is composed of a TiFe phase matrix (94.49 %) with a secondary Ti 2 Fe phase (5.51 %), and it was found that the incorporation of alloying elements in the Ti 46 Fe 46 Nb 2.5 Zr 2.5 V 2 Cr 0.5 Ni 0.5 sample decreases the main TiFe phase to 68.47 % while increasing the proportion of the Ti 2 Fe phase to 31.53 %. On the other hand, the Ti 46 Fe 46 Nb 2.5 Zr 2.5 V 2 Cr 0.5 Ni 0.5 alloy exhibited hydrogen uptake without prior thermal activation at 30 °C and 2 MPa, with an incubation time of approximately 6 min and a maximum first-absorption capacity of 1.41 wt.% H 2 after 660 min. Additionally, the Ti 46 Fe 46 Nb 2.5 Zr 2.5 V 2 Cr 0.5 Ni 0.5 alloy has a lower equilibrium absorption pressure (0.22 MPa compared to 0.36 MPa for the TiFe sample). Finally, both systems exhibited reversible behavior in hydrogen absorption over 15 cycles.