Synthesis and characterization of TiFe(1-x)Ni(x) intermetallic hydrides for hydrogen storage

Nowadays, human activities are heavily dependent on fossil fuels, which has resulted in both an environmental and energy crisis over the years. Hydrogen stands out as the most promising solution to transform energy production into a greener process, thus an efficient hydrogen storage is crucial to avoid energy losses and ensure a reliable energy supply when needed. This research focuses on metallic hydrides based on Ni-substituted TiFe alloys. TiFe is known for its high volumetric density, good sorption kinetics, and reversibility, and it operates under mild temperature and pressure conditions. Furthermore, its performance can be enhanced through stoichiometric tailoring. Nickel is selected for partial substitution of Fe as it improves hydride activation, kinetics, cyclability, and stability, enabling hydrogen production under ambient conditions. Samples with the composition TiFe1−xNix were synthesized with varying nickel content (x = 0.05, 0.10, 0.15, 0.20, 0.30) by arc melting and characterized in terms of composition, morphology, and structure via Scanning Electron Microscopy and X-ray Powder Diffraction. Thermodynamics of hydrogen sorption were investigated using a High-Pressure Differential Scanning Calorimeter and a Sievert apparatus. The study of TiFe(1−x)Ni(x) samples across this compositional range provides a comprehensive review of the hydrogen sorption properties of these intermetallic hydrides and how they vary with Ni concentration. The main conclusion of this work is that partial Ni substitution only slightly modifies the crystal structure, expanding the unit cell volume and enabling hydride formation at lower equilibrium pressures, which is promising in the view of practical applications.