Optimization strategy for compositional ratio and microstructural regulation of TiVNi alloy to enhance hydrogen storage performance

When titanium-based hydrogen storage materials are employed in hydrogen transportation and portable energy storage systems, they face challenges such as limited hydrogen storage capacity, sluggish hydrogen absorption and desorption kinetics, and high residual hydrogen content. To tackle these problems, herein, a synergistic enhancement strategy was proposed to alloy titanium with elements of V (which can regulate phase structure and enhance hydrogen storage capacity) and Ni (which can improve hydrogen absorption/desorption kinetics) via a vacuum suspension melting process, followed with the controlled heat treatment processes. The obtained alloys were consisted of TiV and TiNi phases. Under a hydrogen activation temperature of 313 K and a hydrogen pressure of 4 MPa, various types of hydrides were formed in the alloys including TiH₂, VH₂, and Ti₂NiH_0.5. Among all the prepared alloys, the Ti₆₀V₃₄Ni₆ alloy exhibited the highest hydrogen storage capacity, reaching 2.1 wt% in the as-cast state and 2.4 wt% after annealing. The dehydrogenation activation energy was found to decrease from 122.3 kJ/mol in the as-cast state to 89.4 kJ/mol after annealing. Meanwhile, the hydrogen absorption rate was increased from 1.25 wt% min−1 to 2.17 wt% min−1 after annealing. The as-cast Ti₆₀V₃₄Ni₆ alloy exhibited a good poisoning resistance. Post annealing of TiVNi alloys enhanced formation of more ordered grains and hydrogen storage channels, which facilitated hydrogen diffusion, increased the number of available sites for hydrogen occupation, and enhanced overall hydrogen storage capacity of the alloys.