Engineering Ti–Cr–Mo-based alloys for hydrogen storage: Fe doping as a strategy for improved reversibility and stability

Ti–Cr–Mo-based multi-principal element alloys have emerged as promising candidates for hydrogen storage due to their high capacity and cost-effectiveness. However, their practical application is limited by challenges such as low reversible hydrogen release and poor cyclic stability. In this study, we developed a body-centered cubic (BCC) alloy, Ti₄₀Cr₄₈Mo₁₀Fe₂, which demonstrates a reversible capacity of 2.59 wt% at 303 K. The doping of Fe reduces the dehydrogenation enthalpy ΔH to 32.4 kJ/mol, which is notably more favorable than that of most other reported Ti–Cr–Mo-based alloys. Additionally, the mechanism of capacity attenuation was explored. The results reveal that hydrogen-induced phase transformation leads to the accumulation of stress and strain, which increases the energy barrier for hydrogen diffusion and release. Moreover, the formation of irreversible Ti hydrides plays a key role in capacity loss. These findings offer strategies for developing hydrogen storage alloys with long service life and reduced costs.