Enhanced hydrogen storage properties of Ti_40-xV₄₅Zr₁₅Cr_x alloys by dual-phase nanostructures of eutectic and spinodal decomposition

Multi-principal elements alloys (MPEAs) with body center cubic (BCC) structure have shown great potential in hydrogen storage. However, the multi-cycle activation process and the high desorption temperature have inhibited their applications. In this study, the Ti_40-xV₄₅Zr₁₅Cr_x (x = 1, 2, 3 at. %) alloys with three different BCC phases are synergized, and high hydrogenation capacities of over 2 wt% are achieved in the first hydrogen absorption. Owing to the formation of spinodal decomposition nanostructure in Ti₃₈V₄₅Zr₁₅Cr₂ alloy, 90 % of total hydrogen capacity is reached in 30s at 250 °C under 1 MPa H₂, which indicates no incubation time is needed for activation. The Ti₃₈V₄₅Zr₁₅Cr₂ alloy also shows the highest reversible hydrogen storage capacity with fastest kinetics at 200 °C. The hydrogenation reaction is controlled by the 1D diffusion process of H atoms according to JMAK model. The spinodal decomposition structure can accelerate the decomposition of H₂ molecules and the diffusion of H atoms by providing extra energy from large lattice distortion. The high-density interfaces in nano-eutectic structure can serve as active sites for the nucleation of hydrides and fast paths for the diffusion of H atoms.