Enhanced Hydrogen Storage Properties of Ti40-xV45Zr15Crx 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 Ti40-xV45Zr15Crx (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 degrees 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 degrees 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.