Mechanism of hydrogen residue in metal hydrides formed from high-entropy alloys by inelastic neutron spectroscopy

High-entropy alloys (HEAs) typically contain four or more principle elements in equimolar amounts. We have recently discovered the first bcc HEA-based hydride with reversible hydrogen storage capacity at room-temperature, TiVCrNbH8. In addition, this material excels at many of the traditional showstoppers for applied hydrogen storage in intermetallic hydrides, i.e. degradation after repeated hydrogen absorption/desorption cycling, surface passivation and slow hydrogen sorption kinetics. This material is therefore promising as a future hydrogen storage material. However, the reversible capacity is 1.96 wt.% H2 while the full capacity in TiVCrNbH8 is 3.14 wt.% H2. This means that there are certain interstitial sites within the metal matrix where the H-atoms are bound more tightly than others. If these sites can be destabilized, the full hydrogen storage capacity of would become accessible.

高熵合金（High-entropy alloys, HEAs）通常包含四种及以上等摩尔比的主元元素。我们近期首次发现了具备室温可逆储氢能力的体心立方（body-centered cubic, bcc）基高熵合金氢化物TiVCrNbH8。该材料可有效解决金属间化合物氢化物实用化储氢领域长期存在的多项传统瓶颈：反复吸放氢循环后的性能衰减、表面钝化以及氢吸放动力学迟缓问题。因此，该材料有望成为未来极具应用潜力的储氢候选材料。然而，其可逆储氢容量仅为1.96 wt.% H₂，而TiVCrNbH8的理论总储氢容量可达3.14 wt.% H₂。这表明该金属基体中存在部分氢原子结合强度高于其他位点的间隙位置。若能弱化这些位点的氢结合作用，便可充分释放该材料的全部储氢潜力。