A first-principles study of hydrogen storage of high entropy alloy TiZrVMoNb. (11th June 2021) - Hu, Jutao
Abstract: In this study, density functional theory calculations have been carried out to study the hydrogen storage properties of high entropy alloy (HEA) TiZrVMoNb. It reveals that a BCC→FCC phase transformation occurs when the hydrogen content reaches 1.5 wt% during hydrogenation process, and octahedral and tetrahedral interstitial sites are preferable for hydrogen occupation before and after phase transformation, respectively. Further energetic analyses show that different hydrogen occupations in HEAs play an important role in the thermal stability of hydrides. The maximum hydrogen storage capacity for TiZrVMoNb is predicted to be 2.65 wt%, which is comparable to the largest value of 2.7 wt% for TiZrVHfNb and larger than that of other reported HEA hydrogen storage materials reported in the literature. As compared with the previously reported HEA TiZrHfMoNb with the change of only one principal element, the TiZrVMoNb not only has much higher hydrogen storage capacity, but also has more moderate hydrogen desorption temperature. The difference in hydrogen storage properties between these two HEAs is mainly attributed to the atomic weight, site occupation, lattice distortion and chemical effect of metal elements. The present study thus suggests that the TiZrVMoNb HEA has great potential as hydrogen storage materials and proposes a strategy to enhance the hydrogen storage properties of HEAs. Graphical abstract: Image 1 Highlights: HEA TiZrVMoNb has a maximum hydrogen storage capacity of 2.65 wt%. A BCC to FCC phase transition occurs when the hydrogen content reaches to 1.5 wt%. The thermal stability of HEA hydrides can be influenced by hydrogen occupation. The hydrogen storage property of HEA TiZrVMoNb is superior to HEA TiZrHfMoNb.