First-principles investigation on the effect of Nb and Ta doping on the hydrogen storage performance of ZrCo

The ZrCo alloy has demonstrated significant potential in the storage of hydrogen and its isotopes, but there are still some issues such as insufficient dynamic properties. In this paper, the impact of Nb/Ta doping on the hydride stability of ZrCo was examined based on the density functional theory, and the improvement of H diffusion through Nb/Ta doping was investigated. The focal point lies in exploring the influence of Nb/Ta doping on the alloy's resistance to poisoning and disproportionation. The results demonstrate that the crystal lattice maintains mechanical and thermodynamic stability even after Nb/Ta doping. Nb/Ta doping induces lattice contraction in ZrCo-Hx (x = 1.0–3.0) and reduce the enthalpy of formation, thereby facilitating cyclic hydrogen storage. Additionally, Nb/Ta doping enhances the diffusion performance of H atoms within O-containing lattice, improving the alloy's resistance to poisoning. Furthermore, Nb/Ta doping lowers the energy barrier of H atoms escape from 8e sites, promoting anti-disproportionation.