V-Ti co-substituted ZrCo alloys for enhanced hydrogen and H-isotope storage

The ZrCo alloy stands out as one of the most promising candidates for hydrogen isotope storage materials in nuclear fusion, owing to its extremely low equilibrium hydrogen pressure (10 −3 Pa, 20 ℃). However, ZrCo experiences severe disproportionation reactions during dehydrogenation/hydrogenation processes, which lead to significant performance degradation. To address this, we have introduced V and Ti into the ZrCo alloy, resulting in the Zr 0.8 V x Ti 0.2-x Co (x = 0–0.15) series. Our research indicates that the addition of V and Ti reduces the lattice parameters, thereby increasing the platform pressure for hydrogen desorption and decreasing the enthalpy and entropy of the desorption reaction. This modification allows for a lower desorption temperature and enhances the alloy's resistance to hydrogen-induced degradation. Remarkably, the hydrogen storage capacity of the Zr 0.8 V x Ti 0.2-x Co(x = 0–0.15) alloys remains stable after 19 h of desorption. Furthermore, the Zr 0.8 V 0.05 Ti 0.15 Co alloy demonstrates exceptional cycling stability, retaining over 99 % of its hydrogen storage capacity after 50 cycles. First-principles calculations have clarified the adsorption energies of hydrogen at different binding sites, revealing the following order of stability: E b(Ti-V) < E b(Zr-Ti) < E b(V-Zr) < E b(Zr-Zr) . The hydrogen absorption and desorption kinetics of the Zr 0.8 V x Ti 0.2-x Co alloys follow the trend: Zr 0.8 V 0.15 Ti 0.05 Co > Zr 0.8 V 0.1 Ti 0.1 Co > Zr 0.8 V 0.05 Ti 0.15 Co > ZrCo, indicating optimized performance with the introduction of V and Ti. This study not only provides a viable solution to the disproportionation issue in ZrCo alloys but also offers valuable insights into the design of high-performance hydrogen isotope storage materials for nuclear fusion applications.