Lu Wen,Chaojie Li,Houqun Xiao,Huazhou Hu,Chaobin Lai,Luocai Yi,Qingjun Chen
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.
Wang Li,Wu Fuying,Chen Daifen,Bian Ting,Senin Petr,Zhang Liuting
Owing to the orbital hybridization between the transition metal and the B element and the electron-trapping effect of the B element, transition metal borides are considered very promising materials for energy catalysis. In this work, an amorphous scaly high-entropy boride (HEB) with electron traps was designed and fabricated via a facile reduction method to improve the hydrogen storage properties of magnesium hydride (MgH 2 ). For dehydrogenation, the onset temperature of MgH 2 + 10wt% HEB was dropped to 187.4°C; besides, the composite exhibited superior isothermal kinetics and the activation energy of the composite was reduced from (212.78 ± 3.93) to (65.04 ± 2.81) kJ/mol. In addition, MgH 2 + 10wt% HEB could absorb hydrogen at 21.5°C, and 5.02wt% H 2 was charged in 50 min at 75°C. For reversible hydrogen storage capacity tests, the composite maintained a retention rate of 97% with 6.47wt% hydrogen capacity after 30 cycles. Combining microstructure evidence with hydrogen storage performance, the catalytic mechanism was proposed. During ball milling, scaly high-entropy borides riveted a large number of heterogeneous active sites on the surface of MgH 2 . Driven by the cocktail effect as well as the orbital hybridization of metal borides, numerous active sites steadily enhanced the hydrogen storage reactions in MgH 2 .
Sanyang Guo,Zhichao Yu,Yuan Li,Yaokun Fu,Zhuohan Zhang,Shumin Han
Magnesium hydride (MgH 2 ) is a promising hydrogen storage material with high weight and volume hydrogen capacity. However, higher operating temperature and reversible hydrogen capacity decay inhibit its wide application. To address these issues, Mg-Mg 2 Ni/C was obtained by ball milling magnesium and nickel-Metal Organic Framework (Ni-MOF), and following calcinations . Initial dehydrogenation temperature of the composite is 530 K, 70 K lower than that of MgH 2 , and the apparent activation energy of the composite is 77.6 ± 2.1 kJ/mol, which is only 50% of MgH 2 . At 423 K, the hydrogen capacity of the composite is about 6 wt% within 3600 s, and keeps unchanged after ten cycles. The carbon material introduced by Ni-MOF inhibits the agglomeration of Mg, and Mg 2 Ni/Mg 2 NiH 4 acts as a “hydrogen pump” in de/hydrogenation process. The carbon coating and “hydrogen pump” lead to the improvement of the ab/desorption kinetics and cycling stability. This attempt paves a potential way to achieve high performance Mg-based composite hydrogen storage materials.
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