Synergistic catalytic effects of ZIF-67 and transition metals (Ni, Cu, Pd, and Nb) on hydrogen storage properties of magnesium

• Published in: International journal of hydrogen energy 2020-05, Vol.45 (24), p.13376-13386
• Main Authors: Wang, Yongqing, Lan, Zhiqiang, Fu, Hong, Liu, Haizhen, Guo, Jin
• Format: Article
• Language: English
• Subjects: Cycling stability; Hydrogen storage properties; Magnesium; Transition metals
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2020.03.036

MgTM/ZIF-67 nanocomposites were prepared by the deposition-reduction method using ZIF-67, MgCl2, and TMClx (TM = Ni, Cu, Pd, Nb) as raw materials. The dehydrogenation activation energies of MgTM/ZIF-67 (TM = Ni, Cu, Pd, Nb) nanocomposites were calculated to be 115.4 kJ mol−1 H2, 115.7 kJ mol−1 H2, 113.6 kJ mol−1 H2, and 75.8 kJ mol−1 H2, respectively; hence, the MgNb/ZIF-67 nanocomposite manifested the best comprehensive hydrogen storage performance. The hydrogen storage capacity of the MgNb/ZIF-67 nanocomposite was hardly attenuated after the 100th hydrogen absorption-desorption cycle. The dehydrogenated enthalpies of MgH2 and CoMg2H5 in MgNb/ZIF-67 hydride were calculated to be 72.4 kJ mol−1 H2 and 81.0 kJ mol−1 H2, respectively, which were lower than those of additive-free MgH2 and Mg/ZIF-67. The improved hydrogen storage properties of MgNb/ZIF-67 can be ascribed to the CoMg2–Mg(Nb) core-shell structure and the catalytic effects of NbH and niobium oxide nanocrystals. [Display omitted] •The MgTM/ZIF-67 (TM = Ni, Cu, Pd, Nb) nanocomposites were prepared.•MgNb/ZIF-67 shows excellent dehydrogenation kinetic property.•CoMg2–Mg(Nb) core-shell plays a buffer role to improve cyclic stability.•The NbH and niobium oxide nanocrystalline in MgNb/ZIF-67 act as catalysts.