Highly active bimetallic MOF derivatives for improving the dehydrogenation performance of LiAlH4

Abstract

LiAlH4 is considered an effective hydrogen storage material due to its high hydrogen storage capacity and relative abundance of aluminum. However, LiAlH4 presents disadvantages such as slow kinetics, high dehydrogenation temperature, and poor reversibility. To improve these shortcomings of LiAlH4, we designed and prepared Ni-Ti bimetallic metal-organic framework derivatives with stable structures and high dispersion of metal species, which named as Ni-Ti-NC. A series of tests show that the composite components and circular disk-like structure of Ni-Ti-NC can improve the dehydrogenation behavior of LiAlH4. Benefiting from the addition of Ni-Ti-NC, the initial decomposition temperature of LiAlH4 significantly decreased to 59.5 ℃, and about 6.11 wt% of hydrogen was rapidly released within 25 min at 200 ℃. Meanwhile, the activation energies of the two-step hydrogen evolution reaction decreased to 64.18 kJ·mol−1 and 73.99 kJ·mol−1, respectively. Furthermore, compared with only 0.09 wt% hydrogen absorption of pure LiAlH4 at 30 bar hydrogen pressure and 300 ℃ constant temperature, doping Ni-Ti-NC promoted the hydrogen absorption capacity of LiAlH4 to nearly 0.64 wt% under the same conditions. In addition, the structure and chemical changes of LiAlH4 after the addition of Ni-Ti-NC were investigated in detail. The reasons why Ni-Ti-NC improved the hydrogen storage performance of LiAlH4 were comprehensively analyzed, which helped us design efficient catalysts for solid hydrogen storage materials.