Preparation And Hydrogen Storage Properties Of Mg-TM/C Composites

The energy crisis has promoted the development and application of clean energy,among which hydrogen energy has attracted much attention.Among various hydrogen storage materials,Mg-based hydrogen storage materials stand out because of their advantages such as low raw material cost and large hydrogen storage capacity,but their slow kinetic properties and high thermodynamic stability limit their large-scale application.The effects of transition metals（TM）and carbon materials on the properties of Mg-based hydrogen storage materials were studied by doping organic additives and alloying methods.Ni-MOF was prepared by hydrothermal method,and Mg-Mg₂Ni/C composites were prepared by wet ball milling and high temperature sintering.The results show that the initial dehydrogenation temperature of the composite is 530 K,which is 70 K lower than that of Mg,and the apparent activation energy of the composite is 77.6 k J/mol,which is only 50%of Mg.At 423 K,hydrogen absorption of the composite can reach 6 wt.%in3600 s.At 573 K,the hydrogen emission in 900 s is 1.62 wt.%,which is 90%of the maximum hydrogen absorption.The composite has good cyclic hydrogen absorption and release performance.The carbon material introduced by Ni-MOF inhibits the agglomeration of Mg and gives it a larger specific surface area.Meanwhile,Mg₂Ni generated by the reaction of Ni-MOF with Mg can be intertransformed with Mg₂Ni H₄ as a"hydrogen pump"in the process of hydrogen absorption and desorption,which improves the hydrogen storage performance of the material.La₂Mg₁₇/C composite were prepared from La₂Mg₁₇ and anthracene by high energy ball milling and high temperature sintering.The hydrogen absorption capacity of the composite at 473 K is 4.67 wt.%in 3600 s.At 573 K,the hydrogen emission in 3600 s was 2.22 wt.%.The cyclic performance of the composite is better than that of La₂Mg₁₇and Mg.The initial dehydrogenation temperature of the composite is 535 K,lower than that of La₂Mg₁₇ and Mg,and the apparent activation energy of the composite is 107.6k J/mol,which is significantly lower than that of La₂Mg₁₇ and Mg.The results showed that La₄H_12.19,formed in situ after hydrogen absorption,catalyzed the hydrogen desorption of Mg,and the carbon obtained from anthracene carbonization of organic matter inhibited the agglomeration of Mg.The synergistic effect of the two improved the hydrogen storage performance of the composite.