Hydrogen Storage Behavior of Mg-based Alloy Catalyzed by Carbon-cobalt Composites

The composites comprised of Co nanoparticle and C nanosheet were prepared though a high-temperature carbonization reaction. The catalysis of Co@C composites on the hydrogen storage behavior of Mg₉₀Ce₅Y₅ alloy was investigated in detail by XRD, SEM, TEM, PCI, and DSC method. Because of the synergistic catalytic function of C and Co in C@Co nanocomposites, the Mg₉₀Ce₅Y₅ alloy with 10 wt.% C@Co shows the excellent hydrogen absorption and desorption performances. Time for releasing hydrogen reduces from 150 min to 11 min with the addition of the C@Co composites at the temperature of 300 °C. Meanwhile, the dehydrogenation activation energy also declines from 130.3 to 81.9 kJ mol−1 H₂ after the addition of the C@Co composites. This positive effect attributes to the C layer with the high defect density and the Co nanoparticles, which reduces the energy barriers for the nucleation of Mg/MgH₂ phase and the recombination of hydrogen molecule. Besides, the C@Co composites also improve the activation property of the Mg₉₀Ce₅Y₅ alloy which was fully activated in the first cycle. Moreover, the temperature for initial dehydrogenation and the endothermic peak of the alloy hydride were also decreased. Although the addition of the C@Co composites increases the plateau pressures and decreases the value of the decomposition enthalpy, these differences are so small that the improvement on thermodynamics can hardly be seen.