Kinetic improvement on the CaH2-catalyzed Mg(NH2)2 + 2LiH system

• We studied the effect of CaH2 on the dehydrogenation of the Mg(NH2)2–2LiH system.
• Mg(NH2)2 was obtained by gas–solid reaction with a significant conversion degree.
• Kissinger analysis revealed that addition of CaH2 decreased the activation energy.

In the present work we focused on the catalytic effect of CaH2 on the dehydrogenation process of the Mg(NH2)2–2LiH system. The synthesis, hydrogen storage properties and energy barriers were investigated by X-ray diffraction (XRD), temperature-programmed desorption (TPD) and differential scanning calorimetry (DSC). The TPD measurements proved that desorption of the Mg(NH2)2–2LiH system milled with 0.08 mol of CaH2 started at temperature of 78 °C, lower if compared with the 125 °C observed in the pristine material. Furthermore, Kissinger analysis revealed that CaH2 acted as a catalyst to decrease the activation energy of the first dehydrogenation step from a value of 133.8 ± 4.1 kJ/mol for the pristine material to 105.1 ± 3.2 kJ/mol when CaH2 was dispersed into the mixture.