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

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.