Thermodynamic and kinetic investigations of the hydrogen storage in the Li-Mg-N-H system

Hydrogen desorption from the mixture of Mg(NH2)2 and 2LiH presents two pressure-dependent segments at a given temperature - ∼2/3 of the hydrogen is released at relatively higher pressures and forms a pressure plateau and the other 1/3 is desorbed at lower pressures. The overall reaction heat measured in a differential scanning calorimeter is 44.1 kJ/mol H2, while the heat-of-desorption of H2 in the higher pressure plateau is about 38.9 kJ/mol H2, a favorable thermodynamics for PEM Fuel Cell application. However, the relatively higher activation energy (Ea = 102 kJ/mol) sets a kinetic barrier.