Hydrogen desorption reactions of Li–N–H hydrogen storage system: Estimation of activation free energy

The dehydrogenation reactions of the mixtures of lithium amide (LiNH2) and lithium hydride (LiH) were studied under an Ar atmosphere by means of temperature programmed desorption (TPD) technique. The dehydrogenation reaction of the LiNH2/LiH mixture was accelerated by addition of 1 mol% Ti(III) species (k = 3.1 × 10−4 s−1 at 493 K), and prolonged ball-milling time (16 h) further enhanced reaction rate (k = 1.1 × 10−3 s−1 at 493 K). For the hydrogen desorption reaction of Ti(III) doped samples, the activation energies estimated by Kissinger plot (95 kJ mol−1) and Arrhenius plot (110 kJ mol−1) were in reasonable agreement. The LiNH2/LiH mixture without Ti(III) species, exhibited slower hydrogen desorption process and the kinetic traces deviated from single exponential behavior. The results indicated the Ti(III) additives change the hydrogen desorption reaction mechanism of the LiNH2/LiH mixture.