Cyclic reaction-induced enhancement in the dehydrogenation performances of the KNH2-doped LiNH2 and LiH system.

Ammonia is a vital intermediate in the hydrogen desorption process of Metal-N-H system. KH has strong reactivity with NH 3 to form KNH 2. We speculate that KNH 2 is also an intermediate formed during hydrogen desorption of the potassium-doped M-N-H systems. In this research, the dehydrogenation performance of the KNH 2 -doped LiNH 2 and LiH composition was first studied. Compared with the broad dehydrogenation curve of the composite material of LiNH 2 and LiH without the catalyst, the dehydrogenation curve of 0.05 mol KNH 2 -doped composite material was significantly narrowed. The initial and peak dehydrogenation temperature of the composite to which 0.05 mol of KNH 2 was added was lowered remarkably. Besides, the cyclic dehydrogenation properties of the LiNH 2 and LiH system was also significantly enhanced by the introduction of KNH 2. The cyclic conversion of KNH 2 to KH is the main reason for the enhancement of the hydrogen evolution performance of the LiNH 2 –LiH system doped with KNH 2. We found the KNH 2 -doped Li–N–H system exhibits similar dehydrogenation property with that of the KH-doped Li–N–H system. This work proves that KNH 2 plays a key role in improving the hydrogen desorption performances of the potassium-doped M-N-H systems. Image 1 • Hydrogen desorption properties of the KNH 2 -doped Li–N–H system was examined. • Hydrogen desorption kinetics are significantly enhanced by introducing KNH 2. • The dehydrogenation temperature is lowered drastically. • The improved properties induce from the cyclic conversion from KNH 2 to KH. • KNH 2 may be formed during dehydrogenation of the potassium-doped M-N-H system. [ABSTRACT FROM AUTHOR]