Research and Development of Nano-Composite Materials for Hydrogen Storage

摘要

Hydrides with light elements such as MgH_2, LiH, NH_3 and NH_3BH_3 are known as high hydrogen containing materials. However, the high work temperature and the slow reaction rate limit the practical application of hydride systems. Those properties can be improved by the nano-composite materials. The nano-composite materials for hydrogen storage encompass a catalyst and composite hydrides at the nanometer scale. The catalyst increases reaction rate. The thermodynamic stability of the nano-composite materials can be controlled by the composite hydrides. In addition, the hydrogen absorption kinetics is accelerated by the nano-size materials and they may change the thermodynamic stability of the materials. In this study, we reviewed our experimental results on hydrogen storage properties of light weight nano-composite materials. The Mg-based nano-composite material with Nb_2O_5 showed excellent kinetics as compared with that of Mg. The Li-Mg-N-H system absorbed and desorbed above 5.5 mass % of H_2 at 423K (8LiH + 3Mg(NH_2)_2 ←→3Li_(2.667)MgN_2H_(1.333)+ 8H_2). We found that the H_2 absorption and desorption of the MH-NH_3 (M: Li, Na, K) system takes the following reaction path, MH + NH_3←→MNH_2 + H_2.