Hydrogen desorption from MgH2+NH4Cl/graphene composites at low temperatures

MgH2 is considered one of the most promising candidates for solid-state hydrogen storage. However, the dehydrogenation of MgH2 generally happens at temperatures above 250 degrees C even after catalyzing and/or nanoconfining modifications, thus embarrassing the practical use of MgH2 in fuel cells. NH4Cl is a cheap chemical which has mature synthesis technologies in large industrial productions. The protonic H (H delta+) in NH4Cl and the hydridic H (H delta-) in MgH2 have coulomb interaction which allow MgH2 to release hydrogen at milder temperatures. In this article, by designing the molar ratio of MgH2 and NH4Cl as 2:1 (equal molar ratio of H delta+ and H delta-), the hydrogen release peak temperature can be decreased to 164.8 degrees C, and the ammonia generation is remarkably suppressed. In particular, graphene introduction to the 2MgH(2)+NH4Cl composite can further reduce the hydrogen release temperature to 161.2 degrees C and improve the hydrogen purity up to 97.26%. It is revealed that the smaller particle size and the better dispersion of 2MgH(2)+NH4Cl/graphene composite allows better interaction between H delta+ and H delta-, which brings down the hydrogen desorption temperature and improves the hydrogen purity.

Automated summary

By adjusting the molar ratio of MgH2 and NH4Cl to 2:1, the hydrogen desorption peak temperature can be decreased to 164.8 degrees C, while the generation of ammonia is significantly suppressed. Furthermore, the introduction of graphene to the 2MgH(2)+NH4Cl composite further reduces the hydrogen release temperature to 161.2 degrees C and improves the hydrogen purity to 97.26%. The smaller particle size and better dispersion of the 2MgH(2)+NH4Cl/graphene composite allow for enhanced interaction between H delta+ and H delta-, resulting in improved hydrogen desorption temperature and purity.