Superior Hydrogen Exchange Effect in the MgH2-LiBH4 System

The MgH2-LiBH4 system is one of the promising hydrogen storage materials. In this system, it was found that there was a mutual interaction between the two hydrides, but its detailed mechanism has not been clarified yet. In this work, we found an H-D exchange between MgD2 and LiBH4 during heating. IR absorption spectroscopy revealed that the peak of B-D vibration appeared at 275 degrees C below the melting point, indicating that this exchange proceeded even in solid phases. The hydrogen desorption properties of the composite of catalyst-doped MgH2 and LiBH4 under inert gas were investigated by mass spectrometry. The results showed that the hydrogen desorption temperature of the first step was over 300 degrees C, in spite of catalyst-doped MgH2 being able to release hydrogen at 200 degrees C. The above results suggest the hydrogen desorption from catalyst-doped MgH2 is somehow suppressed by the hydrogen exchange effect between MgH2 and LiBH4.