However, their high working temperature and the slow reaction rate limit the practical application of the nitrogen-based hydrides. Those properties can be improved by the use of nanocomposite materials (Fig.
2). The nanocomposite materials encompass a catalyst and composite chemical hydrides at the nanometer scale.
In this study, we will review our experimental results on hydrogen storage properties and characterization of hydride-magnesium amide (MH-Mg(NH2)2), hydride-ammonia borane (MH-NH3BH3) and hydrideammonia (MH-NH3) systems.
Fuel cell vehicles (FCV) feature 35-70 MPa hydrogen storage tanks (inner volume: 156-171 L) and the tank size of the vehicles is large compared to those of gasoline vehicles. Ammonia borane (NH3BH3) and Ammonia (NH3) has emerged as attractive candidates because of their high percentage of hydrogen (20-18 mass%). It is expected that lightweigt and compact hydrogen storage system can be developed using the nitrogen-based hydrides.
(1) We have developed Li-Mg-N-H (8LiH-3Mg(NH2)2) system which absorbed and desorbed 5.8 mass% of H2 at 150°C.
(2) NaH-NH3BH3 composite material desorbed 11 mass% of hydrogen below 90°C without emission of NH3 and foaming.
(3) LiH-NH3 system desorbed 6 mass% of H2 at room temperature.
(4) H2 and N2 were generated by the decomposition of NaNH2 at 400°C.
(1) The volumetric H2 densities of nitrogen-based composite materials having protide (hydride) (Hδ-)[LiH, NaH] and proton (Hδ+) [Mg(NH2)2, NH3BH3, NH3] provide 0.9-1.4 times of compressed hydrogen at 70 MPa (3.9kgH2/100L).
(2) NH3 shows promise for the application of H2 energy carrier because the cost of H2 in NH3 is below 1/4 of the supply cost of H2.
Patent: Unexamined Publication JP2010-265138, JP2009-215103
Journal: Y. Kojima et al., J. Mater. Res., 24, 2185 (2009), H. Yamamoto et al., Int. J. Hydrogen Energy 34, 9760 (2009), H.
Miyaoka et al., Int. J. Hydrogen Energy 36, 8217 (2011), Y. Kojima, Materials Science Forum, 654-656, 2935 (2010),S. Yamaguchi et al., Extended Abstract, JCREN (2013).
Award: 2007: Highly Cited Researcher (ISI HighlyCited.com), 2009: Presidential Awards (Hiroshima University), 2012：International Steering Committee of the International Symposia on Metal-Hydrogen Systems , CERTIFICATE OF APPRECIATION