Materials designing of metal-N-H system as hydrogen storage materials

FUEL 75

Hironobu Fujii, hfujii@hiroshima-u.ac.jp1, Takayuki Ichikawa, tichi@hiroshima-u.ac.jp1, and Tamio Oguchi, oguchi@hiroshima-u.ac.jp2. (1) Institute for Advanced Materials Research, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, 739-8530, Japan, (2) Graduate School of Advance Sciences of Matter, Hiroshima University, 1-3-1 Kagamuyama, Higashi-Hiroshima, 739-8530, Japan
Among some Metal-N-H systems for hydrogen storage, we have undertaken the experiments for clarifying the mechanism of the H-desorption reaction from LiH + LiNH2 to Li2NH + H2. Through isotopic exchange experiments between H and D atoms, it has been found that the H-desorption reaction is controlled by the 2-step elementary reactions mediated by ammonia. The ammonia mediated reaction model is consistent with first-principles calculation results. According to the ammonia mediated model, we successfully designed a new Li-Mg-N-H system composed of 8LiH and 3Mg(NH2)2 by combining some alkali and alkaline earth metal amides with hydrides. The mechanically milled composite desorbs ~7 wt% H2 in range from 120 to 200 oC and showed the H-desorption pressure higher than 5 MPa at 200 oC, being suitable for on-board application. At present, the stabilities of the Li-N-H as well as Li-Mg-N-H systems are being examined by first-principles calculations.
 

Progress in Computational and Experimental Studies of Materials for Hydrogen Storage
8:25 AM-11:30 AM, Monday, 11 September 2006 Palace -- Mendocino Room, Oral

Division of Fuel Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006