C60-mediated hydrogen desorption in Li-N-H systems.

Hydrogen desorption from a LiH + NH(3) mixture is very difficult due to the formation of the stable LiNH(4) compound. Using cluster models and first-principles theory, we demonstrate that the C(60) molecule can in fact significantly improve the thermodynamics of ammonia-mediated hydrogen desorption from LiH due to the stabilization of the intermediate state, LiNH(4). The hydrogen desorption following the path of LiNH(4)-C(60) → LiNH(3)-C(60) + 1/2H(2) is exothermic. Molecular dynamic simulations show that this reaction can take place even at room temperature (300 K). In contrast, the stable LiNH(4) compound cannot desorb hydrogen at room temperature in the absence of C(60). The introduction of C(60) also helps to restrain the NH(3) gas which is poisonous in proton exchange membrane fuel cell applications.