Synthesis and characterization of two new amide chloride compounds: Potential H2 storage materials

Two new amide chloride phases, with approximate stoichiometries Li7(NH2)6Cl and Li6Mg0.5(NH2)6Cl, have been identified by powder X-ray diffraction, and their hydrogen storage properties studied. Both phases released hydrogen on reaction with LiH at a lower temperature than observed for lithium amide, and ammonia release was suppressed. The chloride ions were maintained within the structure after hydrogen desorption and rehydrogenation, raising the possibility that the materials might be cycled. The desorption properties of Li7(NH2)6Cl were found to be similar to the previously reported amide chloride Li4(NH2)3Cl but with a much reduced gravimetric penalty owing to chloride incorporation. Rehydrogenation of the imide products of reaction of both Li7(NH2)6Cl and Li6Mg0.5(NH2)6Cl with LiH occurred more readily at 90 bar and 300 °C than that of Li4(NH2)3Cl.