Mg-promoted LiH-LiNH2 hydrogen storage system synthesized by using the mechanochemical method

Hydrogenation-dehydrogenation properties in a Mg-added LiH-LiNH2 hydrogen storage system were examined by using a newly developed gas chromatography technique with hydrogen pulse detection as 2LiNH(2) + Mg(surface) <--> Mg(LiNH2)(2) <--> Mg(LiNH)(2) + H-2, Mg(LiNH)(2) + 2LiH <--> Mg(Li2N)(2) + 2H(2) (6.96 mass %). The improved performance of hydrogen storage was found by preparing a Mg additive instead of MgH2 or Mg(NH2)(2). A high plateau pressure of > 0.1 MPa at 175 degrees C, which was obtained from PCT measurements, yielded lower dehydrogenation temperatures of 169 and 193 degrees C in Mg/LiH/LiNH2 = 0.5/1/1 and 0.25/1/1 (DTA results), respectively. The reversibility was confirmed from the results of redehydrogenation after rehydrogenation at a pressure of 1 MPa in the temperature range 150-250 degrees C over 1-3 h, but dehydrogenation properties showed little difference. It was concluded that the change in the dehydrogenation kinetics may be caused by the difference in temperature between hydrogenation and dehydrogenation.