Catalytic effects of in-situ CeN/CeH2.51 on the hydrogen storage properties of Mg(NH2)2–2LiH

The potential of rare earth nitrides as catalysts to improve hydrogen storage performance of Mg(NH2)2–2LiH system was investigated. A series of rare earth nitrides ReN (ReLa, Ce, Sm, Pr, Nd) were added to Mg(NH2)2–2LiH system for the purpose of enhancing its hydrogen storage performance, and the optimal selection was determined to be the addition of 5 wt% CeN. For Mg(NH2)2–2LiH-5wt%CeN sample, the initial hydrogen absorption and desorption temperatures of decrease to 70 °C and 105 °C, and the activation energy for hydrogen release decreases from 120.0 kJ/mol to 112.5 kJ/mol. Addition of CeN also remarkable improved the hydrogen release/absorption kinetics. At 150 °C and within 100 min, the hydrogen release capacity of the sample with 5 wt% CeN addition is 2.18 times that of the pristine sample. At 120 °C, the maximum hydrogen absorption capacity of the sample with 5 wt% CeN addition was more than 3 times that of the pristine sample. In addition, after ten hydrogen release cycles, the hydrogen storage performance remained stable without significant capacity degradation. Further phase structure and morphology analysis showed that the added CeN in situ transformed into CeN/CeH2.51 during the ball milling stage. And the catalytic mechanism of CeN/CeH2.51 to the hydrogen absorption/release process of Mg(NH2)2–2LiH system was discussed.