In-situ synthesis of Mg₂Ni-Ce₆O₁₁ catalyst for improvement of hydrogen storage in magnesium

To decrease the hydrogen sorption temperature and increase the hydrogen sorption rate is important for the practical application of magnesium for hydrogen storage. The binary nano-catalysts Mg2Ni and Ce6O11 with oxygen vacancy defects was in-situ synthesized on Mg surface via the hydrogen activation of Mg-Ni-CeO2. The hydrogen storage material Mg-20Ni-CeO2 can release 4.19 wt% H-2 in 5 min at 320 degrees C, which is significantly higher than that of Mg with 10 wt% Ni (3.44 wt% H-2) or 10 wt% CeO2 (0.34 wt% H-2). The peak temperature and apparent activation energy for hydrogen desorption of Mg-20Ni-CeO2 are reduced by 115.8 degrees C and 63.89 kJ/mol respectively comparing with that without catalyst. Structural analysis suggests that Mg2Ni and Ce6O11 can be in-situ synthesized on Mg surface, which shows a synergistic catalysis for hydrogen storage. During H-2 absorption, the oxygen vacancy defects on Ce6O11 surface can trap H-2 molecules, while the Mg2Ni on Mg/Mg2Ni interface can promote H-2 dissociation. For H-2 desorption, the Mg2Ni can weaken the Mg-H bond and act as "hydrogen pump" to transfer H for H-2 formation with the assistance of Ce3+/Ce4+ transformation in Ce6O11. The results of this study provide a new horizon for a novel binary catalyst design for hydrogen storage.