A striking catalytic effect of facile synthesized ZrMn2 nanoparticles on the de/rehydrogenation properties of MgH2

Zr-based Laves phase alloys, especially ZrMn2, have been widely studied because of their good hydrogen storage properties. In this work, ZrMn2 nanoparticles were successfully prepared by a facile wet-chemical method and then introduced to MgH(2)via ball milling to fabricate MgH2-ZrMn2 composites. Remarkable improvements to the de/rehydrogenation properties were achieved with the addition of ZrMn2 nanoparticles. The MgH2 + 10 wt% nano-ZrMn2 composite started to release hydrogen at 181.9 degrees C, which was about 160 degrees C lower compared with that of additive-free MgH2. At 300 degrees C, the MgH2+ 10 wt% nano-ZrMn2 composite desorbed 6.7 wt% hydrogen in 5 min. More importantly, the dehydrogenated MgH2 + 10 wt% nano-ZrMn2 sample absorbed hydrogen even at room temperature under 3 MPa hydrogen pressure, and approximately 5.3 wt% hydrogen was taken up within 10 min at 100 degrees C. Moreover, compared with additive-free MgH2, the dehydrogenation and rehydrogenation activation energies of the MgH2 + 10 wt% nano-ZrMn2 composites were significantly reduced to 82.2 +/- 2.7 kJ mol(-1) and 22.1 +/- 2.7 kJ mol (-1), respectively. TEM analysis demonstrated the uniform distribution of ZrMn2 nanoparticles in the MgH2 matrix. Further, density functional theory calculations revealed that the presence of ZrMn2 facilitated the breaking of the Mg-H bond, which provided a good explanation for the reduced de/rehydrogenation temperatures of the ZrMn2 modified MgH2.