Metal organic framework supported niobium pentoxide nanoparticles with exceptional catalytic effect on hydrogen storage behavior of MgH2

Nb 2 O 5 nanoparticles with an average particle size of 10 nm supported on a rhombic dodecahedral metal organic framework (MOF) were successfully synthesized by a facile one-pot hydrothermal reaction and subsequent calcination process. Experimental results demonstrated that the prepared catalyst drastically improved the hydrogen storage behavior of MgH 2 . 7 wt% Nb 2 O 5 @MOF doped MgH 2 started to desorb hydrogen at 181.9 °C and 6.2 wt% hydrogen could be released within 2.6 min and 6.3 min at 275 °C and 250 °C, respectively. The fully dehydrogenated composite also displayed excellent hydrogenation by decreasing the onset absorption temperature to 25 °C and taking up 4.9 wt% and 6.5 wt% hydrogen within 6 min at 175 °C and 150 °C, respectively. Moreover, the corresponding activation energy was calculated to be 75.57 ± 4.16 kJ mol −1 for desorption reaction and 51.38 ± 1.09 kJ mol −1 for absorption reaction. After 20 cycles, 0.5 wt% hydrogen capacity was lost for the MgH 2 +7 wt% Nb 2 O 5 @MOF composite, much lower than 1.5 wt% of the MgH 2 +7 wt% Nb 2 O 5 composite. However, the addition of Nb 2 O 5 @MOF had limited effect on reducing the dehydrogenation enthalpy of MgH 2 . Microstructure analysis revealed that Nb 2 O 5 particles were uniformly distributed on surface of the MgH 2 matrix and synergistically improved the hydrogen storage property of MgH 2  with MOF.