International Journal of Energy Research, Vol.45, No.2, 3129-3141, 2021
Synthesis process and catalytic activity ofNb(2)O(5)hollow spheres for reversible hydrogen storage ofMgH(2)
High operation temperatures and slow reaction kinetics are major obstacles to use MgH(2)as a solid hydrogen store. We report here the synthesis of Nb(2)O(5)hollow spheres (o-Nb2O5) with wall thickness of approximately 50 nm and mossy surfaces using a facile hydrothermal and calcination process, which showed high activity in catalysis of MgH(2)for hydrogen storage. The dehydrogenation onset temperature of MgH(2)was decreased to 195 degrees C with 7 wt% of o-Nb2O5. More than 5.5 wt% H(2)can be desorbed at 300 degrees C within 5 minutes. Hydrogen re-absorption starts even at 25 degrees C and reaches 5.6 wt% within 5 minutes at 200 degrees C. Practical hydrogen capacity stabilizes at 5.8 wt% after 10 cycles of hydrogen uptake/release. The o-Nb(2)O(5)was found to be reduced in situ by MgH(2)to low-valence Nb species during the initial dehydrogenation process, which functions as an active catalyst and leads to the enhanced dehydrogenation kinetics.