The MgH2-Nb2O5-carbon nanotube (CNT) composite was fabricated to accommodate the volume change of particles during the hydrogen storage cycles by holding the MgH2-Nb2O5 particles within the sponge-like matrix of the CNT. This allowed for preservation of the composite structure and led to more stable hydrogen sorption properties during 20 cycles, as compared to without CNT. To investigate this effect of CNT on the cyclic stability of MgH2-Nb2O5, CNT and expanded graphite (EG) were added to MgH2-Nb2O5 via ball milling. The MgH2-Nb2O5-CNT powder showed stable cyclic performance, similar to the MgH2-Nb2O5-CNT composite, whereas the MgH2-Nb2O5-EG powder exhibited cyclic degradation similar to MgH2-Nb2O5. From SEM-EDS, it was found that the C/Mg ratio of the surface of the MgH2-Nb2O5-CNT powder was higher than that of the MgH2-Nb2O5-EG powder. Thus, the fibrous CNT on the surface of the MgH2 particles could be responsible for the greater cyclic stability of the MgH2-Nb2O5-CNT composite.
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