Enhanced hydrogen desorption/absorption properties of magnesium hydride with CeF_3@Gn

摘要

In order to improve the hydrogen storage performance of MgH2, graphene and CeF3 co-catalyzed MgH2 (hereafter denoted as MgH2+CeF3@Gn) were prepared by wet method ball milling and hydriding, which is a simple and time-saving method. The effect of CeF3@Gn on the hydrogen storage behavior of MgH2 was investigated. The experimental results showed that co-addition of CeF3@Gn greatly decreased the hydrogen desorption/absorption temperature of MgH2, and remarkably improved the dehydriding/hydriding kinetics of MgH2. The onset hydrogen desorption temperature of Mg + CeF3@Gn is 232 degrees C, which is 86 degrees C lower than that of as-milled undoped MgH2, and its hydrogen desorption capacity reaches 6.77 wt%, which is 99% of its theoretical capacity (6.84 wt%). At 300 degrees C and 200 degrees C the maximum hydrogen desorption rates are 79.5 and 118 times faster than that of the as-milled undoped MgH2. Even at low temperature of 150 degrees C, the dedydrided sample (Mg + CeF3@Gn) also showed excellent hydrogen absorption kinetics, it can absorb 5.71 wt % hydrogen within 50 s, and its maximum hydrogen absorption rate reached 15.0 wt% H-2/min, which is 1765 times faster than that of the undoped Mg. Moreover, no eminent degradation of hydrogen storage capacity occurred after 15 hydrogen desorption/absorption cycles. Mg + CeF3@Gn showed excellent hydrogen de/absorption kinetics because of the MgF2 and CeH2-3 that are formed in situ, and the synergic catalytic effect of these byproducts and unique structure of Gn. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.