Catalytic effect and mechanism of NiCu solid solutions on hydrogen storage properties of MgH2

In this work, the NiCu solid solutions with different Ni/Cu molar ratios were prepared and then doped into MgH2 through ball milling to modify its hydrogen sorption properties. The experimental results show that the Ni-25%Cu and Ni-50%Cu exhibit the superior catalytic effect over pure Ni, pure Cu and Ni -75%Cu on the dehydrogenation of MgH2. Among them, the 5h-milled MgH2/Ni-50%Cu system starts to desorb hydrogen at 205.8 degrees C, which is about 96.9 degrees C lower than that of as-milled pristine MgH2. Moreover, the MgH2/Ni-50% Cu system can release 5.14 wt% hydrogen at 300 degrees C within 15 min, while MgH2 can only release 2.92 wt% hydrogen under the same condition. More importantly, the dehydrogenated MgH2/Ni-50%Cu can reabsorb 4.37 wt% hydrogen even at 250 degrees C for 30 min. The enhanced hydrogen sorption kinetics of MgH2/Ni-50%Cu mainly attributes to the hydrogen spillover effect of in-situ formed Mg2Ni(Cu) phases. Further theoretical calculations reveal that the strong interactions between H and Ni/Cu result in the weakened stability of MgH2, decreased bond strength of Mg-H and enhanced dehydrogenation properties of MgH2. This research provides an important guidance for design multiple transition metals catalysts to improve efficiently hydrogen storage properties of magnesiumbased and other metal-based hydrides. (C) 2020 Elsevier Ltd. All rights reserved.