Visualization of fast “hydrogen pump” in core-shell nanostructured Mg@Pt through hydrogen stabilized Mg3Pt
A core-shell nanostructured Mg@Pt composite, consisting many of icosahedral Mg particles as the core with nano-sized Pt particles distributed homogeneously on different surfaces, was synthesized through an arc plasma method followed by the generic solid-state method. The microstructures and hydrogen sorption properties of the Mg@Pt composite were carefully investigated in comparison to the pure Mg powder. In particular, dehydrogenation behaviors of the hydrogenated Mg@Pt composite were in-situ observed using the high-resolution transmission electron microscope (HRTEM). The results revealed that Pt on Mg particles showed a “spillover” effect on improving the hydrogen absorption kinetics at the early stage. It then transformed into H-stabilized Mg3Pt followed by the formation of MgH2. DFT calculation and in-situ TEM observations demonstrated that H-stabilized Mg3Pt played a role of “hydrogen pump” effect for the dehydrogenation of MgH2 and then transformed to Pt after desorption. Through such an effect, the dehydriding kinetics of hydrogenated Mg@Pt composite was improved and the onset dehydrogenation temperature was reduced when compared to those of pure MgH2 powder.