Hydrogen Storage Properties and Corresponding Phase Transformations of Mg/Pd Laminate Composites Prepared by a Repetitive-Rolling Method

Abstract

Mg/Pd laminate composites (Mg/Pd = 6) prepared by a repetitive-rolling method can reversibly absorb and desorb a large amount of hydrogen, up to 1.47 H/M (4 mass%) at 573 K. Pressure-composition isotherms of the Mg/Pd laminate composites show two plateaux, P L ¼ 0:2 MPa and P H ¼ 2 MPa, during hydrogen absorption and desorption. To clarify the correlation between hydrogen storage properties and phase transformations, we investigated structural changes of the Mg 6 Pd intermetallic compound with in-situ XRD. The low-pressure plateau P L corresponds to the decomposition of Mg 6 Pd into Mg 5 Pd 2 and MgH 2 , and the high-pressure plateau P H to the decomposition of Mg 5 Pd 2 into MgPd and MgH 2 . In subsequent dehydrogenation processes, part of the MgH 2 reformed Mg, and the Mg and MgPd form Mg 5 Pd 2 at the highpressure plateau P H and then the remaining MgH 2 reformed Mg, and the Mg and Mg 5 Pd 2 form Mg 6 Pd at the low-pressure plateau P L . According to this mechanism, the Mg 6 Pd can absorb and desorb hydrogen through reversibly disproportionation and recombination processes.

Mechanochemistry of Metal Hydrides: Recent Advances

“…The effects of CR on magnesium and its alloys have been extensively studied [157,200,201,202,203,204,205,206,207,208,209,210,211,212,213,214,215,216,217,218,219,220,221,222,223,224,225,226,227]. One reason is that magnesium has a high hydrogen storage capacity (7.6 wt%).…”

“…The system Mg-Pd was the subject of some of the early studies on the effect of CR on magnesium alloys [201,202,206,207]. Because of the high price of palladium, this is not attractive for practical applications but, because palladium is a good catalyst and there are few intermetallics in the Mg-Pd phase diagrams, this system is a good candidate for fundamental investigation.…”

Effect of Cold Rolling on Magnesium-Based Metal Hydrides

“…The system Mg/Pd was first studied by Takeichi et al 70) They found that, after cold rolling and activation at 573 K, the intermetallic Mg 6 Pd is formed. Dufour and Huot compared the synthesis of MgPd compounds by cold rolling and ball milling.…”

Enhancing Hydrogen Storage Properties of Metal Hybrides

“…The systems Mg/Ti, Mg/Cu, and Mg/Pd were investigated by Takeichi et al [29][30][31][32]. In the case of Mg/Cu they found that Mg/Cu laminate presents a submicrometer structure with dislocations and stacking faults which enables the composite to reversibly absorb hydrogen [30].…”