Two-dimensional ZrCo nanosheets as highly effective catalyst for hydrogen storage in MgH2

Abstract

Magnesium, a cheap and abundant metal, holds tremendous promise for on-board hydrogen storage over the past several decades. However, the practical application of MgH2 is still hampered by various challenges, including a high efficient catalyst. Zirconium and Zr-based alloys show great potential to serve as hydrogen transfer center due to their high activity in hydrogen dissociation and diffusion. In this paper, ZrCo nanosheets were successfully prepared via a facile wet-chemical technique and then introduced to improve the hydrogen storage properties of MgH2. With the addition of 10 wt% ZrCo nanosheets, the modified MgH2 composite could desorb approximately 6.3 wt% H2 within 5 min at 300 °C and absorb 4.4 wt% H2 under 3 Mpa hydrogen pressure in 10 min even at 120 °C. The de/hydrogenation activation energy were calculated to be 90.4 ± 1.6 kJ/mol and 57.6 ± 1.0 kJ/mol for the MgH2+10 wt% ZrCo composite, which reasonably explain the remarkably improved de/hydrogenation performance. X-Ray Diffraction (XRD) and Transmission electron microscope (TEM) results revealed that hydrogen could be diffused between the composite more easily with the presence of well dispersed ZrCo, which acted as “hydrogen pump” for hydrogen boundaries/interface diffusion along the Mg/MgH2 interfaces. Theoretical calculations revealed that the Mg–H bonds were extracted and weakened when adsorbed on the surface of ZrCo. Furthermore, the MgH2+10 wt% ZrCo composite showed superior cycling performance with the aid of graphene, indicative of potential application in the nearest future in the area of hydrogen storage.