Nanoencapsulated MgBu@ZIF-67 to Construct High Loading Mg-Co@C Nanocomposites: Breaking Through the Barrier of Room Temperature Onset Dehydrogenation.

The synergies of nanoconfinement and catalysis is an effective strategy to improve the kinetic and thermodynamic properties of Mg-based materials. However, obtaining Mg-based materials with high loading, anti-aggregation, and containing nanocatalysts to achieve dehydrogenation at room temperature remains a huge challenge. Herein, a novel and universal preparation strategy for Mg-Co@C nanocomposites with 9.5 nm Mg nanoparticles and 9.4 nm Co nanocatalysts embedded in carbon scaffold is reported. The 9.3 nm MgBu nanosheets precipitated by solvent displacement are encapsulated in ZIF-67 to prepare MgBu@ZIF-67 precursors, then removing excess MgBu on the precursor surface and pyrolysis to obtain Mg-Co@C. It is worth noting that the Mg loading rate of Mg-Co@C is as high as rare 69.7%. Excitingly, the Mg-Co@C begins to dehydrogenate at room temperature with saturate capacity of 5.1 wt.%. Meanwhile, its dehydrogenation activation energy (Ea 68.8 kJ mol) and enthalpy (ΔH = 61.6 kJ mol) significantly decrease compared to bulk Mg. First principles calculations indicate that the hydrogen adsorption energy on the MgCoH surface is only -0.681 eV. This work provides a universally applicable novel method for the preparation of nanoscale Mg-based materials with various nanocatalysts added, and provides new ideas for Mg-based materials to achieve room temperature hydrogen storage.