Nanoencapsulated MgBu2@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 MgBu2 nanosheets precipitated by solvent displacement are encapsulated in ZIF‐67 to prepare MgBu2@ZIF‐67 precursors, then removing excess MgBu2 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(des) = 68.8 kJ mol−1) and enthalpy (ΔH(des) = 61.6 kJ mol−1) significantly decrease compared to bulk Mg. First principles calculations indicate that the hydrogen adsorption energy on the Mg2CoH5 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. The MgBu2 nanosheets are encapsulated in ZIF‐67 to prepare MgBu2@ZIF‐67, which are then pyrolyzed to obtain Mg‐Co@C nanocomposites with 9.5 nm Mg NPs and 9.4 nm Co nanocatalysts embedded in carbon scaffold. The loading rate of Mg‐Co@C reaches a record high of 69.7% and exhibits outstanding kinetic (Ea(abs)/Ea(des) is 44.1/68.8 kJ mol−1) and thermodynamic (ΔH(abs)/ΔH(des) is −62.5/61.6 kJ mol−1) properties.