Reversible Hydrogen Storage in Solid‐State Reaction Derived Core‐Shell NaBH4@Ni Nanocubes

The method to synthesize high‐capacity complex hydride nanostructures, such as borohydrides, decorated with metallic shells has surfaced as an attractive approach for enabling reversible hydrogen storage. However, the current solvent‐based synthesis methods of such core‐shell nanostructures are limited by solvents/hydrides compatibility issues and the low solubility of the shell precursor in such solvents. Herein, for the first time, an alternative solid‐state method to prepare core‐shell‐like nanostructures is reported. Simply, by mixing and heating vanadium (V)‐doped sodium borohydride (V‐NaBH 4 ) cores and nickelocene (as nickel precursor) at 150 °C, it is possible to decorate V‐NaBH 4 with Ni, which shows an improved hydrogen release (≈8 mass% H 2 ) at 350 °C and a net reversible hydrogen capacity of 2 mass%. Detailed structural investigations reveal that the in‐situ formed V x B y and Ni x B y are responsible for superior hydrogen absorption in the core‐shell material, where these boride species around the shell/interfaces suppress the loss of Na or B and the formation of B 12 H 12 during hydrogen release/uptake. This work opens solvent‐free pathways to design and control the chemical composition of core–shell (boro)hydrides for practical hydrogen storage.