Design of Bifunctional Nb/V Interfaces for Improving Reversible Hydrogen Storage Performance of MgH₂

While MgH₂ has been widely regarded as a promising solid‐state hydrogen storage material, the high operating temperature and sluggish kinetics pose a major bottleneck for its practical application. Herein, V₄Nb₁₈O₅₅ microspheres composed of nanoparticles with size of tens of nanometers are fabricated to promote H₂ desorption and absorption properties of MgH₂, which results in the uniform formation of Nb/V interfaces based on a molecular scale during the reversible hydrogen storage process. It is experimentally and theoretically demonstrated that the uniform building of Nb/V interfaces not only preserves the ability of Nb in weakening Mg‐H bonds but also alleviates the strong adsorption capacity of metallic Nb toward hydrogen atoms, leading to a relative energy barrier for the whole dehydrogenation process of MgH₂ of only 0.5 eV, which is 0.22 and 0.43 eV lower than that of Nb and V, respectively. As a result, under the addition of V₄Nb₁₈O₅₅ microspheres, the onset H₂ desorption temperature of MgH₂ is decreased to 165 °C, 125 °C lower than that of bulk MgH₂, and the complete hydrogenation of Mg could be realized even at room temperature, while almost no H₂ adsorption is observed for bulk Mg at a high temperature of 50 °C.