V-, Nb- and Ta-Based Additives for Enhancing the Hydrogen Storage Performance of MgH₂: A Review

As a highly anticipated potential hydrogen storage material, magnesium hydride (MgH₂) has shown important application prospects due to its high hydrogen storage capacity and abundant resource reserves. However, it still faces limitations in hydrogen storage performance in practical applications, including high dehydrogenation temperature, slow hydrogen absorption and desorption kinetics, and insufficient cycle stability, which restrict its large-scale application. In recent years, research has shown that introducing transition-metal-based additives is one of the effective strategies to enhance the hydrogen storage performance of MgH₂. Transition-metal-based additives can significantly optimize the hydrogen absorption/desorption kinetic behavior of MgH₂, manifested by effectively reducing reaction temperature, increasing reaction rate, and enhancing the cycling stability of the system. Among numerous transition metals, the fifth-group-element (vanadium, niobium, tantalum)-based additives have shown significant effects on improving the hydrogen storage performance of MgH₂ due to their unique electronic structure and catalytic activity. This article systematically reviews the effects and mechanisms of vanadium-, niobium-, and tantalum-based additives on the hydrogen storage performance of MgH₂, summarizes current research progress, and looks forward to future development directions in this field.