Advances and perspectives of two-dimensional materials MXenes: Efficient catalysts for magnesium hydride

Magnesium hydride (MgH2) has been considered as a promising solid-state hydrogen storage material due to its advantages, including high gravimetric (∼7.6 wt%), environmental friendliness, and excellent reversibility. However, the stable thermodynamic and sluggish hydrogen absorption/desorption kinetics of MgH2 significantly hinder its commercial application. Considerable efforts have been dedicated to lowering the dehydrogenation temperature and facilitating the hydrogen absorption/desorption reaction rate of MgH2, resulting in substantial progress. Catalyzing is recognized as one of the most effective strategies for ameliorating the hydrogen storage performances of MgH2. Over the past years, two-dimensional (2D) transition metal carbides or nitrides or carbonitrides, i.e., MXenes, have gained widespread applications in energy storage, biomedicine, gas separation and water purification, owing to their 2D layered structure, high specific surface area, tunable surface terminations, and exceptional thermal stability. In particular, MXenes have demonstrated efficiency as catalysts for the de/hydrogenation reactions of MgH2. Herein, this review article systematically reviews the advancement of MXenes, covering their structure, synthesis methods, and potential applications for storing hydrogen. Meanwhile, it comprehensively summarizes the effect of MXenes as catalysts in improving the hydrogen absorption/desorption properties of MgH2, covering three aspects: MXenes themselves, MXenes derivatives and MXenes composites, while highlighting their respective catalytic mechanisms. Furthermore, the future research and development of MXenes catalysts and their application in MgH2 are elucidated.