Intermetallic Compounds for Hydrogen Storage: Current Status and Future Perspectives.

Intermetallic compounds are an emerging class of materials with intriguing hydrogen activation and storage capabilities garnering attention for their application in low-temperature hydrogen storage and metal hydride batteries. However, none of the existing intermetallic compounds have met the gravimetric hydrogen storage capacity target of 5.5 wt.%. Some AB-type intermetallic compounds, like MgNi, MgCo, and MgFe, approach this target but require high temperatures for hydrogen desorption limiting their use in low-temperature hydrogen storage and automotive applications. Conversely, some intermetallic compounds like ZrV and LaNi, exhibit hydrogen desorption at ambient conditions but with comparatively lower hydrogen storage capacities. This review article provides a comprehensive account of the different types of intermetallic compounds, their synthesis using different solidification-based and solid-state diffusion-based approaches, and their metallurgical and structural properties. It examines the complex interdependencies between the structural parameters of intermetallic compounds and hydrogen storage performance. A definitive but non-linear correlation is identified between void volume and gravimetric hydrogen storage capacities while lattice structure, evolution of lattice structure with hydrogen absorption, enthalpy of hydride formation, and hydrogen activation reactivities of intermetallic compounds are identified as critical parameters governing hydrogen storage performance.