Progress on nano-scaled alloys and mixed metal oxides in solid-state hydrogen storage; an overview

Hypothesis: With increased development and electricity generation, great care to energy storage systems is crucial to overcome the discontinuity in the renewable production. Hydrogen is an ideal energy carrier for near future mobility, like automotive applications. Solid-state hydrogen storage materials including nanomaterials and layered systems are the key enablers to the future energy needs. However, the current materials are unable to meet all requirements in the storage capacity and commercialization. The hydrogen storage mechanisms (physical and chemical) are the key-points addressing the shortcomings in hydrogen absorption/adsorption in the interlayer space or on the surface of the material. All above require strategy for designing new hydrogen storage materials. Experiments: This review lays the recent foundations in the materials suitable for hydrogen storage particularly alloys, mixed metal oxides (MMOs), and their respective nanocomposites. Alloys and MMOs are two classes of materials with high discharge capacities, appropriate electrochemical performances, chemical stability, easy production pathways, and almost low cost. In the same vein, highly porous materials with a large surface area such as metal organic frameworks (MOFs), MXenes and carbon materials are thermodynamically and kinetically more favorable. Findings: The literature review illustrates that it is crucial to develop new materials with large-surface area, homogeneous texture, active-conductive profiles, large oxygen vacancies and low-cost. Multiphase materials (nanocomposites/hybrids) composed of at least two of above-mentioned materials can meet the established requirements in this field. Also, the present paper demonstrates a general overview of promoted understanding of hydrogen storage mechanisms on alloy/MMOs-based compounds in the energy storage systems. It is hoped that these observations pave the potential exploration directions to dominate imminent challenges in solid-state hydrogen storage.