Advances in catalysing the hydrogen storage in main group metals and their tetrahydroborates and tetrahydroaluminates

Hydrogen is a promising clean and renewable energy source; however, its efficient storage is one of the key challenges in establishing the sustainable hydrogen economy. The light main group metals and their tetrahydroborates and tetrahydroaluminates show great potential for high hydrogen storage capacity close to ambient conditions; however, their high hydrogenation and dehydrogenation temperatures, sluggish kinetics, and limited reversibility have always been an obstacle for practical applications. Large efforts have been devoted to modifying the thermodynamic and kinetic properties of these systems, and reviewing these efforts and highlighting future directions are the aims of the present review. Based on recent research, the application of multicomponent systems utilizing multiple modification methods, such as catalysis, nanoconfinement, alloying, and structure engineering, is essential for enhancing the storage conditions. The synergistic effect of multiple catalysts is now a key requirement to address various steps of the overall process, including forming/breaking the H-H and metal-H bonds, transporting hydrogen and heat, and suppressing the formation of side products. Compared to pristine systems, tremendous improvement has been achieved. Catalysed AlH3 decomposition can now operate as a one-way hydrogen source below 100 °C and the Mg/MgH2 hydrogen storage system exhibits good cyclic performance at elevated temperatures. Metal hydrides, tetrahydroborates, tetrahydroaluminates, and their composite systems face challenges in achieving close to ambient operating conditions and cyclic stability. As the demand for improved hydrogen energy storage is expected to grow, further research for the enhancement of these systems will continue to advance the state of hydrogen storage technology.