Lightweight hydrides nanocomposites for hydrogen storage: Challenges, progress and prospects

As typical high-capacity complex hydrides, lightweight hydrides have attracted intensive attention due to their high gravimetric and volumetric energy densities of hydrogen storage. However, lightweight hydrides also have high thermodynamic stability and poor kinetics, so they ususally require high hydrogen desorption temperature and show inferior reversibility under mild conditions. This review summarizes recent progresses on the endeavor of overcoming thermodynamic and kinetic challenges for Mg based hydrides, lightweight metal borohydrides and alanates. First, the current state, advantages and challenges for Mg-based hydrides and lightweight metal hydrides are introduced. Then, alloying, nanoscaling and appropriate doping techniques are demonstrated to decrease the hydrogen desorption temperature and promote the reversibility behavior in lightweight hydrides. Selected scaffolds materials, approaches for synthesis of nanoconfined systems and hydriding-dehydriding properties are reviewed. In addition, the evolution of various dopants and their effects on the hydrogen storage properties of lightweight hydrides are investigated, and the relevant catalytic mechanisms are summarized. Finally, the remaining challenges and the sustainable research efforts are discussed.