Role of Co3O4 in improving the hydrogen storage properties of a LiBH4–2LiNH2 composite

Adding a small amount of Co3O4 significantly reduces the operating temperatures of dehydrogenation and improves the hydrogen storage reversibility of the LiBH4–2LiNH2 system. The LiBH4–2LiNH2–0.05/3Co3O4 composite desorbs ∼9.9 wt% hydrogen by a four-step reaction with a 96 °C reduction in the midpoint temperature with respect to the pristine sample. The first and third steps of the dehydrogenation of the 0.05/3Co3O4-added sample are endothermic in nature, which is different from the pristine sample. Upon thermal dehydrogenation, the Co3O4 additive undergoes a series of chemical transformations and finally converts to the metallic Co, which is responsible for the improved thermodynamics and kinetics of the Co3O4-added sample. More importantly, 1.7 wt% of hydrogen is recharged into the 0.05/3Co3O4-added system under 110 bar hydrogen at 220 °C, which is superior to the pristine system.