Morphology-regulated NaNbO3 catalysts for fast reversible hydrogen storage of MgH2

Magnesium hydride (MgH 2 ) is considered a promising solid-state hydrogen storage material owing to its high hydrogen storage capacity and abundant Mg resources. However, its practical application is still limited by sluggish low-temperature hydrogen absorption/desorption kinetics, high dehydrogenation temperature, and insufficient cycling stability. Although NaNbO 3 -based catalysts have recently shown potential for improving the hydrogen storage performance of MgH 2 , the effect of processing-controlled NaNbO 3 morphology on catalyst dispersion, interfacial contact, and hydrogen absorption/desorption kinetics remains unclear. Herein, morphology-regulated NaNbO 3 catalysts were synthesized via a hydrothermal-calcination route by varying the hydrothermal temperature and introduced into MgH 2 through high-energy ball milling. Among the investigated samples, the composite containing 7 wt% NaNbO 3 prepared at 200°C (MgH 2 –7 wt.% NaNbO 3 -200) exhibited fast and reversible hydrogen storage performance, absorbing 5.0 wt% H 2 within 12 s at 200°C and desorbing 6.0 wt% H 2 within 6 min at 300°C. After 30 cycles, it retained 6.12 wt% H 2 , corresponding to 89.7% of its initial dehydrogenation capacity, and showed an apparent dehydrogenation activation energy of 86.96 kJ mol −1 . The enhanced performance is mainly attributed to improved MgH 2 /NaNbO 3 interfacial contact, together with a possible contribution from partially reduced Nb-containing species formed during repeated hydrogen sorption.