Effect of carbon nanotubes on the microstructural evolution and hydrogen storage properties of Mg(BH4)2

Abstract

As an important member of complex hydrides, Mg(BH4)2 has a high gravimetric capacity (14.9 wt%). In this study, the Mg(BH4)2 was synthesized by the ion exchange method. Afterwards, the Mg(BH4)2 composites with different amounts (2, 5, 10, 25 and 50 wt%) of carbon nanotubes (CNTs) were prepared by mechanical milling. Effects of the CNTs on the microstructural evolution and hydrogen storage properties were investigated. The onset desorption temperature of the Mg(BH4)2-5 wt% CNTs is decreased to lower temperature around 120 °C from 275 °C. The desorption plateau of Mg(BH4)2-5 wt% CNTs is the highest, which ascribes that CNTs causes the reaction pathway change. Additionally, the Mg(BH4)2-5 wt% CNTs shows the best dehydriding kinetics properties, and can desorb 6.04 wt% hydrogen within 2000 s at 300 °C. The dehydrogenation activation energy of the Mg(BH4)2-5 wt% CNTs is decreased to 130.2 kJ/mol H2, which is much lower than that of pure Mg(BH4)2.