Improved hydrogen storage performance of Ca(BH<inf>4</inf>)<inf>2</inf>: A synergetic effect of porous morphology and in situ formed TiO<inf>2</inf>

Abstract

A porous Ca(BH4)2-based hydride, CaB2H7, with nano-TiO2introduced in situ, was successfully synthesized via mixing Ca(BH4)2with Ti(OEt)4followed by heat treatment. The effects of the porous structure and introduction of TiO2on both the non-isothermal and isothermal hydrogen desorption-absorption properties of the porous system were systematically investigated. The results show significant improvements on both the kinetics and thermodynamics of hydrogen desorption-absorption of the porous CaB2H7-0.1TiO2system, compared with the dense Ca(BH4)2. The desorption peak temperature is reduced by more than 50 °C and sorption capacity of ca. 5 wt% H2is rapidly achieved below 300 °C. The porous structure was retained in the dehydrogenated products, and rapid hydrogen absorption, approximately 80% of the desorption capacity, is obtained upon heating the product, post-dehydrogenated at 300 °C for 1 h, to 350 °C at 90 bar H2. External addition of nano-TiO2also enhances the hydrogen storage properties of Ca(BH4)2, but to a lesser extent, compared with the synergetic effect of the porous structure and the in situ formed nano-TiO2. In addition, desorption-absorption mechanisms of the porous CaB2H7-0.1TiO2system are also proposed. © 2013 The Royal Society of Chemistry.