Improved hydrogen storage performance of Ca(BH4)2: a synergetic effect of porous morphology and in situ formed TiO2

A porous Ca(BH4)(2)-based hydride, CaB2H7, with nano-TiO2 introduced in situ, was successfully synthesized via mixing Ca(BH4)(2) with Ti(OEt)(4) followed by heat treatment. The effects of the porous structure and introduction of TiO2 on 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 CaB2H7-0.1TiO(2) system, compared with the dense Ca(BH4)(2). The desorption peak temperature is reduced by more than 50 degrees C and sorption capacity of ca. 5 wt% H-2 is rapidly achieved below 300 degrees 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 degrees C for 1 h, to 350 degrees C at 90 bar H-2. External addition of nano-TiO2 also 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 CaB2H7-0.1TiO(2) system are also proposed.