Improvement in desorption kinetics of NaAlH4 catalyzed with TiO2 nanopowder

NaAlH4 has been homogeneously mixed with micron- and nano-sized TiO2 powders by high-energy ball milling and their sorption properties have been investigated during hydrogen absorption/desorption cycles. NaAlH4 with TiO2 nanopowder exhibits as good desorption kinetics as NaAlH4 with TiCl3, whereas poor desorption kinetics is observed with micron-sized TiO2 powder. NaAlH4 with TiO2 nanopowder also provides improved cyclic property compared to NaAlH4 with TiCl3 in terms of both desorption rate and hydrogen capacity. X-ray diffraction analysis shows that micron-sized TiO2 remains stable with NaAlH4 after milling, although thermodynamic calculation predicts that TiO2 reacts with NaAlH4.