Improvement in desorption kinetics of NaAlH_4 catalyzed with TiO_2 nanopowder

摘要

NaAlH_4 has been homogeneously mixed with micron- and nano-sized TiO_2 powders by high-energy ball milling and their sorption properties have been investigated during hydrogen absorption/desorption cycles. NaAlH_4 with TiO_2 nanopowder exhibits as good desorption kinetics as NaAlH_4 with TiCl_3, whereas poor desorption kinetics is observed with micron-sized TiO_2 powder. NaAlH_4 with TiO_2 nanopowder also provides improved cyclic property compared to NaAlH_4 with TiCl_3 in terms of both desorption rate and hydrogen capacity. X-ray diffraction analysis shows that micron-sized TiO_2 remains stable with NaAlH_4 after milling, although thermodynamic calculation predicts that TiO_2 reacts with NaAlH_4.