Superior hydrogen storage kinetics of MgH2 nanoparticles doped with TiF3

MgH2 nanoparticles were obtained by hydriding ultrafine magnesium particles which were prepared by hydrogen plasma-metal reaction. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) results show that the obtained sample is almost pure MgH2 phase, without residual magnesium and with an average particle size of similar to 300 nm. Milled with 5 wt.% TiF3 as a doping precursor in a hydrogen atmosphere, the sample desorbed 4.5 wt.% hydrogen in 6 min under an initial hydrogen pressure of similar to 0.001 bar at 573 K and absorbed 4.2 wt.% hydrogen in 1 min under similar to 20 bar hydrogen at room temperature. Compared with MgH2 micrometer particles doped with 5 wt.% TiF3 under the same conditions as the MgH2 nanoparticles, it is suggested that decrease of particle size is beneficial for enhancing absorption capacity at low temperatures, but has no effect on desorption. In addition, the catalyst was mainly responsible for improving the sorption kinetics and its catalytic mechanism is discussed. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.