Hydrogen sorption kinetics of ball-milled MgH2-TTNT nanotubes with different sodium contents

The hydrogen absorption/desorption properties of the MgH2 with the addition of TTNT (TiTanate Nanotubes) with different Na contents were studied. In order to evaluate the effect of TTNT Na content on hydrogen capacity and absorption/desorption kinetics two types of TTNT were used: water washed TTNT (TTNT-High) and acid washed TTNT (TTNT-Low) with high and low Na content, respectively. The MgH2-TTNT composites were prepared by ball milling. The MgH2 phases decomposition for the two samples containing TTNT and for pure MgH2 after milling was evaluated using DSC. beta-MgH2 temperatures of decomposition are lower (and similar) for both samples containing TTNT than for pure MgH2 indicating that the presence of TTNT can improve the hydrogen desorption. Hydrogen absorption/desorption kinetics measurements were performed at 300 and 350 degrees C. At 300 degrees C both samples containing TTNT showed better absorption kinetics compared to pure MgH2 in the first 5 min. The desorption kinetics at 300 degrees C of samples containing TTNT was significantly faster than of pure MgH2. At 350 degrees C the hydrogen capacity and absorption kinetics of samples containing TTNT-High are much higher than for pure MgH2 and MgH2 + TTNT-Low. The hydrogen desorption kinetics behavior at 350 degrees C are similar for both samples containing TTNT but faster than for pure MgH2. A mechanism for the role of TTNT in the hydrogen absorption/desorption kinetics of MgH2 + TTNT composites is proposed. (C) 2014 Elsevier B.V. All rights reserved.