One step high pressure mechanochemical synthesis of reversible alanates NaA1H4 and KA1H4

The present study suggests high pressure mechanochemical treatment is a better strategy for the synthesis of performance enhanced reversible alanates. The reactants NaH/KH + Al along with catalysts (TiC1(3), TiF3 and TiO2) milled under 100 bar hydrogen pressure for 30 h effectively transforms to products (NaA1H(4) and KA1H(4)) in a single step. The as-synthesized NaA1H4 and KA1H(4) samples release hydrogen at the temperatures of -100 degrees C and 215 degrees C, respectively. The stability of the KA1H(4) phase can be further reduced by extending the high pressure mechanochemical reaction time to 80 h. The XRD and TEM analysis of the residues observed after extracting the NaA1H(4) from the TiC1(3) catalyzed material confirms the presence of Ti-Al alloy and highly dispersed NaC1 nanoparticles. Catalytic activity is therefore attributed to mechano-chemical activation which involves catalytically active species (for e.g. Ti-A1) and defects/vacancies/strain in the system. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.