Synergic effect of ZrCl4 on thermal dehydrogenation kinetics of KBH4

The synergic effect of zirconium tetrachloride (ZrCl4) on the thermal dehydrogenation of KBH4 has been investigated. Zirconium tetrachloride activated the KBH4 surface during ball milling to improve the dehydrogenation kinetics. The activation energy of dehydrogenation is remarkably reduced to 162 +/- 6 kJ/mol as compared to the pure KBH4, which was found to be 274 +/- 12 kJ/mol under identical experimental conditions. The reduced activation energy leads to remarkably decreased onset temperature of hydrogen desorption for catalyzed KBH4 (T-onset < 350 degrees C) as compared to pure KBH4 (T-onset < 550 degrees C). The reduced dehydrogenation temperature will be helpful to manage the potassium evaporation to maintain the reversibility. The Gibbs free-energy calculations and experimental results suggest that the thermal dehydrogenation proceeds via the potassium (K) intermediate rather than via potassium hydride (KH). (C) 2017 Elsevier B.V. All rights reserved.