Thermodynamics, kinetics and microstructural evolution of Ti0.43Zr0.07Cr0.25V0.25 alloy upon hydrogenation

Zr substituted Ti2CrV alloy with Ti0.43Zr0.07Cr0.25V0.25 composition was synthesized by arc melting method and its crystal structure, microstructure and hydrogen storage performance were investigated. XRD and microstructural analyses confirmed that the alloy forms Laves phase related BCC solid solution. The enthalpy of hydride formation as derived from pressure composition absorption isotherms is -56.33 kJ/mol H-2. The desorption temperature of the hydride is significantly lower (by similar to 50 K) than that of Ti2CrV hydride indicating lower thermal stability of the hydride compared to its unsubstituted analogue. The alloy shows better cyclic stability over the unsubstituted one. This work also offers mechanistic insight into hydrogen absorption reaction of Ti0.43Zr0.07Cr0.25V0.25 alloy by analyzing the hydriding kinetics data with standard kinetic models. The rate-determining steps of hydrogen absorption reaction were identified as random nucleation and growth of hydride followed by 1D and 3D diffusion of hydrogen atoms through the hydride layer. The present study is expected to provide valuable information for the better development of Ti-Cr-V based hydrogen storage alloys. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.