Hydrogen storage properties of multi-principal-component CoFeMnTixVyZrz alloys

This study presents an innovative multi-principal-element CoFemnTiVZr alloy system for the absorption and desorption of hydrogen. Pressure-composition-isotherms (PCIs) demonstrate that CoFeMnTixVZr, CoFeMnTiVyZr, and CoFeMnTiVZrz can absorb and desorb hydrogen for x, y, and z that satisfy 0.5 <= x <= 2.5, 0.4 <= y <= 3.0, and 0.4 <= z <= 3.0, respectively. X-ray diffraction (XRD) reveals that CoFeMnTixVyZrz alloys have a simple C14 Laves phase with a single set of lattice parameters before and after PCI tests. The distributions of each element in CoFeMnTixVyZrz alloys are roughly equal, as revealed by SEM/EDS mapping. The effects of values x, y, and z on the hydrogen storage properties are elucidated in terms of lattice constant, element segregation, hydride formation enthalpies of the alloy components and hydrogen, and the averaged formation enthalpy. The high-entropy effect promotes the formation of a single C14 Laves phase, and the maximum hydrogen storage capacity is strongly related to the hydride formation enthalpy of the alloy and hydrogen. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.