Hydrogen storage in a novel BCC-structured TiCrW alloys

Abstract

Body-centered cubic (BCC)-type alloys possess a high theoretical hydrogen storage capacity, yet their high cost, limited effective hydrogen storage capacity, and poor cyclic properties remain challenges. In this work, a novel and cost-effective (Ti0.44Cr0.56)94W6 BCC phase alloy was successful prepared by W doping and heat treatment. The alloy exhibits an effective hydrogen desorption capacity of 2.44 wt% with minimal 9 % degradation over 300 cycles. The microstructural analysis shows that W doping inhibits the formation of Ti-rich phase and Laves phase in the alloy, and makes the alloy form a single BCC phase structure with higher hydrogen storage sites. After heat treatment, the alloy exhibits remarkable hydrogen de-/absorption kinetics and superior plateau characteristics, which reduces the plateau slope factor from 5.32 to 0.18, and increases the effective hydrogen desorption capacity from 1.09 to 2.44 wt%. This alloy’s activation energy and enthalpy change in dehydrogenation process are determined to be 11.64 and 44.31 kJ/mol, respectively. First-principles simulations further illuminated that the incorporation of W doping diminished the migration energy barrier of hydrogen and compromised the structural stability of the hydride. Furthermore, the structural evolution during de-/hydrogenation was analyzed, elucidating the mechanism of the alloy’s cyclic performance decay. These findings offer theoretical insights that guide the development of novel solid state hydrogen storage materials.