Hydrogen absorption/desorption reactions of the (TiVNb)85Cr15 multicomponent alloy

Abstract

Ti-V-Nb-Cr alloys have been reported as potential candidates for hydrogen storage applications. Investigating the processes of absorption and desorption is paramount to understand the hydrogen storage properties of these novel alloys and to develop more efficient hydrogen storage materials. In this work, we investigated the hydrogen absorption/desorption reactions of the (TiVNb)85Cr15 BCC multicomponent alloy by laboratory and synchrotron X-ray diffraction, Pair Distribution Function (PDF) analyses, Transmission Electron Microscopy (TEM) and thermo-desorption analyses (TDS). Hydrogen absorption behavior was studied by pressure-composition-isotherm (PCI) at room temperature, which demonstrated levels of absorption around 2 H/M (H/M = hydrogen-to-metal ratio) with low equilibrium pressure. The results showed a multi-step hydrogenation process: alloy ↔ BCC solid solution ↔ BCC intermediate hydride ↔ FCC dihydride. PDF analyses showed that the partially hydrogenated alloy at different levels of H/M and the fully hydrogenated alloy can be reasonably described by models with phases presenting random atomic distribution in the metal crystallographic sites. Moreover, the partially hydrogenated sample prior to the complete formation of the intermediate hydride showed evidence of two co-existing BCC phases.