In operando study of TiVCr additive in MgH2 composites

• MgH2–TiVCr composites were investigated by in situ synchrotron XRD.
• Hydrogen desorption and absorption processes were studied in operando.
• Non-monotonic changes in the volume of the TiVCrHx were observed concomitantly to the MgH2 decomposition and formation.
• Results provide evidence of a cooperative effect between MgH2 and the additive.

We report an in operando study of the hydrogenation and dehydrogenation of MgH2–TiVCr composites. The experiment was performed by means of in situ synchrotron XRD in order to get insights on the influence of the TiVCr additive on the sorption properties of the MgH2 based composite. Sequential Rietveld refinement analysis was performed to investigate the structural changes of MgH2 and of the additive during hydrogenation and dehydrogenation processes. Significant non-monotonic changes in the lattice volume of the TiVCrHx solid solution were observed concomitantly to the MgH2 formation or decomposition. These volume changes are assigned to the variation of the hydrogen content in TiVCrHx. These results provide evidence of cooperative effects between the H2 storage material and the additive.