In situ High-Energy Synchrotron X-ray Studies in Thermodynamics of Mg-In-Ti Hydrogen Storage System

Abstract

Achieving dual regulation of the kinetics and thermodynamics of MgH2 is essential for the practical applications. In this study, a novel nanocomposite (In@Ti-MX) architected from single-/few-layered Ti3C2 MXenes and ultradispersed indium nanoparticles was prepared by a bottom-up self-assembly strategy and introduced into MgH2 to solve the above-mentioned problems. The MgH2+In@Ti-MX composites demonstrate excellent hydrogen storage performance: The resultant In@Ti-MX demonstrated a positive effect on the hydrogen storage performance of MgH2/Mg: the dehydrogenated rate of MgH2+15 wt%In@Ti-MX reached the maximum at 330 °C, which was 47 °C lower than that of commercial MgH2; The hydrogenation enthalpy of the dehydrided MgH2+15 wt%In@Ti-MX and MgH2+25 wt%In@Ti-MX were determined to be −66.2 ± 1.1 and −61.7 ± 1.4 kJ·mol−1 H2. In situ high-energy synchrotron x-ray diffraction technique together with other microstructure analyses revealed that synergistic effects from Ti3C2 MXenes and In nanoparticles (NPs) contributed to the improved kinetics and thermodynamics of MgH2(Mg): Ti/TiH2 derived from Ti3C2 MXenes accelerated the dissociation and recombination of hydrogen molecule/atoms, while In NPs reduced the thermodynamic stability of MgH2 by forming the Mg-In solution. Such a strategy of using dual-active hybrid structures to modify MgH2/Mg provides a new insight for tuning both the hydrogen storage kinetics and thermodynamics of Mg-based hydrides.