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 MgH 2 is essential for the practical applications. In this study, a novel nanocomposite (In@Ti-MX) architected from single-/few-layered Ti 3 C 2 MXenes and ultradispersed indium nanoparticles was prepared by a bottom-up self-assembly strategy and introduced into MgH 2 to solve the above-mentioned problems. The MgH 2 +In@Ti-MX composites demonstrate excellent hydrogen storage performance: The resultant In@Ti-MX demonstrated a positive effect on the hydrogen storage performance of MgH 2 /Mg: the dehydrogenated rate of MgH 2 +15 wt%In@Ti-MX reached the maximum at 330 °C, which was 47 °C lower than that of commercial MgH 2 ; The hydrogenation enthalpy of the dehydrided MgH 2 +15 wt%In@Ti-MX and MgH 2 +25 wt%In@Ti-MX were determined to be −66.2 ± 1.1 and −61.7 ± 1.4 kJ·mol −1 H 2 . In situ high-energy synchrotron x-ray diffraction technique together with other microstructure analyses revealed that synergistic effects from Ti 3 C 2 MXenes and In nanoparticles (NPs) contributed to the improved kinetics and thermodynamics of MgH 2 (Mg): Ti/TiH 2 derived from Ti 3 C 2 MXenes accelerated the dissociation and recombination of hydrogen molecule/atoms, while In NPs reduced the thermodynamic stability of MgH 2 by forming the Mg-In solution. Such a strategy of using dual-active hybrid structures to modify MgH 2 /Mg provides a new insight for tuning both the hydrogen storage kinetics and thermodynamics of Mg-based hydrides.