Hydrogen storage and phase transformations in Mg-Pd nanoparticles

Microstructure refinement and synergic coupling among different phases are currently explored strategies to improve the hydrogen storage properties of traditional materials. In this work, we apply a combination of these methods and synthesize Mg-Pd composite nanoparticles by inert gas condensation of Mg vapors followed by vacuum evaporation of Pd clusters. Irreversible formation of the Mg6Pd intermetallic phase takes place upon vacuum annealing, resulting in Mg/Mg6Pd composite nanoparticles. Their hydrogen storage properties are investigated and connected to the undergoing phase transformations by gas-volumetric techniques and in-situ synchrotron radiation powder X-ray diffraction. Depending on temperature and hydrogen pressure, the Mg6Pd transforms reversibly into different Mg-Pd intermetallic compounds, thus influencing both the thermodynamics and kinetics of the metal-hydride transformation.