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Updated: Apr 1, 2026
Supercritical Nitrogen Processing for the Purification of Reactive Porous Materials
Published on: May 15, 2015
Nanometer-scale hydrogen 'portals' for the control of magnesium hydride formation
Chia-Jung Chung1, Chinmay Nivargi1, Bruce Clemens1
1Department of Materials Science and Engineering, Stanford University, Stanford, CA - 94305, USA. bmc@stanford.edu.
Abstract:
Magnesium and Mg-based material systems are attractive candidates for hydrogen storage but limited by unsuitable thermodynamic and kinetic properties. In particular, the kinetics are too slow at room temperature and atmospheric pressure. To study the hydride formation kinetics in a controlled way, we have designed a unique 'nanoportal' structure of Pd nanoparticles deposited on epitaxial Mg thin films, through which the hydride will nucleate only under Pd nanoparticles. We propose a growth mechanism for the hydrogenation reaction in the nanoportal structure, which is supported by scanning electron microscopy (SEM) images of hydrogenated samples exhibiting consistent results. Interestingly, the grain boundaries of Mg films play an important role in hydride nucleation and growth processes. Kinetic modeling based on the Johnson-Mehl-Avrami-Kolmogorov (JMAK) formalism seems to agree with the two-dimensional nucleation and growth mechanism hypothesized and the overall reaction rate is limited by hydrogen flux through the interface between the Pd nanoparticle and the underlying Mg film. The fact that in our structure Mg can be transformed completely into MgH2 with only a small percentage of Pd nanoparticles offers possibilities for future on-board storage applications.
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