Journal
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
Volume 17, Issue 43, Pages 28977-28984Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/c5cp04515k
Keywords
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Funding
- Center on Nanostructuring for Efficient Energy Conversion (CNEEC) at Stanford University, an Energy Frontier Research Center - U.S. Department of Energy, Office of Basic Energy Sciences [DE-SC0001060]
- Directorate For Engineering
- Div Of Electrical, Commun & Cyber Sys [1542152] Funding Source: National Science Foundation
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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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