Mg2Si Nanoparticle Synthesis for High Pressure Hydrogenation

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• 作者：Anna-Lisa Chaudhary ; Drew A. Sheppard ; Mark Paskevicius ; Colin J. Webb ; Evan MacA. Gray ; Craig E. Buckley
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：January 16, 2014
• 年：2014
• 卷：118
• 期：2
• 页码：1240-1247
• 全文大小：480K
• ISSN：1932-7455

文摘

The Mg鈥揝i鈥揌 system is economically favorable as a hydrogen storage medium for renewable energy systems while moving toward sustainable energy production. Hydrogen desorption from MgH₂ in the presence of Si is achievable, forming magnesium silicide (Mg₂Si). However, absorbing hydrogen into Mg₂Si remains problematic due to severe kinetic limitations. The objective of this study is to reduce these kinetic limitations by synthesizing Mg₂Si nanoparticles to limit the migration distance for magnesium atoms from the Mg₂Si matrix to produce MgH₂ and Si, thus improving the reversibility of the Mg鈥揝i鈥揌 system. Mg₂Si nanoparticles were synthesized using a reduction reaction undertaken by solid鈥搇iquid mechanochemical ball milling. Particle size was controlled by adding a reaction buffer (lithium chloride) to the starting reagents to restrict particle growth during milling. The reaction buffer was removed from the nanoparticles using tetrahydrofuran and small-angle X-ray scattering revealed an average Mg₂Si particle size of 10 nm, the smallest Mg₂Si nanoparticles synthesized to date. High-pressure hydrogen measurements were undertaken above thermodynamic equilibrium at a range of temperatures to attempt hydrogen absorption into the Mg₂Si nanoparticles. X-ray diffraction results indicate that partial hydrogen absorption took place. Under these absorption conditions bulk Mg₂Si cannot absorb hydrogen, demonstrating the kinetic benefit of nanoscopic Mg₂Si.