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Energies 2016, 9(12), 1073; doi:10.3390/en9121073

Electrodeposited Magnesium Nanoparticles Linking Particle Size to Activation Energy

Merlin Group, School of Chemical Engineering, The University of New South Wales, Sydney 2052, NSW, Australia
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Author to whom correspondence should be addressed.
Academic Editor: Wei-Chiang Hong
Received: 15 September 2016 / Revised: 21 November 2016 / Accepted: 7 December 2016 / Published: 16 December 2016
(This article belongs to the Special Issue Selected Papers from 2nd Energy Future Conference)
View Full-Text   |   Download PDF [2693 KB, uploaded 16 December 2016]   |  

Abstract

The kinetics of hydrogen absorption/desorption can be improved by decreasing particle size down to a few nanometres. However, the associated evolution of activation energy remains unclear. In an attempt to clarify such an evolution with respect to particle size, we electrochemically deposited Mg nanoparticles on a catalytic nickel and noncatalytic titanium substrate. At a short deposition time of 1 h, magnesium particles with a size of 68 ± 11 nm could be formed on the nickel substrate, whereas longer deposition times led to much larger particles of 421 ± 70 nm. Evaluation of the hydrogen desorption properties of the deposited magnesium nanoparticles confirmed the effectiveness of the nickel substrate in facilitating the recombination of hydrogen, but also a significant decrease in activation energy from 56.1 to 37.8 kJ·mol−1 H2 as particle size decreased from 421 ± 70 to 68 ± 11 nm. Hence, the activation energy was found to be intrinsically linked to magnesium particle size. Such a reduction in activation energy was associated with the decrease of path lengths for hydrogen diffusion at the desorbing MgH2/Mg interface. Further reduction in particle size to a few nanometres to remove any barrier for hydrogen diffusion would then leave the single nucleation and growth of the magnesium phase as the only remaining rate-limiting step, assuming that the magnesium surface can effectively catalyse the dissociation/recombination of hydrogen. View Full-Text
Keywords: hydrogen storage; magnesium; particle size; nanosize; activation energy hydrogen storage; magnesium; particle size; nanosize; activation energy
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Shen, C.; Aguey-Zinsou, K.-F. Electrodeposited Magnesium Nanoparticles Linking Particle Size to Activation Energy. Energies 2016, 9, 1073.

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