Thermal desorption of hydrogen from supported nickel catalysts

Миначев, Х. М.; Dmitriev, R. V.; Rustamov, M. I.; Kasimov, Ch. K.; Abad-zade, Kh. I.

doi:10.1007/bf01417966

Cited by 1 publication

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“…Indeed, on the noncatalytic Ti substrate, the onset temperatures for hydrogen desorption significantly differed (by 50 • C) as particle size increased and the surface area decreased accordingly (Figure 5b), in agreement with previous reports [15]. The initial desorption of hydrogen at 210 • C is also consistent with reported thermal desorption spectra of molecular hydrogen adsorbed at Ni surfaces [31][32][33]. It can thus be concluded that the shift in desorption temperature observed on the Ni catalytic substrate from 290 to 390 • C as particle size increased from 68 ± 11 to 421 ± 70 nm is related to rate-limiting steps other than hydrogen recombination at the magnesium surface.…”

Section: Hydrogen Sorption Propertiessupporting

confidence: 91%

Electrodeposited Magnesium Nanoparticles Linking Particle Size to Activation Energy

Shen

Aguey‐Zinsou

2016

Energies

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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 H 2 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 MgH 2 /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.

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