Improving of hydrogen desorption kinetics of MgH2 by NaNH2 addition: Interplay between microstructure and chemical reaction

MgH2 based composites combined with NaNH2 were synthesized by mechanical milling for three different milling times ranging from 15 to 60 minutes. Microstructure and particle size of the samples were analyzed by SEM microscopy while desorption properties were followed by Thermal Desorption Spectrosco...

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Bibliographic Details
Published in:International journal of hydrogen energy 2022-08, Vol.47 (69), p.29858-29865
Main Authors: Milanović, Igor, Milošević Govedarović, Sanja, Kurko, Sandra, Medić Ilić, Mirjana, Rajnović, Dragan, Cvetković, Slobodan, Grbović Novaković, Jasmina
Format: Article
Language:English
Subjects:
Avrami – Erofeev kinetics
Chemical reaction
Hydrogen storage
MgH2-NaNH2 composites
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Summary:MgH2 based composites combined with NaNH2 were synthesized by mechanical milling for three different milling times ranging from 15 to 60 minutes. Microstructure and particle size of the samples were analyzed by SEM microscopy while desorption properties were followed by Thermal Desorption Spectroscopy (TDS). The kinetic properties of NaNH2-MgH2 composites were investigated by isoconversional kinetic method as implemented in code developed by our group. Composites show hydrogen desorption peaks shifted to lower temperatures in comparison to mechanically modified and as received MgH2. All NaNH2-MgH2 composites show enhanced kinetics with lowered apparent activation energy (Ea) in comparison to milled MgH2. The mechanism of desorption changes from Avrami–Erofeev n = 3 for as received MgH2 to Avrami–Erofeev n = 4 for composite materials. The change from 3 to 4 can be due to the modification of the nucleation process or a change in the dimensionality of the growth. Those high values of n disregard a diffusion control as a rate limiting step. It has been shown that there is a synergistic effect on the enhanced hydrogen storage performance of chemical reaction and structural changes caused by ball milling. This can be used as a starting point for synthesis of innovative hydrogen storage materials. •2–75 wt% NaNH2 has been added to MgH2 in milling blend.•Synergy of chemical reaction and mechanochemically induced structural changes cause H2 storage progress.•Mechanism of desorption changes from Avrami–Erofeev n = 3 to 4 due to addition of NaNH2.
ISSN:0360-3199
1879-3487
DOI:10.1016/j.ijhydene.2022.06.302