Journal
JOURNAL OF MATERIALS CHEMISTRY A
Volume 5, Issue 25, Pages 12922-12933Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/c7ta03117c
Keywords
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Funding
- CONICET (Consejo Nacional de Invetigaciones Cientificas y Tecnicas)
- ANPCyT - (Agencia Nacional de Promocion Cientifica y Tecnologica)
- CNEA (Comision Nacional de Energia Atomica)
- HZG (Helmholtz-Zentrum Geesthacht)
- PTB (German National Metrology Institute) FCM-Beamline
- Laboratorio Nacional de Luz Sincrotron (LNLS), Campinas, Brazil [Proposal XAFS1-15239]
- European Marie Curie Actions under ECOSTORE grant [607040]
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Aiming to improve the hydrogen storage properties of 2LiH + MgB2 (Li-RHC), the effect of TiO2 addition to Li-RHC is investigated. The presence of TiO2 leads to the in situ formation of core-shell LixTiO2 nanoparticles during milling and upon heating. These nanoparticles markedly enhance the hydrogen storage properties of Li-RHC. Throughout hydrogenation-dehydrogenation cycling at 400 degrees C a 1 mol% TiO2 doped Li-RHC material shows sustainable hydrogen capacity of similar to 10 wt% and short hydrogenation and dehydrogenation times of just 25 and 50 minutes, respectively. The in situ formed core-shell LixTiO2 nanoparticles confer proper microstructural refinement to the Li-RHC, thus preventing the material's agglomeration upon cycling. An analysis of the kinetic mechanisms shows that the presence of the core-shell LixTiO2 nanoparticles accelerates the one-dimensional interface-controlled mechanism during hydrogenation owing to the high Li+ mobility through the LixTiO2 lattice. Upon dehydrogenation, the in situ formed core-shell LixTiO2 nanoparticles do not modify the dehydrogenation thermodynamic properties of the Li-RHC itself. A new approach by the combination of two kinetic models evidences that the activation energy of both MgH2 decomposition and MgB2 formation is reduced. These improvements are due to a novel catalytic mechanism via Li+ source/sink reversible reactions.
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