A novel catalytic route for hydrogenation-dehydrogenation of 2LiH + MgB2via in situ formed core-shell LixTiO2 nanoparticles

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 5; no. 25; pp. 12922 - 12933
• Main Authors: Puszkiel, JA, Castro Riglos, MV, Ramallo-Lopez, J M, Mizrahi, M, Karimi, F, Santoru, A, Hoell, A, Gennari, F C, Larochette, PArneodo, Pistidda, C, Klassen, T, Bellosta von Colbe, JM, Dornheim, M
• Format: Journal Article
• Language: English
• Published: 01.06.2017
• Subjects: Borides; Catalysts; Dehydrogenation; Hydrogen storage; Hydrogenation; Magnesium compounds; Nanoparticles; Titanium dioxide
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c7ta03117c

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 degree 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.