Science | August 28th, 2017
Improving Hydrogen Storage

Research analyzes the effect of nanoparticles formed during the preparation of Li-RHC with addition of $\rm TiO_2$

The search for clean, renewable and cheap energy sources has intensified in recent years with the growing consensus that the rise in the planet’s average temperature, and the consequent intensification of extreme weather events, is caused by human action. Hydrogen ($\rm H_2$) is one of the best alternatives to fossil fuels, especially because its combustion has only water vapor as final product. However, the economic viability of the production, storage and distribution of hydrogen for power generation still requires solutions for several technological challenges.

One of these challenges is the lack of an efficient and safe hydrogen storage system. Thus, J.A. Puszkiel et al. [1] used the facilities of the Brazilian Synchrotron Light Laboratory (LNLS) to improve hydrogen storage through the addition of $\rm TiO_2$ and formation of nanoparticles during the preparation of solid state hydrides.

The group investigated the effect of the in-situ formation of $\rm Li_xTiO_2 $ nanoparticles in the system known as Li-RHC, which stores and releases hydrogen through the reactions $\rm 2LiBH_4 + MgH_2 \rightleftharpoons 2LiH + MgB_2 + 4H_2 $. This system has a hydrogen storage capacity of about 10% of its weight.

Among the several advanced experimental techniques used, XANES x-ray absorption spectroscopy analyses were performed on the LNLS’ XAFS1 beamline.

According to the researchers, the $\rm Li_x TiO_2$ nanoparticles markedly enhanced the hydrogen storage capabilities of the Li-RHC. The presence of a small amounts of $\rm Li_x TiO_2$ allows the Li-RHC to reversibly store hydrogen through periods of hydrogenation and dehydrogenation of only 25 and 50 minutes at 400°C, respectively. After the hydrogenation/dehydrogenation cycle, the nanoparticles formed help to preserve the Li-RHC microstructure against coarsening.

After dehydrogenation, the nanoparticles $\rm Li_x TiO_2$ do not modify the dehydrogenation thermodynamic properties of the Li-RHC itself. The presence of $\rm Li_x TiO_2$ reduces the time required for the first dehydrogenation by suppressing the parallel reaction leading from $\rm LiBH_4$ to $\rm Li_2 B_{12} H_{12}$, thus allowing the direct formation of $\rm MgB_2$ and a more efficient release of the hydrogen gas.

Source: [1] J. A. Puszkiel, M. V. Castro Riglos, J. M. Ramallo-López, M. Mizrahi, F. Karimi, A. Santoru, A. Hoell, F. C. Gennari, P. A. Larochette, C. Pistidda, T. Klassen, J. M. Bellosta von Colbe and M. Dornheim, A novel catalytic route for hydrogenation–dehydrogenation of 2LiH + MgB2via in situ formed core–shell LixTiO2 nanoparticles, J. Mater. Chem. A, 2017, 5, 12922. DOI: 10.1039/C7TA03117C

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