Adjustment of the decomposition path for Na2LiAlH6 by TiF3 addition

The decomposition of Na2LiAlH6 is studied by in-situ synchrotron diffraction. By addition of TiF3 and dehydrogenation-rehydrogenation cycling of the samples new decomposition paths are found. Na3AlH6 is formed on decomposition in the presence of TiF3. The additive brings the system closer to equilibrium, and decomposition through Na3AlH6 is demonstrated for the first time. The results are in agreement with previously published computational data. For a cycled sample with 10 mol% TiF3 Na2LiAlH6 decomposes fully into Na3AlH6 before further decomposition to NaH and Al. This shows clear changes in the kinetics of the system, and may open possibilities of tailoring the decomposition path by the use of additives.

► The decomposition path of Na2LiAlH6 is changed by addition of TiF3 and cycling.
► A catalytic effect of TiF3 is shown to bring the system closer to equilibrium.
► The decomposition temperature of Na2LiAlH6 is lowered by the additive and cycling.
► Below 200 °C, Na2LiAlH6 decomposes to Na3AlH6, in line with theoretical studies.
► Heating of Na2LiAlH6 in the presence of NaH leads to a reaction forming Na3AlH6.