## 3 Results and Discussion
### Hydrogen Desorption Properties
Similarly, for LiAlH\({}_{4}\)-TDA-10, the initial mass loss observed by TGA and the hydrogen desorption peak at 151 \({}^{\circ}\)C (Figure S22) may be the result of the interaction between LiAlH\({}_{4}\) and the alcohol group (from the reduction of -COOH) as per reaction (3) [84]. \[4\mathrm{LiAlH_{4}}+12\mathrm{ROH}\rightarrow\mathrm{LiAlH_{4}}+3\mathrm{LiAl( OR)_{4}}+12\mathrm{H_{2}} \tag{3}\]  
Figure 10: Relation between the first decomposition stage of LiAlH\({}_{4}\) and particle size of LiAlH\({}_{4}\) (the red dotted lines are a guide to the eye). In contrast to LiAlH\({}_{4}\), for the surfactant stabilized NaAlH\({}_{4}\) particles, no significant reduction in the first decomposition step was observed (Figure 12) and this was similar for the second decomposition step (Figure S30). Interestingly, hydrogen release peak was observed at about 330 \({}^{\circ}\)C for all of the nanosized NaAlH\({}_{4}\). This may be the result of an early decomposition of Na\({}_{3}\)AlH\({}_{6}\) induced by the decomposition of the surfactants and traces of THF at the same temperature. Nevertheless, the majority of Na\({}_{3}\)AlH\({}_{6}\) decomposed into NaH and Al between 376 and 396 \({}^{\circ}\)C (Figures S20 and S30) whereas the bulk material released hydrogen at 372 \({}^{\circ}\)C. The increase in dehydrogenation temperature at this stage may be due to the impurities from thermal decomposition of the surfactants which may further stabilized Na\({}_{3}\)AlH\({}_{6}\). In contrast to nanosized LiAlH\({}_{4}\), no clear trend was obtained when comparing the dehydrogenation temperature of NaAlH\({}_{4}\) as a function of the particle size within the current experimental work. This is possibly due to the fact that the surfactants decompose prematurely and/or do not effectively stabilize the NaAlH\({}_{4}\) nanostructures upon heating. NaAlH\({}_{4}\) infiltrated within nanoporous carbon with a pore size of 2-3 nm decomposes at  
Figure 11: (a) TGA/DSC and (b) MS of LiAlH\({}_{4}\)-HTT. The number in the box corresponds to the decomposition of: 1 LiAlH\({}_{4}\) to Li\({}_{3}\)AlH\({}_{6}\), 2 Li\({}_{3}\)AlH\({}_{6}\) to LiH, and 3 LiH to metallic Li. Figure 12: Relation between the first decomposition stage of NaAlH\({}_{4}\) and particle size of NaAlH\({}_{4}\) (the red dotted lines are a guide to the eye). -185 \({}^{\circ}\)C [16]. At this temperature, the surfactant stabilized NaAlH\({}_{4}\) are already in a molten state (Figure 9b). In this work, it can be seen that the use of surfactants enables an effective stabilization of alanate nanoparticles as well as triggers a low temperature hydrogen release-although limited because of the morphology degradation during hydrogen release. The low dehydrogenation temperature observed in this study is believed to be the combination result of nanosizing and the destabilization through the alanate-surfactant interaction [40; 41]. It is also worth mentioning that the effect of nanosizing alone is not enough to enable rapid hydrogen release at near room temperature for both alanates. As evidenced in a well-nanoconfined LiAlH\({}_{4}\) and NaAlH\({}_{4}\), although the materials were encapsulated within a 2-5 nm porosity, the dehydrogenation event still occurs at above 100 \({}^{\circ}\)C [16; 29; 30; 31; 32]. However, we believe that an effective control of the particle size provides ground for the controlled synthesis of core-shell based nanostructures where the nanostructures can be further tuned and stabilized within a metallic shell to improve their hydrogen desorption properties along their hydrogen reversibility.