Enhanced hydrogen storage properties of K2TiF6 doped Mg-Na-Al composite system

The present investigation has introduced the hydrogen storage properties of MgH2+NaAlH4 (4:1) composite system with the addition of 10 wt% K2TiF6 by ball milling method for the first time. It is found that the K2TiF6-doped MgH2+NaAlH4 composite has better hydrogen storage properties compared to that of undoped composite. From the temperature programmed desorption result, the decomposition temperatures for two-step dehydrogenation stages that attributed to the NaAlH4 and MgH2 were reduced by 70 °C and 225 °C respectively, as compared to the undoped composite. The apparent activation energy of the Mg-relevant decomposition for the 4MgH2+NaAlH4+ K2TiF6 composite was reduced to 96.4 kJ/mol as compared to the undoped 4MgH2+NaAlH4 composite (124.9 kJ/mol). The X-ray diffraction analysis displayed formation of new phases; the Al3Ti, the TiH2 and the KF in the doped composite after de/rehydrogenation processes. It is believed that these new phases may responsible as catalysts in the K2TiF6-doped MgH2+NaAlH4 composite.