Formation of Na3AlH6 from a NaH/Al mixture and Ti-containing catalyst Original Research Article

To investigate the effects of Ti-containing catalyst on the hydride formation in the Na–Al–H system, Ti(OBun)4- and TiF3-doped NaH/Al powders were hydrogenated into Na3AlH6 by controlling the hydrogen pressure at 5 MPa and the temperature at 100–140 °C. X-ray diffraction and differential scanning calorimetry showed that TiF3 was more catalytically favorable than Ti(OBun)4 to enhance the formation of Na3AlH6. X-ray absorption spectroscopy revealed that the initial Ti4+ or Ti3+ ions were reduced to Ti1+ or Ti0 and form Ti–Al pairs with two coordination shells during the doping and hydrogenation processes. The difference in catalytic activity between the two Ti-containing catalysts can be attributed to their ability to form Ti–Al pairs with the NaH/Al mixture.