Understanding the dehydrogenation properties of MgH2 catalysed by Na3AlF6.

The catalytic effect of Na 3 AlF 6 on the dehydrogenation properties of the MgH 2 with X wt% (X = 5, 10, 20 and 50) have been investigated by ball milling technique. Based on the temperature-programme-desorption result, the addition of 10 wt% Na 3 AlF 6 to the MgH 2 has demonstrated the best dehydrogenation properties performance. The dehydrogenation temperature of the un-doped MgH 2 has experienced a reduction for about 60 °C after doped with 10 wt% Na 3 AlF 6. The dehydrogenation kinetics also has been improved with the addition of 10 wt% Na 3 AlF 6. Based on the Kissinger analysis, it was observed that the apparent activation energy of MgH 2 desorption is remarkably decreased from 158 kJ/mol to 129 kJ/mol with the addition of 10 wt% Na 3 AlF 6. Meanwhile, the formations of new species, the NaMgF 3 , the NaF and the AlF 3 in the doped composite after the de/rehydrogenation processes are found in the X-ray diffraction analysis. These new species are expected to act as the active species that probably contributes to enhance the dehydrogenation properties of MgH 2. • The H 2 storage properties of Na 3 AlF 6 -doped MgH 2 have been studied. • Dehydrogenation properties of MgH 2 is improved after adding with Na 3 AlF 6. • E A for hydrogen desorption of MgH 2 /Na 3 AlF 6 composite was lowered to 129.0 kJ/mol. • The in - situ formation of the NaMgF 3 , NaF and AlF 3 species play a synergetic role. [ABSTRACT FROM AUTHOR]