Effect of SrFe12O19 nanopowder on the hydrogen sorption properties of MgH2
In this study, the effects of different amounts (5, 10, 15, 20 and 50 wt%) of an SrFe12O19 nanopowder, doped into MgH2 and prepared by the ball milling method, were investigated with the aim of improving hydrogen storage properties. The results indicated that 10 wt% SrFe12O19 showed the best performance, compared with un-doped MgH2, in terms of the onset dehydrogenation temperature. The desorption temperature of MgH2 + 10 wt% SrFe12O19 decreased to about 270 °C compared to the 350 °C and 420 °C for as-milled and as-received MgH2, respectively. The de/rehydrogenation kinetics of MgH2 also improved after doping with SrFe12O19. Increasing the doping amount of SrFe12O19 to 15, 20 and 50 wt% brought about negative effects, such as lower capacity and slower sorption rates. From Kissinger plot differential scanning calorimetry, the apparent activation energy was 133.31 kJ mol−1 for as-milled MgH2 and 114.22 kJ mol−1 for MgH2 + 10 wt% SrFe12O19, indicating that SrFe12O19 addition decreased the activation energy for hydrogen desorption of MgH2. From the X-ray diffraction results, it is believed that the formation of new phases of Fe, MgFe2O4 and SrO during the dehydrogenation process might be responsible for the catalytic effects which further enhanced the hydrogen storage properties of MgH2.