Catalytic effect of CeCl3 on the hydrogen storage properties of MgH2

• Hydrogen storage properties of CeCl3-doped MgH2 prepared by ball milling were investigated.
• Adding with CeCl3 reduced the decomposition temperature and enhanced the sorption kinetics of MgH2.
• The in-situ formation of Ce–Mg alloy, CeH2.73, and MgCl2 may play an important role.

The effects of CeCl3 addition on the hydrogen storage properties of MgH2 prepared by ball milling were investigated for the first time. The 10 wt.% CeCl3-added MgH2 sample showed an improvement in hydrogenation sorption properties compared to that of undoped MgH2, with the onset dehydrogenation temperature reduced from 350 °C to 300 °C. Kinetic desorption results showed that CeCl3-added MgH2 released about 5.5 wt.% hydrogen within 10 min at 350 °C, while the as-milled MgH2 released below 3.1wt.% hydrogen within the same time period and temperature. Meanwhile, hydrogen absorption capacity of 5.2 wt.% was reached at 280 °C in 5 min for the CeCl3-doped MgH2 sample. In contrast, the ball-milled MgH2 only absorbed 4.0 wt.% hydrogen at 280 °C in 5 min. From the Kissinger plot of differential scanning calorimetry, the apparent activation energy was 167.0 kJ/mol for as-milled MgH2 and 149.0 kJ/mol for 10 wt.% CeCl3-added MgH2, indicating that CeCl3 addition decreased the activation energy for hydrogen desorption of MgH2. The improved hydrogen storage properties of MgH2 in the presence of CeCl3 are believed to be due to the role of in situ formed Ce–Mg alloy, MgCl2, and CeH2.73 as active species to catalyse the hydrogen storage properties of MgH2.