Novel MAX-phase Ti₃AlC₂ catalyst for improving the reversible hydrogen storage properties of MgH₂

A MAX-phase carbide (Ti₃AlC₂) with purity 99% was synthesized by first ball milling a mixture of Ti, Al and C and subsequently sintering at 1500 °C. The catalytic effects of the as-prepared Ti₃AlC₂ on the hydrogen storage reaction of MgH₂ were evaluated for the first time. The results indicated that the MgH₂-7 wt% Ti₃AlC₂ sample had optimal hydrogen storage properties. The dehydrogenation onset temperature of the MgH₂-7 wt% Ti₃AlC₂ sample decreased to 205 °C, which is 70 °C lower than that of the as-milled pristine MgH₂. While heating to 340 °C, the hydrogen desorption reached 6.9 wt%. The dehydrogenated MgH₂-7 wt% Ti₃AlC₂ sample absorbed 5.8 wt% hydrogen within 60 s at 150 °C, while the hydrogen uptake amount in dehydrogenated pristine MgH₂ was only 2.7 wt%, even after 2000 s. The apparent activation energy was calculated to be 104.7 kJ/mol for the MgH₂-7 wt% Ti₃AlC₂ sample, which is 50.4 kJ/mol lower than that of the pristine MgH₂. The existence state of Ti₃AlC₂ during dehydrogenation was also analyzed and discussed.