Enhanced Hydrogen-Storage Properties of MgH2 Catalyzed via a Cerium Doped TiCrV BCC Alloy

Abstract

In this work, Ce-doped Ti6Cr14V80 BCC hydrogen-storage alloys have been synthesized as catalysts to enhance the hydrogen-storage performance of MgH2 based on its room-temperature activation features and excellent durability. The Ti6Cr14V80Ce1 alloy was pre-ball milled under a hydrogen atmosphere into a Ti6Cr14V80Ce1Hx hydride. Different amounts of the Ti6Cr14V80Ce1Hx hydride were incorporated into MgH2 by ball milling to obtain the MgH2 + y wt%Ti6Cr14V80Ce1Hx (y = 0, 3, 5, 10, 15) nano-composites. With an optimization doping of 10 wt%Ti6Cr14V80Ce1Hx, the initial dehydrogenated temperature was decreased to 160 °C. Moreover, the composite can rapidly release 6.73 wt% H2 within 8 min at 230 °C. Also, it can absorb 2.0 wt% H2 within 1 h even at room temperature and uptake 4.86 wt% H2 within 10 s at 125 °C. In addition, the apparent dehydrogenated activation energy of the MgH2 + 10 wt%Ti6Cr14V80Ce1Hx composite was calculated to be 62.62 kJ mol−1 fitted by the JMAK model. The capacity retention was kept as 84% after 100 cycles at 300 °C. The ball milled Ti6Cr14V80Ce1Hx transformed from the initial FCC phase structure into a BCC phase after complete dehydrogenation and back into an FCC phase when fullly hydrogenated. A catalyst mechanism analysis revealed that the ‘autocatalytic effect’ originating in Ti6Cr14V80Ce1Hx plays a crucial role in boosting the de-/hydrogenation properties of MgH2. This work provides meaningful insights into rational designs of nano-compositing with different hydrogen-storage alloy catalyzed MgH2.