Constructing Ni/CeO2 synergistic catalysts into LiAlH4 and AlH3 composite for enhanced hydrogen released properties

The high hydrogen release temperature and thermodynamic stability of the coordination hydride LiAlH 4 render it unsuitable for direct application. This work intends to improve the hydrogen release properties via compositing LiAlH 4 and AlH 3 with similar initial hydrogen release temperatures and introduce efficient additive Ni/CeO 2 composite. The thermal stability of the composite system LiAlH 4 -AlH 3 is enormously reduced compared to that of LiAlH 4 . In addition, the preferential release of hydrogen from LiAlH 4 in the composite system provides additional heat for the subsequent release of hydrogen from AlH 3 , accelerating the hydrogen release process. As a result, LiAlH 4 -AlH 3 -Ni/CeO 2 composite performs enhanced hydrogen release performance with a hydrogen release capacity of 8.27 wt% hydrogen within 300 ℃ and a dehydrogenation onset temperature as low as 72.9 ℃. The enthalpy change of the first step hydrogen release reaction decreases from −11.99 kJ mol −1 (LiAlH 4 ) to −2.02 kJ mol −1 (LiAlH 4 -AlH 3 ). Theoretical calculations indicate that both atomic dehybridisation and electron redistribution expedite the breaking of the Al-H bond and the consequent release of hydrogen.