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

Abstract

The high hydrogen release temperature and thermodynamic stability of the coordination hydride LiAlH4 render it unsuitable for direct application. This work intends to improve the hydrogen release properties via compositing LiAlH4 and AlH3 with similar initial hydrogen release temperatures and introduce efficient additive Ni/CeO2 composite. The thermal stability of the composite system LiAlH4-AlH3 is enormously reduced compared to that of LiAlH4. In addition, the preferential release of hydrogen from LiAlH4 in the composite system provides additional heat for the subsequent release of hydrogen from AlH3, accelerating the hydrogen release process. As a result, LiAlH4-AlH3-Ni/CeO2 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 (LiAlH4) to −2.02 kJ mol−1 (LiAlH4-AlH3). Theoretical calculations indicate that both atomic dehybridisation and electron redistribution expedite the breaking of the Al-H bond and the consequent release of hydrogen.