In situ synchrotron X-ray diffraction study on the improved dehydrogenation performance of NaAlH4–Mg(AlH4)2 mixture

Highlights: •The dehydrogenation reactions of NaAlH4–Mg(AlH4)2 mixture were explored by in situ XRD. •NaAlH4–Mg(AlH4)2 mixture exhibited multiple-step dehydrogenation processes. •The mutual catalytic roles of NaAlH4 and Mg(AlH4)2 in the mixture were investigated. •NaAlH4–Mg(AlH4)2 mixture release 5.35 wt% H2 at an initial temperature of 120 °C. -- Abstract: The dehydrogenation performance and mechanism of the synthesized NaAlH4–Mg(AlH4)2 powders were investigated by performing thermogravimetric analysis and in situ synchrotron X-ray diffraction analysis. NaAlH4 not only facilitates the first step dehydrogenation of Mg(AlH4)2 in lowering its initial dehydrogenation temperature but also increases the total amount of H2 released. Besides, MgH2 and/or Al phases, the products of the first step dehydrogenation reaction, play a catalytic role in lowering the initial dehydrogenation temperature of NaAlH4. The synthesized NaAlH4–Mg(AlH4)2 mixture has an initial dehydrogenation temperature as low as 120 °C, and is able to release 5.35 wt% H2 below 350 °C. The self-catalytic dehydrogenation behavior of the NaAlH4–Mg(AlH4)2 mixture was elaborated in this work with the aid of in situ synchrotron XRD