Composition-Dependent Reaction Pathways and Hydrogen Storage Properties of LiBH4/Mg(AlH4)2 Composites

Herein, an initial attempt to understand the relationships between hydrogen storage properties, reaction pathways, and material compositions in LiBH4-xMg(AlH4)(2) composites is demonstrated. The hydrogen storage properties and the reaction pathways for hydrogen release from LiBH4-xMg(AlH4)(2) composites with x=1/6, 1/4, and 1/2 were systematically investigated. All of the composites exhibit a four-step dehydrogenation event upon heating, but the pathways for hydrogen desorption/absorption are varied with decreasing LiBH4/Mg(AlH4)(2) molar ratios. Thermodynamic and kinetic investigations reveal that different x values lead to different enthalpy changes for the third and fourth dehydrogenation steps and varied apparent activation energies for the first, second, and third dehydrogenation steps. Thermodynamic and kinetic destabilization caused by the presence of Mg(AlH4)(2) is likely to be responsible for the different hydrogen desorption/absorption performances of the LiBH4-xMg(AlH4)(2) composites.