Tuning the Hydrogen Storage in Magnesium Alloys

Mixing Mg with Ti leads to an alloy with markedly faster hydrogenation kinetics as compared to that of pure Mg, but the resulting hydrides are too stable for hydrogen storage applications. Moreover, Mg Ti alloys are thermodynamically unstable with respect to decomposition into the elements. In this Letter, we show by means of first-principles density functional theory calculations that adding Al or Si to mg Ti makes the alloys more stable and their hydrides less stable. Controlling the structure of Mg-Ti-X (X = Al or Si) alloys by growing multilayers of mg and TiX allows for tuning the hydrogenation energy and improves the alloys as hydrogen storage materials.