First-principles study on a potential hydrogen storage medium of Mg/TiAl sandwiched films

Interaction between atoms in Mg/TiAl sandwiched films and hydrogenation of the films are studied by first-principles calculations. The formation energy is used to estimate the energetic stability of the Mg/TiAl films. The Mg/TiAl sandwiched films are more stable than the pure Mg film. The adsorptions of hydrogen in the Mg/TiAl films are investigated. Inserting TiAl layers can improve the hydrogenation properties of Mg film. The lowest hydrogen adsorption energy of -1.163 eV appears in hydrogen adsorbed Mg(0001)/TiAl(110) film, and the second lowest adsorption energy is -0.333 eV for hydrogen adsorbed Mg(0001)/TiAl(111) film, while the adsorption energy reaches a positive value of 0.089 eV for hydrogen adsorbing in Mg(0001) film. The electronic structure analysis illustrates that strong interactions between H and its surrounding Ti and Mg atoms are expectable. Thus, in the Mg/TiAl films Ti and Mg act as active sites to capture hydrogen atoms and, therefore, hydrogenation properties of Mg/TiAl films are improved compared to the pure Mg film.