Dehydrogenation of pure and Ti-doped Na3AlH6 surfaces from first principles calculations

We have studied the dehydrogenation properties of pure and Ti-doped Na3AlH6 surfaces using density functional theory. For the clean surface dehydrogenation is a multistep process, and involves the desorption of AlH4 complexes which disrupt the structure of the surface. By doping the system with Ti, we found that the segregation energy of Ti is negative, therefore favoring localization of the impurity to the surface of Na3AlH6. Here Ti doping is shown to kinetically favor H2 desorption, by reducing the energy barrier that the molecule needs to climb to leave the surface.

► Ti as catalyst for Na3AlH6 hydrogen desorption.
► Hydrogen desorption from pure Na3AlH6 disrupts surface.
► Ti doping stabilizes surface geometry upon hydrogen desorption.
► Ti doping reduces desorption energy.