Remarkable hydrogen storage, structural and optical properties in multi-layered Pd/Mg thin films

In this paper, we review our recent results on hydrogen storage, structural and optical properties in multi-layered Pd/Mg thin films. The thin films were prepared using a RF associated magnetron sputtering method, in which the structure in Mg layer was controlled into columnar-like textures with several tens nanometer in diameter by optimizing the sputtering conditions. The results obtained indicate that hydrogen of ∼5 mass% absorbs at 373 K in Mg under a hydrogen pressure of 0.1 MPa in multi-layered Pd/Mg films and the hydrogen desorbs at 360 K in vacuum. Such excellent hydrogen storage properties are explained by cooperative phenomena that hydrogen displays in nano-composite interface boundary regions between the Pd and Mg films. In addition, we experimentally confirmed at the first time that the rare earth and nickel free two-layered Pd/Mg film displayed optical transparency upon hydrogenation.