Remarkable hydrogen storage properties in three-layered Pd/Mg/Pd thin films

We have investigated hydrogen storage and structural properties in nano-composite three-layered Pd(50 nm)/Mg(x nm)/Pd(50 nm) films with x=25, 50, 200, 400 and 800 prepared by an RF-associated magnetron sputtering method. After hydrogenation under a hydrogen gas pressure of 0.1 MPa at 373 K for 24 h, the TDS profiles indicated that the Pd layers contain only 0.15-0.30 mass% hydrogen, whereas the Mg film contains ∼5.0 mass% hydrogen for all the films. The most striking feature is that the temperature corresponding to maximum dehydrogenation rate remarkably shifts to low temperature with increasing the thickness of Mg film, which decreased from 465 K at x=25 nm to 360 K at x=800 nm. These improvements could be understood by the concept of cooperative phenomenon which hydrogen shows in nano-scale composite regions.