In situ study of hydriding–dehydriding properties in some Pd/Mg thin films with different degree of Mg crystallization

Abstract

Abstract A new in situ system with the functions of thin film formation and analysis of hydrogen absorption–desorption properties has been developed to clarify hydrogen storage properties in nano-scaled composites. In this work, some Pd/Mg films (Pd (25 nm)-coated Mg (200 nm) films) with different degree of crystallization in the Mg layer were prepared in different sputtering conditions by changing RF coil powers and argon pressures. Hydrogenation under hydrogen gas pressure of 0.1 MPa at 373 K for 24 h indicated that MgH2 and non-crystalline Mg hydrides were formed in all the Pd/Mg films and the hydrogen content reached 2.9∼6.6 mass% independent of the degree of Mg crystallization. From the thermal desorption spectrum, it was deduced that the dehydriding temperature decreased with decreasing the degree of crystallization in the Mg layer in Pd/Mg films and the Pd/Mg film with lowest crystallization absorbed 5.6 mass% of hydrogen and all the hydrogen desorbed at a temperature lower than 463 K in vacuum.