Spectroscopic evidence for reversible hydrogen storage in unordered Mg5Ni1 thin films

Thin magnesium-nickel films grown on Mo( 110) under ultra-high vacuum conditions were hydrogenated with atomic H and studied by high-resolution core-level photoelectron spectroscopy ( PES) and thermal desorption spectroscopy (TDS). We show spectroscopic evidence for reversible hydrogen storage and clear evidence that no Mg segregation or desorption occurs when hydrogen is desorbed from the film. During the heat-up of the hydrogenated Mg5Ni1 film (0.7 K s(-1)) TDS shows that hydrogen desorption starts at 350 K and reaches its maximum at 420 K. Mg desorption starts at 450 K. The stability of the storage can be enhanced by cooling.