Hydrogen selective membranes based on palladium are important for technological processes such as isotopic separation and gas purification.In general, a Pd membrane when hydrogenated becomes brittle after a certain number of cycles of the α-β hydride transformation due to the subsequent lattice expansion. On the contrary, in Pd-Ag alloys, the lattice has been already expanded by the effect of Ag substitutional atoms, and so it is much less influenced by hydrogen uploading and, consequently, less brittle than in the pure Pd case Recently elastic and inelastic neutron scattering measurements were performed at ILL (D1B) and ISIS (MARI) to assess H occupancy and PDoS. H diffusivity at micro-scale is important to be measured for a thorough characterization of these materials. We propose a QENS measurement on OSIRIS at the same (T,p) of the MARI and D!B experiments.