Hydrogen selective membranes based on palladium are very important for technological processes such as isotopic separation and gas purification. As a matter of fact, both tensile strength and permeability show a maximum for a silver content in the range of 20-40 %wt., which exactly corresponds to commercial Pd-Ag alloy used for membrane applications (such as fuel cycle in fusion reactors). The structure of Pd-Ag membranes loaded with deuterium was investigated at ILL (D1B and D2B instruments), while the density of vibrational states projected on the proton was measured on MARI. QENS measurements were performed on OSIRIS in the range of p=1-2 bar and T=70-300 °C. We propose a QENS experiment to extend the p and T range up to 4 bar and T up to 400 °C to have a more complete picture of the microscopic diffusion process to be compared to the macroscopic one measurable in the ENEA laboratory.