Thin film permeation membranes for hydrogen purification

Hydrogen has the well known property to diffuse through some metals such as nickel or alloys like palladium-silver. This property is used to separate hydrogen from gas mixtures to obtain very pure hydrogen. Thin film nickel and palladium membranes supported by a microporous substrate have been carried out. They allow for a significant increase of the permeation rate of pure hydrogen compared to that of bulky materials. For nickel thin film membranes the measurements have been performed between 98° and 227°C, the calculated diffusion coefficient is D = 0.13 exp(-6450/ T). The technology which allows the reduction of the membrane thickness could improve the performances of the purification units.