Hydrogen diffusion constants, DH, were obtained from steady-state fluxes through Pd membranes with the down-stream side maintained at pH2 ≈ 0. Good linearity of plots of H flux versus (1/d), where d was the thickness, indicated that H permeation was bulk diffusion-controlled at 423 to 523K and pH2 ≤ 0.2MPa). The DH values were determined at both constant pup and at constant H content. The H fluxes through Pd membranes with three different surface treatments were investigated (table 129). Palladized and oxidized membranes gave similar DH values, but polished membranes gave values which were about 12% lower. Activation energies for diffusion, ED(cH), were determined, and ED was found to increase with cH; this being attributed to the thermodynamic factor.

Diffusion of H through Pd Membranes: Effects of Non-Ideality. T.B.Flanagan, D.Wang, K.L.Shanahan: Journal of Membrane Science, 2007, 306[1-2], 66-74