Abstract
An electrochemical permeation method was employed to study the diffusion behaviour of hydrogen and deuterium in palladium. Solutions of 0.1 m LiOD (in D 2 O) and 0.1 m LiOH (in H 2 O) and their mixtures were used as the catholytes. More than one hundred diffusivity data from 20 palladium membranes were collected. Statistical analysis of these data was made to examine the validity of the reversed isotope dependence for hydrogen diffusion in palladium. It was concluded that the effective diffusivities increased with the concentration of deuterium in the electrolyte. In addition, an in situ experiment was also performed by adding to the cathodic cell an equivalent amount of LiOD solution to the original LiOH solution, or vice versa. Graphical comparison of the corresponding permeation transients showed that the permeation rate increased when deuterium was added to the solution of H 2 O, and the rate decreased when hydrogen was added to the solution of D 2 O. This constitutes direct evidence for the higher diffusivity of deuterium than that of hydrogen in palladium. © 1995 Chapman & Hall.