Permeation of hydrogen through nickel foils: surface reaction rates at low temperatures

Determination of parameters in surface limited hydrogen permeation through metal membrane

“…In short, the number of constraints is smaller than number of unknowns as already noted in ref. [19] for 0 → p a step change, while this is not the case for symmetric membrane where the unknown parameters can be determined as demonstrated by Grant et al [1,2,7]. To avoid this obstacle in the case of asymmetric membrane, the value of solubility is most often taken from the literature despite the considerable scatter and unreliability of K S values at low hydrogen pressures that can introduce a significant error in the subsequent determination of K L,1 and γ.…”

“…Ward and Dao [18] followed a model of Pick and Sonnenberg and extended it by the description of dissociative adsorption that takes into account the interaction between adsorbed H atoms on Pd surface. Several investigators [1][2][3]7] ignored the adsorbed phase and assumed symmetric membrane which considerably simplified the model and made it easier to apply. Such approach expresses the reaction rates of all surface reactions of hydrogen (adsorption, desorption, dissociation, recombination, solution and de-solution) by an effective absorption and recombination coefficient that govern the single reversible reaction H 2 (gas phase)…”