Improvement of Electrochemical Methods for Studying Metal‐Hydrogen Systems

Abstract

Correct diffusion measurements using electrochemical methods must be carried out under careful consideration of the boundary conditions. — It is shown that the diffusion of recombined H‐atoms from the metal surface into the electrolyte does not seem to be the main reason for a loss of hydrogen concentration, but the presence of oxidizing species (generally oxygen), solved in the electrolyte, which lead to an enhanced electrochemical oxidation of hydrogen. In order to avoid this source of systematic errors, deaerated H2SO4 was used for measuring time lag curves of hydrogen diffusion in palladium. Measured time lag curves, obtained by the current pulse method, agree very well with theoretical curves, evaluated from the solution of Fick's second law. — When determining diffusion coefficients by measuring the break‐through time one has to take into account the ratio of the amount of hydrogen, discharged on the entry side of the diffusion foil, to the content of hydrogen within the sample from precharging runs.

Effects of Self Stress on the Transport of Guest Species in Solids: Transport of Hydrogen in Metals

“…The following parameters were commonly assumed for the M−H system (the same as for TFs): 25,26 V = 1.77 × 10 -6 m 3 mole -1 , ,, Ȳ = 1.844 × 10 11 Pa, D = 1 × 10 -11 m 2 s -1 (close to this value for Pd 81 Pt 19 H n , and three times smaller than for α-PdH n ), ,,,,,− L = 5 × 10 -5 m (as for Pd and Pd 81 Pt 19 specimens in EIS), , and T = 298.2 K. As in the (linear) TF f analysis, the explored spectrum of frequencies was 1 × 10 -4 ≤ f ≤ 1 × 10 1 Hz.…”

Numerical simulation of diffusivity of hydrogen in thin tubular metallic membranes affected by self-stresses

“…The actual metal (alloy) surface and bulk processes are complex [11,[32][33][34][35], for example, surface reactions (e.g. the Tafel and Heyrovsky steps) at electrode will diminish the permeation ux during hydrogen absorption [11].…”