New advancements in the analysis procedures of the electrochemical hydrogen permeation experimental data

This thesis presents two major breakthroughs on the analysis procedures of the hydrogen permeation data of the electrochemical hydrogen permeation technique to determine all relevant parameters for the hydrogen evolution reaction (HER) and hydrogen absorption reaction (HAR). These include major modifications to the original Iyer-Pickering-Zamanzadeh (IPZ) analysis.; The first advancement was modifying the original IPZ analysis for competitive adsorption by including the surface coverage of a second adsorbate. This modification was applied to experimental data from the literature where the effect of iodide ions on HER and HAR was studied and qualitatively evaluated using the original IPZ analysis which ignores the surface coverage of iodide ions and to experimental data carried out in this research on the effect of hexamethylenetetramine, HMTA, on HER and HAR. The new analysis was able to evaluate all relevant parameters which include the exchange current density of the HER, i _o, the discharge rate constant, k₁, the recombination rate constant, k₂, the hydrogen surface coverage, &thetas;_H, and the kinetic-diffusion constant, k, which includes the absorption rate constant, k _abs, the desorption rate constant, k_des, hydrogen diffusivity, D_H, and the membrane thickness, L, in addition to the surface coverage of iodide ions, &thetas; _I−, and HMTA, &thetas;_HMTA. The &thetas; _I− and &thetas;_HMTA values were also determined using EQCM and polarization date and showed reasonable agreement with the one determined by the new IPZ analysis.; The second advancement was modifying the IPZ analysis to include the thickness effect so that the analysis will be able to evaluate all the parameters including the k_abs and k _des instead of determining k using one membrane thickness. The original IPZ analysis can evaluate kabs and kdes only if at least three thicknesses are used to evaluate k. This modification will still keep the competitive adsorption conditions and will be bale to determine the surface coverage of a second adsorbate. The modification was applied to data from the literature where the effect of chloride ions on HER and HAR was investigated. The modification was able to evaluate all parameters including kabs, kdes and &thetas;_Cl−.