Constant Correlation Factors between Temkin and Langmuir or Frumkin Adsorption lsotherms at Poly-Pt, Re, and Ni/Aqueous Electrolyte Interfaces

Abstract

The constant correlation factors between the Temkin and the Langmuir or the Frumkin adsorption isotherms of over-potentially deposited hydrogen (OPD H) for the cathodic H2 evolution reaction (HER) at poly-Pt and Re/0.5 M H2SO4 and poly-Ni/0.05 M KOH aqueous electrolyte interfaces have been experimentally and consistently found using the phase-shift method. At intermediate values of the fractional surface coverage (), i.e., 0.2 0.8, the Langmuir and Temkin adsorption isotherms of OPD H for the cathodic HER are correlated to each other even though the adsorption conditions or processes are different from each other. At the same range of , correspondingly, the Frumkin and Temkin adsorption isotherms of OPD H for the cathodic HER are correlated to each other. The equilibrium constants (Ko) for the Temkin adsorption isotherms ( vs. E) are consistently ca. 10 times greater than those (K, Ko) for the corresponding Langmuir or Frumkin adsorption isotherms ( vs. E). The interaction parameters (g) for the Temkin adsorption isotherms ( vs. E) are consistently ca. 4.6 greater than those (g) for the corresponding Langmuir or Frumkin adsorption isotherms ( vs. E). These numbers (10 times and 4.6) can be taken as constant correlation factors between the corresponding adsorption isotherms (Temkin, Langmuir, Frumkin) at the interfaces. The Temkin adsorption isotherm corresponding to the Langmuir or the Frumkin adsorption isotherm, and vice versa, can be effectively verified or confirmed using the constant correlation factors. Both the phase-shift method and constant correlation factors are useful and effective for determining or confirming the suitable adsorption isotherms (Temkin, Langmuir, Frumkin) of intermediates for sequential reactions in electrochemical systems.