Determination of the Langmuir and Temkin Adsorption Isotherms of H for the Cathodic H2 Evolution Reation at a Pt/KOH Solution Interface Using the Phase-Shift Method

Abstract

The phase-shift method for determining the Langmuir, Frumkin, and Temkin adsorption isotherms (θH vs. E) of H for the cathodic H2 evolution reaction (HER) at a Pt/0.1 M KOH solution interface has been proposed and verified using cyclic voltammetric, differential pulse voltammetric, and electrochemical impedance techniques. At the Pt/0.1 M KOH solution interface, the Langmuir and Temkin adsorption isotherms (θH vs. E), the equilibrium constants (KH = 2.9 × 104 mol1 for the Langmuir and KH = 2.9 × 103exp(4.6θH) mol1 for the Temkin adsorption isotherm), the interaction parameters (g = 0 for the Langmuir and g = 4.6 for the Temkin adsorption isotherm), the rate of change of the standard free energy of H with θH (r = 11.4 kJ mol1 for g = 4.6), and the standard free energies (Gadso = 20.2 kJ mol1 for KH = 2.9 × 104 mol1, i.e., the Langmuir adsorption isotherm, and 16.7 < Gθo < 23.6 kJ mol1 for KH = 2.9