The Frumkin and Temkin adsorption isotherms (theta vs. E) of over-potentially deposited hydrogen (OPD H) for the cathodic H-2 evolution reaction (HER) and related electrode kinetic and thermodynamic parameters at a Pd/0.5M H2SO4 aqueous solution interface are determined using the phase-shift method and correlation constants. The Frumkin and Temkin adsorption isotherms (theta vs. E), equilibrium constants (K = 3.3 x 10(-5) exp(- 1.4 theta) mol(-1) for the Frumkin and K = 3.3 x 10(-4) exp(-6 theta) mol(-1) for the Temkin adsorption isotherm), interaction parameters (g = 1.4 for the Frumkin and g = 6 for the Temkin adsorption isotherm), rates of change of the standard free energy of OPD H with theta (r = 3.5 kJ mol(-1) for g 1.4 and r = 14.9 kJ mol(-1) for g = 6), and standard free energies (25.6 <= Delta G(theta)(0) <= 29.0 KJ mol(-1) for the Frumkin and 22.8 < Delta G(theta)(0) < 31.8 KJ mol for the Temkin adsorption isotherm) of OPD H are determined using the phase-shift method and correlation constants. At the intermediate values of theta, i.e., 0.2 < theta < 0.8, the Temkin adsorption isotherm (theta vs. E) correlating with the Frumkin or the Langmuir adsorption isotherm (theta vs. E), and vice versa, is readily determined using the correlation constants. The phase-shift method and correlation constants are unique, useful, and effective ways to determine the Langmuir, Frumkin, and Temkin adsorption isotherms (theta vs. E) of intermediates for sequential reactions and related electrode kinetic and thermodynamic parameters (K, g, r, AGO) at interfaces. (c) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.