Kinetic and thermodynamic analysis of hydrogen evolution at nickel electrodes

Abstract

iR-corrected steady-state polarization curves for hydrogen evolution in alkaline solution at crystalline and amorphous nickel electrodes were measured at different temperatures, showing at higher c.d. the establishment of a limiting c.d. due to increasing H ad coverage. The experimental behaviour is in perfect agreement with a complete kinetic model based on the Volmer—Tafel mechanisms. Symmetry factors and rate constants for forward and backward direction of both reactions were determined by a non-linear fitting procedure. Activation energies, enthalpic and entropic components of the symmetry factor, and thermodynamic quantities as equilibrium constant of the Tafel reaction, equilibrium potential of the Volmer reaction, enthalpy and entropy of adsorbed hydrogen atoms could be derived from these data providing new quantitative knowledge of elementary steps of hydrogen evolution at crystalline and amorphous nickel electrodes.