THE DETERMINATION OF KINETICS PARAMETERS OF THE HYDROGEN EVOLUTION ONTI-NI ALLOYS BY AC-IMPEDANCE

The kinetics and mechanism of hydrogen evolution at Ti-Ni alloys elect rode has been studied by means of steady-state potentiostatic polariza tion and ac impedance spectrum measurements. Complex-plane spectrum pl ots are derived for the h.e.r. at one of the most inactive, typical hy dridic, Ti-Ni, and one of the most active, typical electrocatalytic, T i-Ni-3, intermetallic alloy compounds at various potentials. The rate constants of the forward and backward reactions of the corresponding s teps were estimated by a nonlinear fitting method. It has been found t hat the overall reaction proceeds through a coupled Volmer-Heyrovsky m echanism. The electrocatalytic activity decreases in the order TiNi2 > TiNi3 > TiNi4 > Ti2Ni > TiNi > Ti3Ni > TiNi0.7. Copyright (C) 1996 El sevier Science Ltd