AN ELECTROCHEMICAL IMPEDANCE STUDY ON THE KINETICS AND MECHANISM OF THE HYDROGEN EVOLUTION REACTION ON NICKEL MOLYBDENITE ELECTRODES

Electrodeposited Ni/NiMoS2 electrodes have shown good electrocatalytic activity towards the hydrogen evolution reaction as well satisfactory long-term operational performance. The hydrogen evolution reaction on these electrodes, which in previous investigations using steady-state polarizations, cyclic voltammetry and scanning electron microscopy re vealed high surface area and a very heterogeneous surface morphology, has been studied by applying electrochemical impedance spectroscopy (E IS). The kinetics and mechanism of the hydrogen evolution reaction (HE R) on electrodeposited Ni/NiMoS2 electrodes have been investigated in the frequency range 5 mHz less than or equal to f less than or equal t o 10 kHz. A detailed dynamic system analysis is presented taking into account the contributions of Tafel-Volmer-Heyrovsky reaction steps as well as the absorption and diffusion of hydrogen atoms into the electr ode material. For comparison results obtained for the HER on electrode posited Ni electrodes are also discussed. Copyright (C) 1997 Elsevier Science Ltd.