ADDITIONAL CRITERIA FOR THE MECHANISM OF HYDROGEN EVOLUTION REACTION IN THE IMPEDANCE SPECTROSCOPY METHOD

Abstract

The time constant  = R2C2 and the products of resistances R1 and R2 by current density i (R1, R2, C2 are the Faradaic impedance parameters) are discussed as criteria for the hydrogen evolution mecha- nisms. The values of dlog/d ( is the overvoltage) do not depend on the nature of rate-limiting step in discharge – electrochemical desorption route, but essentially depend on the nature of slow step in discharge – chemical combination route. Possibilities to distinguish between hydrogen evolution mechanisms within the limits of the discharge – electrochemical desorption route are more considera- ble when using iR1 and iR2 than analyzing . The influence of the hydrogen absorption reaction on the dependences of , iR1 and iR2 on  is briefly discussed. Experimental iR1 and iR2 data for Co2Si and CoSi2 electrodes in 1 M KOH are considered.