Diagnostic criteria for hydrogen evolution mechanisms in electrochemical impedance spectroscopy

Diagnostic criteria for hydrogen evolution reaction mechanisms in acidic and alkaline solutions, based on the dependence of equivalent circuit elements on the overvoltage and H+ or OH− ion concentration, are proposed. Determination of the kinetic parameters (rate constants and transfer coefficients) of hydrogen evolution reaction steps on the basis of the impedance data has been considered. Hydrogen evolution reaction on CoSi2 electrode in acidic solutions is discussed using the proposed criteria, and it is shown that hydrogen evolution on cobalt silicide proceeds through the Volmer-Tafel-Heyrovsky mechanism.