Influence of hydrogen absorption on the potential dependence of the Faradaic impedance parameters of hydrogen evolution reaction

The influence of hydrogen absorption reaction (HAR) proceeding through Hads with kinetic or with diffusion control on the dependence of the elements R1, R2, C2 of the equivalent electrical circuit for hydrogen evolution reaction (HER) on the electrode potential E has been considered. It has been shown that if HER proceeds through the Volmer-Heyrovsky mechanism, then the presence of HAR reduces the slope dlogR2/dE at all Е and the slope dlogС2/dE at sufficiently high cathodic polarisations. In the case of the Volmer-Tafel mechanism the presence of HAR mainly affects the resistance R2. The character of the dependences of R1, R2, C2 on Е is the same for both kinetic and diffusion control of HAR. An interpretation of the experimental impedance data for HER on CoSi2 in 0.5 M H2SO4 has been presented.