Investigation of the hydrogen evolution reaction at a 10wt% palladium-dispersed carbon electrode using electrochemical impedance spectroscopy

Abstract

The hydrogen evolution reaction (h.e.r.) at a 10 wt % palladium-dispersed carbon (Pd/C) electrode in 0.1 M NaOH solution has been investigated with reference to that on carbon (Vulcan XC-72) and palladium foil electrodes by analysing the a.c.-impedance spectra combined with cyclic voltammograms. From the coincidence of the maximum charge transfer resistances and the minimum hydrogen evolution resistances for the h.e.r. at the respective electrode potential for the Pd/C, carbon and Pd foil electrodes, it is suggested that the h.e.r. at the Pd/C electrode takes place along with the absorption and diffusion of hydrogen above - 1.10 V vs SCE, whereas the former dominates over the latter below -1.10 V vs SCE. In the case of the Pd foil electrode the transition of absorption and diffusion to evolution occurs at -0.96 V vs SCE. In contrast to the Pd/C and Pd foil electrodes the h.e.r. occurs strongly at the carbon electrode below -1.20 V vs SCE. The hydrogen evolution overpotential on the Pd/C electrode is decreased by 0.10 V in comparison to the carbon electrode due to the larger electrochemical active area of the finely dispersed Pd particles.