Kinetics of the hydrogen evolution reaction on gold electrode. A new case of the barrierless discharge

Kinetics of hydrogen evolution reaction on the electrodeposited gold electrode is studied. In semi-logarithmic coordinates, polarization curves consist of two linear segments with Tafel slopes 0.06 V at lower overpotentials and 0.12 V at the higher ones. The kinetics in the higher-slope region depends on the solution pH and the ψ1-potential (effects of the ionic strength and of the presence of the surface-active tetrabutylammonium cation) as it is predicted by the theory of the ordinary slow discharge. In the lower-slope region, overpotential does not depend on pH and ψ1-potential; this is in full accordance with the theory of the barrierless discharge. We nevertheless analyze also several alternatives to the theory of barrierless discharge for the explanation of the low-slope region, but we show that they are not consistent with the experimental data.