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

► Hydrogen evolution reaction on gold displays two Tafel slopes of 0.06 V and 0.12 V. ► Kinetic dependences on solution composition evidence the barrierless discharge. ► The alternative explanations of the low Tafel slope are shown to be incorrect. ► The barrierless discharge is described in terms of the quantum-mechanical theory.