Voltammetry of aqueous chloroauric acid with hanging mercury drop electrode

In d.c. voltammetry of dilute aqueous chloroauric acid with hanging mercury drop electrode, when potential scanning proceeds from negative to positive values, a prominent maximum of cathodic current appears on the curve near 0 V. The effect is explained as due to catalytic evolution of hydrogen on the electrode initially covered by adsorbed Au-hydroxidic layer. Once the layer dissolves in the acidic solution during the positive scan, a fast evolution of hydrogen takes place, catalysed by short-lived adsorbed gold particles.