ELECTROCHEMICAL STUDIES OF MERCURY(II)

The reduction of Hg2+ is studied by linear sweep voltammetry, rotated disk electrode voltammetry, and chronoamperometry in a non-complexing medium at a vitreous carbon electrode (VCE). At the VCE which is completely free of any mercury deposit, the reduction of Hg2+ is found to be of first order, involving two electrons and reversible at slow sweep rates. When the VCE is partially covered with mercury droplets, the reduction mechanism is different and occurs in two steps. At the most active sites on the VCE where mercury droplets are formed during a previous cathodic sweep, Hg2+ undergoes disproportionation to Hg22+ which is subsequently reduced to Hg. The second step involves the simple two-electron, diffusion-controlled reduction of Hg2+ to Hg at the bare electrode surface. © 1979 Elsevier Sequioa S.A., Lausanne.