Deposition and Stripping Properties of Mercury on Iridium Electrodes

Abstract

The reduction of mercury on a fresh iridium surface is reversible with a half‐wave potential of +162 mV (vs. SCE). A Hg(O) monolayer is formed by underpotential deposition (UPD) at +600 mV during the initial scans of a repetitive cyclic voltammogram. This monolayer acts as bulk Hg(O) during further cycles, and the reduction half‐wave potential then shifts towards +410 mV. Anodization of the electrode at a potential > +1000 mV returns the reduction wave to its original position. The peak for the oxidation of bulk Hg(O) from the surface occurs at +430 mV followed by a peak for the underpotential stripping (UPS) of the Hg(O) monolayer at +650 mV. The quantity of Hg(O) for the monolayer corresponds to a 40% coverage of the Ir surface. The underpotential shift for the bulk and monolayer stripping of Hg(O) from Ir was found to be 210 mV. No indications of a Hg‐soluble compound formation between Hg and Ir were found.