In this report, electrochemical oxidation of hydrogen peroxide (H2O2) at the bare polycrystalline gold [Au (poly)] electrode and the Au (poly) electrode modified with a submonolayer of iodine (sub I) [sub I vertical bar Au (poly)] electrode in 0.1 M KOH solution has been described. At the bare Au (poly) electrode, electrochemical oxidation of H2O2 proceeds probably via a rate-determining chemical step, i.e., adsorption of H2O2 at the Au (poly) electrode. While modification of the Au (poly) electrode by the sub I results in a change of the reaction pathway to a diffusion-controlled one and a tremendous enhancement of the H2O2 oxidation current. Five times larger oxidation peak current has been achieved at the sub I vertical bar Au (poly) electrode compared with the potential-independent oxidation plateau current at the bare Au (poly) electrode. Strong electrostatic attraction between the anionic HO2- molecules and the iodine-adlayer-induced positively polarized Au (poly) electrode surface has been proposed to be responsible for the enhancement of the electrode activity toward H2O2 oxidation. The effect of surface coverage of I and the concentration of KOH on the oxidation of H2O2 at the sub I vertical bar Au (poly) electrode has also been investigated. Experimental investigation has been performed on the basis of the open-circuit potential measurement and cyclic and linear sweep voltammetric studies. (c) 2006 The Electrochemical Society.