Electrocatalytic Oxidation of As(III): I . Voltammetric Studies at Pt Electrodes in

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Abstract
Hydrodynamic voltammetry and hydrodynamically modulated voltammetry at a disk electrode, and shielding experiments at a ring‐disk electrode, were applied in a study of the electrochemical response of As (III). The adsorption of As(III) occurs at Pt electrodes with partial charge transfer. The adsorption isotherm was determined and a maximum coverage is established for . The oxidation of As(III) is electrocatalyzed dramatically by formation of on the electrode, but is slow for a surface covered by a well developed layer of . The rate‐determining step (rds) for As(III) oxidation at the electrode does not involve charge transfer in the region vs.SCE. The log of the rate constant for the rds measured at 1.1V decreases linearly with the increasing charge equivalent to the surface oxide. The oxidation of As(III) at an oxide‐covered electrode is catalyzed by evolution of . The electrocatalysis is concluded to be the result of ·OH generated at the electrode surface.

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