Electrostatic Stimulation of Monopolar Electrodes

Changes in the electrostatic potential within an aqueous acidic solution induced by the passage of current between the Au disk of a stationary Au|Au ring disk electrode or stimulating electrode, SE, and a distant counter electrode made it possible to <i>stimulate</i> the reduction of selenous acid, H₂SeO₃, to elemental selenium at the concentric Au ring polarized at a fixed potential, just positive to its otherwise expected onset. This effect was ascribed to variations in the surface overpotential, η_s, and, thus, in the rates of H₂SeO₃ reduction along the ring, which we define, hereafter, as a <i>monopolar electrode,</i> ME. The <i>stimulation</i> efficiency could be accurately determined from a coulometric analysis of the peak for Se oxidation observed by subsequently scanning the ring linearly toward positive potentials to yield H₂SeO₃. Excellent quantitative agreement was obtained between the current flowing through the ME, <i>I</i>_ME, and <i>E</i>_ME^o, as a function of <i>I</i>_SE, and theoretical simulations employing COMSOL using parameters extracted from independent measurements performed under otherwise identical experimental conditions. This novel tactic is expected to open new prospects for gaining insight into surface diffusion and other interfacial dynamics phenomena, as well as local modifications in the microstructure of electrodes, such as etching.