Electrolytic flux imaging on band electrodes by interferometric microscopy

Abstract

In this paper we present mass transfer mapping in solution at the micron scale using interferometric microscopy. In its present form, the technique is sensitive to the solution refractive index component parallel to the surface of the electrode. The technique is able to detect optical path differences of the order of the picometer. We show the feasibility and performances of our set-up, an interferometric microscope equipped with a CCD camera and a multichannel lock-in detection, by imaging ionic fluxes in solution between band electrodes. The experiments are performed with the usual electrochemical conditions on the following systems: Fe 3+/Fe 2+ in sulphuric acid, Fe(CN) 6 3−/Fe(CN) 6 4− in KCl aqueous solution and Ce 4+/Ce 3+ in nitric acid. The electrolytic flux imaging is analyzed along transverse and longitudinal profiles of the concentration gradients in relation with the current flowing through the cell.