Quantitative Aspects of Ohmic Microscopy

The potential difference between two microreference electrodes, Delta phi(sol), immersed in an aqueous sulfuric acid solution was monitored while performing conventional cyclic voltammetric experiments with a Pt disk electrode embedded in an insulating surface in an axisymmetric cell configuration. The resulting Delta phi(sol) vs E curves, where E is the potential applied to the Pt disk electrode were remarkably similar to the voltammograms regardless of the position of the microreference probes. Most importantly, the actual values of Delta phi(sol) were in very good agreement with those predicted by the primary current distribution using Newman's formalism (Newman, J. J. Electrochem. Soc. 1966, 113, 501-502). These findings afford a solid basis for the development of ohmic microscopy as a quantitative tool for obtaining spatially resolved images of electrodes displaying nonhomogenous surfaces.