iR Drop in Scanning Electrochemical Cell Microscopy

Nanoscale electrochemical mapping techniques, e.g., scanning electrochemical cell microscopy (SECCM), have been increasingly used to study the local electrochemistry in electrocatalysis. Its capability of local electrochemistry mapping helps to reveal the heterogeneity in the electrode kinetics and mechanisms which are otherwise averaged out in ensemble measurement. Accurate determination of the electrode kinetics requires careful assessment of the ohmic potential drop in the solution, i.e., iR drop. Herein, iR drop in SECCM experiments is assessed. We showed that iR drop in single-barrel SECCM can be estimated using the solution conductivity and the mass transfer limiting current without the assumption of pipette geometry. For dual-barrel SECCM, we developed a method of measuring the solution resistance directly, which can be used to compensate the iR drop and the potential shift in the experiments. These methods offer a convenient way to estimate and compensate the iR drop in SECCM, allowing more accurate measurement of local electrode kinetics for the determination of local mechanisms in electrocatalysis.