Theory and Simulations for the Electron-Transfer/Ion-Transfer Mode of Scanning Electrochemical Microscopy in the Presence or Absence of Homogenous Kinetics
Theory and Simulations for the Electron Transfer/Ion Transfer Mode of SECM in the Presence or Absence of Homogenous Kinetics, ChemElectroChem 2017
The development of nanometer-sized electrochemical probes allowed scanning electrochemical microscopy (SECM) to evolve as a powerful tool for imaging topography and investigating chemical processes on the nanoscale. Although a conventional SECM probe is a metal micro-or nanoelectrode, the use of a pipette supporting the interface between two immiscible electrolyte solutions (ITIES) at its tip can expand the range of useful applications of this technique. Several processes that can occur at the liquid/liquid interface (but not at the metal/solution interface) include ion transfer (IT) of redox inactive ions and partitioning of a neutral solute between two liquid phases. The SECM with a nano- or micropipette tip filled with organic phase and immersed in aqueous solution was employed in a wide range of experiments, including catalysis studies, imaging surface topography and ion transport, local electrodeposition, surface patterning and studies of biomembranes.
This work was aimed to investigate and predict the ionic current, across the nano-ITIES interface supported at the tip of a nanopipette that is used to deliver an electroactive species, A, to the electrode surface and capture the electrogenerated ionic species, B. Three commonly encountered experimental situations have been considered, viz., the surface generated ionic species is either chemically stable or participates in a first or second order homogeneous reaction.
The electron transfer/ion transfer (ET/IT) mode of the scanning electrochemical microscopy (SECM) was developed recently and applied to studies of heterogeneous reactions at the substrate surface. The charged products or intermediates are detected by measuring the ion transfer current of this species across the liquid/liquid interface supported at the tip of a nanopipette. In this article, we developed the theory for this technique and explored its potential advantages and limitations. Using COMSOL Multiphysics package, the approach curves were simulated for three commonly encountered experimental situations, viz., the surface generated ionic species is either chemically stable or participates in a first or second order homogeneous reaction. The simulation results are generalized in the form of analytical approximations derived under limiting conditions.
Theory and Simulations for the Electron Transfer/Ion Transfer Mode of SECM in the Presence or Absence of Homogenous Kinetics.
Alexander Oleinick; Yun Yu; Irina Svir; Michel V. Mirkin; Christian Amatore