Development and characterization of electrochemical flow cells for hydrodynamic scanning electrochemical microscopy

Abstract

In the frame of this contribution, two electrochemical flow cells developed for scanning electrochemical microscopy (SECM) are presented. Forced convection was generated by a flow of the mediator solution through the flow cells. A description of the mandatory design aspects of the experimental flow cell setups is included. Using a macroscopic working electrode as a substrate electrode, forced convection leads to the formation of a stable diffusion layer during amperometric experiments in contrast to a growing diffusion layer in quiescent solution. To characterize the effects of forced convection, the diffusion layer around a platinum substrate electrode integrated into the cells was investigated utilizing chronoamperometric measurements and hydrodynamic SECM imaging in amperometric substrate generation-tip collection (SG/TC) mode. Both methods proved the stability and the time-independency of the diffusion layer. Mathematical simulations using COMSOL Multiphysics were computed to investigate the flow profile generated by the flowing mediator solution in the relevant region close to the substrate electrode. In summary, two different electrochemical flow cells for SECM were developed and characterized. Both cell designs enabled steady-state diffusion layer characteristics at a macroscopic substrate electrode offering interesting possibilities such as time-independent measurements in the context of the SG/TC mode.

Graphical abstract