Abstract
Insight into dynamic electrochemical processes can be obtained with in situ ec-S/TEM, which utilizes microfluidic electrochemical cells to characterize electrochemical processes with S/TEM imaging, diffraction or spectroscopy. The microfluidic electrochemical cell is composed of microfabricated devices with glassy carbon and platinum microband electrodes in a three-electrode cell configuration. To establish the validity of this method for quantitative in situ electrochemistry research, cyclic voltammetry, choronoamperometry and electrochemical impedance spectroscopy were performed using a standard one electron transfer redox couple using a [Fe(CN)6]3-/4- based electrolyte. Established relationships of the electrode geometry and microfluidic conditions were fitted with cyclic voltammetry and chronoamperometic measurements of analyte diffusion coefficients and was found to agree with well-accepted values that are on the order of 10-5 cm2 s-1. Influence of the electron beam on electrochemical measurements was found to be negligible during CV scans where the current profile varied only within a few nA with the electron beam on and off which is well within the hysteresis between multiple CV scans. The combination of experimental results provides a validation that quantitative electrochemistry experiments can be performed with these small-scale microfluidic electrochemical cells provided that accurate geometrical electrode configurations, diffusion boundary layers and microfluidic conditions are accounted for.
