Electrochemical Conversion on a Microchip: Comparison of Experiments with Simulations

Electrochemical Conversion on a Microchip: Comparison of Experiments with Simulations.

A. Wright, L. Qin, H. Beyenal and C.F. Ivory

Gene and Linda Voiland School of Chemical Engineering and Bioengineering Washington State University, Pullman WA 99164

Abstract: A 50:50 mixture of ferricyanide:ferrocyanide flowing at 400 nl/min is electrochemically reduced over a 100 µm diameter platinum "working electrode" installed in a 150 µm wide by 40 µm deep by 4.4 cm long channel imprinted on a poly(methylmethacrylate) substrate. A second "sensing" microelectrode located 1.4 cm downstream is then used to determine the degree of conversion at the working electrode. A pair of Gamry potentiostats is used to set the voltage at the working and sensing electrodes relative to a silver:silver chloride pseudo-reference electrode and to measure the current at each electrode against a counter-electrode located at the end of the microchannel. The results of a series of experiments on this microchip are then compared with predictions from 2D and 3D models. Computer simulations based on these models were carried out using the Laminar Flow, Transport of Diluted Species and AC/DC physics in COMSOL Multiphysics^® v5.1 and compared with experimental data. This comparison indicates that our model, which uses the Butler-Volmer equation to describe redox reactions on the electrodes, provides good qualitative agreement with experiment.