Looking at electrochemical reactors (e.g. fuel cell, chloor-alkali process, water electrolyzer) the conductive support typically consist of a flat substrate with the electrolyte flowing sideways along the electrode [3]. Inevitably a stagnant boundary layer arises which reacting species have to surpass to reach the electrocatalytic surface, even when using turbulence promotors. As transport across this stagnant layer is solely due to diffusion it has a major impact on the mass transfer resistance and concomitantly on the position of the limiting current plateau. However, when the electrode is no longer considered as a flat substrate a plethora of options arise, where not only the surface area can be increased, but also where the electrode itself can provoke mixing effects, reducing this boundary layer.
In the present work such integrated mixer and electrode configurations have been constructed and evaluated using additive manufacturing technology. Doing so these electrode mixers shift the limiting current plateau with over 70%. At the one hand this is attributed due to shear forces reducing the stagnant boundary layer, at the other hand as no longer a turbulence promotor or even a spacer is required the inter-electrode distance can be reduced to sub-millimeter range, having a beneficial impact on the ohmic resistance.
References:
- A. Kloke, F. Von Stetten, R. Zengerle, S. Kerzenmacher, Strategies for the fabrication of porous platinum electrodes. Adv. Mater. 23, 4976–5008 (2011).
- C. J. Brown, F. C. Walsh, J. K. Hammond, D. Robinson, Local mass transport effects in the FMO1 laboratory electrolyser. J. Appl. Electrochem. 22, 613–619 (1992).
- D. Pauwels et al., The application of an electrochemical microflow reactor for the electrosynthetic aldol reaction of acetone to diacetone alcohol. Chem. Eng. Res. Des. 128, 205–213 (2017).