A Modular Double Electrode Flow Cell with Exchangeable Generator and Detector Electrodes

Abstract

Generator-collector experiments offer insights into the mechanisms of electrochemical reactions by correlating the product and generator currents. Most commonly, these experiments are performed using commercially-available rotating ring-disk electrodes (RRDE). We developed a modular double electrode flow cell (DEFC) with exchangeable generator and detector electrodes where the electrode width equals the channel width. As a test case, we considered the ferri-/ferrocyanide redox couple in experiments, analytical calculations and multiphysics simulations. Wall effects reduce the current density by less than 10 % in our geometry for the investigated conditions and the analytical solution for the limiting current at the generator electrode applies to widths up to 5 mm. The collection efficiency for all investigated electrode widths is close to the expected 35.4 % above a flow rate of 1.0 (mL/min)1/3 but only independent of the flow rate for electrodes with width 5 mm and larger. Kinetic constants of 1.3–1.9 ⋅ 10−3 cm/s are obtained from Koutecký-Levich analysis and 21.0–5.0 ⋅ 10−3 cm/s from Nicholson analysis for the DEFC, which falls within the range reported previously. We conclude that our DEFC with exchangeable electrodes is an attractive alternative to commercial RRDEs which offers the flexibility to optimize both the generator and collector materials for the desired reaction.