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 À 3 cm/s are obtained from Koutecký-Levich analysis and 21.0-5.0 • 10 À 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.

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 a rotating ring-disk electrode (RRDE). We developed a double electrode flow cell (DEFC) with exchangeable generator and detector electrodes where the electrode width equals the channel width. Commonalities and differences between the RRDE and DEFC are discussed based on analytical solutions, numerical simulations and measurements of the ferri-/ferrocyanide redox couple on Pt electrodes in a potassium chloride electrolyte. The analytical solutions agree with the measurements using electrode widths of 5 and 2 mm. Yet, we find an unexpected dependence on the exponent of the width so that wider electrodes cannot be analysed using the conventional analytical solution. In contrast, all the investigated electrodes show a collection efficiency of close to 35.4% above a minimum rotation speed or flow rate, where the narrowest electrode is most accurate at the cost of precision and the widest electrode the least accurate but most precise. Our DEFC with exchangeable electrodes is an attractive alternative to commercial RRDEs due to the flexibility to optimize the electrode materials and geometry for the desired reaction.

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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 a rotating ring-disk electrode (RRDE). We developed a double electrode flow cell (DEFC) with exchangeable generator and detector electrodes where the electrode width equals the channel width. Commonalities and differences between the RRDE and DEFC are discussed based on analytical solutions, numerical simulations and measurements of the ferri-/ferrocyanide redox couple on Pt electrodes in a potassium chloride electrolyte. The analytical solutions agree with the measurements using electrode widths of 5 and 2 mm. Yet, we find an unexpected dependence on the exponent of the width so that wider electrodes cannot be analysed using the conventional analytical solution. In contrast, all the investigated electrodes show a collection efficiency of close to 35.4% above a minimum rotation speed or flow rate, where the narrowest electrode is most accurate at the cost of precision and the widest electrode the least accurate but most precise. Our DEFC with exchangeable electrodes is an attractive alternative to commercial RRDEs due to the flexibility to optimize the electrode materials and geometry for the desired reaction.