Analytical theory for the cyclic voltammetry of co-reactant ECL systems in closed bipolar cells

• Analytical model for co-reactant ECL cyclic voltammetry in closed bipolar cells. • Interfacial concentrations and potentials are also theoretically modeled and analyzed. • Peak shift with co-reactant concentration reveals ECL kinetics. • For fast ECL reactions, ECL signal scales with v¹ / ² and total counts with v −1/2 . • Experimental data for Ru(bpy)₃²⁺–oxalate confirm theoretical predictions. Closed bipolar cells (cBPCs) play a crucial role in electrochemical applications by enabling redox reactions at both ends of a bipolar electrode (BPE) without requiring direct wiring to an external power source. This feature is particularly advantageous in electroanalytical systems utilizing electrochemiluminescence (ECL), allowing for the independent optimization of the electrolytes in the sample and ECL compartments. Theoretical and experimental studies on cBPCs have highlighted unique electrochemical behaviors, which arise from the interplay between the interfacial potential distributions and charge transfer rate. While these effects have been characterized for simple electron transfer reactions, their impact on more complex ECL mechanisms, including those involving catalytic co-reactants, remains insufficiently explored. In this work, an analytical theoretical model is developed to describe the cyclic voltammetric response of cBPCs in the presence of a homogeneous catalytic reaction at one electrode, as observed in ECL co-reactant systems. The model provides mathematical expressions for the electrochemical and luminescent signals, as well as the interfacial potential differences and reactant concentrations, as functions of the catalytic rate constant and scan rate. Experimental validation is performed using the Ru(bpy)₃²⁺–oxalate system, confirming the theoretical predictions and demonstrating the relevance of the model in understanding and optimizing ECL-based sensing platforms.