Automated Measurement of Electrogenerated Redox Species Degradation Using Multiplexed Interdigitated Electrode Arrays

Characterizing the decomposition of electrogenerated species in solution is essential for applications involving electrosynthesis, homogeneous electrocatalysis, and energy storage with redox flow batteries. In this work, we present an automated, multiplexed, and highly robust platform for determining the rate constant of chemical reaction steps following electron transfer, known as the EC mechanism. We developed a generation-collection methodology based on microfabricated interdigitated electrode arrays (IDAs) with variable gap widths on a single device. Using a combination of finite-element simulations and statistical analysis of experimental data, our results show that the natural logarithm of collection efficiency is linear with respect to gap width, and this quantitative analysis is used to determine the decomposition rate constant of the electrogenerated species (k(c)). The integrated IDA method is used in a series of experiments to measure k(c) values between similar to 0.01 and 100 s(-1) in aqueous and nonaqueous solvents and at concentrations as high as 0.5 M of the redox-active species, conditions that are challenging to address using standard methods based on conventional macroelectrodes. The versatility of our approach allows for characterization of a wide range of reactions including intermolecular cyclization, hydrolysis, and the decomposition of candidate molecules for redox flow batteries at variable concentration and water content. Overall, this new experimental platform presents a straightforward automated method to assess the degradation of redox species in solution with sufficient flexibility to enable high-throughput workflows.

Automated summary

In this study, a novel platform is developed for determining the rate constant of chemical reactions in solution. The platform uses microfabricated interdigitated electrode arrays (IDAs) with variable gap widths to achieve automated, multiplexed, and robust measurements. The results show that the natural logarithm of collection efficiency is linear with respect to gap width, enabling the determination of the decomposition rate constant of electrogenerated species. The platform allows for the characterization of a wide range of reactions under various conditions and can be applied in high-throughput workflows.