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

Abstract

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 ∼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.

Highly Selective TEMPO Catalyzed Bulk Electrooxidation of Isopropanol to Acetone for Application in Electrochemical Heat Pumping

“…In this case, while the oxidized mediator can engage in the EC′ mechanism, there is a parallel EC i mechanism, where C i represents an irreversible chemical step causing the degradation of the mediator. 31 This phenomenon can be explained by the base induced decomposition of the oxoammonium cation (OXO in Figure 2b) at high pH, which leads to the cleavage of the C−N bond and a ring opening reaction. 32−34 This parasitic reaction is more prominent in the case of electron deficient aminoxyl derivatives, 25 which explains the irreversibility observed at higher pH levels for these two derivatives.…”

Hard Potato: A Python Library to Control Commercial Potentiostats and to Automate Electrochemical Experiments

“…For example, immediate systematic experiments similar to the one here tested are found in electrochemical applications such as potential window opening studies, the Koutecky–Levich analysis, the implementation of sampled current voltammetry, − the measurement of electrochemical kinetics with macro and microelectrodes, capacitance and solution resistance measurements with voltammetry and electrochemical impedance spectroscopy, , and the electrochemistry part of a homemade scanning electrochemical microscope . For example, in our group, we have recently reported the use of automated tools to estimate chemical decomposition rates using a set of interdigitated electrode arrays and an early version of Hard Potato . The Hard Potato library enables researchers to automate these tasks, especially when dealing with repetition and/or characterization of large libraries of redox species .…”

“… 27 For example, in our group, we have recently reported the use of automated tools to estimate chemical decomposition rates using a set of interdigitated electrode arrays and an early version of Hard Potato. 28 The Hard Potato library enables researchers to automate these tasks, especially when dealing with repetition and/or characterization of large libraries of redox species. 29 The ability to interface with third-party libraries for data analysis, plotting, simulations, machine learning, and even other instruments such as spectrophotometers and (micro)fluidics makes this a very powerful tool.…”

Legion: An Instrument for High-Throughput Electrochemistry

“…Array analysis by mass spectrometry has also contributed to significant discoveries, especially in the realm of biomolecules where libraries produced with molecular biology tools find great utility. While electrochemical arrays have also found application in synthesis and reaction screening, − far fewer commercial systems are available. Applications of hardware for electrochemical research have been developed for the last several decades and were recently reviewed extensively .…”