5. Chronoamperometry

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Lesson Overview

This lesson explores the fundamentals of chronoamperometry (CA), how to verify diffusion control, the limits of the Cottrell equation, non‑idealities, microelectrode behavior, multi‑analyte strategies, and an introduction to chronocoulometry.

Basics & Theory

This video introduces chronoamperometry, potential steps, diffusion‑limited currents, and the Cottrell equation. You will learn how repeated potential steps help confirm whether mass‑transfer control holds across different applied potentials.

Concentration Profiles

This video demonstrates how concentration profiles evolve after a potential step and compares soluble versus insoluble products. You will see how diffusion layers form, shift, and reset when reversing the applied potential.

Non-Idealities in CA: When the Cottrell Equation Breaks

This video discusses conditions that cause deviations from Cottrell behavior, including ohmic drop, double‑layer charging, nucleation, convection, and radial diffusion. You will learn how to recognize artifacts and avoid misinterpreting late‑time regions.

A Diagnostic Tool for CA

You will learn how to verify Cottrell behavior using 1/√t plots, linear‑region identification, and log–log slopes. The log-log plots help ensure that diffusion‑limited regions are correctly identified before extracting diffusion coefficients or concentration.

Microelectrodes & Electrode Roughness in CA

This video compares microelectrode geometries, transient vs. steady‑state behavior, and how surface roughness affects current responses. You will begin to understand where microelectrodes provide advantages and when roughness impacts measurements.

Multiple Analytes and Chronocoulometry

This video explains how chronoamperometry can be extended to multi‑species systems using potential‑independent regions, along with the limitations of overlapping currents. The lesson concludes with chronocoulometry, showing how integrating current improves signal‑to‑noise and separates diffusion, charging, and adsorption effects.

References for Further Learning

1. Williams, T., Shum, R., & Rappleye, D. (2021). Concentration measurements in molten chloride salts using electrochemical methods. Journal of The Electrochemical Society, 168(12), 123510. https://doi.org/10.1149/1945-7111/ac436a
2. Tylka, M. M., Willit, J. L., & Williamson, M. A. (2017). Electrochemical nucleation and growth of uranium and plutonium from molten salts. Journal of The Electrochemical Society, 164(8). https://doi.org/10.1149/2.0471708jes
3. Heerman, L., & Tarallo, A. (1999). Theory of the chronoamperometric transient for electrochemical nucleation with diffusion-controlled growth. Journal of Electroanalytical Chemistry, 470(1), 70–76. https://doi.org/10.1016/S0022-0728(99)00221-1
4. Rappleye, D. S. (2016). Electrochemical concentration measurements for multianalyte mixtures in simulated electrorefiner salt. (Doctoral dissertation, The University of Utah). ProQuest. https://www.proquest.com/docview/1839262770