Chronoamperometry
Also known as: CA, chronoamperometric method
Chronoamperometry (CA) is an electrochemical technique that measures current as a function of time when a potential step is applied to an electrode. Developed by Delahay in the 1950s, CA reveals diffusion-controlled electrochemical processes and enables determination of diffusion coefficients, surface coverage, and kinetic rate constants by analyzing the transient current decay.
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When to use it
Apply CA to study electrode kinetics and diffusion-controlled electrochemical processes: electron-transfer rate determination, chronoamperometric stripping analysis, and fundamental electrokinetics. CA is ideal for fast processes (millisecond to second timescale). Assumes the electrode is stable during the potential step and that the process is controlled by diffusion or electron transfer, not by chemical complications.
Strengths & limitations
- Fast timescale: transient currents reveal kinetics on millisecond timescales
- Detailed mechanistic information: reaction orders and rate constants extractable from transient shapes
- Quantitative: diffusion coefficients determined with high accuracy using well-established theory
- Single-step experiment: no need for potential sweeping or multiple scans
- Capacitive current at the electrode-solution interface masks the faradaic signal, especially at short times
- Assumption of diffusion control: chemical reactions following electron transfer complicate interpretation
- Double-layer charging: rapid current rise at short times makes early data difficult to analyze
- Limited to systems with well-defined diffusion (stirred solutions or rotating electrodes needed for quantitative work)
Frequently asked
What is the Cottrell equation and when does it apply?
The Cottrell equation (i = nFAD^0.5C / (πt)^0.5) predicts current as a function of time for diffusion-limited electrochemistry on a planar electrode. It applies when electron transfer is fast (not rate-limiting) and diffusion is linear (1D) to a large planar electrode. At very short times or with spherical electrodes, deviations occur.
Why is capacitive current a problem in chronoamperometry?
At the instant the potential changes, the electrode-solution interface acts as a capacitor, passing a large current (ic = C_dl dE/dt) as the double layer charges. This capacitive current decays on timescales of microseconds to milliseconds, obscuring the faradaic signal at short times. Discarding data from the first 10-100 ms is common practice.
How do microelectrodes improve chronoamperometry?
Microelectrodes (diameter < 10 micrometers) have short diffusion times (microseconds), allowing measurement of very fast kinetics before bulk solution depletion occurs. They also produce smaller capacitive currents due to smaller double-layer capacitance, improving signal-to-noise ratio.
Sources
How to cite this page
ScholarGate. (2026, June 3). Chronoamperometry. ScholarGate. https://scholargate.app/en/spectroscopy/chronoamperometry
Which method?
Set this method beside its closest kin and read them side by side — the library lays the books on the table; the choice is yours.
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