Calculator Input
Example Data Table
| Case | n | Area cm² | Concentration mM | D cm²/s | Scan rate mV/s | Expected use |
|---|---|---|---|---|---|---|
| Ferricyanide check | 1 | 0.071 | 1.00 | 7.60e-6 | 100 | Reversible diffusion test |
| Slow electron transfer | 1 | 0.125 | 0.50 | 5.20e-6 | 50 | Irreversible estimate |
| Modified electrode | 1 | 0.196 | 1.00 | 6.00e-6 | 25 | Surface process review |
Formula Used
Reversible Diffusion Current
The calculator uses the temperature-aware Randles-Sevcik form:
Ip = 0.4463 n F A C √(n F D v / R T)
Irreversible Diffusion Current
For a totally irreversible peak, it uses:
Ip = 0.4958 n F A C √(α nα F D v / R T)
Surface-Confined Current
For an adsorbed reversible species, it uses:
Ip = n² F² A Γ v / 4 R T
Capacitive Current
Double-layer current is added as:
Ic = Cdl A v
Here, Ip is peak current. F is Faraday constant. R is gas constant. A is electrode area. C is bulk concentration. D is diffusion coefficient. v is scan rate. T is absolute temperature. Γ is surface coverage.
How to Use This Calculator
Select the current model that matches your experiment. Use reversible diffusion for a fast and Nernstian redox couple. Use irreversible diffusion when electron transfer is slow. Use surface confined for adsorbed films or modified electrodes.
Enter the electron number, electrode area, concentration, diffusion coefficient, scan rate, and temperature. Choose units carefully. Add transfer data for the irreversible model. Add surface coverage for the surface model. Include double-layer capacitance and baseline current when you want a closer measured current estimate.
Press the calculate button. The result appears above the form. Review the Faradaic current, capacitive current, total current, and current density. Download CSV for spreadsheets. Download PDF for lab notes or reports.
About Cyclic Voltammetry Current Calculation
Why Peak Current Matters
Cyclic voltammetry is a practical method for studying redox behavior. It shows how current changes as potential is swept forward and backward. The peak current is often the first value checked. It helps estimate concentration, diffusion, electrode area, and reaction control.
Diffusion Controlled Response
In a reversible diffusion controlled system, the peak current rises with the square root of scan rate. This relation is useful. It can test whether mass transport is mainly linear diffusion. A straight line in a current versus square root scan rate plot supports diffusion control.
Role of Electrode Area
Electrode area has a direct effect. A larger area gives a larger current when other values stay fixed. Real electrodes may behave differently from their polished geometric area. Surface roughness, coatings, and fouling can change the active area. This is why calibration remains important.
Concentration and Diffusion Effects
Concentration also has a direct effect on current. Higher analyte concentration gives a larger Faradaic signal. Diffusion coefficient affects how quickly species reach the electrode. Small molecules usually diffuse faster than large molecules. Viscosity, solvent, electrolyte, and temperature can shift diffusion values.
Scan Rate Choice
Scan rate controls the experiment time scale. Slow scans allow more time for mass transfer. Fast scans raise current but can increase capacitive background. Very fast scans may also reveal kinetic limits. This calculator includes a capacitive current estimate to separate charging effects from redox current.
Temperature and Kinetics
Temperature appears in the full peak current equations. Many quick estimates use the 25 Celsius coefficient. This tool uses absolute temperature, so it can support warmer or colder experiments. Irreversible mode also uses transfer coefficient and rate step electrons, which help represent sluggish charge transfer.
Using Results Carefully
Treat calculated current as an estimate. Real voltammograms may include uncompensated resistance, adsorption, convection, electrode contamination, and reference drift. Use the value to design experiments and compare trends. Confirm final conclusions with measured data, blanks, standards, and repeated scans under controlled conditions.
FAQs
What does this calculator estimate?
It estimates cyclic voltammetry peak current, capacitive current, total current, and current density using selected electrochemical models and user supplied experimental values.
Which model should I choose?
Choose reversible diffusion for fast electron transfer. Choose irreversible diffusion for slow charge transfer. Choose surface confined when the redox species is adsorbed on the electrode.
Why does scan rate affect current?
Scan rate changes the experiment time scale. Diffusion peak current commonly follows the square root of scan rate, while capacitive current rises linearly.
What units should concentration use?
You may enter mM, µM, M, or mol/cm³. The calculator converts the value internally to mol/cm³ for the equations.
What is double-layer capacitance?
Double-layer capacitance represents electrode charging at the interface. It creates background current, especially at high scan rates or large electrode areas.
Can this replace measured voltammograms?
No. It gives a model estimate. Real experiments may include resistance, noise, fouling, convection, adsorption, and instrument limits.
Why is temperature entered in Kelvin?
Electrochemical equations use absolute temperature. Entering Kelvin keeps the gas constant term consistent and avoids Celsius conversion mistakes.
What does current density show?
Current density divides total current by electrode area. It helps compare electrodes of different sizes under similar experimental conditions.